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Sample records for srbi2nb2o9 sbn doped

  1. Impedance spectroscopy of SrBi2Ta2O9 and SrBi2Nb2O9 ceramics correlation with fatigue behavior

    International Nuclear Information System (INIS)

    Chen, T.; Thio, C.; Desu, S.B.

    1997-01-01

    In this research, a fatigue model for ferroelectric materials is proposed. The reasons for the electrical fatigue resistance of SrBi 2 Ta 2 O 9 (SBT), SrBi 2 Nb 2 O 9 (SBN), and PbZr 1-x Ti x O 3 (PZT) are discussed in terms of the bulk ionic conductivities of the compounds. To obtain the bulk ionic conductivity of SBT and SBN, we have used impedance spectroscopy which provides an effective method that allows us to separate the individual contributions of bulk, grain boundaries, and electrode-ferroelectric interfaces from the total capacitor impedance. The bulk ionic conductivities of SBT and SBN (∼10 -7 S/cm) are much higher than those of the perovskite ferroelectrics, e.g., PZT (∼10 -11 -10 -10 S/cm). The high ionic conductivities led us to conclude that the good fatigue resistance of SrBi 2 Ta 2 O 9 and SrBi 2 Nb 2 O 9 is due to easy recovery of defects. Specifically, oxygen vacancies entrapped within the capacitors are easily released, resulting in limited space charge buildup and domain wall pinning during the polarization reversal process. However, the oxygen vacancies in PZT are trapped at trap sites to become space charges, resulting in capacitor fatigue. copyright 1997 Materials Research Society

  2. Production of ferroelectric ceramic SrBi_2Nb_2O_9 (SBN) by high energy milling and their characterization

    International Nuclear Information System (INIS)

    Sancho, E.O.; Pires Junior, G.F.M.; Rodrigues, H.O.; Sombra, A.S.B.; Sales, J.C.

    2011-01-01

    Bismuth compounds, such as SrBi_2Nb_2O_9 (SBN), lead-free, is an alternative to the use of PZT because of its excellent ferroelectric properties, especially regarding the change of polarization. SBN is synthesized by the method of the solid state by high energy ball milling in reactive polymer with zirconia beads, which were subsequently doped with Bi_2O_3 and La_2O_3 aiming to promote intentional changes in the chemical structure of the ceramic, resulting in changes in properties electrical, magnetic and optical materials. The quantitative analysis obtained by Rietveld refinement confirmed the orthorhombic crystal structure with lattice parameters (a = 5.5158 Å, b = 5.5133 Å and c = 25.0765 Å, α = β = γ = 90 °) for indices convergence S = 1.72 (goodness of fit), where S is given by the ratio RWP / Rexp. And, the Raman shifts at 174, 204, 570 and 834 cm-1 indicated the formation of SBN perovskita type. (author)

  3. Structural, electric and dielectric properties of Eu-doped SrBi2Nb2O9 ceramics obtained by co-precipitation route

    Directory of Open Access Journals (Sweden)

    Mohamed Afqir

    2018-03-01

    Full Text Available This paper presents a study of the structure and dielectric properties of Eu-doped SrBi2Nb2O9 ceramics prepared by co-precipitation route and sintered at 850 °C. The materials were examined using XRD and FTIR methods. XRD data indicated the formation of well crystallized structure of the pure and doped SrBi2Nb2O9, without the presence of undesirable phases. FTIR spectra do not bring a significant shift in the band positions. Moreover, the AC conductivity, dielectric constant and dielectric loss of the ceramics were determined through the frequency range [50 kHz–1 MHz]. In particular, the dielectric constant (ε′ and dielectric losses (tan δ of the SrBi2Nb2O9 and SrBi1.6Eu0.4Nb2O9 ceramics were measured as a function of temperature at various frequencies.

  4. High dielectric permittivity in the microwave region of SrBi2Nb2O9 (SBN) added La2O3, PbO and Bi2O3, obtained by mechanical alloying

    Science.gov (United States)

    Rocha, M. J. S.; Silva, P. M. O.; Theophilo, K. R. B.; Sancho, E. O.; Paula, P. V. L.; Silva, M. A. S.; Honorato, S. B.; Sombra, A. S. B.

    2012-08-01

    This paper presents the microwave dielectric properties and a structural study of SrBi2Nb2O9 (SBN) added La2O3, PbO or Bi2O3 obtained by a solid state procedure. High-energy mechanical milling was used to reduce the particle size, which allows for a better shaping of the green body and an increased reactivity. The mechanical milling activation process produced a reduced sintering temperature in the material, decreasing the loss of the volatile elements and controlling the growth of the grain that is produced when a high temperature is required to obtain dense ceramics. The incorporation of La3+, or Pb2+, or Bi3+ of different amounts (0, 3, 5, 10 and 15 wt%) was used to improve the densification without changing the crystal structure, since with a low doping content these ions can occupy the A site of the perovskite blocks; they can also occupy the Bi3+ sites in Bi2O3 layers. A single orthorhombic phase was formed after calcination at 800 °C for 2 h. X-ray diffraction, Fourier transformation, infrared and Raman spectroscopy have been carried out in order to investigate the effects of doping on SBN. The dielectric permittivity (ɛ‧r) and loss in the microwave region (2-4 GHz) of SBN ceramics with additions of Bi2O3, La2O3 and PbO were studied. Higher values of permittivity (ɛr‧ = 154.6) have been obtained for the SBN added La (15 wt%) a lower loss (tg δ = 0.01531) was also achieved in the SBN added La (15 wt%) sample with PVA and TEOS, respectively. The samples that showed the highest dielectric permittivities were all lanthanum doped, all with values of permittivity above 90. A comparative study associated with different types of binders was completed (with glycerin, PVA and TEOS). This procedure allowed us to obtain phases at lower temperatures than usually appear in the literature. The microwave dielectric properties (permittivity and loss) in the region 2-4 GHz, were studied for all samples. The structural and microwave dielectric properties of SBN show a

  5. High-Power Characteristics of Thickness Shear Mode for Textured SrBi2Nb2O9 Ceramics

    Science.gov (United States)

    Ogawa, Hirozumi; Kawada, Shinichiro; Kimura, Masahiko; Higuchi, Yukio; Takagi, Hiroshi

    2009-09-01

    The high-power piezoelectric characteristics of the thickness shear mode for oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi2Nb2O9 (SBN), were studied by the constant current driving method. These textured ceramics were fabricated by the templated grain growth (TGG) method, and the Lotgering factor was 95%. The vibration of the thickness shear mode in the textured SBN ceramics was stable at the vibration velocity of 2.0 m/s. The resonant frequency was almost constant with increasing vibration velocity in the textured SBN ceramics, however, it decreased with increasing vibration velocity in the randomly oriented SBN ceramics. In the case of Pb(Mn,Nb)O3-Pb(Zr,Ti)O3 ceramics, the vibration velocity of the thickness shear mode was saturated at more than 0.3 m/s, and the resonant frequency decreased at lower vibration velocity than in the case of SBN ceramics. The dissipation power density of the textured SBN ceramics was the lowest among those of the randomly oriented SBN and Pb(Mn,Nb)O3-PZT ceramics. The thickness shear mode of textured SBN ceramics is a good candidate for high-power piezoelectric applications.

  6. High-Power Piezoelectric Vibration Characteristics of Textured SrBi2Nb2O9 Ceramics

    Science.gov (United States)

    Kawada, Shinichiro; Ogawa, Hirozumi; Kimura, Masahiko; Shiratsuyu, Kosuke; Niimi, Hideaki

    2006-09-01

    The high-power piezoelectric vibration characteristics of textured SrBi2Nb2O9 (SBN) ceramics, that is bismuth-layer-structured ferroelectrics, were studied in the longitudinal mode (33-mode) by constant current driving method and compared with those of ordinary randomly oriented SBN and widely used Pb(Ti,Zr)O3 (PZT) ceramics. In the case of textured SBN ceramics, resonant properties are stable up to a vibration velocity of 2.6 m/s. Vibration velocity at resonant frequency increases proportionally with the applied electric field, and resonant frequency is almost constant in high-vibration-velocity driving. On the other hand, in the case of randomly oriented SBN and PZT ceramics, the increase in vibration velocity is not proportional to the applied high electric field, and resonant frequency decreases with increasing vibration velocity. The resonant sharpness Q of textured SBN ceramics is about 2000, even at a vibration velocity of 2.6 m/s. Therefore, textured SBN ceramics are good candidates for high-power piezoelectric applications.

  7. Influence of La doping on structural and dielectric properties of SrBi2Nb2O9 ceramics

    Science.gov (United States)

    Verma, Maya; Sreenivas, K.; Gupta, Vinay

    2009-01-01

    Lanthanum doped SrBi2Nb2O9 ceramics with the chemical formula SrBi2-xLaxNb2O9 (SBLN) (x =0-0.5) have been prepared through conventional solid state route. X-ray diffraction reveals the shrinkage of unit cell of strontium bismuth niobate with incorporation of La3+ dopant, having no lone pair electrons. Shifting of Raman phonon modes indicates the reduced rattling space of NbO6 octahedra with increase in La doping concentration. Further, the softening of lowest frequency phonon mode with increasing x in SBLN shows the transition from ferroelectric to paraelectric at room temperature. The dielectric properties for all the compositions are studied as a function of temperature (25 to 500 °C) over the frequency range of 10 kHz-1 MHz. With increase in lanthanum doping concentration the phase transition becomes diffused and transition temperature gets shifted toward lower temperature. A phase transition from normal ferroelectric to paraelectric has been observed via relaxor-type ferroelectrics with increase in x. The frequency dependence of transition temperature was studied in terms of Vogel-Fulcher relation for SBLN (x =0.4).

  8. Influence of La doping on structural and dielectric properties of SrBi2Nb2O9 ceramics

    International Nuclear Information System (INIS)

    Verma, Maya; Sreenivas, K.; Gupta, Vinay

    2009-01-01

    Lanthanum doped SrBi 2 Nb 2 O 9 ceramics with the chemical formula SrBi 2-x La x Nb 2 O 9 (SBLN) (x=0-0.5) have been prepared through conventional solid state route. X-ray diffraction reveals the shrinkage of unit cell of strontium bismuth niobate with incorporation of La 3+ dopant, having no lone pair electrons. Shifting of Raman phonon modes indicates the reduced rattling space of NbO 6 octahedra with increase in La doping concentration. Further, the softening of lowest frequency phonon mode with increasing x in SBLN shows the transition from ferroelectric to paraelectric at room temperature. The dielectric properties for all the compositions are studied as a function of temperature (25 to 500 deg. C) over the frequency range of 10 kHz-1 MHz. With increase in lanthanum doping concentration the phase transition becomes diffused and transition temperature gets shifted toward lower temperature. A phase transition from normal ferroelectric to paraelectric has been observed via relaxor-type ferroelectrics with increase in x. The frequency dependence of transition temperature was studied in terms of Vogel-Fulcher relation for SBLN (x=0.4)

  9. Synthesis, structural and dielectric properties of SrBi2- x La x Nb2O9 ceramics prepared by hydrothermal treatment

    Science.gov (United States)

    Afqir, Mohamed; Tachafine, Amina; Fasquelle, Didier; Elaatmani, Mohamed; Carru, Jean-Claude; Zegzouti, Abdelouahad; Daoud, Mohamed

    2018-01-01

    SrBi2- x La x Nb2O9 ( x = 0.2, 0.4 and 0.6) Aurivillius materials were prepared by hydrothermal treatment. The powder prepared by this method is highly pure and not agglomerated. The morphology of the samples was characterized by SEM. The dielectric properties of all the compositions were investigated in the temperature range from 25 °C to 500 °C and in the frequency range between 100 Hz and 1 MHz. The dielectric properties at room temperature of the proposed materials can match up with La-doped SrBi2Nb2O9 ceramics prepared via the solid-state reaction method. Partial substitution of bismuth by lanthanum greatly affects the ferroelectric-paraelectric transition temperature, as the ferroelectric-paraelectric phase transition becomes diffuse and the Curie temperature shifts toward lower temperatures typically from 375 to 290 °C. The conductivity results obtained for the samples are explained taking into account the metal-binding energies.

  10. Evolution of ferroelectric SrBi2Nb2O9 phase embedded in tellurite glass

    Science.gov (United States)

    Mohamed, E. A.

    2017-12-01

    Glasses with the composition, [(100-x)TeO2- x(SrO-Bi2O3-Nb2O5)] with x = 20, 30 and 40 (in mol %) were prepared. The X-ray diffraction (XRD) pattern and differential thermal analysis (DTA) for the as-prepared samples confirmed the amorphous and glassy characteristics, respectively. The SrBi2Nb2O9 phase in tellurite glass for HT773 sample at x = 40 mol % is formed and confirmed by the Rietveld refinement. DTA curves for all glass samples exhibit two endothermic dips while the two broad exothermic peaks at lower x reduced to one at higher x. Infrared (IR) results revealed that the glassy matrix are composed of TeO3, TeO3+1, TeO4, BiO6 and NbO6 structural units. The changes in the density (ρ), molar volume (Vm), oxygen molar volume (V0) and oxygen packing fraction (OPD) have correlated with structural changes in the glass network. The optical studies show an absorption bands below the absorption edge in the glass samples.

  11. Effect of the heat flux direction on electrical properties of SrBi2Nb2O9 thin films crystallized using a microwave oven

    International Nuclear Information System (INIS)

    Vasconcelos, J.S.; Vasconcelos, N.S.L.S.; Zanetti, S.M.; Leite, E.R.; Varela, J.A.; Longo, E.

    2004-01-01

    Ferroelectric SrBi 2 Nb 2 O 9 (SBN) thin films were prepared by the polymeric precursors method and deposited by spin coating onto Pt/Ti/SiO 2 /Si substrate and crystallized using a domestic microwave oven. It was studied the influence of the heat flux direction and the duration of the thermal treatment on the films crystallization. An element with high dielectric loss, a SiC susceptor, was used to absorb the microwave energy and transfers the heat to the film. Influence of the susceptor position to the sample crystallization was verified, the susceptor was placed or below the substrate or above the film. The SBN perovskite phase was observed after a thermal treatment at 700 deg. C for 10 min when the susceptor was placed below the substrate and for 30 min when the susceptor was placed above the film. Electrical measurements revealed that the film crystallized at 700 deg. C for 10 min, with the susceptor placed below the film, presented dielectric constant, dielectric loss, remanent polarization and coercive field of, 67, 0.011, 4.2 μC/cm 2 and 27.5 kV/cm, respectively. When the films were crystallized at 700 deg. C for 30 min, with the susceptor placed above the film, the dielectric constant was 115 and the dissipation factor was around of 0.033, remanent polarization and coercive field were 10.8 μC/cm 2 and 170 kV/cm, respectively

  12. Properties of SrBi2Nb2O9 thin films on Pt-coated Si

    International Nuclear Information System (INIS)

    Avila, R.E.; Navarro, P.O.; Martin, V. del C.; Fernandez, L.M.; Sylvester, G.; Retuert, P.J.; Gramsch, E.

    2002-01-01

    SrBi 2 Nb 2 O 9 powders and thin films, on Pt-coated Si, were synthesised by the sol-gel method. Three-layer thin films appear homogeneous down to the 100 nm scale, polycrystalline in the tetragonal Aurivillius phase, at a average thickness of 40 nm per layer. The index of refraction at the center of the visible range increases with the sintering temperature from roughly 2.1 (at 400 Centigrade) to 2.5 (at 700 Centigrade). The expression n 2 -1 increases linearly with the relative density of the thin films, in similar fashion as previous studies in PbTiO 3 thin films. The dielectric constant in quasistatic and high frequency (1 MHz) modes, is between 160 and 230. (Author)

  13. Temperature dependence of piezoelectric properties for textured SBN ceramics.

    Science.gov (United States)

    Kimura, Masahiko; Ogawa, Hirozumi; Kuroda, Daisuke; Sawada, Takuya; Higuchi, Yukio; Takagi, Hiroshi; Sakabe, Yukio

    2007-12-01

    Temperature dependences of piezoelectric properties were studied for h001i textured ceramics of bismuth layer-structured ferroelectrics, SrBi(2)Nb(2)O(9) (SBN). The textured ceramics with varied orientation degrees were fabricated by templated, grain-growth method, and the temperature dependences of resonance frequency were estimated. Excellent temperature stability of resonance frequency was obtained for the 76% textured ceramics. The resonance frequency of the 76% textured specimens varied almost linearly over a wide temperature range. Therefore, the variation was slight, even in a high temperature region above 150 degrees C. Temperature stability of a quartz crystal oscillator is generally higher than that of a ceramic resonator around room temperature. The variation of resonance frequency for the 76% textured SrBi(2)Nb(2)O(9) was larger than that of oscillation frequency for a typical quartz oscillator below 150 degrees C also in this study. However, the variation of the textured SrBi(2)Nb(2)O(9) was smaller than that of the quartz oscillator over a wide temperature range from -50 to 250 degrees C. Therefore, textured SrBi(2)Nb(2)O(9) ceramics is a major candidate material for the resonators used within a wide temperature range.

  14. Properties of SrBi sub 2 Nb sub 2 O sub 9 thin films on Pt-coated Si

    CERN Document Server

    Avila, R E; Martin, V D C; Fernandez, L M; Sylvester, G S; Retuert, P J; Gramsch, E

    2002-01-01

    SrBi sub 2 Nb sub 2 O sub 9 powders and thin films, on Pt-coated Si, were synthesised by the sol-gel method. Three-layer thin films appear homogeneous down to the 100 nm scale, polycrystalline in the tetragonal Aurivillius phase, at a average thickness of 40 nm per layer. The index of refraction at the center of the visible range increases with the sintering temperature from roughly 2.1 (at 400 Centigrade) to 2.5 (at 700 Centigrade). The expression n sup 2 -1 increases linearly with the relative density of the thin films, in similar fashion as previous studies in PbTiO sub 3 thin films. The dielectric constant in quasistatic and high frequency (1 MHz) modes, is between 160 and 230. (Author)

  15. Estudio dieléctrico de cerámicas de textura y microestructura controladas con composiciones (SrBi2Nb2O91-x(Bi3TiNbO9x

    Directory of Open Access Journals (Sweden)

    Pardo, L.

    2002-02-01

    Full Text Available Ceramics of composition (SrBi2Nb2O91-x(Bi3TiNbO9x with x = 0.35, 0.65 and 1.00 and Aurivillius type structure have been prepared by natural sintering and hot pressing. Amorphous precursors were obtained by mechanochemical activation of stoichiometric mixtures of oxides and carbonates, which allows using moderate processing temperatures. These materials are interesting for their use as high temperature piezoelectrics. Dielectric characterisation allows to know the temperature at what takes place the ferro-paraelectric transition, which limits the working temperature of the material. It also gives information on how the electric properties, especially the d. c. conductivity, affect the polarizability of the ceramics. The properties relation with the microstructure and the texture is studied. In this work, dielectric studies of these materials have been made, in the frequency interval from 100 Hz to 5 MHz and in the temperature range from 200 ºC up to the ferroparaelectric transition temperatures (>900 ºC for Bi3TiNbO9.Se han preparado cerámicas de la solución sólida (SrBi2Nb2O91-x(Bi3TiNbO9x con x = 0.35, 0.65 y 1.00 y estructura tipo Aurivillius obtenidas por sinterización natural y por prensado en caliente. Se parte de precursores amorfos obtenidos por activación mecanoquímica de una mezcla estequiométrica de óxidos y carbonatos, lo que permite utilizar temperaturas moderadas de procesado. Estos materiales son interesantes por su posible uso como piezoeléctricos de alta temperatura. La caracterización dieléctrica permite establecer a qué temperatura se encuentra la transición ferro-paraeléctrica que limita la temperatura de uso del material y como afectan las propiedades eléctricas, especialmente la conductividad d. c., a la polarizabilidad de las cerámicas, así como su relación con su microestructura y textura. En este trabajo se ha realizado el estudio dieléctrico de estos materiales en el intervalo de frecuencias de 100

  16. Effect of CASP glass doping on sintering and dielectric properties of SBN ceramics

    International Nuclear Information System (INIS)

    Chen Guohua; Qi Bing

    2009-01-01

    16CaO-29Al 2 O 3 -34SiO 2 -13PbO-4B 2 O 3 -2ZnO-2P 2 O 5 (CASP) glass doped-Sr 0.5 Ba 0.5 Nb 2 O 6 (SBN50) ceramics have been synthesized by solid-state ceramic route. The effects of CASP glass on the firing, microstructure and dielectric characterization of SBN50 ceramics are investigated. The densities of the ceramic samples firstly increase and then slightly decrease with increasing CASP glass content. The appropriate amount of doping glass is 2%. The SBN50 ceramics doped with CASP glass can be sintered at a relatively low temperature, 1200 deg. C. X-ray diffraction analysis shows the single phase (tetragonal tungsten bronze type structure) is preserved for all the samples. The diffuse character of the ceramic system increases and the dielectric constant at phase transition temperature (T c ) markedly decreases as CASP glass content increases. Interestingly, the CASP glass addition drastically alters the microstructure of the sintered ceramics. The isotropic grains in the pure SBN50 ceramics transform to rod like grains after the addition of CASP glass. The grain size of SBN phase is found to obviously increase with increase in CASP glass doping level

  17. Influence of oxygen annealing on the dielectric properties of SrBi2(V0.1Nb0.9)2O9 ceramics

    International Nuclear Information System (INIS)

    Wu, Y.; Forbess, M.; Seraji, S.; Limmer, S.; Chou, T.; Cao, G.Z.

    2001-01-01

    The influences of O 2 and N 2 annealing on the dielectric properties of SrBi 2 (V 0.1 Nb 0.9 ) 2 O 9 (SBVN) ferroelectrics were studied. Ceramic samples were prepared by reaction sintering a powder mixture of constituent oxides at 950 deg. C for 2 h in air. Some samples were also subsequently annealed at 800 deg. C for 3 h in O 2 or N 2 . With O 2 annealing, the Curie point of the SBVN ferroelectrics changed from ∼433 to ∼438 deg. C and the peak dielectric constant increased from ∼760 to ∼1010 (at 100 kHz). However, no change in the Curie point was found with N 2 annealing. Furthermore, O 2 annealing was found to reduce significantly both the dielectric constant and loss tangent of the SBVN ferroelectrics at frequencies below 1000 Hz. XRD results revealed a small reduction in the lattice constants with O 2 annealing, but no appreciable change with N 2 annealing. In addition, no detectable change in the microstructure of the SBVN samples was found with annealing. These results imply that some V 4+ ions, which are compensated by the formation of oxygen vacancies, existed in the SBVN ferroelectrics prior to O 2 annealing. V 4+ ions were oxidized to V 5+ with O 2 annealing, which resulted in improved dielectric properties. (author)

  18. Substitution-induced near phase transition with Maxwell-Wagner polarization in SrBi{sub 2}(Nb{sub 1-x}A{sub x}){sub 2}O{sub 9} ceramics [A = W, Mo and x = 0, 0.025

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Prasun; Franco, Adolfo Jr. [Instituto de Fisica, Universidade Federal de Goias, Goiania (Brazil)

    2017-10-15

    The synthesis, micro-structure, spectroscopic, and dielectric properties of SrBi{sub 2}(Nb{sub 1-x}A{sub x}){sub 2}O{sub 9} [with A=W, Mo and x = 0, 0.025] ceramics were systematically studied. A relative density of ≥98% was obtained for all the samples using a two-step solid state sintering process. XRD images showed that a single phase layered perovskite structure of SrBi{sub 2}Nb{sub 2}O{sub 9} (SBN) was formed. The orthorhombic structure with A2{sub 1}am phase group was found up to ∝2.5 at.% substitution of W and Mo into the SBN matrix. SEM revealed the rod-like grain structure similar to the Maxwell-Wagner (MW) parallel plate capacitor model in SBN ceramic, whereas smaller heterogeneous grain structure was observed in W and Mo donor doped ceramics. The initial high value of real and imaginary part of relative permittivity also indicated the presence of interfacial MW relaxation in the SBN ceramics. The experimental data fit well to the theoretical data obtained from MW polarization model in SBN ceramics. The possible origin of the difference of the properties present in the doped sample has been explained based on grain size, orientation, and modification done in the ceramic matrices. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Growth and properties of SrBi2TaNbO9 ferroelectric thin films using pulsed laser deposition

    International Nuclear Information System (INIS)

    Yang Pingxiong; Deng Hongmei; Shi Meirong; Tong Ziyang; Qin Sumei

    2007-01-01

    High quality SrBi 2 TaNbO 9 (SBTN) ferroelectric thin films were fabricated on platinized silicon by pulsed laser deposition. Microstructure and ferroelectric properties of the films were characterized. Optical fatigue (light/bias) for the thin films was studied and the average remanent polarization dropped by nearly 55% due to the bias/illumination treatment. Optical properties of the thin films were studied by spectroscopic ellipsometry (SE) from the ultraviolet to the infrared region. Optical constants, n ∼ 0.16 in the infrared region and n ∼ 2.12 in the visible spectral region, were determined through refractive index functions. The band gap energy is estimated to be 3.93 eV

  20. Ho-doped SrBi{sub 2}Nb{sub 2}O{sub 9} multifunctional ceramics with bright green emission and good electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Lei; Hao, Jigong; Li, Wei [College of Materials Science and Engineering, Liaocheng University, Liaocheng (China); Xu, Zhijun; Chu, Ruiqing [School of Environmental and Materials Engineering, Yantai University, Yantai (China)

    2017-10-15

    Ho{sup 3+}-doped SrBi{sub 2}Nb{sub 2}O{sub 9} multifunctional ferroelectric ceramics with bright green light emission and good electrical properties were fabricated in this work. Under blue light excitation, samples showed bright green light with two typical emission bands: a strong green emission centered at 545 nm corresponding to the intra f-f transition from the excited {sup 5}S{sub 2} to the ground state {sup 5}I{sub 8} and a relatively weak red emission located 653 nm induced by the {sup 5}F{sub 5} → {sup 5}I{sub 8} transition of Ho{sup 3+}. Due to the concentration quenching effect, the intensity of emission was strongly dependent on the doping concentration. Furthermore, the electrical properties have improved by Ho{sup 3+} doping. At x = 0.004, samples exhibit optimal electrical properties with high Curie temperature (T{sub c} = 441 C) and large 2P{sub r} and d{sub 33} values (2P{sub r} = 15.54 μC cm{sup -2}, d{sub 33} = 19 pC/N). These results demonstrate that the SBN-xHo ceramics possess excellent multifunctional properties to achieve a variety of applications. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Sintering and characterization of SrBi_2Ta_2O_9 obtained by high-pressure processing at low temperatures

    International Nuclear Information System (INIS)

    Souza, Ricson R.; Kirchner, Rejane K.; Jurado, Jose R.; Pereira, Altair S.; Sousa, Vânia C.

    2016-01-01

    High-pressure processing is a very attractive approach for the production of materials with new and/or improved properties. In this work, pressures in the order of 7.7 GPa and 2.5 GPa were induced in SrBi_2Ta_2O_9 samples at different temperatures placed in a specific reaction cell and generated different effects on phase formation. The microstructural evolution during high-pressure processing was investigated by scanning electron microscopy in association with energy dispersion spectroscopy and with the support of an X-ray diffraction analyzer. Frequency response analysis was used to obtain the dielectric curves by electrochemical impedance spectroscopy. A SrBi_2Ta_2O_9 single-phase sample, treated at 2.5 GPa and 900 °C, was used to evaluate the electrical properties, obtaining a dielectric response similar to SrBi_2Ta_2O_9 samples sintered by conventional processes at temperatures above 1000 °C. In addition, by this method, it was possible to obtain ceramics with uniform microstructure and a relative density of 93%. - Highlights: • The first production of SrBi_2Ta_2O_9 using the technique of high-pressure processing. • The ability to produce single-phase SrBi_2Ta_2O_9 treated at 2.5 GPa and 900 °C. • The electrical properties are compatible with SBT sintered at high temperatures.

  2. Structural and vibrational investigations of Nb-doped TiO2 thin films

    International Nuclear Information System (INIS)

    Uyanga, E.; Gibaud, A.; Daniel, P.; Sangaa, D.; Sevjidsuren, G.; Altantsog, P.; Beuvier, T.; Lee, Chih Hao; Balagurov, A.M.

    2014-01-01

    Highlights: • We studied the evolutions of structure for TiO 2 thin film as changes with Nb doping and temperatures. • Up to 800 °C, the grain size of Nb 0.1 Ti 0.9 O 2 is smaller than for pure TiO 2 because doped Nb hinders the growth of the TiO 2 grains. • There was no formation of the rutile phase at high temperature. • Nb doped TiO 2 films have high electron densities at 400–700 °C. • Nb dope extends the absorbance spectra of TiO 2 which leads to the band gap reduce. - Abstract: Acid-catalyzed sol–gel and spin-coating methods were used to prepare Nb-doped TiO 2 thin film. In this work, we studied the effect of niobium doping on the structure, surface, and absorption properties of TiO 2 by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectometry (XRR), X-ray photoelectron spectroscopy (XPS), Raman, and UV–vis absorption spectroscopy at various annealing temperatures. EDX spectra show that the Nb:Ti atomic ratios of the niobium-doped titania films are in good agreement with the nominal values (5 and 10%). XPS results suggest that charge compensation is achieved by the formation of Ti vacancies. Specific niobium phases are not observed, thus confirming that niobium is well incorporated into the titania crystal lattice. Thin films are amorphous at room temperature and the formation of anatase phase appeared at an annealing temperature close to 400 °C. The rutile phase was not observed even at 900 °C (XRD and Raman spectroscopy). Grain sizes and electron densities increased when the temperature was raised. Nb-doped films have higher electron densities and lower grain sizes due to niobium doping. Grain size inhibition can be explained by lattice stress induced by the incorporation of larger Nb 5+ ions into the lattice. The band gap energy of indirect transition of the TiO 2 thin films was calculated to be about 3.03 eV. After niobium doping, it decreased to 2.40 eV

  3. Effect of Nb-doped TiO{sub 2} on nanocomposited aligned ZnO nanorod/TiO{sub 2}:Nb for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Saurdi, I., E-mail: saurdy788@gmail.com; Ishak, A. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); UiTM Sarawak Kampus Kota Samarahan Jalan Meranek, Sarawak (Malaysia); Shafura, A. K.; Azhar, N. E. A.; Mamat, M. H. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); Malek, M. F.; Rusop, M. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), (Centre for Nano-Science and Nano-Technology), Institute of Science, Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Alrokayan, A. H. Salman; Khan, Haseeb A. [Department of Biochemistry, College of Science, Bldg. 5, King Saud University (KSU) P.O: 2455 Riyadh 1145 (Saudi Arabia)

    2016-07-06

    The Nb-doped TiO{sub 2} films were deposited on glass substrate at different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively and their electrical and structural properties were investigated. Subsequently, the Nb-doped TiO{sub 2} films were deposited on top of aligned ZnO Nanorod on ITO glass substrates using spin coating technique. The nanocomposited aligned ZnO nanorod/Nb-doped TiO{sub 2} (TiO{sub 2}:Nb) were coated with different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively. The Dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO{sub 2}:Nb photoanodes and their effects on the performance of the DSSCs were investigated. From the solar simulator measurement of DSSC the solar energy conversion efficiency (η) of 5.376% under AM 1.5 was obtained for the ZnO nanorod/TiO{sub 2}:Nb-5at.%.

  4. Electrical and ferroelectric properties of RF sputtered PZT/SBN on silicon for non-volatile memory applications

    Science.gov (United States)

    Singh, Prashant; Jha, Rajesh Kumar; Singh, Rajat Kumar; Singh, B. R.

    2018-02-01

    We report the integration of multilayer ferroelectric film deposited by RF magnetron sputtering and explore the electrical characteristics for its application as the gate of ferroelectric field effect transistor for non-volatile memories. PZT (Pb[Zr0.35Ti0.65]O3) and SBN (SrBi2Nb2O9) ferroelectric materials were selected for the stack fabrication due to their large polarization and fatigue free properties respectively. Electrical characterization has been carried out to obtain memory window, leakage current density, PUND and endurance characteristics. Fabricated multilayer ferroelectric film capacitor structure shows large memory window of 17.73 V and leakage current density of the order 10-6 A cm-2 for the voltage sweep of -30 to +30 V. This multilayer gate stack of PZT/SBN shows promising endurance property with no degradation in the remnant polarization for the read/write iteration cycles upto 108.

  5. Vertically aligned nitrogen doped (Sn,Nb)O_2 nanotubes – Robust photoanodes for hydrogen generation by photoelectrochemical water splitting

    International Nuclear Information System (INIS)

    Patel, Prasad Prakash; Hanumantha, Prashanth Jampani; Velikokhatnyi, Oleg I.; Datta, Moni Kanchan; Gattu, Bharat; Poston, James A.; Manivannan, Ayyakkannu; Kumta, Prashant N.

    2016-01-01

    Graphical abstract: - Highlights: • Nb and N co-doping provides excellent optoelectronic properties for SnO_2 NTs. • The optoelectronic properties of doped SnO_2 are studied by first principles study. • (Sn_0_._9_5Nb_0_._0_5)O_2:N-600 NTs exhibits superior ABPE (4.1%) to date. • Excellent photoelectrochemical stability of (Sn_0_._9_5Nb_0_._0_5)O_2:N-600 NTs. - Abstract: Hydrogen generation from photoelectrochemical (PEC) water splitting is on the forefront of clean energy generation landscape. The efficiency of PEC system is dependent on the engineering of semiconductors with tailored narrow band gap coupled with superior photoelectrochemical activity and desired stability vital for the commercialization of PEC water splitting cells. We report herein the study of vertically aligned Nb and N doped SnO_2 nanotubes (NTs), i.e., (Sn_0_._9_5Nb_0_._0_5)O_2:N NTs for PEC water splitting. (Sn_0_._9_5Nb_0_._0_5)O_2 NTs was selected for co-doping with nitrogen by systematic analysis of applied bias photon-to-current efficiency of various Nb doped SnO_2 (x = 0–0.1) compositions. Consequently, excellent photoelectrochemical stability and the highest efficiency of 4.1% is obtained for (Sn_0_._9_5Nb_0_._0_5)O_2:N-600 NTs never observed for other known TiO_2, ZnO, and Fe_2O_3 systems to date. Additionally, theoretical first principles study provides understanding of Nb and N co-doping on the electronic structure and band gap of SnO_2 semiconductor, further corroborating results of the experimental study.

  6. Effect of cerium addition on the microstructure, electrical and relaxor behavior of Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Velayutham, T.S., E-mail: t_selvi@um.edu.my; Salim, N.I.F.; Gan, W.C.; Abd Majid, W.H.

    2016-05-05

    Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} (SBN50) ceramic doped with different concentrations of Cerium (Ce) according to the stoichiometry formulation of Sr{sub 0.5-3y/2}Ba{sub 0.5}Ce{sub y}Nb{sub 2}O{sub 6} (Ce-SBN) with y = 0, 0.01, 0.02, 0.03, 0.04 and 0.05 was prepared using the conventional solid state reaction method. The morphology, structure, and electrical properties of the samples were studied using field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), ferroelectric and dielectric spectroscopy, respectively. The FESEM images reveal a strong influence of cerium on the SBN microstructure. The X-ray diffraction patterns show that all compositions of SBN ceramic exhibit tetragonal tungsten bronze structure. As the dopant concentration, y increased, both unit cell volume and axial ratio c/a decreased gradually. In addition, dopant incorporation lowers the phase transition temperature, T{sub m}. As a result, all practical parameters are sufficiently increased, i.e. the dielectric constant and remnant polarization. SBN50 doped with a 3% Ce sample is most attractive for practical applications due to its high remnant polarization, P{sub r} = 58.6 μC/cm{sup 2} and dielectric constant, ε’ ≈ 8000 (10 kHz) at room temperature, respectively. - Highlights: • Sr{sub 0.5-3y/2}Ba{sub 0.5}Ce{sub y}Nb{sub 2}O{sub 6} synthesized using solid-state reaction method. • Cerium dopant improved the overall properties of SBN. • Dopant incorporation lowers the phase transition temperature, T{sub m}. • 3% Ce dopant exhibits best functional properties among the rest of the composition. • The P{sub r} of 3%Ce-doped SBN is 58.6 μC/cm{sup 2} and ε’ ≈ 8000 (10 kHz) at room temperature.

  7. RBS characterisation of SrxBa1-xNb2O6 (SBN) thin films obtained by laser deposition

    International Nuclear Information System (INIS)

    Pantelica, D.; Petris, M.; Negoita, F.; Dinescu, M.; Dinu, R.; Bauerle, D.; Pedarnig, J.; Bauer-Gogonea, S.; Bauer, S.

    1999-01-01

    Sr x Ba 1-x Nb 2 O 6 (SBN) is an attractive material for many applications such as nonvolatile ferroelectric random-access memories. SBN thin films have been grown by different techniques, such as solid source metalorganic chemical vapor deposition, liquid phase epitaxy, sol-gel synthesis and rf-sputter deposition. Pulsed laser deposition (PLD) is a relatively new growth technique which is ideally suited to the epitaxial growth of multicomponent oxides, because complex target compositions can be stoichiometrically reproduced at the substrate. Multilayer SBN/LSCO/TiN/MgO was prepared as follows: the (100) MgO substrate was glued onto a Ni holder with silver paint and the whole assembly was heated radiatively to the deposition temperatures in the range 450-800 deg. C. MgO substrates were annealed in oxygen at 1050 deg. C for 12 hours prior to the deposition of films. A UV-excimer laser (KrF, λ = 248 nm, t(FWHM) = 25 ns) operating at a repetition rate of 5 Hz was used for ablation. The laser fluence was varied between 0.8-2.6 J/cm 2 ; 4000 pulses were given for the deposition of LSCO film and 8000 pulses for the deposition of SBN film. The composition of the film was analysed using RBS. The measurements were conducted using a 7 Li ++ beam at 4.5 MeV provided by the Van de Graaff Tandem accelerator of IFIN-HH. An ordinary backscattering setup was used. The backscattered particles were detected using a passivated ion implanted silicon detector, placed at 145 angle with respect with the beam. The energy resolution for 7 Li at 4 MeV was about 30 keV. The sample surface was perpendicular to the beam direction. For the quantitative analysis of RBS spectra we used the code RUMP. A typical RBS spectrum of a SBN/LSCO/TiN/MgO sample is shown. A simulation is plotted on the same graph. The simulation curve fit well the experimental data. The profiles for different element are flat topped, indicating that the composition is constant with depth. The sharp high and low energy

  8. Phase transition sequence in ferroelectric Aurivillius compounds investigated by single crystal X-ray diffraction

    Science.gov (United States)

    Boullay, P.; Tellier, J.; Mercurio, D.; Manier, M.; Zuñiga, F. J.; Perez-Mato, J. M.

    2012-09-01

    The investigation of the phase transition sequence in SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) is reported using single-crystal X-ray diffraction. By monitoring specific reflections as a function of temperature, sensitive either to the superstructure formation or to polar displacements, it was possible to check the existence or not of an intermediate phase. This latter was confirmed in SBT, but within experimental accuracy could not be detected in SBN.

  9. Electrode contacts on ferroelectric Pb(Zr x Ti1−x )O3 and SrBi2Ta2O9 thin films and their influence on fatigue properties

    OpenAIRE

    Lee, J. J.; Thio, C. L.; Desu, Seshu B.

    1995-01-01

    The degradation (fatigue) of dielectric properties of ferroelectric Pb(ZrxTi1-x)O-3 (PZT) and SrBi2Ta2O9 thin films during cycling was investigated. PZT and SrBi2Ta2O9 thin films were fabricated by metalorganic decomposition and pulsed laser deposition, respectively. Samples with electrodes of platinum (Pt) and ruthenium oxide (RuO2) were studied. The interfacial capacitance (if any) at the Pt/PZT, RuO2/PZT, and Pt/SrBi2Ta2O9 interfaces was determined from the thickness dependence of low-fiel...

  10. Surface energy effects on the stability of anatase and rutile nanocrystals: A predictive diagram for Nb_2O_5-doped-TiO_2

    International Nuclear Information System (INIS)

    Silva, Andre Luiz da; Hotza, Dachamir; Castro, Ricardo H.R.

    2017-01-01

    Highlights: • Anatase-rutile phase transition diagram was built for nano Nb_2O_5-doped-TiO_2. • Nb_2O_5-doping postpones the anatase-to-rutile transition. • The stability crossover for TiO_2 was 17.3 nm, for 2 mol% Nb_2O_5-doped-TiO_2 ∼30 nm. • The surface energy for Nb_2O_5-doped-TiO_2 decreases systematically with Nb concentration. - Abstract: Titanium dioxide nanoparticles are widely used for photocatalysis, and the relative fraction of titanium dioxide polymorph, i.e. anatase, rutile, or brookite, significantly affects the final performance. Even though conventional phase diagrams indicate a higher stability for the rutile polymorph, it is well established that nanosizes benefit the anatase phase due to its smaller surface energy. However, doping elements are expected to change this behavior, once changes in both surface and bulk energies may occur. Nb_2O_5 is commonly added to TiO_2 to allow property control. However, the effect of niobium on the relative stability of anatase and rutile phases is not well understood from the thermodynamic point of view. The objective of this work was to build a new predictive nanoscale phase diagram for Nb_2O_5-doped TiO_2. Water adsorption microcalorimetry and high temperature oxide melt solution were used to obtain the surface and bulk enthalpies. The phase diagram obtained shows the stable titania polymorph as a function of the composition and size.

  11. Nanostructured rare earth doped Nb2O5: Structural, optical properties and their correlation with photonic applications

    International Nuclear Information System (INIS)

    Pereira, Rafael Ramiro; Aquino, Felipe Thomaz; Ferrier, Alban; Goldner, Philippe; Gonçalves, Rogéria R.

    2016-01-01

    In the present work, we report on a systematic study on structural and spectroscopic properties Eu 3+ and Er 3+ -doped Nb 2 O 5 prepared by sol–gel method. The Eu 3+ ions were used as structural probe to determine the symmetry sites occupied by lanthanide ions. The Eu 3+ -doped Nb 2 O 5 nanocrystalline powders were annealed at different temperatures to verify how the different Nb 2 O 5 crystalline phases affect the structure and the luminescence properties. Er 3+ -doped Nb 2 O 5 was prepared showing an intense NIR luminescence, and, visible luminescence on the green and red, deriving from upconversion process. The synthetized materials can find widespread applicability in photonics as red luminophor for white LED (with tricolor), optical amplifiers and upconverter materials. - Highlights: • Vis and NIR emission from nanostructured lanthanide doped Nb 2 O 5 . • Eu 3+ -doped Nb 2 O 5 as Red luminophor. • Multicolor tunability of intense upconversion emission from lanthanide doped Nb 2 O 5 . • Potential application as biological markers. • Broad band NIR emission.

  12. The creep of UO2 fuel doped with Nb2O5

    International Nuclear Information System (INIS)

    Sawbridge, P.T.; Reynolds, G.L.; Burton, B.

    1981-01-01

    The creep of UO 2 containing small additions of Nb 2 O 5 has been investigated in the stress range 0.5-90 MN/m 2 at temperatures between 1422 and 1573 K. The functional dependence of the creep rate of five dopant concentrations up to 0.8 mol% Nb 2 O 5 has been examined and it was established that in all the materials the secondary creep rate could be represented by the equation epsilonkT = Asigmasup(n) exp(-Q/RT), where epsilon is the steady state creep rate per hour, Q the activation energy and A and n are constants for each material. It was observed that Nb 2 O 5 additions can cause a dramatic increase in the steady state creep rate as long as the niobium ion is maintainde in the Nb 5+ valence state. Material containing 0.4 mol% Nb 2 O 5 creeps three orders of magnitude faster than the pure material. Analysis of the results in terms of grain size compensated viscosity suggest that, like pure UO 2 , the creep rate of Nb 2 O 5 doped fuel is diffusion-controlled and proportional to the reciprocal square of the grain size. A model is developed which suggests that the increase in creep rate results from suppression of the U 5+ ion concentration by the addition of Nb 5+ ions, which modifies the crystal defect structure and hence the uranium ion diffusion coefficient. (orig.)

  13. Ferroelectric properties of bilayer structured Pb(Zr0.52Ti0.48)O3/SrBi2Ta2O9 (PZT/SBT) thin films on Pt/TiO2/SiO2/Si substrates

    International Nuclear Information System (INIS)

    Zhang Wenqi; Li Aidong; Shao Qiyue; Xia Yidong; Wu Di; Liu Zhiguo; Ming Naiben

    2008-01-01

    Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thin films with large remanent polarization and SrBi 2 Ta 2 O 9 (SBT) thin films with excellent fatigue-resisting characteristic have been widely studied for non-volatile random access memories, respectively. To combine these two advantages , bilayered Pb(Zr 0.52 Ti 0.48 )O 3 /SrBi 2 Ta 2 O 9 (PZT/SBT) thin films were fabricated on Pt/TiO 2 /SiO 2 /Si substrates by chemical solution deposition method. X-ray diffraction patterns revealed that the diffraction peaks of PZT/SBT thin films were completely composed of PZT and SBT, and no other secondary phase was observed. The electrical properties of the bilayered structure PZT/SBT films have been investigated in comparison with pure PZT and SBT films. PZT/SBT bilayered thin films showed larger remanent polarization (2P r ) of 18.37 μC/cm 2 than pure SBT and less polarization fatigue up to 1 x 10 9 switching cycles than pure PZT. These results indicated that this bilayered structure of PZT/SBT is a promising material combination for ferroelectric memory applications

  14. Polarization fatigue in ferroelectric Pb(Zr0.52Ti0.48)O3-SrBi2Nb2O9 ceramics

    Science.gov (United States)

    Namsar, Orapim; Pojprapai, Soodkhet; Watcharapasorn, Anucha; Jiansirisomboon, Sukanda

    2015-09-01

    Ferroelectric fatigue induced by cyclic electric loading of the (1- x)PZT- xSBN ceramics (0.1 ≤ x ≤ 0.3) have been investigated in comparison with pure PZT and SBN ceramics. The results showed that pure PZT ceramic possessed severe polarization fatigue after long bipolar switching pulses. This was mainly attributed to the appearance of microstructural damage at the near-electrode regions. Whereas, pure SBN ceramic exhibited no fatigue at least up to 1 × 106 switching cycles. The fatigue-free behavior of SBN ceramics was due primarily to weak domain wall pinning. PZT-SBN ceramics showed less polarization fatigue up to 1 × 106 switching cycles than pure PZT. This could be attributed to their low oxygen vacancy concentration. Therefore, this new ceramic PZT-SBN system seems to be an alternative material for replacing PZT in ferroelectric memory applications. [Figure not available: see fulltext.

  15. Preparation and electrical properties of MoO{sub 3}-modified SrBi{sub 2}Nb{sub 2}O{sub 9}-based lead-free piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Zhongran, E-mail: ruiqingchu@sohu.com [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Chu, Ruiqing, E-mail: rqchu@lcu.edu.cn [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Xu, Zhijun; Hao, Jigong; Wei, Denghu; Cheng, Renfei [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Li, Guorong [The State Key Lab of High Performance Ceramics and Superfinemicrostructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200050 (China)

    2016-05-05

    Lead-free piezoelectric ceramics, SrBi{sub 2}(Nb{sub 1-x}Mo{sub x}){sub 2}O{sub 9} (SBNM-x), were prepared by a conventional solid-state reaction method. The crystal structure, microstructure and electrical properties were systematically investigated. The X-ray diffraction analysis suggested that the substitution formed layered perovskite structure. Plate-like morphology of the grains which is characteristic for layer-structure Aurivillius compounds was clearly observed for all the samples. The excellent electrical properties (e.g., d{sub 33}∼18 pC/N, 2P{sub r}∼20.34 μC/cm{sup 2}) and a high Curie temperature (e.g., T{sub c}∼458 °C) are simultaneously obtained in the ceramics with x = 0.12. Additionally, thermal annealing studies indicated that piezoelectric constant (d{sub 33}) of SBNM-0.12 ceramic remains almost unchanged (16 pC/N, only decrease by 12%) at temperatures below 400 °C, demonstrating that the Mo-modified SBN-based ceramics are the promising candidates for high-temperature applications. - Highlights: • Higher valent cation Mo{sup 6+} substituted for B-site Nb{sup 5+} in the perovskite layers ions. • The piezoelectric constant (d{sub 33}) of SrBi{sub 2}Nb{sub 2}O{sub 9} ceramic is increased to be 18 pC/N. • The remnant polarization (2P{sub r}) of SrBi{sub 2}Nb{sub 2}O{sub 9} ceramic is increased to be 20.34 μC cm{sup −2}. • SBNM-x ceramics show good temperature stability for high temperature applications.

  16. Fabrication and characterization of perovskite-type solar cells with Nb-doped TiO{sub 2} layers

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Jo; Oku, Takeo, E-mail: oku@mat.usp.ac.jp; Suzuki, Atsushi; Akiyama, Tsuyoshi [The University of Shiga Prefecture, Hikone, Shiga 522-8533 (Japan)

    2016-02-01

    Organic-inorganic hybrid heterojunction solar cells containing perovskite CH{sub 3}NH{sub 3}PbI{sub 3} using Nb-doped TiO{sub 2} as an electron-transporting layer were fabricated and characterized. Nb-doped TiO{sub 2} layer showed an improvement of the short-circuit current density and power conversion efficiency using Ti{sub 0.95}Nb{sub 0.05}O{sub 2}.

  17. Nanostructured rare earth doped Nb{sub 2}O{sub 5}: Structural, optical properties and their correlation with photonic applications

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Rafael Ramiro; Aquino, Felipe Thomaz [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP CEP 14040-901 (Brazil); Ferrier, Alban [PSL Research University, Chimie ParisTech-CNRS, Institut de Recherche de Chimie Paris, 75005 Paris (France); Sorbonne Universités, UPMC Univ Paris 06, 75005 Paris (France); Goldner, Philippe [PSL Research University, Chimie ParisTech-CNRS, Institut de Recherche de Chimie Paris, 75005 Paris (France); Gonçalves, Rogéria R., E-mail: rrgoncalves@ffclrp.usp.br [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP CEP 14040-901 (Brazil)

    2016-02-15

    In the present work, we report on a systematic study on structural and spectroscopic properties Eu{sup 3+} and Er{sup 3+}-doped Nb{sub 2}O{sub 5} prepared by sol–gel method. The Eu{sup 3+} ions were used as structural probe to determine the symmetry sites occupied by lanthanide ions. The Eu{sup 3+}-doped Nb{sub 2}O{sub 5} nanocrystalline powders were annealed at different temperatures to verify how the different Nb{sub 2}O{sub 5} crystalline phases affect the structure and the luminescence properties. Er{sup 3+}-doped Nb{sub 2}O{sub 5} was prepared showing an intense NIR luminescence, and, visible luminescence on the green and red, deriving from upconversion process. The synthetized materials can find widespread applicability in photonics as red luminophor for white LED (with tricolor), optical amplifiers and upconverter materials. - Highlights: • Vis and NIR emission from nanostructured lanthanide doped Nb{sub 2}O{sub 5}. • Eu{sup 3+}-doped Nb{sub 2}O{sub 5} as Red luminophor. • Multicolor tunability of intense upconversion emission from lanthanide doped Nb{sub 2}O{sub 5}. • Potential application as biological markers. • Broad band NIR emission.

  18. Spectroscopic and optical properties of the VO2+ ion doped TeO2-TiO2-ZnO-Nb2O5 glass system

    Science.gov (United States)

    Swapna; Upender, G.; Sreenivasulu, V.; Prasad, M.

    2016-04-01

    Studies such as optical absorption, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Electron paramagnetic resonance (EPR) spectroscopy and Differential scanning calorimetry (DSC) were carried out on VO2+ ion doped TeO2-TiO2-ZnO-Nb2O5 glass system. Raman and FTIR spectra of the glasses revealed the presence of [TeO3], [TeO4] and [NbO6] structural units in the glass network. The Urbach energy (Δ E), cut-off wavelength (λ c ), optical band gap ( E opt ), optical basicity (Λ) and electron polarizability ( α) of the glasses were determined from optical absorption studies. The density ( ρ), molar volume ( V m ), oxygen molar volume ( V o ) and refractive index ( n) were also measured. Spin-Hamiltonian parameters were calculated from the EPR studies. When Nb2O5 was increased at the expense of ZnO, the density, optical band gap and Urbach energy of the glasses increased, and the electronic polarizability and optical basicity decreased. The EPR spectra clearly showed that vanadium was in the glass as VO2+ and occupied octahedral sites with tetrahedral compression. Spin-Hamiltonian parameters g‖ and g⊥ decreased as Nb2O5 content increased in the glass. The glass transition temperature ( T g ) also increased with increasing Nb2O5 content in the glass.

  19. Electrical properties of niobium doped Bi4Ti3O12-SrBi4Ti4O15 intergrowth ferroelectrics

    International Nuclear Information System (INIS)

    Parida, Geetanjali; Bera, J.

    2013-01-01

    Bismuth layer structured ferroelectrics (BLSFs) have attracted much attention because of their potential applications in non-volatile ferroelectric random access memories and high temperature piezoelectric. They are very attractive for these applications due to their fatigue free nature and environment friendly lead-free composition. BLSF crystal structure has layers of bismuth oxide and pseudo perovskite block stacked alternately along their c-direction, For commercial application, numerous efforts have been made to improve the electrical properties of BLSFs. Some effective approaches are: (i) doping at A-site, (ii) high valentcation doping at B-site and (iii) formation of intergrowth between different BLSFs. The intergrowth BLSFs are consist of regular stacking of one half the unit cell of m-member structure and one half the unit cell of (m+1) member BLSF structure along their c-axis. In this report, Nb-doped Bi 4 Ti 3 O 12 -SrBi 4 Ti 4 O 15 intergrowth ceramics have been prepared by modified oxalate route. XRD phase analysis confirmed the formation of single phase compound. Nb-doping does not affect the basic crystal structure of the intergrowth. SEM micrographs showed that the grain size of the ceramics decreases with Nb-doping. The temperature dependence of dielectric constant and losses was investigated in the temperature range 30 to 800℃ and frequency range 1 kHz to 1 MHz. With Nb-doping, the T c of the ferroelectrics reduces and peak permittivity increases. Doping also introduces small relaxor behaviour in the ferroelectrics. The dc conductivity of the ceramics decreases with doping. The remnant polarization (Pr) of the intergrowth ferroelectrics is increased with Nb doping. (author)

  20. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    International Nuclear Information System (INIS)

    Sasani, Alireza; Baktash, Ardeshir; Mirabbaszadeh, Kavoos; Khoshnevisan, Bahram

    2016-01-01

    Highlights: • Formation energy of Mg and Mg-Nb co-doped TiO_2 anatase surface (101) is studied. • Effect of Mg defect to the TiO_2 anatase (101) surface and bond length distribution of the surface is studied and it is shown that Mg defects tend to stay far from each other. • Effect of Mg and Nb to the bond length distribution of the surface studied and it is shown that these defects tend to stay close to each other. • Effects of Mg and Mg-Nb defects on DSSCs using TiO_2 anatase hosting these defects are studied. - Abstract: In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO_2 anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO_2 surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase J_S_C of the surface while slightly decreasing V_O_C compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  1. Cr3+ and Nb5+ co-doped Ti2Nb10O29 materials for high-performance lithium-ion storage

    Science.gov (United States)

    Yang, Chao; Yu, Shu; Ma, Yu; Lin, Chunfu; Xu, Zhihao; Zhao, Hua; Wu, Shunqing; Zheng, Peng; Zhu, Zi-Zhong; Li, Jianbao; Wang, Ning

    2017-08-01

    Ti2Nb10O29 is an advanced anode material for lithium-ion batteries due to its large specific capacity and high safety. However, its poor electronic/ionic conductivity significantly limits its rate capability. To tackle this issue, a Cr3+-Nb5+ co-doping is employed, and a series of CrxTi2-2xNb10+xO29 compounds are prepared. The co-doping does not change the Wadsley-Roth shear structure but increases the unit-cell volume and decreases the particle size. Due to the increased unit-cell volumes, the co-doped samples show increased Li+-ion diffusion coefficients. Experimental data and first-principle calculations reveal significantly increased electronic conductivities arising from the formation of impurity bands after the co-doping. The improvements of the electronic/ionic conductivities and the smaller particle sizes in the co-doped samples significantly contribute to improving their electrochemical properties. During the first cycle at 0.1 C, the optimized Cr0.6Ti0.8Nb10.6O29 sample delivers a large reversible capacity of 322 mAh g-1 with a large first-cycle Coulombic efficiency of 94.7%. At 10 C, it retains a large capacity of 206 mAh g-1, while that of Ti2Nb10O29 is only 80 mAh g-1. Furthermore, Cr0.6Ti0.8Nb10.6O29 shows high cyclic stability as demonstrated in over 500 cycles at 10 C with tiny capacity loss of only 0.01% per cycle.

  2. Carrier compensation mechanism in heavily Nb-doped anatase Ti{sub 1-x}Nb{sub x}O{sub 2+{delta}} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Nogawa, H; Chikamatsu, A; Hirose, Y; Hasegawa, T [Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan); Nakao, S [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Kumigashira, H; Oshima, M, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp [Department of Applied Chemistry, University of Tokyo, Tokyo 113-8656 (Japan)

    2011-09-14

    We investigated the electronic structures of anatase Ti{sub 1-x}Nb{sub x}O{sub 2+{delta}} (TNO) thin films as a function of Nb concentration x using photoemission spectroscopy (PES) measurements to elucidate the origin of the abrupt decrease in carrier activation in heavily Nb-doped regime. The existing intensity ratio of Nb{sup 5+} evaluated from Nb 3d core-level PES spectra maintained a constant value of {approx}0.8 at x = 0.06-0.3, implying that electron carriers generated by Nb doping are compensated by p-type defects. Ti 2p-3d and O1s-2p resonant PES measurements of x = 0.06-0.3 films revealed that the in-gap states positioned {approx}1 eV below the Fermi level (E{sub F}) have a mixed character of Ti 3d and O 2p orbitals, whereas the states at E{sub F} mainly have a Ti 3d nature. We proposed a carrier compensation mechanism that interstitial oxygen atoms strongly combined with surrounding Nb atoms kill conduction electrons in heavily Nb-doped anatase TiO{sub 2}.

  3. Electro-optic properties of epitaxial Sr0.6Ba0.4Nb2O6 films grown on MgO substrates using LixNi2-xO buffer layer

    Science.gov (United States)

    Li, X. T.; Du, P. Y.; Ye, H.; Mak, C. L.; Wong, K. H.

    2008-08-01

    Textured LixNi2-xO (LNO) thin films have been fabricated on (001)MgO substrates by pulsed laser deposition technique. The as-deposited LNO films shows a conductivity of 2.5×10-3 Ω m and possess a transmittance of about 35% in the visible region. Subsequent deposition of Sr0.6Ba0.4Nb2O6 (SBN60) thin film on these LNO-coated MgO substrates resulted in a textured SBN layer with a orientation perpendicular to the substrate plane. Phi scans on the (221) plane of the SBN layer indicated that the films have two in-plane orientations with respect to the substrate. The SBN unit cells were rotated in the plane of the film by ± 8.2° as well as ± 45° with respect to the LNO/MgO substrate. Besides the highly (00l)-orientation, the SBN films also exhibited a dense microstructure as shown by scanning electron microscopy. The electro-optic coefficient (r33) of the SBN film was measured to be 186 pm/V. On the basis of our results, we have demonstrated that the LNO film can be used as a buffer layer as well as a transparent bottom electrode for waveguide applications. The SBN/LNO heterostructure is also a suitable candidate for integrated electro-optics devices.

  4. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    Energy Technology Data Exchange (ETDEWEB)

    Sasani, Alireza [Department of Science, Karaj Islamic Azad University, Karaj, Alborz, P.O. Box 31485-313 (Iran, Islamic Republic of); Baktash, Ardeshir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of); Mirabbaszadeh, Kavoos, E-mail: mirabbas@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, P. O. Box 15875-4413 (Iran, Islamic Republic of); Khoshnevisan, Bahram [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of)

    2016-10-30

    Highlights: • Formation energy of Mg and Mg-Nb co-doped TiO{sub 2} anatase surface (101) is studied. • Effect of Mg defect to the TiO{sub 2} anatase (101) surface and bond length distribution of the surface is studied and it is shown that Mg defects tend to stay far from each other. • Effect of Mg and Nb to the bond length distribution of the surface studied and it is shown that these defects tend to stay close to each other. • Effects of Mg and Mg-Nb defects on DSSCs using TiO{sub 2} anatase hosting these defects are studied. - Abstract: In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO{sub 2} anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO{sub 2} surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase J{sub SC} of the surface while slightly decreasing V{sub OC} compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  5. Nb/sub 2/Te/sub 2/O/sub 9/ and Ta/sub 2/Te/sub 2/O/sub 9/: Two new mixed oxides of Te(IV)

    International Nuclear Information System (INIS)

    Gaitan, M.; Jerez, A.; Pico, C.; Veiga, M.L.

    1987-01-01

    Nb/sub 2/Te/sub 2/O/sub 9/ and Ta/sub 2/Te/sub 2/O/sub 9/ were prepared by solid state reactions between amorphous TeO/sub 3/(s) and metallic pentoxides of Nb and Ta. A crystallographic analysis carried out by X-ray diffraction showed that these compounds are isostructural (space group: P2/sub 1//C. a = 6.883 A, b = 7.853 A, c = 14.591 A, β = 103.66 for Nb/sub 2/Te/sub 2/O/sub 9/ and a = 7.10 A, b = 7.48 A, c = 14.62 A, β = 102.9 for Ta/sub 2/Te/sub 2/O/sub 9/). The IR spectra and thermal decomposition processes of both mixed oxides were studied

  6. Colossal Dielectric Behavior of Ga+Nb Co-Doped Rutile TiO2.

    Science.gov (United States)

    Dong, Wen; Hu, Wanbiao; Berlie, Adam; Lau, Kenny; Chen, Hua; Withers, Ray L; Liu, Yun

    2015-11-18

    Stimulated by the excellent colossal permittivity (CP) behavior achieved in In+Nb co-doped rutile TiO2, in this work we investigate the CP behavior of Ga and Nb co-doped rutile TiO2, i.e., (Ga(0.5)Nb(0.5))(x)Ti(1-x)O2, where Ga(3+) is from the same group as In(3+) but with a much smaller ionic radius. Colossal permittivity of up to 10(4)-10(5) with an acceptably low dielectric loss (tan δ = 0.05-0.1) over broad frequency/temperature ranges is obtained at x = 0.5% after systematic synthesis optimizations. Systematic structural, defect, and dielectric characterizations suggest that multiple polarization mechanisms exist in this system: defect dipoles at low temperature (∼10-40 K), polaronlike electron hopping/transport at higher temperatures, and a surface barrier layer capacitor effect. Together these mechanisms contribute to the overall dielectric properties, especially apparent observed CP. We believe that this work provides comprehensive guidance for the design of new CP materials.

  7. Structural study of intermediate phase in layered perovskite SrBi sub 2 Ta sub 2 O sub 9 single crystal

    CERN Document Server

    Onodera, A; Yamashita, H

    2003-01-01

    The crystal structure of an intermediate phase of Bi-layered ferroelectric SrBi sub 2 Ta sub 2 O sub 9 single crystals was studied by means of X-ray diffraction. An analysis of the extinction rules and X-ray intensities demonstrated that the crystal structure is orthorhombic with space group A2 sub 1 am in the ferroelectric phase and Amam in the intermediate phase; this conclusion is in good agreement with the findings of previous powder neutron diffraction studies.

  8. Filmes finos de SrBi2Ta2O9 processados em forno microondas SrBi2Ta2O9 thin films processed in microwave oven

    Directory of Open Access Journals (Sweden)

    J. S. Vasconcelos

    2003-03-01

    Full Text Available Filmes finos de SrBi2Ta2O9 foram depositados em substratos de Pt/Ti/SiO2/Si e, pela primeira vez, sinterizados em forno microondas doméstico. Os padrões de difração de raios X mostraram que os filmes são policristalinos. O processamento por microondas permite utilizar baixa temperatura na síntese e obter filmes com boas propriedades elétricas. Ensaios de microscopia eletrônica de varredura (MEV e de Força Atômica (MFA revelam boa aderência entre filme e substrato, com microestrutura de superfície apresentando grãos finos e esféricos e rugosidade de 4,7 nm. A constante dielétrica e o fator de dissipação, para freqüência de 100 KHz, à temperatura ambiente, foram de 77 e 0,04, respectivamente. A polarização remanescente (2Pr e o campo coercitivo (Ec foram 1,04 miC/cm² e 33 kV/cm. O comportamento da densidade de corrente de fuga revela três mecanismos de condução: linear, ôhmico e outro mecanismo que pode ser atribuído à corrente de Schottky. Dos padrões de DRX, análises das imagens por MEV e topografia de superfície por MFA observa-se que 10 min de tratamento térmico a 550 ºC, em forno microondas, é tempo suficiente para se obter a cristalização do filme.SrBi2Ta2O9 thin films were deposited on Pt/Ti/SiO2/Si substrates and, for the first time, sintered in a domestic microwave oven. The X-ray diffraction patterns showed that the films are polycrystalline. The microwave processing allows to use a low temperature for the synthesis, obtaining films with good electrical properties. Scanning Electron Microscopy (SEM and Atomic Force Microscopy (AFM results reveal good adherence between film and substrate and a surface microstructure presenting thin and spherical grains and roughness of 4.7 nm. The dielectric constant and the dissipation factor, for a frequency of 100 KHz at room temperature, were 77 and 0.04, respectively. The remaining polarization (2Pr and the coercive field (Ec were 1.04 C/cm² and 33 k

  9. Mesostructured niobium-doped titanium oxide-carbon (Nb-TiO2-C) composite as an anode for high-performance lithium-ion batteries

    Science.gov (United States)

    Hwang, Keebum; Sohn, Hiesang; Yoon, Songhun

    2018-02-01

    Mesostructured niobium (Nb)-doped TiO2-carbon (Nb-TiO2-C) composites are synthesized by a hydrothermal process for application as anode materials in Li-ion batteries. The composites have a hierarchical porous structure with the Nb-TiO2 nanoparticles homogenously distributed throughout the porous carbon matrix. The Nb content is controlled (0-10 wt%) to investigate its effect on the physico-chemical properties and electrochemical performance of the composite. While the crystalline/surface structure varied with the addition of Nb (d-spacing of TiO2: 0.34-0.36 nm), the morphology of the composite remained unaffected. The electrochemical performance (cycle stability and rate capability) of the Nb-TiO2-C composite anode with 1 wt% Nb doping improved significantly. First, a full cut-off potential (0-2.5 V vs. Li/Li+) of Nb-doped composite anode (1 wt%) provides a higher energy utilization than that of the un-doped TiO2-C anode. Second, Nb-TiO2-C composite anode (1 wt%) exhibits an excellent long-term cycle stability (100% capacity retention, 297 mAh/g at 0.5 C after 100 cycles and 221 mAh/g at 2 C after 500 cycles) and improved rate-capability (192 mAh/g at 5 C), respectively (1 C: 150 mA/g). The superior electrochemical performance of Nb-TiO2-C (1 wt%) could be attributed to the synergistic effect of improved electronic conductivity induced by optimal Nb doping (1 wt%) and lithium-ion penetration (high diffusion kinetics) through unique pore structures.

  10. Structural study of Sr0.3Ba0.7Nb2O6 and La0.030Sr0.255Ba0.700Nb2O6 ceramic systems

    International Nuclear Information System (INIS)

    Luna-Lopez, J.A.; Portelles, J.; Raymond, O.; Siqueiros, J.M.

    2009-01-01

    Sr 0.3 Ba 0.7 Nb 2 O 6 (SBN) and La 0.030 Sr 0.255 Ba 0.700 Nb 2 O 6 (LSBN) ceramic compounds have been prepared using the traditional ceramic method at two different calcination temperatures (900 and 1000 deg. C) and later sintered both at 1400 deg. C. A study of the effects of the calcination temperatures and La substitution on the morphological, compositional, and structural properties of SBN and LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. From Rietveld refinement processes, the XRD patterns were interpreted to evaluate such effects in the structural parameters and the site occupation factors of the heavy metals and oxygen atoms. The effect of the incorporation of La resulted in a 0.25% cell contraction and turned out to be higher than the 0.08% dilation effect produced by the increase of calcination temperature. The La ion with similar effective ionic radius and higher electronegativity is incorporated into the structure occupying the A 1 site just like the Sr ions in the SBN compound. Differences in the site occupation factors between the SBN and LSBN samples lead to substantial changes in the physical properties such as temperature of relative dielectric constant maximum, relative dielectric constant, and dielectric loss, correlated with the distortion and the relative orientation of the oxygen octahedra.

  11. Optical absorption and spectroscopic properties of thulium doped (TeO{sub 2})(Nb{sub 2}O{sub 5})(TiO{sub 2}) glasses

    Energy Technology Data Exchange (ETDEWEB)

    Kabalci, Idris [Department of Physics Education, Education Faculty, Harran University, Sanliurfa (Turkey); Tay, Turgay [Department of Chemistry, Science Faculty, Anadolu University, Eskisehir (Turkey); Oezen, Goenuel [Department of Physics, Science and Arts Faculty, Istanbul Technical University, Istanbul (Turkey)

    2011-09-15

    A type of thulium doped tellurite based optical glasses was prepared through conventional melt quenching technique. In the experiments, the effect of different Tm{sup 3+} ion concentration and glass composition on optical properties of (TeO{sub 2}){sub (1-x-y)}(Nb{sub 2}O{sub 5}){sub (x)}(TiO{sub 2}){sub (y)} (x=0.05, 0.10, 0.15, and 0.20 mol) glasses have been investigated by using UV-VIS-NIR optical spectrophotometry measurements in a wavelength range 400-2000 nm. Considering absorption measurements for the 1.0mol% Tm{sup 3+} doped of (TeO{sub 2}){sub 0.9}(Nb{sub 2}O{sub 5}){sub 0.05}(TiO{sub 2}){sub 0.05} glass, {sup 1}G{sub 4}, {sup 3}F{sub 2}, {sup 3}F{sub 3}, {sup 3}F{sub 4}, {sup 3}H{sub 5}, and {sup 3}H{sub 4} absorption bands were observed from the {sup 3}H{sub 6} ground level, at 463, 660, 687, 793, 1211 and 1700 nm wavelengths, respectively. Furthermore, spontaneous emission probabilities, and the radiative lifetimes for the 4f-4f transitions of the Tm{sup 3+} ions were calculated. The spectral intensities were determined in terms of Judd-Ofelt parameters ({omega}{sub 2}, {omega}{sub 4}, {omega}{sub 6}). Luminescence analysis was realized for the different Tm{sup 3+} ion concentration (0.002, 0.005 and 0.01mol) at room temperature. The luminescence band intensity of the {sup 3}F{sub 4}{yields}{sup 3}H{sub 4} transition was measured as a function of Tm{sup 3+} ion concentration (0.002, 0.005 and 0.01mol). Furthermore, luminescence data of the thulium doped glass samples were used to determine the compositional dependence of the emission cross sections at 1470 nm (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Nb-doped TiO2 cathode catalysts for oxygen reduction reaction of polymer electrolyte fuel cells

    KAUST Repository

    Arashi, Takuya

    2014-09-01

    Nb-doped TiO2 particles were studied as electrocatalysts for the oxygen reduction reaction (ORR) under acidic conditions. The Nb-doped TiN nanoparticles were first synthesized by meso-porous C3N4 and then fully oxidized to Nb-doped TiO2 by immersing in 0.1 M H 2SO4 at 353 K for 24 h. Although the ORR activity of the as-obtained sample was low, a H2 treatment at relatively high temperature (1173 K) dramatically improved the ORR performance. An onset potential as high as 0.82 VRHE was measured. No degradation of the catalysts was observed during the oxidation-reduction cycles under the ORR condition for over 127 h. H2 treatment at temperatures above 1173 K caused the formation of a Ti4O7 phase, resulting in a decrease in ORR current. Elemental analysis indicated that the Nb-doped TiO 2 contained 25 wt% residual carbon. Calcination in air at 673 or 973 K eliminated the residual carbon in the catalyst, which was accompanied by a dramatic decrease in ORR activity. This post-calcination process may reduce the conductivity of the sample by filling the oxygen vacancies, and the carbon residue in the particle aggregates may enhance the electrocatalytic activity for ORR. The feasibility of using conductive oxide materials as electrocatalysts is discussed. © 2013 Elsevier B.V.

  13. Nb-doped TiO2 cathode catalysts for oxygen reduction reaction of polymer electrolyte fuel cells

    KAUST Repository

    Arashi, Takuya; Seo, Jeongsuk; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2014-01-01

    Nb-doped TiO2 particles were studied as electrocatalysts for the oxygen reduction reaction (ORR) under acidic conditions. The Nb-doped TiN nanoparticles were first synthesized by meso-porous C3N4 and then fully oxidized to Nb-doped TiO2 by immersing in 0.1 M H 2SO4 at 353 K for 24 h. Although the ORR activity of the as-obtained sample was low, a H2 treatment at relatively high temperature (1173 K) dramatically improved the ORR performance. An onset potential as high as 0.82 VRHE was measured. No degradation of the catalysts was observed during the oxidation-reduction cycles under the ORR condition for over 127 h. H2 treatment at temperatures above 1173 K caused the formation of a Ti4O7 phase, resulting in a decrease in ORR current. Elemental analysis indicated that the Nb-doped TiO 2 contained 25 wt% residual carbon. Calcination in air at 673 or 973 K eliminated the residual carbon in the catalyst, which was accompanied by a dramatic decrease in ORR activity. This post-calcination process may reduce the conductivity of the sample by filling the oxygen vacancies, and the carbon residue in the particle aggregates may enhance the electrocatalytic activity for ORR. The feasibility of using conductive oxide materials as electrocatalysts is discussed. © 2013 Elsevier B.V.

  14. Nanostructured TiO2 Doped with Nb as a Novel Support for PEMFC

    Directory of Open Access Journals (Sweden)

    Edgar Valenzuela

    2013-01-01

    Full Text Available Nowadays, one of the major issues of the PEMFC concerns the durability. Historically, carbon has been used as a catalyst support in PEMFC; nevertheless, under the environmental conditions of the cell, the carbon is oxidized, leaving the catalyst unsupported. In order to increase the stability and durability of the catalyst in the PEMFC, a novel nanostructured metallic oxide support is proposed. In this work, TiO2 was doped with Nb to obtain a material that combines chemical stability, high surface area, and an adequate electronic conductivity in order to be a successful catalyst support candidate for long-term PEMFC applications. The TiO2-Nb nanostructured catalyst support was physically and electrochemically characterized. According to the results, the TiO2-Nb offers high surface area and good particle dispersion; also, the electrochemical activity and stability of the support were evaluated under high potential conditions, where the TiO2-Nb proved to be much more stable than carbon.

  15. Study of SrBi4Ti4O15 (SBTi) dielectric properties of doped PbO

    International Nuclear Information System (INIS)

    Rodrigues Junior, C.A.; Silva Filho, J.M.; Freitas, D.B.; Oliveira, R.G.M.; Sombra, B.; Sales, J.C.

    2012-01-01

    The ceramic SrBi 4 Ti 4 O 15 (SBTI), cation-deficient perovskite A 5 B 4 O 15 , was prepared by the method of solid state reaction and then doped with PbO (in the range 2-10% by weight). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy at room temperature. The X-ray analysis was performed by the Rietveld refinement. The micrographs of the samples show globular-shaped grains (doped PbO). The dielectric properties: dielectric constant (Κ' or έ) and dielectric loss tangent (tan δ), were measured at room temperature in the frequency range 100 Hz - 1 MHz dielectric properties of these 1 MHz sample doped with 10 % PbO showed the dielectric constant Κ'= 168.34 and dielectric loss tangent tanδ, = 7,1.10 -2 . These results show a good possibility of miniaturization of electronic devices such as capacitors. (author)

  16. Influencia de parámetros de síntesis sobre las características de los polvos cerámicos nanométricos del compuesto SrxBa1-xNb2O6 (SBN

    Directory of Open Access Journals (Sweden)

    Gaona J, S.

    2013-12-01

    Full Text Available Results on the synthesis process of nanometric ceramic powders of the SrxBa1-xNb2O6 compound (SBN for two values of x (0.33 and 0.50, and two synthesis methods (Pechini and controlled coprecipitation are presented. Parameters such as pH of solution, niobium precursor and heat treatment were varied. The phase purity of obtained powders was analysed by X-ray diffraction and their morphology by scanning electron microscopy. The effect of both synthesis methods and of the above mentioned parameters in obtaining pure phase and particle size were concluded from the characterization analysis. Pechini method (with pH = 9.7 yielded the pure phase SBN for x = 0.33 and particle size of the order of 50 nm, while the controlled co-precipitation method was not possible to obtain pure phase.En este trabajo se exponen los resultados del proceso de obtención de polvos cerámicos nanométricos del sistema SrxBa1-xNb2O6 (SBN, para dos valores de x (0.33 y 0.50 que se encuentran dentro del rango para el cual el sistema tiene estructura tetragonal bronce de tungsteno y propiedad ferroeléctrica. Fueron comparados dos métodos de obtención (Pechini y coprecipitación controlada variando parámetros de síntesis tales como pH de solución, precursor de niobio y tratamiento térmico. Los polvos obtenidos fueron caracterizados estructuralmente por medio de difracción de rayos X y morfológicamente por medio de microscopía electrónica de barrido. A partir del análisis de los resultados se concluyó sobre el efecto de los métodos de síntesis y de los parámetros mencionados, en la obtención de la fase pura y en tamaño de las partículas. El método Pechini (con pH igual a 9.7 permitió obtener la fase pura de SBN para x=0.33 y tamaño de partícula del orden de los 50 nm, mientras que con el método coprecipitación controlada no fue posible obtener fase pura.

  17. Study of fluorine doped (Nb,Ir)O_2 solid solution electro-catalyst powders for proton exchange membrane based oxygen evolution reaction

    International Nuclear Information System (INIS)

    Kadakia, Karan Sandeep; Jampani, Prashanth H.; Velikokhatnyi, Oleg I.; Datta, Moni Kanchan; Patel, Prasad; Chung, Sung Jae; Park, Sung Kyoo; Poston, James A.; Manivannan, Ayyakkannu; Kumta, Prashant N.

    2016-01-01

    Graphical abstract: High surface area (∼300 m"2/g) nanostructured powders of nominal composition (Nb_1_−_xIr_x)O_2 and (Nb_1_−_xIr_x)O_2:10F have been synthesized and tested as oxygen evolution electro-catalysts for PEM based water electrolysis using a simple two-step chemical synthesis procedure. Superior electrochemical activity was demonstrated by fluorine doped compositions of (Nb_1_−_xIr_x)O_2 with an optimal composition (Nb_0_._7_5Ir_0_._2_5)O_2:10F (x = 0.25) demonstrating on-par performance with commercial hydrated IrO_2 and nanostructured in-house chemically synthesized IrO_2. Using first principles calculations, the electronic structure modification resulting in ∼75 at.% reduction (experimentally observed) in noble metal content without loss in catalytic performance and stability has been established. - Highlights: • (Nb_1_−_xIr_x)O_2:10F nanopowder electrocatalysts have been wet chemically synthesized. • (Nb_0_._7_5Ir_0_._2_5)O_2:10F exhibits superior electrochemical activity than pure IrO_2. • Stability of the (Nb,Ir)O_2:10F nanomaterials is comparable to pure (Nb,Ir)O_2. • High surface area F doped (Nb,Ir)O_2 are promising OER anode electro-catalysts. - Abstract: High surface area (∼300 m"2/g) nanostructured powders of (Nb_1_−_xIr_x)O_2 and (Nb_1_−_xIr_x)O_2:10F (∼100 m"2/g) have been examined as promising oxygen evolution reaction (OER) electro-catalysts for proton exchange membrane (PEM) based water electrolysis. Nb_2O_5 and 10 wt.% F doped Nb_2O_5 powders were prepared by a low temperature sol-gel process which were then converted to solid solution (Nb,Ir)O_2 and 10 wt.% F doped (Nb,Ir)O_2 [(NbIr)O_2:10F] electro-catalysts by soaking in IrCl_4 followed by heat treatment in air. Electro-catalyst powders of optimal composition (Nb_0_._7_5Ir_0_._2_5)O_2:10F with ∼75 at.% reduction in noble metal content exhibited comparable OER activity to commercial hydrated IrO_2 and nanostructured in-house chemically synthesized IrO_2

  18. Photoluminescence of rare-earth ion (Eu3+, Tm3+, and Er3+)-doped and co-doped ZnNb2O6 for solar cells

    Science.gov (United States)

    Gao, Sen-Pei; Qian, Yan-Nan; Wang, Biao

    2015-08-01

    Visible converted emissions produced at an excitation of 286 nm in ZnNb2O6 ceramics doped with rare-earth ions (RE = Eu3+, Tm3+, Er3+ or a combination of these ions) were investigated with the aim of increasing the photovoltaic efficiency of solar cells. The structure of RE:ZnNb2O6 ceramics was confirmed by x-ray diffraction patterns. The undoped ZnNb2O6 could emit a blue emission under 286-nm excitation, which is attributed to the self-trapped excitons’ recombination of the efficient luminescence centers of edge-shared NbO6 groups. Upon 286-nm excitation, Eu:ZnNb2O6, Tm:ZnNb2O6, and Er:ZnNb2O6 ceramics showed blue, green, and red emissions, which correspond to the transitions of 5D0 → 7FJ (J = 1-4) (Eu3+), 1G4 → 3H6 (Tm3+), and 2H11/2/4S3/2 → 4I15/2 (Er3+), respectively. The calculated CIE chromaticity coordinates of Eu:ZnNb2O6, Tm:ZnNb2O6, and Er:ZnNb2O6 are (0.50, 0.31), (0.14, 0.19), and (0.29, 0.56), respectively. RE ion-co-doped ZnNb2O6 showed a combination of characteristic emissions. The chromaticity coordinates of Eu/Tm:ZnNb2O6, Eu/Er:ZnNb2O6, and Tm/Er:ZnNb2O6 were calculated to be (0.29, 0.24), (0.45, 0.37), and (0.17, 0.25). Project supported by the National Natural Science Foundation of China (Grant Nos. 10572155 and 10732100) and the Research Fund for the Doctoral Program of Ministry of Education, China (Grant No. 20130171130003).

  19. Effects of Y{sub 2}O{sub 3}/CeO{sub 2} co-doping on microwave dielectric properties of Ba(Co{sub 0.6}Zn{sub 38}){sub 1/3}Nb{sub 2/3}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yuqin; Zhou, Xiaohua, E-mail: 1250590698@qq.com; Yang, Xinshi; Sun, Chengli; Yang, Fan; Chen, Hetuo

    2016-09-15

    The effects of CeO{sub 2}/Y{sub 2}O{sub 3} co-doping on the microstructure and microwave dielectric properties of Ba(Co{sub 0.6}Zn{sub 0.38}){sub 1/3}Nb{sub 2/3}O{sub 3}-xA-xB (x = 0,1,2,3,4,6; A = 0.1204 wt%Y{sub 2}O{sub 3}; B = 0.1 wt%CeO{sub 2}) ceramics prepared by the conventional solid-state route technique were investigated. The X-ray diffraction (XRD) results presented that all the well sintered samples exhibited the main phase BaZn{sub 0.33}Nb{sub 0.67}O{sub 3}−Ba{sub 3}CoNb{sub 2}O{sub 9}. A certain amount of Ba{sub 8}CoNb{sub 6}O{sub 24} surface secondary phase and minority phase of Ba{sub 5}Nb{sub 4}O{sub 15} were also observed in all sintered ceramics. The 1:2 B-site cation ordering degree was found to influenced by the substitution of Y{sup 3+} and Ce{sup 4+} in the crystal lattice, especially for x = 0.02. Then the scanning electron microscopy (SEM) picture of the optimally well-sintered (1350 °C for 20 h) ceramic has shown a dense microstructure. Although the ε{sub r} almost kept unchanged, appropriate doping content would greatly improve the Q × f value. Meanwhile, the τ{sub f} value first declined and then increased with increasing x. At last, the excellent microwave dielectric properties of ε{sub r} = 36.09, Q × f = 72006 GHz, τ{sub f} = 3.35 ppm/ºC were obtained for the ceramic with x = 0.02 sintered in air at 1350 °C for 20 h. - Graphical abstract: Fig. SEM images of as-sintered Ba(Co{sub 0.6}Zn{sub 0.38}){sub 1/3}Nb{sub 2/3}O{sub 3}-xA-Xb (A = 0.1204 wt%Y{sub 2}O{sub 3}; B = 0.1 wt%CeO{sub 2)}ceramics: (a) x = 0,(b) x = 0.01,(c) x = 0.02,(d) x = 0.03, (e) x = 0.04,(f) x = 0.06. The images confirmed the presences of two phases on the surface of the ceramics, plate-shaped grains (Ba{sub 8}(C{sub O},Zn){sub 1}Nb{sub 6}O{sub 24}phase) and needle-shaped grains (Ba{sub 3}(Co{sub 0.6}Zn{sub 0.38}){sub 1}Nb{sub 2}O{sub 9} phase). As a small content of CeO{sub 2}/Y{sub 2}O{sub 3} (x = 0.01–0.04) was codoped into the BCZN ceramics, the

  20. Synthesis, structural characterization and dielectric properties of Nb doped BaTiO3/SiO2 core–shell heterostructure

    International Nuclear Information System (INIS)

    Cernea, M.; Vasile, B.S.; Boni, A.; Iuga, A.

    2014-01-01

    Highlights: • Optimal parameters for preparation by sol–gel of core–shell (BT-Nb 0.005 )/SiO 2 are presented in this paper. • Single crystalline BT-Nb 0.005 /SiO 2 core–shell composite with ∼34 nm shell thick was prepared. • The core–shell ceramic exhibits good dielectric properties and ferroelectric characteristics. -- Abstract: Perovskite complex ceramic oxides, BaTiO 3 doped with 0.5 mol%Nb 2 O 5 and then nanocoated with SiO 2 (abbreviated as BT-Nb 0.005 /SiO 2 ) was successful prepared using conventional sol–gel processing. Phase composition, particle morphology, structure, and electric properties of BT-Nb 0.005 core and BT-Nb 0.005 /SiO 2 core–shell were examined and compared, using X-ray diffraction, transmission electron microscopy and, dielectric and ferroelectric measurements. Core–shell composite with well-defined perovskite tetragonal phase of BaTiO 3 was achieved. Furthermore, single crystalline BT-Nb 0.005 /SiO 2 core–nanoshell heterostructure with ∼34 nm shell thick was prepared, which is a novelty in ferroelectrics field. The ferroelectric quality of BT-Nb 0.005 has suffered an alteration when the (BT-Nb 0.005 )/SiO 2 core–shell heterostructure was realized. One-dimensional BT-Nb 0.005 /SiO 2 core–shell heterostructure exhibits an improvement of dielectric losses and a decrease of dielectric constant, compared to uncoated BT-Nb 0.005 . The (BT-Nb 0.005 )/SiO 2 core–shell material could be interesting for application in the composite capacitors

  1. Enhanced reducibility and electronic conductivity of Nb or W doped Ce0.9Gd0.1O1.95 - δ

    DEFF Research Database (Denmark)

    Chatzichristodoulou, Christodoulos; Ricote, Sandrine; Foghmoes, Søren Preben Vagn

    2015-01-01

    The transport and thermomechanical properties of acceptor (Gd) and donor (Nb or W) co-doped ceria were investigated. The solubility limit of Nb in Ce0.9Gd0.1O2 - δ (CGO10) exceeds 4 at.%, whereas that of W is approximately 2 at.%. Both the thermal and stoichiometric expansion coefficients...... are decreased relative to that of CGO10. Charge compensation of the donor dopants takes place primarily by annihilation of oxide ion vacancies, and a sharp decrease in ionic mobility is observed upon Nb or W doping of CGO10. On the other hand, the n-type electronic conductivity, associated with the reduction...... of Ce4+, increases upon doping with Nb or W, due to enhanced reducibility of cerium. This is beneficial for applications where electronic conductivity is also required, like oxygen permeation membranes. Modeling shows that 4 at.% Nb or W doped CGO10 will deliver higher oxygen fluxes than CGO10, due...

  2. Study of fluorine doped (Nb,Ir)O{sub 2} solid solution electro-catalyst powders for proton exchange membrane based oxygen evolution reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kadakia, Karan Sandeep [Chemical and Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Jampani, Prashanth H., E-mail: pjampani@pitt.edu [Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Velikokhatnyi, Oleg I.; Datta, Moni Kanchan [Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, PA 15261 (United States); Patel, Prasad [Chemical and Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Chung, Sung Jae [Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Park, Sung Kyoo [Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Poston, James A.; Manivannan, Ayyakkannu [US Department of Energy, National Energy Technology Laboratory, Morgantown, WV 26507 (United States); Kumta, Prashant N. [Chemical and Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Bioengineering, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, PA 15261 (United States); Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, PA 15261 (United States); Department of Oral Biology, School of Dental Medicine, University of Pittsburgh, PA 15217 (United States)

    2016-10-15

    Graphical abstract: High surface area (∼300 m{sup 2}/g) nanostructured powders of nominal composition (Nb{sub 1−x}Ir{sub x})O{sub 2} and (Nb{sub 1−x}Ir{sub x})O{sub 2}:10F have been synthesized and tested as oxygen evolution electro-catalysts for PEM based water electrolysis using a simple two-step chemical synthesis procedure. Superior electrochemical activity was demonstrated by fluorine doped compositions of (Nb{sub 1−x}Ir{sub x})O{sub 2} with an optimal composition (Nb{sub 0.75}Ir{sub 0.25})O{sub 2}:10F (x = 0.25) demonstrating on-par performance with commercial hydrated IrO{sub 2} and nanostructured in-house chemically synthesized IrO{sub 2}. Using first principles calculations, the electronic structure modification resulting in ∼75 at.% reduction (experimentally observed) in noble metal content without loss in catalytic performance and stability has been established. - Highlights: • (Nb{sub 1−x}Ir{sub x})O{sub 2}:10F nanopowder electrocatalysts have been wet chemically synthesized. • (Nb{sub 0.75}Ir{sub 0.25})O{sub 2}:10F exhibits superior electrochemical activity than pure IrO{sub 2}. • Stability of the (Nb,Ir)O{sub 2}:10F nanomaterials is comparable to pure (Nb,Ir)O{sub 2}. • High surface area F doped (Nb,Ir)O{sub 2} are promising OER anode electro-catalysts. - Abstract: High surface area (∼300 m{sup 2}/g) nanostructured powders of (Nb{sub 1−x}Ir{sub x})O{sub 2} and (Nb{sub 1−x}Ir{sub x})O{sub 2}:10F (∼100 m{sup 2}/g) have been examined as promising oxygen evolution reaction (OER) electro-catalysts for proton exchange membrane (PEM) based water electrolysis. Nb{sub 2}O{sub 5} and 10 wt.% F doped Nb{sub 2}O{sub 5} powders were prepared by a low temperature sol-gel process which were then converted to solid solution (Nb,Ir)O{sub 2} and 10 wt.% F doped (Nb,Ir)O{sub 2} [(NbIr)O{sub 2}:10F] electro-catalysts by soaking in IrCl{sub 4} followed by heat treatment in air. Electro-catalyst powders of optimal composition (Nb{sub 0.75}Ir

  3. DFT insights into the electronic and optical properties of fluorine-doped monoclinic niobium pentoxide (B-Nb{sub 2}O{sub 5}:F)

    Energy Technology Data Exchange (ETDEWEB)

    El-Shazly, Tamer S.; Rehim, Sayed S.A. [Ain-Shams University, Chemistry Department, Faculty of Science, Cairo (Egypt); Hassan, Walid M.I. [Cairo University, Chemistry Department, Faculty of Science, Giza (Egypt); Allam, Nageh K. [American University in Cairo, Energy Materials Lab (EML), School of Sciences and Engineering, New Cairo (Egypt)

    2016-09-15

    We report on the effect of fluorine doping on the electronic structure and optical properties of monoclinic niobium pentoxide (B-Nb{sub 2}O{sub 5}) as revealed by the first principles calculations. Density functional theory (DFT) along with generalized gradient approximation (GGA) at the revised Perdew-Burke-Ernzerhof (PBEsol) exchange-correlation functional was used in this study. The band calculations revealed that the studied materials are indirect bandgap semiconductors, with bandgap energies of 2.67 and 2.28 eV for the undoped and F-doped B-Nb{sub 2}O{sub 5}, respectively. Upon doping B-Nb{sub 2}O{sub 5}, the Fermi level shifts towards the conduction band, allowing optical absorption in the visible region with enhanced transmittance in the wavelength range 400-1000 nm. The calculated static refractive index of the undoped B-Nb{sub 2}O{sub 5} is in good agreement with the reported experimental value, which is enhanced upon F-incorporation resulting in cladding properties for the F-doped B-Nb{sub 2}O{sub 5}. Also, the effective mass of free charge carriers increased upon F-doping. The enhanced properties were attributed to the effect of the excessive valent electron of the incorporated F atom. (orig.)

  4. Preparation and Characterization of PbO-SrO-Na2O-Nb2O5-SiO2 Glass Ceramics Thin Film for High-Energy Storage Application

    Science.gov (United States)

    Tan, Feihu; Zhang, Qingmeng; Zhao, Hongbin; Wei, Feng; Du, Jun

    2018-03-01

    PbO-SrO-Na2O-Nb2O5-SiO2 (PSNNS) glass ceramic thin films were prepared by pulsed laser deposition technology on heavily doped silicon substrates. The influence of annealing temperatures on microstructures, dielectric properties and energy storage performances of the as-prepared films were investigated in detail. X-ray diffraction studies indicate that Pb2Nb2O7 crystallizes at 800°C and disappears at 900°C, while NaNbO3 and PbNb2O6 are formed at the higher temperature of 900°C. The dielectric properties of the glass ceramics thin films have a strong dependence on the phase assemblages that are developed during heat treatment. The maximum dielectric constant value of 171 was obtained for the film annealed at 800°C, owing to the high electric breakdown field strength, The energy storage densities of the PSNNS films annealed at 800°C were as large as 36.9 J/cm3, These results suggest that PSNNS thin films are promising for energy storage applications.

  5. A Humidity Sensor Based on Nb-doped Nanoporous TiO2 Thin Film

    Directory of Open Access Journals (Sweden)

    Mansoor Anbia

    2011-11-01

    Full Text Available The humidity sensing properties of the sensor fabricated from Nb-doped nanoporous TiO2 by screen-printing on the alumina substrate with Ag-Pd interdigital electrodes have been investigated. The nanoporous thin film has been prepared by sol-gel technique. The product has been characterized by X-ray diffraction and scanning electron microscopy to analyze the structure and its morphology. It is found that the impedance of this sensor changes more than four orders of magnitude in the relative humidity (RH range of 11–95 % at 25 °C. The response and recovery time of the sensor are about 19 and 25 s, respectively, during the RH variation from 11 to 95 %. The sensor shows high humidity sensitivity, rapid response and recovery, prominent stability, good repeatability and narrow hysteresis loop. These results indicate that Nb-doped nanoporous TiO2 thin films have a great potential for humidity sensing applications in room temperature operations.

  6. High-power piezoelectric characteristics of textured bismuth layer structured ferroelectric ceramics.

    Science.gov (United States)

    Ogawa, Hirozumi; Kawada, Shinichiro; Kimura, Masahiko; Shiratsuyu, Kousuke; Sakabe, Yukio

    2007-12-01

    Abstract-The high-power piezoelectric characteristics in h001i oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi(2)Nb(2)O(9) (SBN), (Bi,La)(4)Ti(3)O(12) (BLT), and CaBi(4)Ti(4)O(15) (CBT), were studied by a constant voltage driving method. These textured ceramics were fabricated by a templated grain growth (TGG) method, and their Lotgering factors were 95%, 97%, and 99%, respectively. The vibration velocities of the longitudinal mode (33-mode) increased proportionally to an applied electric field up to 2.5 m/s in these textured BLSF ceramics, although, the vibration velocity of the 33-mode was saturated at more than 1.0 m/s in the Pb(Mn,Nb)O(3)-PZT ceramics. The resonant frequencies were constant up to the vibration velocity of 2.5 m/s in the SBN and CBT textured ceramics; however, the resonant frequency decreased with increasing over the vibration velocity of 1.5 m/s in the BLT textured ceramics. The dissipation power density of the BLT was almost the same as that of the Pb(Mn,Nb)O(3)-PZT ceramics. However, the dissipation power densities of the SBN and CBT were lower than those of the BLT and Pb(Mn,Nb)O(3)-PZT ceramics. The textured SBN and CBT ceramics are good candidates for high-power piezoelectric applications.

  7. An investigation of the Nb doping effect on structural, morphological, electrical and optical properties of spray deposited F doped SnO2 films

    Science.gov (United States)

    Turgut, G.; Keskenler, E. F.; Aydın, S.; Yılmaz, M.; Doǧan, S.; Düzgün, B.

    2013-03-01

    F and Nb + F co-doped SnO2 thin films were deposited on glass substrates by the spray pyrolysis method. The microstructural, morphological, electrical and optical properties of the 10 wt% F doped SnO2 (FTO) thin films were investigated specifically for niobium (Nb) doping in the range of 0-4 at.% with 1 at.% steps. As shown by the x-ray diffraction patterns, the films exhibited a tetragonal cassiterite structure with (200) preferential orientation. It was observed that grain sizes of the films for (200) and (301) peaks depended on the Nb doping concentration and varied in the range of 25.11-32.19 and 100.6-183.7 nm, respectively. The scanning electron microscope (SEM) micrographs showed that the FTO films were made of small pyramidal grains, while doubly doped films were made of small pyramidal grains and big polyhedron grains. From electrical studies, although 1 at.% Nb doped FTO films have the lowest sheet resistance and resistivity values, the highest figure-of-merit and optical band gap values obtained for FTO films were 16.2 × 10-2 Ω-1 and 4.21 eV, respectively. Also, infrared reflectivity values of the films were in the range of 97.39-98.98%. These results strongly suggest that these films are an attractive candidate for various optoelectronic applications and for photothermal conversion of solar energy.

  8. Enhanced photovoltaic performance of a quantum dot-sensitized solar cell using a Nb-doped TiO2 electrode

    International Nuclear Information System (INIS)

    Jiang, Lei; You, Ting; Deng, Wei-Qiao

    2013-01-01

    In this work Nb-doped anatase TiO 2 nanocrystals are used as the photoanode of quantum-dot-sensitized solar cells. A solar cell with CdS/CdSe quantum dots co-sensitized 2.5 mol% Nb-doped anatase TiO 2 nanocrystals can achieve a photovoltaic conversion efficiency of 3.3%, which is almost twice as high as the 1.7% obtained by a cell based on undoped TiO 2 nanocrystals. The incident photon-to-current conversion efficiency can reach as high as 91%, which is a record for all quantum-dot-sensitized solar cells. Detailed analysis shows that such an enhancement is due to improved lifetime and diffusion length of electrons in the solar cell. (paper)

  9. Enhanced photovoltaic performance of a quantum dot-sensitized solar cell using a Nb-doped TiO2 electrode.

    Science.gov (United States)

    Jiang, Lei; You, Ting; Deng, Wei-Qiao

    2013-10-18

    In this work Nb-doped anatase TiO2 nanocrystals are used as the photoanode of quantum-dot-sensitized solar cells. A solar cell with CdS/CdSe quantum dots co-sensitized 2.5 mol% Nb-doped anatase TiO2 nanocrystals can achieve a photovoltaic conversion efficiency of 3.3%, which is almost twice as high as the 1.7% obtained by a cell based on undoped TiO2 nanocrystals. The incident photon-to-current conversion efficiency can reach as high as 91%, which is a record for all quantum-dot-sensitized solar cells. Detailed analysis shows that such an enhancement is due to improved lifetime and diffusion length of electrons in the solar cell.

  10. Heat capacity measurement of Ba3SrNb2O9

    International Nuclear Information System (INIS)

    Singh, B.M.; Samui, Pradeep; Agarwal, Renu; Mukerjee, S.K.

    2016-01-01

    Barium, Strontium and Niobium are important fission products in nuclear reactor with reasonable fission yields. During irradiation of oxide fuels, they can combine to form compounds of Ba-Sr-Nb-O system. Therefore, thermodynamic properties of Ba 3 SrNb 2 O 9 are required for modelling fuel behaviour however thermodynamic data of this compound is not available in literature. Ba 3 SrNb 2 O 9 was prepared by solid state route, by mixing stoichiometric amounts of finely grounded SrCO 3 , BaCO 3 and Nb 2 O 5 . Finally mixed powder was pressed into a pellet at 5 ton pressure for 2 minutes in a hydraulic press and the pellet was heated at 1123 K for 60 h in air. The pellet was cooled, finely grounded, re-pelletised and heated at 1473 K for 120 h. The formation of compound was confirmed by X-ray diffraction pattern, collected at room temperature using Cu-K α radiation (λ = 1.54 nm), scanned over the angular range 20-80° (2θ) with steps of 0.02°. Heat capacity of the compound was measured by the classical three-step method, in continuous mode, using LABSYS EVO, in temperature range of 370 and 950 K. No transition was observed in the investigated temperature range

  11. STRUCTURAL AND DIELECTRIC STUDIES ON Sr0.5-3y/2LayBa0.5Nb2O6 CERAMIC SYSTEMS WITH VARIED SINTERING TIME AND La CONCENTRATION

    Directory of Open Access Journals (Sweden)

    Zahariman S. R.

    2013-12-01

    Full Text Available Sr0.5Ba0.5Nb2O6 (SBN50 ceramic doped with different concentration of Lanthanum, La according to stoichiometric formulation of Sr0.5-3y/2LayBa0.5Nb2O6 (LSBN with y = 0.01, 0.03, 0.05 and 0.07 prepared using traditional ceramic method at the calcination temperature of 1200°C and sintered at 1300°C at varied sintering time. The effects of the sintering time and La3+ substitution on the morphological, compositional, structural and electrical properties of the LSBN is presented using scanning electronic microscopy (SEM, energy dispersive spectroscopy (EDS, X-ray diffraction (XRD and dielectric analysis. The XRD spectra confirm the presence of TTB structure in the ceramics. The Curie temperature (Tc of the ceramic identified from the dielectric studies performed in the temperature range of 28°C to 300°C. The temperature dependent dielectric exhibits broad peaks indicating a diffuse phase transition and relaxor behavior of the ceramic. The measured density of the samples is proportional to the sintering time and inversely proportional to the amount of the La3+ substitution. The solubility limit of La3+ ions in the SBN solid solution is at y ~ 0.05. This observation is also supported by the dielectric results where the dielectric properties of the ceramic deteriorate for y > 0.05 La substitution.

  12. Piezoelectric ceramic material, containing PbNb2O6, K2Nb2O6

    International Nuclear Information System (INIS)

    Fesenko, E.G.; Filip'ev, V.S.; Razumovskaya, O.N.; Cherner, Ya.E.; Rudkovskaya, L.M.; Zav'yalov, V.P.; Molchanova, R.A.; Kryshtop, V.G.; Panich, A.E.; Servuli, V.A.

    1984-01-01

    A new piezoelectric ceramic material including PbNb 2 O 6 , K 2 Nb 2 O 6 is prepared. Above the new material contains Nb 2 O 5 . The invention relates to piezotechnique. The principal advantage of this material for acoustic converters is high anisotropy of piezoelectric properties as well as high Curie temperature (T C =539-553 deg C). The composition containing 93.96 mole% PbNb 2 O 6 ; 2.48 mole% K 2 Nb 2 O 6 and 3.56 mole% Nb 2 O 5 has optimum content of parameters

  13. Crystallization of Sr0.5Ba0.5Nb2O6 Thin Films on LaNiO3 Electrodes by RF Magnetron Reactive Sputtering

    Science.gov (United States)

    Jong, Chao-An; Gan, Jon-Yiew

    2000-02-01

    Strontium barium niobium (Sr0.5Ba0.5Nb2O6) (SBN) thin films are prepared on conductive-oxide LNO (LaNiO3) electrodes by the rf magnetron sputtering system. Instead of conventional furnace annealing, SBN thin films are crystallized by rapid thermal annealing (RTA) above 700°C for 5 min. The textured SBN films are crystallized with two orientations: one is the (001) or (310) direction, and the other is the (002) or (620) direction. Films compositions measured by the electron spectroscopy of chemical analysis (ESCA) quantitative analysis method show nearly the same stoichiometric ratio as the target. The depth profiles of SBN films and the target are examined by secondary ion mass spectrometer (SIMS). The concentrations of the films are quite uniform. After being heat treated at 800°C for 5 min by RTA, La and Ni diffuse into the SBN film. The diffusion coefficient of La in SBN films is also calculated.

  14. Effect of interfacial layers on dielectric properties in very thin SrBi2Ta2O9 capacitors

    International Nuclear Information System (INIS)

    Moon, Bum-Ki; Isobe, Chiharu; Hironaka, Katsuyuki; Hishikawa, Shinichi

    2001-01-01

    The effect of interfacial layers on the dielectric properties in very thin SrBi 2 Ta 2 O 9 (SBT) capacitors has been investigated using static measurements. Total permittivity (ε t ) decreased as the film thickness was reduced in both Pt/SBT/Pt and Ir/SBT/Pt capacitors. The contribution of the interfacial capacitance (C int ) and bulk capacitance to the total capacitance indicates that C int of the Ir/SBT/Pt structure was lower than that of the Pt/SBT/Pt structure, while the bulk permittivity (ε b ) was essentially the same. The dispersion of all capacitors followed the power law, while the Ir/SBT/Pt capacitor showed a larger dispersion of C int . These results suggest that the Pt/SBT/Pt capacitor is preferred for obtaining the high performance with less effect of the interfacial layers on the dielectric properties. [copyright] 2001 American Institute of Physics

  15. Raman and NMR study in MgO-doped LiNbO3 crystal

    International Nuclear Information System (INIS)

    Hu, L.J.; Chang, Y.H.; Chang, C.S.; Yang, S.J.; Hu, M.L.; Tse, W.S.

    1991-01-01

    This paper reports on the MgO-doped LiNbO 3 crystal grown and studied by NMR and Raman techniques. The solubility of MgO in the LiNbO 3 crystal is as much as 30 mole %. It is shown in NMR spectra that the number of Nb 5+ cations at A-site (Li-site) decrease as Mg concentration increased when the Mg content is lower than 5 mole %. The vibration of (NbO 6 ) octahedron and translations involving Li + and Mg 2+ cations motion can be identified by replacing Nb 5+ and Li + cations with Ta 5+ and Mg 2+ cations through Raman spectra. The 115 cm -1 and 151 cm -1 peaks are due to the translational modes of Mg 2+ and Li + cations. The doping mechanisms of MgO are proposed

  16. Defect and electrical transport properties of Nb-doped SrTiO3

    DEFF Research Database (Denmark)

    Blennow Tullmar, Peter; Hagen, Anke; Kammer Hansen, Kent

    2008-01-01

    analyzed with SEM, XRD, TGA, and XANES. The electrical conductivity of Nb-doped strontium titanate (Sr0.94Ti0.9Nb0.1O3 - sintered in 9% H-2/N-2 at 1400 degrees C for 12 h) decreased with increasing temperature and showed a phonon scattering conduction mechanism with (sigma>120 S/cm at 1000 degrees C (in 9...

  17. Preparation and properties of the (Sr,BaNb2O6 thin films by using the sputtering method

    Directory of Open Access Journals (Sweden)

    Diao Chien-Chen

    2017-01-01

    Full Text Available Strontium barium niobate (Sr0.3Ba0.7Nb2O6, SBN thin films were deposited on silicon substrate by using the radio frequency magnetron sputtering and under different deposition power and time at room temperature. Surface morphology and thicknesses of the SBN thin films were characterized by field emission scanning electron microscopy. The crystallization films at different deposition power and time were analyzed by X-ray diffraction (XRD using CuKα radiation from a Rigaku rotating anode with an incident angle of 2°. The remnant polarization (Pr, saturation polarization (Ps, and minimum coercive field (Ec properties of the metal-ferroelectric-metal (MFM structure were measured using ferroelectric material test instrument. The SBN thin films deposited at 90 min and 125 W had the maximum Pr, Ps, and minimum Ec of 1.26 μC/cm2, 2.41 μC/cm2, and 201.6 kV/cm, respectively. From above results, it knows that the SBN thin films suit for application on ferroelectric random access memory (FeRAM.

  18. Role of alkali carbonate and salt in topochemical synthesis of K1/2Na1/2NbO3 and NaNbO3 templates

    Science.gov (United States)

    Lee, Jae-Seok; Jeon, Jae-Ho; Choi, Si-Young

    2013-11-01

    Since the properties of lead-free piezoelectric materials have thus far failed to meet those of lead-based materials, either chemical doping or morphological texturing should be employed to improve the piezoelectric properties of lead-free piezoelectric ceramics. The goal of this study was to synthesize plate-like K1/2Na1/2NbO3 and NaNbO3 particles, which are the most favorable templates for morphological texturing of K1/2Na1/2NbO3 ceramics. To achieve this goal, Bi2.5Na3.5Nb5O18 precursors in a plate-like shape were first synthesized and subsequently converted into K1/2Na1/2NbO3 or NaNbO3 particles that retain the morphology of Bi2.5Na3.5Nb5O18. In this study, we found that sodium or potassium carbonate does not play a major role in converting the Bi2.5Na3.5Nb5O18 precursor to K1/2Na1/2NbO3 or NaNbO3, on the contrary to previous reports; however, the salt contributes to the conversion reaction. All synthesis processes have been performed via a molten salt method, and scanning electron microscopy, scanning probe microscopy, and inductively coupled plasma mass spectroscopy were used to characterize the synthesized K1/2Na1/2NbO3 or NaNbO3 templates.

  19. Electron transport investigation of layered MoO3 oxides doped with different concentrations of Nb2O5 oxide

    International Nuclear Information System (INIS)

    Al-Khawaja, S.; Kasem, M.

    2008-07-01

    The dc and ac electric conductivity has been studied for numerous samples of molybdenum oxide MoO 3 doped with niobium oxide Nb 2 O 5 elaborated via the solid state reactions. By means of the electric resistivity and dielectricity curves obtained as a function of temperature, and according to the dopant concentration, the behaviour of these compounds has been allocated. Most of the investigated samples, which are insulating at room temperature, have been witnessed to exhibit simultaneously two different electric comportments; metallic and semiconducting within the range of low and high temperatures respectively, designated by a critical temperature related to the nature of the material. Both of these behaviours are attributed electronically to ionic conduction mechanism, occurring in the solid material formed upon doping with Nb 2 O 5 , which is utterly diffused into the layered structure of MoO 3 particularly for x≥40% concentrations and accompanied by relaxation in the dielectric function between 5 Hz and 13 M Hz.(Authors)

  20. Piezoelectric and electromechanical properties of ultrahigh temperature CaBi2Nb2O9 ceramics

    International Nuclear Information System (INIS)

    Wang, Jin-Feng; Zhang, Shujun; Shrout, Thomas R.; Wang, Chun-Ming

    2009-01-01

    The piezoelectric, dielectric, and electromechanical properties of the (KCe) co-substituted calcium bismuth niobate (CaBi 2 Nb 2 O 9 , CBN) were investigated. The piezoelectric activities of CBN ceramics were significantly enhanced and the dielectric loss tan δ decreased by (KCe) substitution. The Ca 0.9 (KCe) 0.05 Bi 2 Nb 2 O 9 ceramics possess the optimal piezoelectric properties, and the piezoelectric coefficient (d 33 ), Curie temperature (T C ), and electromechanical coupling factors (k p and k t ) were found to be 16 pC/N, 868 C, 8.6%, and 23.8%, respectively. The excellent dielectric and electromechanical spectra, together with the high piezoelectric activities and ultrahigh Curie temperature, make CBN ceramics promising candidates for high temperature piezoelectric applications. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Phase equilibria and crystal chemistry in the ternary system BaO-TiO 2-Nb 2O 5. II. New barium polytitanates with <5 mole% Nb 2O 5

    Science.gov (United States)

    Roth, R. S.; Ettlinger, L. D.; Parker, H. S.

    1987-06-01

    Four new compounds were found in the BaO-TiO 2-Nb 2O 5 system, each containing orth ≈ 9.9A˚, b mon ≈ a orth ≈ 17A˚). Ba 14Ti 40Nb 2O 99 is a 20-layer orthorhombic phase, Cmc*, withc ≈ 46.86A˚. Ba 10Ti 28Nb 2O 72 is a 7-layer monoclinic phase, C2m, c ≈ 16.72A˚, β ≈ 101.2°. Ba 18Ti 54Nb 2O 132 is a 13-layer monoclinic phase, C2m, c ≈ 30.65A˚, β ≈ 96°. The compositions were derived by analogy to the layers in Ba 4Ti 13 O 30 and Ba 6Ti 17O 40 and are consistent with limited phase equilibria data.

  2. Magnetic structure driven ferroelectricity and large magnetoelectric coupling in antiferromagnet Co4Nb2O9

    Science.gov (United States)

    Srivastava, P.; Chaudhary, S.; Maurya, V.; Saha, J.; Kaushik, S. D.; Siruguri, V.; Patnaik, S.

    2018-05-01

    Synthesis and extensive structural, pyroelectric, magnetic, dielectric and magneto-electric characterizations are reported for polycrystalline Co4Nb2O9 towards unraveling the multiferroic ground state. Magnetic measurements confirm that Co4Nb2O9 becomes an anti-ferromagnet at around 28 K. Associated with the magnetic phase transition, a sharp peak in pyroelectric current indicates the appearance of strong magneto-electric coupling below Neel temperature (TN) along with large coupling constant upto 17.8 μC/m2T. Using temperature oscillation technique, we establish Co4Nb2O9 to be a genuine multiferroic with spontaneous electric polarization in the anti-ferromagnetic state in the absence of magnetic field poling. This is in agreement with our low temperature neutron diffraction studies that show the magnetic structure of Co4Nb2O9 to be that of a non-collinear anti-ferromagnet with ferroelectric ground state.

  3. Studies of metallic species incorporation during growth of SrBi2Ta2O9 films on YBa2Cu3O7-x substrates using mass spectroscopy of recoiled ions

    International Nuclear Information System (INIS)

    Dhote, A. M.

    1999-01-01

    The incorporation of metallic species (Bi, Sr and Ta) during the growth of layered perovskite SrBi 2 Ta 2 O 9 (SBT) on a-axis oriented YBa 2 Cu 3 O 7-x (YBCO) conducting oxide substrates has been investigated using in situ low energy mass spectroscopy of recoiled ions (MSRI). This technique is capable of providing monolayer-specific surface information relevant to the growth of single and multi-component thin films and layered heterostructures. The data show a temperature dependence of metallic species incorporation during co-deposition of Sr, Bi and Ta on YBCO surfaces. At high temperatures (400 400 C. SBT films grown at temperatures ≤ 400 C and annealed in oxygen or air at 800 C exhibit a polycrystalline structure with partial a-axis orientation

  4. Electrochemical characterization and redox behavior of Nb-doped SrTiO3

    DEFF Research Database (Denmark)

    Blennow Tullmar, Peter; Kammer Hansen, Kent; Wallenberg, L. Reine

    2009-01-01

    Sr-vacancy compensated Nb-doped SrTiO3 with the nominal composition Sr0.94Ti0.9Nb0.1O3 has been evaluated as a solid oxide fuel cell (SOFC) anode material in terms of redox stability and electrochemical properties. Sr0.94Ti0.9Nb0.1O3 has been synthesized with a recently developed modified glycine......-nitrate process. The phase purity and redox behavior have been analyzed with XRD and TGA. The electrochemical properties of Sr0.94Ti0.9Nb0.1O3 and a composite electrode of Sr0.94Ti0.9Nb0.1O3/YSZ have been investigated by electrochemical impedance spectroscopy (EIS) on cone shaped electrodes and on electrodes...... in a symmetrical cell configuration. The experiments indicated that the Nb-doped SrTiO3 electrodes were redox stable and showed a potential ability to be used as a part of a SOFC anode. The electrochemical activity appeared to be governed by the concentration of defect species (especially Ti3+ and V-0...

  5. Nonlinear optical properties of TeO2-P2 O5- ZnO-LiNbO3 glass doped with Er3+ ions

    Science.gov (United States)

    Miedzinski, R.; Fuks-Janczarek, I.; El Sayed Said, Y.

    2016-10-01

    A series of lithium niobate LiNbO3 (LN) single crystals doped with Er3+ were grown under the same conditions by melt-quenching method. The distribution coefficients of rare-earth (RE) elements in the "crystal-melt" system of LN were determined at the beginning of the crystal growth. Their dependence on the dopant concentration in melt for 0.4 and 0.8 wt % was investigated. The procedure is applied to RE-doped lithium niobate (LiNbO3), a material of great interest for optoelectronic applications. We have obtained the real χR(3) and imaginary parts χI(3) of the third-order, nonlinear optical susceptibility to the nonlinear refractive index n2 and the nonlinear absorption coefficient β that are valid for absorbing systems. We show that nonlinear refractive or absorptive effects are the consequence of the interplay between the real and imaginary parts of the third-order susceptibilities of the materials. The method for measuring non-linear absorption coefficients and nonlinear refractive index based on well-known Z-scan is presented.

  6. Z-contrast imaging of ordered structures in Pb(Mg1/3Nb2/3)O3 and Ba(Mg1/3Nb2/3)O3

    International Nuclear Information System (INIS)

    Yan, Y.; Pennycook, S.J.; Xu, Z.; Viehland, D.

    1998-02-01

    Lead-based cubic perovskites such as Pb(B 1/3 2+ B 2/3 5+ )O 3 (B 2+ Mg, Co, Ni, Zn; B 5+ = Nb, Ta) are relaxor ferroelectrics. Localized order and disorder often occur in materials of this type. In the Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) family, previous studies have proposed two models, space-charge and charge-balance models. In the first model, the ordered regions carry a net negative charge [Pb(Mg 1/2 Nb 1/2 )O 3 ], while in the second model it does not carry a net charge [Pb((Mg 2/3 Nb 1/3 ) 1/2 Nb 1/2 )O 3 ]. However, no direct evidence for these two models has appeared in the literature yet. In this paper the authors report the first direct observations of local ordering in undoped and La-doped Pb(Mg 1/3 Nb 2/3 )O 3 , using high-resolution Z-contrast imaging. Because the ordered structure in Ba(Mg 1/3 Nb 2/3 )O 3 is well known, the Z-contrast image from an ordered domain is used as a reference for this study

  7. Low-Temperature Sintering Li3Mg1.8Ca0.2NbO6 Microwave Dielectric Ceramics with LMZBS Glass

    Science.gov (United States)

    Wang, Gang; Zhang, Huaiwu; Liu, Cheng; Su, Hua; Jia, Lijun; Li, Jie; Huang, Xin; Gan, Gongwen

    2018-05-01

    Li3Mg1.8Ca0.2NbO6 ceramics doped with Li2O-MgO-ZnO-B2O3-SiO2 glass (LMZBS) were prepared via a solid-state route. The LMZBS glass effectively reduced the sintering temperature of Li3Mg1.8Ca0.2NbO6 ceramics to 950°C. The effects of the LMZBS glass on the sintering behavior, microstructures and microwave dielectric properties of Li3Mg1.8Ca0.2NbO6 ceramics are discussed in detail. Among all the LMZBS doped Li3Mg1.8Ca0.2NbO6 ceramics, the sample with 1 wt.% of LMZBS glass sintered at 950°C for 4 h exhibited good dielectric properties: ɛ r = 16.7, Q × f = 31,000 GHz (9.92 GHz), τ f = - 1.3 ppm/°C. The Li3Mg1.8Ca0.2NbO6 ceramics possessed excellent chemical compatibility with Ag electrodes, and could be applied in low temperature co-fired ceramics (LTCC) applications.

  8. UV Photocatalytic Activity for Water Decomposition of SrxBa1−xNb2O6 Nanocrystals with Different Components and Morphologies

    Directory of Open Access Journals (Sweden)

    Guoqiang Han

    2017-01-01

    Full Text Available Strontium barium niobate SrxBa1-xNb2O6 (SBN nanocrystals with different components (x=0.2, 0.4, 0.6, and 0.8 were synthesized by Molten Salt Synthesis (MSS method at various reaction temperatures (T = 950°C, 1000°C, 1050°C, and 1100°C. The SBN nanocrystals yielded through flux reactions possess different morphologies and sizes with a length of about ~100 nm~7 μm and a diameter of about ~200~500 nm. The Scanning Electron Microscopy (SEM and X-ray Diffraction (XRD techniques were used to study the compositions, structures, and morphologies of the nanocrystals. The absorption edges of the SBN nanocrystals are at a wavelength region of approximate 390 nm, which corresponds to band-gap energy of ~3.18 eV. The SBN nanocrystals with different sizes display different photocatalytic activity under ultraviolet light in decomposition of water. The SBN60 nanocrystals exhibit stable photocatalytic rates (~100~130 μmol of H2·g−1·h−1 for hydrogen production. The SBN nanocrystals can be a potential material in the application of photocatalysis and micro/nanooptical devices.

  9. Room-temperature ferromagnetism in Co and Nb co-doped TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Hachisu, M.; Mori, K.; Hyodo, K.; Morimoto, S.; Yamazaki, T.; Ichiyanagi, Y.

    2015-01-01

    Co- and Nb-doped TiO 2 nanoparticles encapsulated with amorphous SiO 2 were synthesized by our novel preparation method. An anatase TiO 2 single-phase structure was confirmed using X-ray diffraction. The particle size could be controlled to be about 5 nm. The composition of these nanoparticles was investigated by X-ray fluorescence analysis. X-ray absorption near-edge structure spectra showed that the Ti 4+ and Co 2+ states were dominant in our prepared samples. A reduction in the coordination number was also confirmed. The dependence of the electrical conductivity on the frequency was measured by an LCR meter, and the carrier concentration was determined. The magnetization curves for the nanoparticles indicated ferromagnetic behavior at room temperature. We concluded that the ferromagnetism originated in oxygen vacancies around the transition metal ions

  10. Topotactic dehydration of the lamellar oxide HK2Ti5NbO14 x H2O: the oxide K4Ti10Nb2O27

    International Nuclear Information System (INIS)

    Grandin, A.; Borel, M.M.; Hervieu, M.; Raveau, B.

    1987-01-01

    The lamellar oxide HK 2 Ti 5 NbO 14 x H 2 O can be topotactically dehydrated to K 4 Ti 10 Nb 2 O 27 . Electron diffraction and X-ray diffraction studies of this phase lead to a monoclinic cell with the parameters a = 17.005, b = 3.78, c = 9.01 A and β 92.14 0 . Diffusion streaks on the electron diffraction patterns indicate disorder whereas the existence of two sets of lattices on the same crystal give evidence of the topotactic character of the reaction. A structural model is proposed for K 4 Ti 10 Nb 2 O 27 , which corresponds to the intergrowth of K 3 TiNbO 14 layers with the K 2 Ti 6 O 13 tunnel structure. The possibility of formation of various intergrowths such as (KTi 5 NbO 13 )/sub n/ (HK 2 Ti 5 NbO 14 )/sub n/' is suggested

  11. Up-conversion emission of Er{sup 3+}/Yb{sup 3+}co-doped BaBi{sub 2}Nb{sub 2}O{sub 9} (BBN) phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Façanha, M.X., E-mail: marcello.facanha@uece.br [Departamento de Química, Centro de Ciências, Universidade Federal do Ceará (UFC), Fortaleza, Ceará (Brazil); Faculdade de Educação de Crateús (FAEC), Universidade Estadual do Ceará (UECE), Fortaleza, Ceará (Brazil); Laboratório de Telecomunicações e Ciências e Engenharia de Materiais (LOCEM), Universidade Federal do Ceará (UFC), Fortaleza, Ceará (Brazil); Nascimento, J.P.C. do [Departamento de Química, Centro de Ciências, Universidade Federal do Ceará (UFC), Fortaleza, Ceará (Brazil); Laboratório de Telecomunicações e Ciências e Engenharia de Materiais (LOCEM), Universidade Federal do Ceará (UFC), Fortaleza, Ceará (Brazil); Silva, M.A.S., E-mail: marceloassilva@yahoo.com.br [Laboratório de Telecomunicações e Ciências e Engenharia de Materiais (LOCEM), Universidade Federal do Ceará (UFC), Fortaleza, Ceará (Brazil); and others

    2017-03-15

    On this paper, polycrystalline samples of the tetragonal systems BaBi{sub 2}Nb{sub 2}O{sub 9} (BBN) and BBN co-doped with Er{sup 3+}/Yb{sup 3+} (BBN: 0.04Er{sup 3+}yYb{sup 3+}, where y=0.02, 0.04, 0.06 and 0.08 mol%) were synthesized by the solid state method. The crystalline structure and photoluminescent properties of the ceramic phosphors were investigated by powder X-ray diffraction (PXRD), Raman spectroscopy and spectral analysis of up-conversion (UC) emission. The results reveal that all compositions crystallize in the I4/mmm space group at room temperature, and show UC green emissions (centered at 525 nm and 550 nm) and red (around 660 nm) coming from ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2}) and ({sup 4}F{sub 9/2}→{sup 4}I{sub 15/2}) transitions, respectively, under excitation at 980 nm. Increasing variations of the Yb{sup 3+} sensitizer concentration in the host BBN, lead to a significant intensity increase in both UC emissions due to the efficiency of the energy-transfer process. The BBN: 0.04 mol%Er{sup 3+}0.08 mol%Yb{sup 3+} composition showed the higher intensity bands, thus establishing the BBN as an alternative host material for luminescent centers.

  12. Influence of Nb dopant on the structural and optical properties of nanocrystalline TiO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaleji, Behzad Koozegar, E-mail: bkaleji@yahoo.com [Department of Materials Engineering, Faculty of Engineering, Tarbiat Modares University, P.O. Box:14115-143, Tehran (Iran, Islamic Republic of); Sarraf-Mamoory, Rasoul, E-mail: rsarrafm@modares.ac.ir [Department of Materials Engineering, Faculty of Engineering, Tarbiat Modares University, P.O. Box:14115-143, Tehran (Iran, Islamic Republic of); Fujishima, Akira [Photo-catalyst Group, Kanagawa Academy of Science and Technology, KSP East 412, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012 (Japan)

    2012-01-16

    Highlights: Black-Right-Pointing-Pointer We coated Nb-doped TiO{sub 2} films on glazed porcelain via sol-gel dip coating method. Black-Right-Pointing-Pointer We examined coatings by degradation of MB solution and optical light transmittance. Black-Right-Pointing-Pointer Coatings show enhanced photo-catalytic activity in 1 mol% Nb. Black-Right-Pointing-Pointer Nb doping inhibited the grain growth, and which are found to inhibit the anatase to rutile phase transformation. - Abstract: In this study, preparation of Nb-doped (0-20 mol% Nb) TiO{sub 2} dip-coated thin films on glazed porcelain substrates via sol-gel process has been investigated. The effects of Nb on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films was examined by atomic force microscope and X-ray photoelectron spectroscopy. XRD and Raman study showed that the Nb doping inhibited the grain growth. The photo-catalytic activity of the film was tested on degradation of methylene blue. Best photo-catalytic activity of Nb-doped TiO{sub 2} thin films were measured in the TiO{sub 2}-1 mol% Nb sample. The average optical transmittance of about 47% in the visible range and the band gap of films became wider with increasing Nb doping concentration. The Nb{sup 5+} dopant presented substitutional Ti{sup 4+} into TiO{sub 2} lattice.

  13. Effect of Nb2O5 doping on improving the thermo-mechanical stability of sealing interfaces for solid oxide fuel cells.

    Science.gov (United States)

    Zhang, Qi; Du, Xinhang; Tan, Shengwei; Tang, Dian; Chen, Kongfa; Zhang, Teng

    2017-07-13

    Nb 2 O 5 is added to a borosilicate sealing system to improve the thermo-mechanical stability of the sealing interface between the glass and Fe-Cr metallic interconnect (Crofer 22APU) in solid oxide fuel cells (SOFCs). The thermo-mechanical stability of the glass/metal interface is evaluated experimentally as well as by using a finite element analysis (FEA) method. The sealing glass doped with 4 mol.% Nb 2 O 5 shows the best thermo-mechanical stability, and the sealing couple of Crofer 22APU/glass/GDC (Gd 0.2 Ce 0.8 O 1.9 ) remains intact after 50 thermal cycles. In addition, all sealing couples show good joining after being held at 750 °C for 1000 h. Moreover, the possible mechanism on the thermo-mechanical stability of sealing interface is investigated in terms of stress-based and energy-based perspectives.

  14. Microwave-Hydrothermal Synthesis and Characterization of High-Purity Nb Doped BaTiO3 Nanocrystals

    Directory of Open Access Journals (Sweden)

    A. Khanfekr

    2014-01-01

    Full Text Available The synthesis of Nb doped BaTiO3 has been investigated under Microwave-Hydrothermal (MH conditions in the temperature of 150°C for only 2 h using C16H36O4Ti, BaH2O2.8H2O and NbCl5 as Ba, Ti and  Nb sources, respectively.  Typical experiments performed on MH processing have not yet reported for Nb doped BaTiO3.  In the MH process, the formation of high purity nano tetragonal Nb-BaTiO3 was strongly enhanced. New hydrothermal method was used instead of the previous solid state reaction for the BaTiONb2O3 system. The new method uses high pressure to create nano dimension particles in a lower time and temperature. In case of the phase evolution studies, the XRD pattern measurements and Raman spectroscopy were performed. TEM and FE-SEM images were taken for the detailed analysis of the particle size, surface and morphology.  Synthesis of Nb doped BaTiO3 with the Microwave-hydrothermal provides an advantage of fast crystallization and reduced crystal size when compared to existing methods.

  15. Photocatalytic activity of TiO2/Nb2O5/PANI and TiO2/Nb2O5/RGO as new nanocomposites for degradation of organic pollutants.

    Science.gov (United States)

    Zarrin, Saviz; Heshmatpour, Felora

    2018-06-05

    In this study, highly active titanium dioxide modified by niobium oxide (Nb 2 O 5 ), polymer (PANI) and reduced graphene oxide (RGO) were successfully prepared. The morphology, structure, surface area and light absorption properties of the present nanocomposites for removal of methylene blue (MB) and methyl orange (MO) were investigated and compared with those of TiO 2 /Nb 2 O 5 and TiO 2 nanoparticles. The characterization techniques such as XRD, FT-IR, UV-vis, SEM, EDX, BET and TEM were employed in order to identify the nanocomposites. Also, photocatalytic properties of TiO 2 /Nb 2 O 5 /PANI and TiO 2 /Nb 2 O 5 /RGO nanocomposites under visible light irradiation were studied. In this way, the obtained results were compared to each other and also compared to TiO 2 /Nb 2 O 5 and TiO 2 nanoparticles. In this context, the chemical oxygen demand (COD) removal follows the photodegradation in observed performance. The results indicate that reduced TiO 2 /Nb 2 O 5 nanocomposite is effectively modified by graphene oxide to give TiO 2 /Nb 2 O 5 /RGO composite. The TiO 2 /Nb 2 O 5 /RGO exhibits significantly higher photocatalytic activity in degradation of organic dyes under visible light rather than that of TiO 2 /Nb 2 O 5 /PANI, TiO 2 /Nb 2 O 5 and pure TiO 2 . Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Dielectric, piezoelectric properties of MnO2-doped (K0.5Na0.5)NbO3–0.05LiNbO3 crystal grown by flux-Bridgman method

    International Nuclear Information System (INIS)

    Liu, Ying; Xu, Guisheng; Liu, Jinfeng; Yang, Danfeng; Chen, Xiaxia

    2014-01-01

    Highlights: • KNN–0.05LN based single crystals were grown by flux-Bridgman method. • Dielectric, piezoelecrc and ferroelectric properties were studied. • The effect of MnO 2 doping on the crystals' properties. • Dielectric and other properties were improved due to MnO 2 doping. - Abstract: Lead-free potassium sodium niobate piezoelectric single crystals substituted with lithium and then doped with MnO 2 (K 0.5 Na 0.5 )NbO 3 –0.05LiNbO 3 –yMnO 2 (y = 0%, 1.0% and 1.5%) (abbreviated as KNN–0.05LN–yMnO 2 ) have been grown by flux-Bridgman method using KCl–K 2 CO 3 eutectic composition as the flux. Their actual composition as well as the dielectric and piezoelectric properties were studied. Their actual composition deviated from the ratio of the raw materials due to different segregation coefficients of K and Na. The orthorhombic–tetragonal (T o–t ) and tetragonal–cubic phase transition temperature (the Curie temperature T c ) of the single crystal appears at 186 °C and 441 °C, respectively, for KNN–0.05LN–1.0%MnO 2 , shift to higher temperatures compared with that of pure KNN–0.05LN crystals, according to the dielectric permittivity versus temperature loops. The KNN–0.05LN–1.0%MnO 2 (001) plate shows higher piezoelectric coefficient d 33 and dielectric permittivity ε r when compared with pure KNN–0.05LN crystal, being on the order of 226 pC/N and 799 (161 pC/N and 530 for KNN–0.05LN), respectively. These excellent properties show that MnO 2 dopant is effective in improving KNN–0.05LN based piezoelectric crystals

  17. Nb-TiO{sub 2}/polymer hybrid solar cells with photovoltaic response under inert atmosphere conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lira-Cantu, Monica; Khoda Siddiki, Mahbube; Munoz-Rojas, David; Amade, Roger [Centre d' Investigacio en Nanociencia i Nanotecnologia (CIN2, CSIC), Laboratory of Nanostructured Materials for Photovoltaic Energy, Campus UAB, Barcelona (Spain); Gonzalez-Pech, Natalia I. [Centre d' Investigacio en Nanociencia i Nanotecnologia (CIN2, CSIC), Laboratory of Nanostructured Materials for Photovoltaic Energy, Campus UAB, Barcelona (Spain); Instituto Tecnologico y de Estudios Superiores de Monterrey (ITESM), Ave. Eugenio Garza Sada, 64640 Monterrey, N.L. (Mexico)

    2010-07-15

    Hybrid Solar Cells (HSC) applying Nb-TiO{sub 2} in direct contact with a conducting organic polymer, MEH-PPV, show higher stability than the bare TiO{sub 2}-based HSC when analyzed under inert atmosphere conditions. IPCE analyses revealed that inert atmospheres affect directly the semiconductor oxide in the first stages of the analyses but photovoltaic performance stabilizes after several hours. A 20 wt% Nb-doped TiO{sub 2} presented the highest stability and photovoltaic properties. The behavior has been attributed to the solubility limit of Nb within the TiO{sub 2} beyond 20 wt% doping level where the co-existence of NbO{sub 2} is observed. The HSCs were analyzed under controlled N{sub 2} atmosphere and 1000 W/m{sup 2} (AM 1.5) irradiation. (author)

  18. Photoinduced changes in the fatigue behavior of SrBi2Ta2O9 and Pb(Zr,Ti)O3 thin films

    International Nuclear Information System (INIS)

    Dimos, D.; Al-Shareef, H.N.; Warren, W.L.; Tuttle, B.A.

    1996-01-01

    It is shown that SrBi 2 Ta 2 O 9 (SBT) thin films can be made to exhibit significant polarization fatigue by electric-field cycling under broad-band, optical illumination. Photoinduced fatigue is also observed for Pb(Zr,Ti)O 3 (PZT) thin-film capacitors with (La,Sr)CoO 3 (LSCO) electrodes. These results demonstrate that both the Pt/SBT/Pt and the LSCO/PZT/LSCO systems are susceptible to fatigue effects, which are attributed primarily to pinning of domain walls due to charge trapping. Capacitors that have been fatigued under illumination can be fully rejuvinated by applying a dc saturating bias with light or by electric-field cycling without light, which indicates an intrinsic, field-assisted recovery mechanism. We suggest that fatigue is essentially a competition between domain wall pinning and unpinning and that domain pinning is not necessarily absent in these nominally fatigue-free systems, but rather these systems are ones in which unpinning occurs at least as rapidly as any pinning. In both cases, the extent of photoinduced fatigue decreases with increased cycling voltage, indicating the relative importance of field-assisted unpinning. Finally, the observation of photoinduced fatigue implies that increased injection rates, potentially due to oxygen vacancy accumulation, may account for the electrode dependence on fatigue in PZT thin films

  19. Raman spectroscopy, thermal and optical properties of TeO2-ZnO-Nb2O5-Nd2O3 glasses.

    Science.gov (United States)

    Kamalaker, V; Upender, G; Ramesh, Ch; Mouli, V Chandra

    2012-04-01

    The glasses with composition 75TeO2-10ZnO-(15-x)Nb2O5-xNd2O3 (0≤x≤9 mol%) were prepared using melt quenching method and their physical properties such as density (ρ), molar volume (VM), average crosslink density (nc¯), oxygen packing density (OPD) and number of bonds per unit volume (nb) were determined. Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1, TeO3 and NbO6 units as basic structural units. The glass transition temperature (Tg), crystallization onset (To) and thermal stability (ΔT) were determined from DSC thermograms. The Raman and DSC results were found to be correlated with the physical properties. In the optical absorption spectra six absorption bands were observed with different relative intensities at around 464, 522, 576, 742, 801 and 871 nm which are assigned to the transition of electrons from (ground state) 4I9/2→G11/2; 4I9/22K3/2, 2G7/2; 4I9/2→4G5/2, 4G7/2; 4I9/2→4S3/2; 4F7/22H9/2, 4F5/2 and 4I9/22F3/2 respectively. From optical absorption data the energy band gap (Eopt) and Urbach energy (ΔE) were calculated. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Enhanced multiferroic properties in scandium doped Bi2Fe4O9

    International Nuclear Information System (INIS)

    Dutta, Dimple P.; Tyagi, A. K.

    2013-01-01

    Undoped and Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles have been synthesized using sonochemical method. The phase purity of the samples was checked using powder X-rau diffraction technique. EDS analysis was done to confirm the extent of Sc 3+ doping in the samples. The size and morphology of the nanoparticles have been analyzed using transmission electron microscopy (TEM). The Bi 2 Fe 4 O 9 nanoparticles show a weak ferromagnetic behavior at room temperature, which is quite different from the linear M–H relationship reported for bulk Bi 2 Fe 4 O 9 . This is mainly attributed to the uncompensated moments at the disordered particle surface resulting from the reduced coordination of the surface spins, arising due to lattice strain or oxygen deficiency. Addition of Sc 3+ dopant in varying concentrations in these Bi 2 Fe 4 O 9 nanoparticles, improves their magnetic as well as ferroelectric properties. The leakage current is considerably reduced and electric polarization increases significantly in case of Bi 2 Fe 4(1-x) Sc x O 9 (x = 0.1) nanoparticles. Hence it can be inferred that Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles shows promise as good multiferroic materials.

  1. Optical properties of Mg2+, Yb3+, and Ho3+ tri-doped LiNbO3 crystals

    Science.gov (United States)

    Dai, Li; Liu, Chun-Rui; Tan, Chao; Yan, Zhe-Hua; Xu, Yu-Heng

    2017-04-01

    A series of LiNbO3 crystals tri-doped with Mg{}2+, Yb{}3+, and Ho{}3+ are grown by the conventional Czochraski technique. The concentrations of Mg{}2+, Yb{}3+, and Ho{}3+ ions in Mg:Yb:Ho:LiNbO3 crystals are measured by using an inductively coupled plasma atomic emission spectrometry. The x-ray diffraction is proposed to determine the lattice constant and analyze the internal structure of the crystal. The light-induced scattering of Mg:Yb:Ho:LiNbO3 crystal is quantitatively described via the threshold effect of incident exposure energy flux. The exposure energy ({E}{{r}}) is calculated to discuss the optical damage resistance ability. The exposure energy of Mg(7 mol):Yb:Ho:LiNbO3 crystal is 709.17 J/cm2, approximately 425 times higher than that of the Mg(1 mol):Yb:Ho:LiNbO3 crystal in magnitude. The blue, red, and very intense green bands of Mg:Yb:Ho:LiNbO3 crystal are observed under the 980-nm laser excitation to evaluate the up-conversion emission properties. The dependence of the emission intensity on pumping power indicates that the up-conversion emission is a two-photon process. The up-conversion emission mechanism is discussed in detail. This study indicates that Mg:Yb:Ho:LiNbO3 crystal can be applied to the fabrication of new multifunctional photoluminescence devices. Project supported by the National Natural Science Foundation of China (Grant No. 51301055), the Youth Science Fund of Heilongjiang Province, China (Grant No. QC2015061), the Special Funds of Harbin Innovation Talents in Science and Technology Research, China (Grant No. 2015RQQXJ045 ), and the Science Funds for the Young Innovative Talents of Harbin University of Science and Technology, China (Grant No. 201501).

  2. Mechanism of luminescent enhancement in Ba{sub 2}GdNbO{sub 6}:Eu{sup 3+} perovskite by Li{sup +} co-doping

    Energy Technology Data Exchange (ETDEWEB)

    Rezende, Marcos Vinicius dos Santos [Departamento de Física, Universidade Federal de Sergipe, 49500-000, Itabaiana, SE (Brazil); Valério, Mario Ernesto Giroldo [Departamento de Física, Universidade Federal de Sergipe, 49100-000 São Cristóvão, SE (Brazil); Mouta, Rodolpho; Diniz, Eduardo Moraes [Departamento de Física, CCET, Universidade Federal do Maranhão, 65085-580 São Luís, MA (Brazil); Paschoal, Carlos William de Araujo, E-mail: paschoal@ufma.br [Departamento de Física, CCET, Universidade Federal do Maranhão, 65085-580 São Luís, MA (Brazil); Department of Materials Science and Engineering, University of California Berkeley, 94720-1760 Berkeley, CA (United States); Department of Physics, University of California Berkeley, 94720-7300 Berkeley, CA (United States)

    2015-02-15

    We investigated the Li{sup +} ion incorporation in Ba{sub 2}GdNbO{sub 6}:Eu{sup 3+} perovskite by atomistic simulations based on energy minimization. We predicted the most probable sites occupied by Eu{sup 3+} and Li{sup +} ions and the related charge-compensation mechanisms involved into these substitutions. The results show that the Eu{sup 3+} and Li{sup +} ions are incorporated mainly at the Gd{sup 3+} site. In the Li{sup +} ion case, there is a charge compensation by Nb{sub Gd}{sup •} {sup •} antisite. The crystal field parameters and the transition levels for the Eu{sup 3+} ion in the BGN:Eu{sup 3+} were calculated with basis on the simulated local symmetry of the Eu{sup 3+} site. The results show that the mechanism of luminescent properties enhancement is the symmetry distortion induced by the Li{sup +} co-doping. - Highlights: • We performed a full defect calculations in Ba{sub 2}GdNbO{sub 6} double perovskite. • We modeled with excellent agreement the optical transition of Ba{sub 2}GdNbO{sub 6}:Eu{sup 3+} crystal. • We explained the mechanism of luminescent enhancement in Ba{sub 2}GdNbO{sub 6}:Eu{sup 3+} perovskite by Li{sup +} co-doping.

  3. Effects of donor doping and acceptor doping on rutile TiO2 particles for photocatalytic O2 evolution by water oxidation

    Science.gov (United States)

    Amano, Fumiaki; Tosaki, Ryosuke; Sato, Kyosuke; Higuchi, Yamato

    2018-02-01

    Crystalline defects of photocatalyst particles may be considered to be the recombination center of photoexcited electrons and holes. In this study, we investigated the photocatalytic activity of cation-doped rutile TiO2 photocatalysts for O2 evolution from an aqueous silver nitrate solution under ultraviolet light irradiation. The photocatalytic activity of rutile TiO2 was enhanced by donor doping of Ta5+ and Nb5+ with a valence higher than that of Ti4+, regardless of increased density of electrons and Ti3+ species (an electron trapped in Ti4+ sites). Conversely, acceptor doping of lower valence cations such as In3+ and Ga3+ decreased photocatalytic activity for O2 evolution by water oxidation. The doping of equal valence cations such as Sn4+ and Ge4+ hardly changed the activity of non-doped TiO2. This study demonstrates that Ti3+ species, which is a crystalline defect, enhanced the photocatalytic activity of semiconductor oxides, for example rutile TiO2 with large crystalline size.

  4. Effect of Nb and F Co-doping on Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material for High-Performance Lithium-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Lei Ming

    2018-04-01

    Full Text Available The Li1.2Mn0.54−xNbxCo0.13Ni0.13O2−6xF6x (x = 0, 0.01, 0.03, 0.05 is prepared by traditional solid-phase method, and the Nb and F ions are successfully doped into Mn and O sites of layered materials Li1.2Mn0.54Co0.13Ni0.13O2, respectively. The incorporating Nb ion in Mn site can effectively restrain the migration of transition metal ions during long-term cycling, and keep the stability of the crystal structure. The Li1.2Mn0.54−xNbxCo0.13Ni0.13O2−6xF6x shows suppressed voltage fade and higher capacity retention of 98.1% after 200 cycles at rate of 1 C. The replacement of O2− by the strongly electronegative F− is beneficial for suppressed the structure change of Li2MnO3 from the eliminating of oxygen in initial charge process. Therefore, the initial coulombic efficiency of doped Li1.2Mn0.54−xNbxCo0.13Ni0.13O2−6xF6x gets improved, which is higher than that of pure Li1.2Mn0.54Co0.13Ni0.13O2. In addition, the Nb and F co-doping can effectively enhance the transfer of lithium-ion and electrons, and thus improving rate performance.

  5. Understanding cation ordering and oxygen vacancy site preference in Ba3CaNb2O9 from first-principles

    Science.gov (United States)

    Ding, Hepeng; Virkar, Anil; Liu, Feng

    2014-03-01

    We investigate the physical mechanism underlying the formation of the B-site cation ordering and the oxygen vacancy site selection in Ba3CaNb2O9 using density functional theory calculations. We found that either cation site exchange or oxygen vacancy formation induces negligible lattice strain. This implies that the ionic radius plays an insignificant role in governing these two processes. Furthermore, the electrostatic interactions are found dominant in the ordering of mixed valence species on one or more sites, the ionic bond strength is identified as the dominant force in governing both the 1:2 B-site cation ordering along the direction and the oxygen vacancy site preference in Ba3CaNb2O9. Specifically, the cation ordering can be rationalized by the increased mixing bonding energy of the Ca-O-Nb bonds over the Ca-O-Ca and Nb-O-Nb bonds, i.e., 1/2(Ca-O-Ca + Nb-O-Nb) Grant Number DE-SC0001061 as a flow through from the University of South Carolina.

  6. Effects of milling method and calcination condition on phase and morphology characteristics of Mg4Nb2O9 powders

    International Nuclear Information System (INIS)

    Wongmaneerung, R.; Sarakonsri, T.; Yimnirun, R.; Ananta, S.

    2006-01-01

    Magnesium niobate, Mg 4 Nb 2 O 9 , powders has been synthesized by a solid-state reaction. Both conventional ball- and rapid vibro-milling have been investigated as milling methods, with the formation of the Mg 4 Nb 2 O 9 phase investigated as a function of calcination conditions by DTA and XRD. The particle size distribution of the calcined powders was determined by laser diffraction technique, while morphology, crystal structure and phase composition were determined via a combination of SEM, TEM and EDX techniques. The type of milling method together with the designed calcination condition was found to show a considerable effect on the phase and morphology evolution of the calcined Mg 4 Nb 2 O 9 powders. It is seen that optimization of calcination conditions can lead to a single-phase Mg 4 Nb 2 O 9 in both milling methods. However, the formation temperature and dwell time for single-phase Mg 4 Nb 2 O 9 powders were lower with the rapid vibro-milling technique

  7. Improved ferroelectric and pyroelectric properties of Pb-doped SrBi4Ti4O15 ceramics for high temperature applications

    International Nuclear Information System (INIS)

    Venkata Ramana, E.; Graça, M.P.F.; Valente, M.A.; Bhima Sankaram, T.

    2014-01-01

    Highlights: • Sr 1−x Pb x Bi 4 Ti 4 O 15 (SPBT, x = 0 − 0.4) ceramics were synthesized by soft chemical method. • X-ray diffraction analysis confirmed the formation of bismuth layered structure. • SEM images showed plate like grain morphology with random orientation of plate faces. • Pb-doping resulted in improved ferroelectricity of SrBi 4 Ti 4 O 15 ceramics. • Pb-doped SrBi 4 Ti 4 O 15 exhibited improved pyroelectric properties with high T C . -- Abstract: Ferroelectric properties of Pb-modified strontium bismuth titanate ceramics with chemical formula Sr 1−x Pb x Bi 4 Ti 4 O 15 (x = 0–0.4) were investigated. Polycrystalline ceramics were synthesized by soft chemical method to study the effect of Pb-doping on its physical properties. X-ray diffraction analysis revealed a bismuth layered structure for all the compounds. The doping resulted in an increased tetragonal strain and improved ferroelectric properties. Scanning electron microscope images showed plate like grain morphology with random orientation of platelets. The ferroelectric transition temperature of the ceramics increased systematically from 525 °C to 560 °C with the increase of doping concentration. The piezoelectric coefficient (d 33 ) of the ceramics was enhanced significantly with Pb doping, exhibiting a maximum value of 21.8 pC/N for 40 mol.% Pb-doped SBT. Pyroelectric studies carried out using the Byer–Roundy method indicated that the modified SBT ceramics are promising candidates for high temperature pyroelectric applications

  8. Evolution of electrical properties and domain configuration of Mn modified Pb(In1/2Nb1/2)O3-PbTiO3 single crystals

    Science.gov (United States)

    Qiao, Huimin; He, Chao; Yuan, Feifei; Wang, Zujian; Li, Xiuzhi; Liu, Ying; Guo, Haiyan; Long, Xifa

    2018-04-01

    The acceptor doped relaxor-based ferroelectric materials are useful for high power applications such as probes in ultrasound-guided high intensity focused ultrasound therapy. In addition, a high Curie temperature is desired because of wider temperature usage and improved temperature stability. Previous investigations have focused on Pb(Mg1/3Nb2/3)O3-PbTiO3 and Pb(Zn1/3Nb2/3)O3-PbTiO3 systems, which have a ultrahigh piezoelectric coefficient and dielectric constant, but a relatively low Curie temperature. It is desirable to study the binary relaxor-based system with a high Curie temperature. Therefore, Pb(In1/2Nb1/2)O3-PbTiO3 (PINT) single crystals were chosen to study the Mn-doped influence on their electrical properties and domain configuration. The evolution of ferroelectric hysteresis loops for doped and virgin samples exhibit the pinning effect in Mn-doped PINT crystals. The relaxation behaviors of doped and virgin samples are studied by fit of the modified Curie-Weiss law and Volgel-Fucher relation. In addition, a short-range correlation length was fitted to study the behavior of polar nanoregions based on the domain configuration obtained by piezoresponse force microscopy. Complex domain structures and smaller short-range correlation lengths (100-150 nm for Mn-doped PINT and >400 nm for pure PINT) were obtained in the Mn-doped PINT single crystals.

  9. Effect of Nb doping on the structural, morphological, optical and electrical properties of RF magnetron sputtered In{sub 2}O{sub 3} nanostructured films

    Energy Technology Data Exchange (ETDEWEB)

    Reshmi Krishnan, R.; Chalana, S.R.; Suresh, S.; Sudheer, S.K.; Mahadevan Pillai, V.P. [Department of Optoelectronics, University of Kerala (India); Sudarsanakumar, C. [School of Pure and Applied Physics, Mahatma Gandhi University, Kerala (India); Santhosh Kumar, M.C. [Optoelectronic Materials and Devices Lab, Department of Physics, National Institute of Technology, Tiruchirappalli (India)

    2017-01-15

    Undoped and niobium (Nb) doped indium oxide (In{sub 2}O{sub 3}) thin films are prepared by radio frequency magnetron sputtering technique. The effect of Nb on the structural, morphological, optical and electrical properties of In{sub 2}O{sub 3}films are analyzed using techniques such as X-ray diffraction (XRD), micro-Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy, UV-visible spectroscopy, spectroscopic ellipsometry, photoluminescence spectroscopy and Hall effect measurements. XRD analysis reveals that the as-deposited undoped and Nb doped films are polycrystalline in nature with cubic bixbyite structure. Raman analysis supports the presence of cubic bixbyite structure of In{sub 2}O{sub 3}in the films. XPS analysis shows a decrease of oxygen deficiency due to Nb and the existence of Nb as Nb{sup 4+} in the In{sub 2}O{sub 3}lattice. The band gap energy of the films increases with increase in Nb concentration. PL spectra reveal intense UV and visible emissions in all the films. Optical constants of the films are determined using spectroscopic ellipsometry. The thickness of films estimated using FESEM and ellipsometry are in good agreement. The carrier concentration, mobility and nature of carriers are measured using Hall measurement technique in Van der Pauw configuration at room temperature. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. 3-D MnNb{sub 2}O{sub 6} nanogears from 1-D Nb{sub 2}O{sub 5} nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Hu Weibing, E-mail: w.hu@tom.com [School of Chemical and Environmental Engineering, Hubei Institute for Nationalities, Enshi 445000 (China); Cui Zhicai [School of Chemical and Environmental Engineering, Hubei Institute for Nationalities, Enshi 445000 (China); Mi Yuanzhu [School of Chemistry and Environmental Engineering, Yangtze University, Nanhuan Road 1, Jingzhou 434023 (China)

    2012-04-16

    Graphical abstract: The geometry morphology of Nb-based nanomaterial evolved from long Nb{sub 2}O{sub 5} nanorods to a mixture of short Nb{sub 2}O{sub 5} nanorods and MnNb{sub 2}O{sub 6} 6-teeth nanogears, and eventually to fully developed pure 3-D nanogears. Highlights: Black-Right-Pointing-Pointer MnNb{sub 2}O{sub 6} nanogears have been generated by a simple solvothermal process when the Mn: Nb ratio was 1:1. Black-Right-Pointing-Pointer MnNb{sub 2}O{sub 6} 6-teeth nanogears accompanied with MnNb{sub 2}O{sub 6} 5-teeth nanogears are got when the Mn:Nb ratio reached 1:2. Black-Right-Pointing-Pointer The nanomaterial consists of nanorods and 6-teeth nanogears at low Mn:Nb molar ratio(1:4). Black-Right-Pointing-Pointer Pure long Nb{sub 2}O{sub 5} nanorods are achieved by only using NbCl{sub 5} - Abstract: MnNb{sub 2}O{sub 6} nanogears have been generated by using mixed NbCl{sub 5} and MnCl{sub 2} at an optimized ratio of 1:1 in a cyclohexanol solvent in a simple solvothermal process. It has shown that the Mn:Nb ratio determines the shape of the products. Detailed characterization by electron microscopy has shown that increasing the Mn{sup +2} concentration during the solvo-thermal synthesis promotes a morphological evolution from relatively long Nb{sub 2}O{sub 5} nanorods to a mixture of short Nb{sub 2}O{sub 5} nanorods and MnNb{sub 2}O{sub 6} 6-teeth nanogears, then to a mixture of short Nb{sub 2}O{sub 5} nanorods and more MnNb{sub 2}O{sub 6} 6-teeth nanogears, then to more and more MnNb{sub 2}O{sub 6} 6-teeth nanogears that are occasionally accompanied with under-developed MnNb{sub 2}O{sub 6} 5-teeth nanogears, and eventually to fully developed pure 3-D nanogears. The driving force for such interesting geometry transformations is attributed to the inclusion of Mn{sup 2+} into the Nb{sub 2}O{sub 5} template at low Mn{sup 2+} concentrations, which introduces internal stresses to the Nb{sub 2}O{sub 5} nanorods. At high Mn{sup 2+} concentrations, close to the

  11. Study on surface defect structures of ZrO2 and some doped ZrO2 by means of work function measurement

    International Nuclear Information System (INIS)

    Yamawaki, M.; Suzuki, A.; Ono, F.; Yamaguchi, K.

    1997-01-01

    The work function change of the ZrO 2 +2%Y 2 O 3 sintered pellet, caused by a change of the composition of the sweep gas, was measured using a high temperature Kelvin probe. The Pt reference electrode was calibrated by using ZrO 2 +2%Y 2 O 3 as a standard material. Work function changes of undoped ZrO 2 and Nb-doped ZrO 2 (2%Nb 2 O 5 ) were measured as a function of equilibrium oxygen partial pressure, P O 2 . The thus obtained exponents of P O 2 , 1/n, were 1/6.2 and 1/33.6 for ZrO 2 and ZrO 2 +2%Nb 2 O 5 , respectively. These exponent values were discussed in terms of defect chemistry of the surface layer. (orig.)

  12. Piezoelectric properties and temperature stability of Mn-doped Pb(Mg1/3Nb2/3)-PbZrO3-PbTiO3 textured ceramics

    OpenAIRE

    Yan, Yongke; Cho, Kyung-Hoon; Priya, Shashank

    2012-01-01

    In this letter, we report the electromechanical properties of textured 0.4Pb(Mg1/3Nb2/3) O-3-0.25PbZrO(3)-0.35PbTiO(3) (PMN-PZT) composition which has relatively high rhombohedral to tetragonal (R-T) transition temperature (TR-T of 160 degrees C) and Curie temperature (T-C of 234 degrees C) and explore the effect of Mn-doping on this composition. It was found that MnO2-doped textured PMN-PZT ceramics with 5 vol.% BaTiO3 template (T-5BT) exhibited inferior temperature stability. The coupling f...

  13. Enhanced carrier density in Nb-doped SrTiO3 thermoelectrics

    KAUST Repository

    Ozdogan, K.

    2012-03-08

    We study epitaxial SrTiO3 interfaced with Nb-doped SrTi1-x Nb x O3 (x = 0, 0.125, 0.25, 0.375, and 0.5) by full-potential density functional theory. From the electronic band structures obtained by our ab-initio calculations we determine the dependence of the induced metallicity on the Nb concentration. We obtain a monotonous increase of the carrier density with the Nb concentration. The results are confirmed by experiments for SrTi0.88Nb0.12O3 and SrTi0.8Nb0.2O3, demonstrating the predictive power and limitations of our theoretical approach. We also show that the Seebeck coefficient decreases monotonously with increasing temperature.

  14. Enhanced carrier density in Nb-doped SrTiO3 thermoelectrics

    KAUST Repository

    Ozdogan, K.; Upadhyay Kahaly, M.; Sarath Kumar, S. R.; Alshareef, Husam N.; Schwingenschlö gl, Udo

    2012-01-01

    We study epitaxial SrTiO3 interfaced with Nb-doped SrTi1-x Nb x O3 (x = 0, 0.125, 0.25, 0.375, and 0.5) by full-potential density functional theory. From the electronic band structures obtained by our ab-initio calculations we determine the dependence of the induced metallicity on the Nb concentration. We obtain a monotonous increase of the carrier density with the Nb concentration. The results are confirmed by experiments for SrTi0.88Nb0.12O3 and SrTi0.8Nb0.2O3, demonstrating the predictive power and limitations of our theoretical approach. We also show that the Seebeck coefficient decreases monotonously with increasing temperature.

  15. Enhanced magnetic and ferroelectric properties in scandium doped nano Bi2Fe4O9

    International Nuclear Information System (INIS)

    Dutta, Dimple P.; Sudakar, C.; Mocherla, Pavana S.V.; Mandal, Balaji P.; Jayakumar, Onnatu D.; Tyagi, Avesh K.

    2012-01-01

    In this study we report the synthesis of undoped and Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles using sonochemical technique. X-ray diffraction reveals that all samples are single phase with no impurities detected. EDS analysis was done to confirm the extent of Sc 3+ doping in the samples. The size and morphology of the nanoparticles have been analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Bi 2 Fe 4 O 9 nanoparticles show a weak ferromagnetic behavior at room temperature, which is quite different from the linear M–H relationship reported for bulk Bi 2 Fe 4 O 9 . A magnetization of 0.144 μB/f.u. is obtained at 300 K, which is mainly attributed to the uncompensated moments at the disordered particle surface resulting from the reduced coordination of the surface spins, arising due to lattice strain or oxygen deficiency. Addition of Sc 3+ dopant in varying concentrations in these Bi 2 Fe 4 O 9 nanoparticles, improves their magnetic as well as ferroelectric properties. The leakage current is considerably reduced and electric polarization increases significantly in case of Bi 2 Fe 4(1−x) Sc x O 9 (x = 0.1) nanoparticles. Thus it can be inferred that Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles shows promise as good multiferroic materials. -- Graphical abstract: Undoped and Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles have been synthesized using sonochemical technique. The bi-functionalities of Sc 3+ doped Bi 2 Fe 4 O 9 nanoparticles have been demonstrated. The Bi 2 Fe 4(1−x) Sc x O 9 (x = 0.1) nanoparticles showed enhanced magnetic and ferroelectric properties with considerably less lossy characteristics compared to the bulk Bi 2 Fe 4 O 9 . Highlights: ► Phase pure Bi 2 Fe 4 O 9 nanostructures synthesized using a facile sonochemical technique. ► Nanoparticles show a weak ferromagnetic order at room temperature. ► Sc 3+ doping in Bi 2 Fe 4 O 9 nanoparticles alters their magnetic and ferroelectric properties. ► A

  16. Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

    Directory of Open Access Journals (Sweden)

    Nam-Hee Park

    2015-07-01

    Full Text Available To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO3 nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO3 nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO2/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface.

  17. Synthesis and crystal structure of Mg0.5NbO2: An ion-exchange reaction with Mg2+ between trigonal [NbO2]- layers

    Science.gov (United States)

    Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

    2013-01-01

    A new layered niobate, Mg0.5NbO2, was synthesized from LiNbO2 through a cation-exchange reaction with Mg2+ at 450-550 °C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO2]- layers. It is proposed to be isostructural with LiNbO2 (space group; P63/mmc) with lattice parameters of a=2.9052(6) Å, c=10.625(15) Å. The lattice parameters and formation energy of Mg0.5NbO2 crystallized in LiNbO2 form and other layered CaNb2O4 one were calculated by density functional theory.

  18. Nb and Ta Co-Doped TiO2 Transparent Conductive Thin Films by Magnetron Sputtering: Fabrication, Structure, and Characteristics

    Science.gov (United States)

    Liu, Yang; Peng, Qian; Qiao, Yadong; Yang, Guang

    2018-06-01

    Nb and Ta co-doped anatase titanium dioxide (NTTO) nanocrystalline thin films were deposited on quartz and Si (100) substrates by RF magnetron sputtering. The influence of RF power on the growth, structure, morphology, and properties of the samples are discussed in detail. X-ray diffraction measurements show that the films are polycrystalline with anatase tetragonal structure, which is further confirmed by Raman spectroscopy analysis. Meanwhile, Raman spectroscopy results indicate that the peak width of E g(1) mode, which is directly correlated to the carrier density, changes obviously with RF power. It is found that the substitution of Nb5+ and Ta5+ at Ti site is significantly improved with the increase of RF power from 150 W to 210 W. For the sample deposited at 210 W, the optical transmittance is above 82% in the visible range and the electrical resistivity is as low as 1.3 × 10-3 Ω cm with carrier density of 1.1 × 1021 cm-3 and Hall mobility of 4.5 cm2 V-1 s-1. The optical and electrical properties of NTTO thin films can be compared to those of Nb or Ta doped anatase TiO2. However, co-doping with Nb and Ta gives a possible platform to complement the limitations of each individual dopant.

  19. Promotion of Nb2O5 on the wustite-based iron catalyst for ammonia synthesis

    International Nuclear Information System (INIS)

    Han, Wenfeng; Huang, Shiliang; Cheng, Tianhong; Tang, Haodong; Li, Ying; Liu, Huazhang

    2015-01-01

    Highlights: • Niobium enhances the reduction of wustite-based ammonia synthesis catalyst significantly. • Nb 2 O 5 inhibits the segregation or formation of solid solutions on the catalyst surface. • Nb 2 O 5 doping enhances the growth rates of [2 1 1] and [2 0 0] planes rather than their amounts. - Abstract: Niobium was selected and investigated as a potential promoter for wustite-based catalyst (WBC) for ammonia synthesis. Experiments on reduction performance, activity test and H 2 -TGA, in situ XRD as well as XPS were carried out to obtain the promotion effect and mechanism involved. Niobium as a promoter was confirmed to enhance the reduction of WBC significantly. This behavior is highly desired for industry in terms of catalyst regeneration and lesser pretreatment time for fabrication regardless the unimproved catalytic performance for Nb 2 O 5 -doped wustite-based catalyst (Nb-WBC). Possible reasons for these phenomena are discussed. It is suggested that Nb 2 O 5 is not favorable for the segregation or formation of solid solutions on the catalyst surface, which are difficult to be reduced. However, it seems that niobium does not promote the growth of [2 1 1] plane, which is active for ammonia synthesis.

  20. Fabrication and photovoltaic performance of niobium doped TiO{sub 2} hierarchical microspheres with exposed {001} facets and high specific surface area

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yongqiang; Ran, Huili [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Fan, Jiajie, E-mail: fanjiajie@zzu.edu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Zhang, Xiaoli; Mao, Jing [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Shao, Guosheng [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Institute for Renewable Energy and Environmental Technologies, University of Bolton, Bolton BL3 5AB (United Kingdom)

    2017-07-15

    Highlights: • Nb-doped hierarchical TiO{sub 2} microsphere DSSCs show enhanced performance. • Nb{sup 5+} dopant replaces Ti{sup 4+} cation in TiO{sub 2} lattice. • Electrons transport was enhanced due to the down-shifted conduction band minimum. • Exposed (001) facets and high specific surface area allows high dye-loading. - Abstract: The niobium doped hierarchical anatase TiO{sub 2} microspheres, which are consist of a serried nano-thorns and plicate nano-ribbons with exposed {001} facets, were synthesized using hydrothermal method followed by heat treatment. The effects of niobium on the microstructures and photovoltaic performances of the dye-sensitized solar cells (DSSCs) were studied. The results revealed that Nb{sup 5+} doping replaces Ti{sup 4+} cations in TiO{sub 2} lattice, and the bandgap of the films varies with increasing Nb doping concentration because of the downshift of the conduction band minimum (CBM). The niobium-doped TiO{sub 2} DSSCs with moderate loadings show enhanced performance comparing with their pure TiO{sub 2} counterparts. Optimally, the conversion efficiency of the Nb-3.5 (Nb 3.5 mol%) DSSC is 4.99%. This is higher than that (4.39%) of pure TiO{sub 2} cells by 13.7%. This is due to the fact that the Nb-doped solar cells have increased the number of the photo-induced electrons because of their exposed (001) facets and higher specific surface area; and enhanced electrons collection and transport because of the downshifted CBM of the Nb-doped TiO{sub 2}. However, heavy Nb doping results in the decrease of the performance of the niobium-doped cells due to the excessive defects within the Nb-TiO{sub 2} samples resulting in enhanced charge recombination at defects.

  1. Isolation and structures of sulfonium salts derived from thioethers: [{o-C(6)H(4)(CH(2)SMe)(2)}H][NbF(6)] and [{[9]aneS(3)}H][NbF(6)].

    Science.gov (United States)

    Jura, Marek; Levason, William; Reid, Gillian; Webster, Michael

    2009-10-07

    Two very unusual sulfonium salts, [{o-C(6)H(4)(CH(2)SMe)(2)}H][NbF(6)] and [{[9]aneS(3)}H][NbF(6)], obtained from reaction of the thioethers with NbF(5) in CH(2)Cl(2) solution, are reported and their structures described; the eight-coordinate tetrafluoro Nb(v) cation of the dithioether is obtained from the same reaction.

  2. Influence of VB group doped TiO2 on photovoltaic performance of dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Liu, Jia; Duan, Yandong; Zhou, Xiaowen; Lin, Yuan

    2013-01-01

    Dye-sensitized solar cell with V B group (vanadium (V), niobium (Nb) and tantalum (Ta)) doped TiO 2 prepared by hydrothermal method shows a higher photovoltaic efficiency compared with the undoped TiO 2 . All the V B doping shift the flat band potential positively and increase the doping density which is investigated by Mott–Schottky plot. The positive shift of flat band potential improves the driving force of injecting electron from the LUMO of dye to the conduction band of TiO 2 and the photocurrent. On the other hand, the increase of doping density accelerates transfer rate of electrons in TiO 2 than the un-doped, which is confirmed by intensity-modulated photocurrent. V-, Nb-, Ta-doped TiO 2 exhibited photovoltaic performance with 7.80%, 8.33%, 8.18%, respectively, compared with that of the cells based on pure TiO 2 (7.42%).

  3. Colossal magnetodielectric effect and spin flop in magnetoelectric Co4Nb2O9 crystal

    International Nuclear Information System (INIS)

    Yin, L. H.; Yang, J.; Dai, J. M.; Song, W. H.; Zhu, X. B.; Zou, Y. M.; Sun, Y. P.

    2016-01-01

    We have investigated the detailed magnetic, magnetoelectric (ME), magnetodielectric (MD) and thermal expansion properties in Co 4 Nb 2 O 9 crystal. A magnetic-field-induced spin flop was observed below antiferromagnetic (AFM) transition temperature T N . Dielectric constant at applied magnetic field nearly diverges around the AFM transition, giving rise to a colossal MD effect as high as ∼138% around T N . Theoretical analysis of the ME and MD data revealed a major contribution of critical spin fluctuation to the colossal MD effect in Co 4 Nb 2 O 9 . These results suggest that linear ME materials with large ME coupling might be potentially used to realize large MD effect for future application.

  4. Thermal diffuse scattering in time-of-flight neutron diffraction studied on SBN single crystals

    International Nuclear Information System (INIS)

    Prokert, F.; Savenko, B.N.; Balagurov, A.M.

    1994-01-01

    At time-of-flight (TOF) diffractometer D N-2, installed at the pulsed reactor IBR-2 in Dubna, Sr x Ba 1-x Nb 2 O 6 mixed single crystals (SBN-x) of different compositions (0.50 < x< 0.75) were investigated between 15 and 773 K. The diffraction patterns were found to be strongly influenced by the thermal diffuse scattering (TDS). The appearance of the TDS from the long wavelength acoustic models of vibration in single crystals is characterized by the ratio of the velocity of sound to the velocity of neutron. Due to the nature of the TOF Laue diffraction technique used on D N-2, the TDS around Bragg peaks has rather a complex profile. An understanding of the TDS close to Bragg peaks is essential in allowing the extraction of the diffuse scattering occurring at the diffuse ferroelectric phase transition in SBN crystals. 11 refs.; 9 figs.; 1 tab. (author)

  5. Electrical properties of SrBi2Ta2O9 thin films deposited on Si (100) substrates by rf magnetron sputtering

    International Nuclear Information System (INIS)

    Roy, A.; Jha, G.; Dhar, A.; Ray, S.K.; Manna, I.

    2008-01-01

    Recently, metal-ferroelectric-semiconductor (MFS) structures have attracted much attention because of its potentials as nonvolatile memory device with nondestructive readout operation. In the present study ferroelectric SrBi 2 Ta 2 O 9 (SBT) thin films are grown on p-type (100) Si substrates by rf magnetron sputtering method at different deposition conditions. The crystallinity of the films is studied using grazing incidence X-ray diffraction (GIXRD) pattern. The spectra show the film are polycrystalline with dominant orientation along (115) plane. The capacitance-voltage (C-V) characteristics of Al/SBT/Si capacitors were measured at 100 kHz. The (C-V) characteristic of AI/SBT/Si capacitor post-annealed at 700-800 deg C shows a hysteresis nature with a clockwise rotation and the memory window of the hysteresis loop is 0.88 V when the gate voltage is ± 5 V. The interface trap density (D it ) calculated by using Hills method at room temperature and a value in the order of 10 11 -10 12 eV -1 cm -2 was found at mid gap region depending on the crystallization temperature. The surface morphology was investigated by atomic force microscope (AFM). The study showed the potential of SBT for application in metal- ferroelectric-silicon nonvolatile memory devices. (author)

  6. Comparative study of the magnetic properties of La3Ni2B‧O9 for B‧ = Nb, Taor Sb

    Science.gov (United States)

    Chin, Chun-Mann; Battle, Peter D.; Blundell, Stephen J.; Hunter, Emily; Lang, Franz; Hendrickx, Mylène; Paria Sena, Robert; Hadermann, Joke

    2018-02-01

    Polycrystalline samples of La3Ni2NbO9 and La3Ni2TaO9 have been characterised by X-ray and neutron diffraction, electron microscopy, magnetometry and muon spin relaxation (μSR); the latter technique was also applied to La3Ni2SbO9. On the length scale of a neutron diffraction experiment, the six-coordinate sites of the monoclinic perovskite structure are occupied in a 1:1 ordered manner by Ni and a random ⅓Ni/⅔B‧ mixture. Electron microscopy demonstrated that this 1:1 ordering is maintained over microscopic distances, although diffuse scattering indicative of short-range ordering on the mixed site was observed. No magnetic Bragg scattering was observed in neutron diffraction patterns collected from La3Ni2B‧O9 (B‧ = Nb or Ta) at 5 K although in each case μSR identified the presence of static spins below 30 K. Magnetometry showed that La3Ni2NbO9 behaves as a spin glass below 29 K but significant short-range interactions are present in La3Ni2TaO9 below 85 K. The contrasting properties of these compounds are discussed in terms of their microstructure.

  7. Sintering and Electrical Characterization of La and Nb Co‐doped SrTiO3 Electrode Materials for Solid Oxide Cell Applications

    DEFF Research Database (Denmark)

    Sudireddy, Bhaskar Reddy; Agersted, Karsten

    2014-01-01

    Single‐phase lanthanum and niobium co‐doped strontium titanate (Sr1–3x/2LaxTi0.9Nb0.1O3; x = 0–0.02) ceramics were prepared. Dilatometry in reducing atmosphere showed an increase in the sintering rate and sintered density with an increase in La amount. Microscopy of fractured surfaces of sintered...... samples showed that the average grain size increased drastically in reducing conditions with increasing La content (and associated A‐site vacancies). By incorporating 2 mol.% La, the electronic conductivity significantly improved from 80 to 135 S cm−1 at 1,000 °C, and even larger improvements were...... observed at lower temperatures. These observations demonstrate the flexibility in tailoring the microstructure and electronic transport properties by doping small amounts of La into the Nb‐doped SrTiO3 and show that Sr1–3x/2LaxTi0.9Nb0.1O3 is a potential electrode material for solid oxide cells....

  8. Synthesis and characterization of Ag-doped TiO2 nanotubes on Ti-6Al-4V and Ti-6Al-7Nb alloy

    Science.gov (United States)

    Ulfah, Ika Maria; Bachtiar, Boy M.; Murnandityas, Arnita Rut; Slamet

    2018-05-01

    The present paper is focused on comparative behavior of nanotubes growth on Ti-6Al-4V and Ti-6Al-7Nb alloy using electrochemical anodization method. These alloys were anodized in electrolytes solution containing glycerol, water and 0.5wt.% of NH4F. Silver-doped TiO2 nanotubes were synthesized using photo-assisted deposition (PAD) at various Ag loading concentration in 0.05 M, 0.10 M, and 0.15 M. The phase composition and morphological characteristics were investigated by XRD and FESEM/EDX, respectively. The surface wettability was measured by contact angle meter. The results showed that TiO2 nanotubes can be grown on these surface alloys. XRD profiles revealed crystal formation of anatase, rutile and Ag on these surface alloys. According to FESEM images, the average nanotube diameter of Ti-6Al-4V alloy and Ti-6Al-7Nb alloy are 134 nm and 120 nm, respectively. EDX-Mapping analysis showed that Ag desposited over surface of TiO2 nanotubes. The surface wettability indicated hydrophilicity properties on Ti-4Al-4V alloy and Ti-6Al-7Nb alloy surface. This study may contribute to the development of silver-doped TiO2 nanotubes on Ti-6Al-4V alloy and Ti-6Al-7Nb alloy can be considered in various photocatalytic applications such as biomedical devicesdue to photocatalytic mechanism and antibacterial ability.

  9. Spectroscopic properties and thermal stability of Er3+ -doped TeO2-B2O3-Nb2O5-ZnO glass for potential WDM amplifier.

    Science.gov (United States)

    Xu, Tiefeng; Zhang, Xudong; Li, Guangpo; Dai, Shixun; Nie, Qiuhua; Shen, Xiang; Zhang, Xianghua

    2007-06-01

    A series of novel 70TeO2-(15-x)B2O3-xNb2O5-15ZnO-1wt.% Er2O3 (TBN x=0, 3, 6, 9, 12 and 15 mol%) tellurite glasses were prepared. The thermal stability, absorption spectra, emission spectra, and the lifetime of the (4)I(13/2) level of Er(3+) ions were measured and investigated. Three Judd-Ofelt intensity parameters Omega(t) (t=2, 4 and 6) (Omega(2)=(5.42-6.76)x10(-20)cm(2); Omega(4)=(1.37-1.73)x10(-20)cm(2); Omega(6)=(0.70-0.94)x10(-20)cm(2)) of Er(3+) ions were calculated by Judd-Ofelt theory. It is found that the Omega(6) first increases with the increase of Nb2O5 content from 0 to 6 mol% and then decreases, which is mainly affected by the number of non-bridging oxygen ions of the glass network. The high peak of stimulated emission cross-section (sigma(e)(peak)=(0.77-0.91)x10(-20)cm(2)) of Er(3+): (4)I(13/2)-->(4)I(15/2) transition were obtained according to McCumber theory and broad full width at half maximum (FWHM=65-73 nm) of the (4)I(13/2)-->(4)I(15/2) transition of Er(3+) ions were measured. The results indicate that these new TBN glasses can be used as a candidate host material for potential broadband optical amplifiers.

  10. Optical and dielectric properties of isothermally crystallized nano-KNbO3 in Er3+-doped K2O-Nb2O5-SiO2 glasses.

    Science.gov (United States)

    Chaliha, Reenamoni Saikia; Annapurna, K; Tarafder, Anal; Tiwari, V S; Gupta, P K; Karmakar, Basudeb

    2010-01-01

    Precursor glass of composition 25K(2)O-25Nb(2)O(5)-50SiO(2) (mol%) doped with Er(2)O(3) (0.5 wt% in excess) was isothermally crystallized at 800 degrees C for 0-100 h to obtain transparent KNbO(3) nanostructured glass-ceramics. XRD, FESEM, TEM, FTIRRS, dielectric constant, refractive index, absorption and fluorescence measurements were carried out to analyze the morphology, dielectric, structure and optical properties of the glass-ceramics. The crystallite size of KNbO(3) estimated from XRD and TEM is found to vary in the range 7-23 nm. A steep rise in the dielectric constant of glass-ceramics with heat-treatment time reveals the formation of ferroelectric nanocrystalline KNbO(3) phase. The measured visible photoluminescence spectra have exhibited green emission transitions of (2)H(11/2), (4)S(3/2)-->(4)I(15/2) upon excitation at 377 nm ((4)I(15/2)-->(4)G(11/2)) absorption band of Er(3+) ions. The near infrared (NIR) emission transition (4)I(13/2)-->(4)I(15/2) is detected around 1550 nm on excitation at 980 nm ((4)I(15/2)-->(4)I(11/2)) of absorption bands of Er(3+) ions. It is observed that photoluminescent intensity at 526 nm ((2)H(11/2)-->(4)I(15/2)), 550 nm ((4)S(3/2)-->(4)I(15/2)) and 1550 nm ((4)I(13/2)-->(4)I(15/2)) initially decrease and then gradually increase with increase in heat-treatment time. The measured lifetime (tau(f)) of the (4)I(13/2)-->(4)I(15/2) transition also possesses a similar trend. The measured absorption and fluorescence spectra reveal that the Er(3+) ions gradually enter into the KNbO(3) nanocrystals. Copyright 2009 Elsevier B.V. All rights reserved.

  11. Raman effect in ferroelectric Cd2Nb2O7 and in other crystals with pyrochlorine-type structure

    International Nuclear Information System (INIS)

    Pisarev, R.V.; Sinij, I.G.; Kuz'minov, E.G.; Myl'nikova, I.E.

    1976-01-01

    Vibrational structure of cadmium and lead pyroniobates and a number of other crystals with a pyrochlore structure has been investigated by Raman scattering. The scattering has been studied using a double monochromator, HeNe laser, and a photons counter. In the Raman spectrum of cadmium and lead pyroniobates three frequency band1 can be distinguished. In the spectrum of rhombohedral lead pyroniobate the band structure in resolved much better than in the spectrum of cubic cadmium pyroniobate. The spectrum of lead pyroniobate crystals doped with magnesium and zinc ions has a medium (in the sense of complexity) structure, because big lead ions deteriorate the pyrochlore structure but doping of lead pyroniobate with Mg 2+ and Zn 2+ ions improves it. More than six bands in the Raman spectrum is associated with the presence of impurities in cubic cadmium pyroniobate that deteriorate its cubic structure. The decrease of temperature leads to a big change of the Cd 2 Nb 2 O 7 spectrum. However, the spectrum of Pb 2 Nb 2 O 7 -Zn cubic crystal measured ar temperatures below 100 deg K remais unchanged. The chages of the Cd 2 Nb 2 O 7 spectrum are associated with phase transitions at 200 and 85 K and also with ferroelectric transition at 185 K

  12. Highly sensitive formaldehyde resistive sensor based on a single Er-doped SnO_2 nanobelt

    International Nuclear Information System (INIS)

    Li, Shuanghui; Liu, Yingkai; Wu, Yuemei; Chen, Weiwu; Qin, Zhaojun; Gong, Nailiang; Yu, Dapeng

    2016-01-01

    SnO_2 nanobelts (SnO_2 NBs) and Er"3"+-doped SnO_2 nanobelts (Er–SnO_2 NBs) were synthesized by thermal evaporation. The obtained samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersion spectrometer (EDS), and X-ray photoelectron spectrometer (XPS). It is found that Er–SnO_2 NBs have a good morphology with smooth surface and their thickness are about 30 nm, widths between 200 nm and 600 nm, and lengths 30–80 mm. The nanobelts with good morphology were taken to develop sensors based on a single Er–SnO_2 NB/SnO_2 NB for studying sensitive properties. The results reveal that the response of a single Er–SnO_2 nanobelt device is 9 to the formaldehyde gas with a shorter response (recovery time) of 17 (25) s.

  13. Dielectric properties of BaMg1/3Nb2/3O3 doped Ba0.45Sr0.55Tio3 thin films for tunable microwave applications

    Science.gov (United States)

    Alema, Fikadu; Pokhodnya, Konstantin

    2015-11-01

    Ba(Mg1/3Nb2/3)O3 (BMN) doped and undoped Ba0.45Sr0.55TiO3 (BST) thin films were deposited via radio frequency magnetron sputtering on Pt/TiO2/SiO2/Al2O3 substrates. The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy, resulting in an improved insulating properties of the BST film. Dielectric tunability, loss, and leakage current (LC) of the undoped and BMN doped BST thin films were studied. The BMN dopant has remarkably reduced the dielectric loss (˜38%) with no significant effect on the tunability of the BST film, leading to an increase in figure of merit (FOM). This is attributed to the opposing behavior of large Mg2+ whose detrimental effect on tunability is partially compensated by small Nb5+ as the two substitute Ti4+ in the BST. The coupling between MgTi″ and VO•• charged defects suppresses the dielectric loss in the film by cutting electrons from hopping between Ti ions. The LC of the films was investigated in the temperature range of 300-450K. A reduced LC measured for the BMN doped BST film was correlated to the formation of defect dipoles from MgTi″, VO•• and NbTi• charged defects. The carrier transport properties of the films were analyzed in light of Schottky thermionic emission (SE) and Poole-Frenkel (PF) emission mechanisms. The result indicated that while the carrier transport mechanism in the undoped film is interface limited (SE), the conduction in the BMN doped film was dominated by bulk processes (PF). The change of the conduction mechanism from SE to PF as a result of BMN doping is attributed to the presence of uncoupled NbTi• sitting as a positive trap center at the shallow donor level of the BST.

  14. Effect of Nb doping on electrochemical properties of LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} at high cutoff voltage for lithium-ion battery

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jiefan [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); Liu, Hongguang, E-mail: hongguangliu_01@163.com [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); CNOOC Tianjin Chemical Research & Design Institute, Tianjin 300131 (China); Ye, Xuehai; Xia, Jiping; Lu, Yang; Lin, Chaowang; Yu, Xiaowei [CNOOC Tianjin Chemical Research & Design Institute, Tianjin 300131 (China)

    2015-09-25

    Highlights: • Nb substituted LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3−x}Nb{sub x}O{sub 2} (x = 0–0.03) was prepared by sol–gel method. • 2% Nb-substituted sample showed better cycle performance at high cutoff voltage. • Ex situ analysis was used to show the structure changes of Nb-doped samples. - Abstract: Nb doped cathode materials with the formula LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3−x}Nb{sub x}O{sub 2} (x = 0, 0.01, 0.02, 0.03) have been prepared successfully by sol–gel method. The effect of Nb substitution on the crystal structure and electrochemical properties of LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} were studied systematically by X-ray diffraction (XRD) and various electrochemical measurements. The results showed Nb substitution played an important role in the good cycling performance of LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2}. Charge/discharge tests revealed that LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3–0.02}Nb{sub 0.02}O{sub 2} showed a capacity retention of 94.1% at 1 C after 50 cycles in a high cutoff voltage range (3.0–4.6 V), while discharge capacity of LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} remains only 89.4% of that at 1 C. Ex-situ XRD analysis and EIS analysis indicated that the improved electrochemical properties of Nb-doped sample result from the more stable structure and lower resistance during the electrochemical cycling.

  15. Preparation of Ferroelectric Thin Films of Bismuth Layer Structured Compounds

    Science.gov (United States)

    Watanabe, Hitoshi; Mihara, Takashi; Yoshimori, Hiroyuki; Araujo, Carlos

    1995-09-01

    Ferroelectric thin films of bismuth layer structured compounds, SrBi2Ta2O9, SrBi2Nb2O9, SrBi4Ti4O15 and their solid solutions, were formed onto a sputtered platinum layer on a silicon substrate using spin-on technique and metal-organic decomposition (MOD) method. X-ray diffraction (XRD) analysis and some electrical measurements were performed on the prepared thin films. XRD results of SrBi2(Ta1- x, Nb x)2O9 films (0≤x≤1) showed that niobium ions substitute for tantalum ions in an arbitrary ratio without any change of the layer structure and lattice constants. Furthermore, XRD results of SrBi2 xTa2O9 films (0≤x≤1.5) indicated that the formation of the bismuth layer structure does not always require an accurate bismuth content. The layer structure was formed above 50% of the stoichiometric bismuth content in the general formula. SrBi2(Ta1- x, Nb x)2O9 films with various Ta/Nb ratios have large enough remanent polarization for nonvolatile memory application and have shown high fatigue resistance against 1011 cycles of full switching of the remanent polarization. Mixture films of the three compounds were also investigated.

  16. Crystal structure and optical property of complex perovskite oxynitrides ALi0.2Nb0.8O2.8N0.2, ANa0.2Nb0.8O2.8N0.2, and AMg0.2Nb0.8O2.6N0.4 (A = Sr, Ba)

    Science.gov (United States)

    Moon, Keon Ho; Avdeev, Maxim; Kim, Young-Il

    2017-10-01

    Oxynitride type complex perovskites AM0.2Nb0.8O3-xNx (A = Sr, Ba; M = Li, Na, Mg) were newly synthesized by the solid state diffusion of Li+, Na+, or Mg2+ into the layered oxide, A5Nb4O15, with concurrent O/N substitution. Neutron and synchrotron X-ray Rietveld refinement showed that SrLi0.2Nb0.8O2.8N0.2, SrNa0.2Nb0.8O2.8N0.2, and SrMg0.2Nb0.8O2.6N0.4 had body-centered tetragonal symmetry (I4/mcm), while those with A = Ba had simple cubic symmetry (Pm 3 ̅ m). In the tetragonal Sr-compounds, the nitrogen atoms were localized on the c-axial 4a site. However, the octahedral cations, M/Nb (M = Li, Na, Mg) were distributed randomly in all six compounds. The lattice volume of AM0.2Nb0.8O3-xNx was dependent on various factors including the type of A and the electronegativity of M. Compared to the simple perovskites, ANbO2N (A = Sr, Ba), AM0.2Nb0.8O3-xNx had wider band gaps (1.76-2.15 eV for A = Sr and 1.65-2.10 eV for A = Ba), but significantly lower sub-gap absorption.

  17. Anatase phase stability and doping concentration dependent refractivity in codoped transparent conducting TiO2 films

    International Nuclear Information System (INIS)

    Chen, T L; Furubayashi, Y; Hirose, Y; Hitosugi, T; Shimada, T; Hasegawa, T

    2007-01-01

    Nb 0.06 Sn x Ti 0.94-x O 2 (x ≤ 0.3) thin films were grown by a pulsed-laser deposition method with varying Sn concentration. Through a combinatorial technique, we find that Sn concentration can reach a maximum of about x = 0.3 while maintaining the stable anatase phase and epitaxy. A doping concentration dependence of the refractivity is revealed, in which refractivity reduction at a wavelength of λ = 500 nm is estimated to be 12.4% for Nb 0.06 Sn 0.3 Ti 0.64 O 2 thin film. Sn doping induced band-gap blue shift can be contributed to the mixing of extended Sn 5s orbitals with the conduction band of TiO 2 . Low resistivity on the order of 10 -4 Ω cm at room temperature and high internal transmittance of more than 95% in the visible light region are exhibited for Nb 0.06 Sn x Ti 0.94-x O 2 thin films (x ≤ 0.2). Optical and transport analyses demonstrate that doping Sn into Nb 0.06 Ti 0.94 O 2 can reduce the refractivity while maintaining low resistivity and high transparency

  18. Structural and electrical properties of Nb doped TiO{sub 2} films prepared by the sol–gel layer-by-layer technique

    Energy Technology Data Exchange (ETDEWEB)

    Duta, M., E-mail: mduta@icf.ro [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Simeonov, S. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia (Bulgaria); Teodorescu, V. [National Institute of Material Physics, 105 bis Atomistilor Street, 077125 Bucharest, Magurele (Romania); Predoana, L.; Preda, S.; Nicolescu, M.; Marin, A. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Spasov, D. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia (Bulgaria); Gartner, M.; Zaharescu, M. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Szekeres, A. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia (Bulgaria)

    2016-02-15

    Highlights: • TiO{sub 2}:Nb (1.2 at.%) multilayer films were deposited by sol–gel method on glass and Si. • 5 and 10 layers TiO{sub 2}:Nb films crystallize only in the anatase phase. • E{sub g} values are within 3.24–3.32 eV showing a decrease with increasing the layer number. • The specific resistivity, effective donor and sheet energy densities were obtained. • Nb donor compensation by acceptor levels in TiO{sub 2}:Nb film was suggested. - Abstract: Thin films of 5 and 10-layered sol–gel TiO{sub 2} were doped with 1.2 at.% Nb and their structural, optical and electrical properties were investigated. The films crystallized only in anatase phase, as evidenced by X-ray diffraction and selected area electron diffraction analyses. High resolution transmission electron microscopy revealed nanosized crystallites with amorphous boundaries. Current-voltage measurements on metal-TiO{sub 2}–Si structures showed the formation of n{sup +}–n heterojunction at the TiO{sub 2}–Si interface with a rectification ratio of 10{sup 4}. The effective donor density varies between 10{sup 16} and 10{sup 17} cm{sup −3}, depending on film thickness. The sheet energy densities under forward and reverse bias are in the order of 10{sup 12} and 10{sup 10} cm{sup −2} eV{sup −1}, respectively. These values and the high specific resistivity (10{sup 4} Ω cm) support the existence of compensating acceptor levels in these films. It was established that the conduction mechanism is based on space charge limited current via deep levels with different energy positions in the band gap.

  19. Phase formation of V2O5.xNb2O5 compounds via gels and freeze-dried precursors

    International Nuclear Information System (INIS)

    Langbein, Hubert; Mayer-Uhma, Tobias

    2009-01-01

    An X-ray powder diffraction study of the phase formation in the system V 2 O 5 /Nb 2 O 5 is performed. Freeze-dried ammonium vanadate and ammonium oxalato niobate, alkoxide-derived xerogels and a mixture of active oxides are used as precursors to compare the resulting phase composition. Thermal decomposition of the freeze-dried precursor is monitored with DTA/TG and mass spectrometry. In the quasi-binary system V 2 O 5 -Nb 2 O 5 metastable VNbO 5 , V 4 Nb 18 O 55 , VNb 9 O 25 and solid solutions of V 2 O 5 in TT-Nb 2 O 5 as also thermodynamically stable VNb 9 O 25 exist. The thermal decomposition of freeze-dried vanadate-oxalatoniobate solution allows the synthesis of all these phases in a relative simple manner. Structural relationships between an intermediate phase and the product, or, in the case of solid-state reactions, between one of the starting oxide and the product, favour the desired reaction. Therefore, the structure of a former phase influences or directs the structure of the product similar to a topotactic reaction

  20. Nb and Ta layer doping effects on the interfacial energetics and electronic properties of LaAlO3/SrTiO3 heterostructure: first-principles analysis.

    Science.gov (United States)

    Nazir, Safdar; Behtash, Maziar; Cheng, Jianli; Luo, Jian; Yang, Kesong

    2016-01-28

    The two-dimensional electron gas (2DEG) formed at the n-type (LaO)(+1)/(TiO2)(0) interface in the polar/nonpolar LaAlO3/SrTiO3 (LAO/STO) heterostructure (HS) has emerged as a prominent research area because of its great potential for nanoelectronic applications. Due to its practical implementation in devices, desired physical properties such as high charge carrier density and mobility are vital. In this respect, 4d and 5d transition metal doping near the interfacial region is expected to tailor electronic properties of the LAO/STO HS system effectively. Herein, we studied Nb and Ta-doping effects on the energetics, electronic structure, interfacial charge carrier density, magnetic moment, and the charge confinements of the 2DEG at the n-type (LaO)(+1)/(TiO2)(0) interface of LAO/STO HS using first-principles density functional theory calculations. We found that the substitutional doping of Nb(Ta) at Ti [Nb(Ta)@Ti] and Al [Nb(Ta)@Al] sites is energetically more favorable than that at La [Nb(Ta)@La] and Sr [Nb(Ta)@Sr] sites, and under appropriate thermodynamic conditions, the changes in the interfacial energy of HS systems upon Nb(Ta)@Ti and Nb(Ta)@Al doping are negative, implying that the formation of these structures is energetically favored. Our calculations also showed that Nb(Ta)@Ti and Nb(Ta)@Al doping significantly improve the interfacial charge carrier density with respect to that of the undoped system, which is because the Nb(Ta) dopant introduces excess free electrons into the system, and these free electrons reside mainly on the Nb(Ta) ions and interfacial Ti ions. Hence, along with the Ti 3d orbitals, the Nb 4d and Ta 5d orbitals also contribute to the interfacial metallic states; accordingly, the magnetic moments on the interfacial Ti ions increase significantly. As expected, the Nb@Al and Ta@Al doped LAO/STO HS systems show higher interfacial charge carrier density than the undoped and other doped systems. In contrast, Nb@Ti and Ta@Ti doped systems may

  1. Nb-doped TiO2 thin films as photocatalytic materials

    Indian Academy of Sciences (India)

    Administrator

    that hydrophilicity is ruled by a different mechanism than photocatalysis. Keywords. Nb-doped ... studied for a large area of applications: solar cells,1–3 hydrogen ... our previous work.12,13 Results show that all the films are amorphous and ...

  2. Electrical and microstructural properties of CaTiO3-doped K1/2Na1 ...

    Indian Academy of Sciences (India)

    KNN) and CaTiO3- modified K1/2Na1/2NbO3 (CTO-KNN) systems, were investigated. Discs doped with 0 to 0.55% mol of CaTiO3 (CTO) were sintered at 1125°C for 2 h. Although minority phases were found in doped samples, CaTiO3 was not ...

  3. Study of A-site doping of SrBi4Ti4O15 Bi-layered compounds using micro-Raman spectroscopy

    International Nuclear Information System (INIS)

    Hao, H.; Liu, H.X.; Cao, M.H.; Min, X.M.; Ouyang, S.X.

    2006-01-01

    The temperature-dependent Raman spectra of Mg- and La-doped SrBi 4 Ti 4 O 15 (SBT) were studied in the range 40-590 C. A quantum chemistry calculation was employed to estimate these two substitution states. It was found that A-site doping in this study not only caused multiplicative substitution states, but also the Raman spectra changed with the substitution amount. In a La-doped perovskite-like layer, La would occupy the Bi site when x>0.10 and the 314 and 550 cm -1 modes related to the rotating and tilting of the TiO 6 octahedron firstly became wide and then became sharp. With the increase of the substitution amount, both substitution states of Mg-doped SBT lead to the widening of 270 and 520 cm -1 peaks. (orig.)

  4. Study of A-site doping of SrBi4Ti4O15 Bi-layered compounds using micro-Raman spectroscopy

    Science.gov (United States)

    Hao, H.; Liu, H. X.; Cao, M. H.; Min, X. M.; Ouyang, S. X.

    2006-10-01

    The temperature-dependent Raman spectra of Mg- and La-doped SrBi4Ti4O15 (SBT) were studied in the range 40 590 °C. A quantum chemistry calculation was employed to estimate these two substitution states. It was found that A-site doping in this study not only caused multiplicative substitution states, but also the Raman spectra changed with the substitution amount. In a La-doped perovskite-like layer, La would occupy the Bi site when x>0.10 and the 314 and 550 cm-1 modes related to the rotating and tilting of the TiO6 octahedron firstly became wide and then became sharp. With the increase of the substitution amount, both substitution states of Mg-doped SBT lead to the widening of 270 and 520 cm-1 peaks.

  5. Al2O3 doped TiO2 ceramic waste forms

    International Nuclear Information System (INIS)

    Uno, Masayoshi; Kinoshita, Hajime; Sakai, Etsuro; Ikeda, Akira; Matsumoto, Y.; Yamanaka, Shinsuke

    1999-01-01

    Melting of the mixture of Nd 2 O 3 , CeO 2 , SrO, TiO 2 and Al 2 O 3 at 1673 K for 1 hour produced one RE 2 Ti 3 O 9 phase compound. Differential Scanning Calorimetry (DSC) measurement showed that the melting temperature of this compound was 1646 K. Density of the alumina doped oxide was higher than that of the oxide obtained by the pressing and sintering without alumina. Vickers hardness of the oxide obtained by the pressing and sintering was 5.3 GPa and nearly same as that of glass waste. That of the alumina doped oxide was around 7 GPa. 7 days Soxhlet leach test (MCC-5) followed by Inductively Coupled Plasma Spectrometry (ICP) showed that normalized leaching rate of Ti for the oxide obtained by the pressing and sintering was 5.54 x 10 -3 kg/m 2 and that for the alumina doped oxide was 2.24 x 10 -3 kg/m 2 . The value of Sr for the pressed and sintered sample was 0.034 x 10 -3 kg/m 2 but that for alumina doped sample was below the detection limit (0.01 x 10 -3 kg/m 2 ). Al was not detected from the leachate of the alumina doped sample. (author)

  6. Amorphous-crystalline transition in thermoelectric NbO2

    International Nuclear Information System (INIS)

    Music, Denis; Chen, Yen-Ting; Bliem, Pascal; Geyer, Richard W

    2015-01-01

    Density functional theory was employed to design enhanced amorphous NbO 2 thermoelectrics. The covalent-ionic nature of Nb–O bonding is identical in amorphous NbO 2 and its crystalline counterpart. However, the Anderson localisation occurs in amorphous NbO 2 , which may affect the transport properties. We calculate a multifold increase in the absolute Seebeck coefficient for the amorphous state. These predictions were critically appraised by measuring the Seebeck coefficient of sputtered amorphous and crystalline NbO 2 thin films with the identical short-range order. The first-order phase transition occurs at approximately 550 °C, but amorphous NbO 2 possesses enhanced transport properties at all temperatures. Amorphous NbO 2 , reaching  −173 μV K −1 , exhibits up to a 29% larger absolute Seebeck coefficient value, thereby validating the predictions. (paper)

  7. Effect of the doping on the energy of direct and indirect optical gap of KSr2Nb5O15 nanopowders

    International Nuclear Information System (INIS)

    Lanfredi, S.; Silva, G.D.; Genova, D.H.M.; Bellucci, F.S.; Constantino, C.J.L.; Nobre, M.A.L.

    2009-01-01

    Lead-free ferroelectric oxides with tetragonal tungsten bronze TTB type structure have exhibited several applications in recent piezoelectric/dielectric technologies. In TTB niobates, the cationic specie and its distribution exhibit strong influence on the electrical and optical proprieties. Solid solution development from transition-metals cations doping occurs on the niobium site allowing an intrinsic-ferro electricity modulation. In this work, the effect of the concentration of nickel cations on the semiconductor properties of KSr 2 Nb 5 O 15 nanoparticles was investigated by invisible spectroscopy via gap energy determination. Single phase and nanocrystalline powders of KSr 2 NixNb 5 -xO 15 -σ with x = 0.75 and 1 was prepared by high energy ball milling. Powders were characterized by x-ray diffraction. Increase in temperature of calcination leads to decreasing of the gap energy. The influence of concentration of Ni 3+ in the semiconductor character of KSr 2 NixNb 5 -xO 15 -σ is discussed based on the thermal evolution of structural parameters. (author)

  8. The role of the Mg2+ ions in Cr3+ spectroscopy for near-stoichiometric LiNbO3 crystals

    International Nuclear Information System (INIS)

    Han, T P J; Jaque, F; Bermudez, V; Dieguez, E

    2003-01-01

    The optical spectroscopy of Cr 3+ ions doped into near-stoichiometric LiNbO 3 crystals, pure and co-doped with MgO, has been investigated. In the near-stoichiometric LiNbO 3 :Cr(0.2 mol%):Mg(2 mol%) crystal, the optical spectra resemble those previously observed for congruent LiNbO 3 :Cr:MgO samples when the total MgO content exceeds the 4.6 mol% threshold. The coexistence of two types of Cr 3+ centre ([Cr] Li and [Cr] Nb ) characterized the optical and luminescence spectra of this sample. The concentration equilibrium between the two types of centre is strongly displaced towards the [Cr 3+ ] Nb centre, permitting us to obtain with accuracy the parameters of the broad bands. The R-line associated with the [Cr] Nb centre is only observable in the low-temperature emission spectrum. The Fano anti-resonance lines present have been observed to be more pronounced for the near-stoichiometric samples than for congruent ones

  9. An ultrasonic therapeutic transducers using lead-free Na0.5K0.5NbO3-CuNb2O6 ceramics

    International Nuclear Information System (INIS)

    Yang, Ming-Ru; Chu, Sheng-Yuan; Tsai, Cheng-Che

    2010-01-01

    Research highlights: → In this paper, CN was added to NKN ceramics to decrease the sintering temperature and to improve the density and piezoelectric characteristics. The influence of CuNb 2 O 6 (CN) content on the microstructure, electrical properties, temperature stability, and mechanical properties of the synthesized samples was investigated. Results show that the samples synthesized with CN-doped not only improved the density but also exhibited superior piezoelectric characteristic, temperature stability of resonance frequency (TCF), and elastic stiffness coefficient than those of pure NKN piezoelectric ceramics. → The bulk density (4.47 g/cm 3 ), k p (40%), k t (45%), Q m (1642), C 33 D (19.64 x 10 10 N/m 2 ), TCF (-0.011%/ o C) and TCC (0.135%/ o C) values for NKN-01CN ceramics obtained from experiments show excellent 'hard' piezoelectric properties. Furthermore, a lead-free NKN-01CN ultrasonic therapeutic transducer was successfully driven by a self-tuning circuit. - Abstract: In this work, we reports on the CuNb 2 O 6 (CN) modified lead-free Na 0.5 K 0.5 NbO 3 (NKN) based piezoelectric ceramics were synthesized by solid-state reaction methods and sintered at 1075 o C for 3 h. A secondary phase of K 4 CuNb 8 O 23 was found in the XRD pattern of NKN-based ceramics as the CN dopants is 1 mol%. Microstructural analyses of un-doped and CN-doped ceramics were performed in a scanning electron microscope. The influence of CN content on the microstructure, electrical properties, temperature stability, and mechanical properties of the synthesized ceramics was investigated. The results show that the synthesized ceramics with CN-doped not only had improved density but also exhibited superior piezoelectric characteristics, temperature stability of resonance frequency (TCF), and a better elastic stiffness coefficient than those of pure NKN piezoelectric ceramics. The bulk density (4.47 g/cm 3 ), k p (40%), k t (45%), Q m (1642), C 33 D (19.64 x 10 10 N/m 2 ), TCF (-0

  10. Synthesis of Nb doped TiO2 nanotube/reduced graphene oxide heterostructure photocatalyst with high visible light photocatalytic activity

    Science.gov (United States)

    Niu, Xiaoyou; Yan, Weijing; Zhao, Hongli; Yang, Jingkai

    2018-05-01

    Limited by the narrowed photoresponse range and unsatisfactory recombination of photoinduced electron-hole pairs, the photocatalytic efficiency of TiO2 is still far below what is expected. Here, we initially doped TiO2 nanotubes (TNTS) by transition metal ion Nb, then it is coupled with reduced graphene oxide (rGO) to construct a heterostructure photocatalyst. The defect state presented in TiO2 leading to the formation of localized midgap states (MS) in the bandgap, which regulating the band structure of TiO2 and extending the optical absorption to visible light region. The internal charge transport and transfer behavior analyzed by electrochemical impedance spectroscopy (EIS) reveal that the coupling of rGO with TNTS results in the formation of electron transport channel in the heterostructure, which makes a great contribution to the photoinduced charge separation. As expected, the Nb-TNTS/rGO exhibits a stable and remarkably enhanced photocatalytic activity in the visible-light irradiation degradation of methylene blue (MB), up to ∼5 times with respect to TNTS, which is attributed to the effective inhibition of charge recombination, the reduction of bandgap and higher redox potential, as well as the great adsorptivity.

  11. Integration of SrBi2Ta2O9 thin films for high density ferroelectric random access memory

    Science.gov (United States)

    Wouters, D. J.; Maes, D.; Goux, L.; Lisoni, J. G.; Paraschiv, V.; Johnson, J. A.; Schwitters, M.; Everaert, J.-L.; Boullart, W.; Schaekers, M.; Willegems, M.; Vander Meeren, H.; Haspeslagh, L.; Artoni, C.; Caputa, C.; Casella, P.; Corallo, G.; Russo, G.; Zambrano, R.; Monchoix, H.; Vecchio, G.; Van Autryve, L.

    2006-09-01

    Ferroelectric random access memory (FeRAM) is an attractive candidate technology for embedded nonvolatile memory, especially in applications where low power and high program speed are important. Market introduction of high-density FeRAM is, however, lagging behind standard complementary metal-oxide semiconductor (CMOS) because of the difficult integration technology. This paper discusses the major integration issues for high-density FeRAM, based on SrBi2Ta2O9 (strontium bismuth tantalate or SBT), in relation to the fabrication of our stacked cell structure. We have worked in the previous years on the development of SBT-FeRAM integration technology, based on a so-called pseudo-three-dimensional (3D) cell, with a capacitor that can be scaled from quasi two-dimensional towards a true three-dimensional capacitor where the sidewalls will importantly contribute to the signal. In the first phase of our integration development, we integrated our FeRAM cell in a 0.35μm CMOS technology. In a second phase, then, possibility of scaling of our cell is demonstrated in 0.18μm technology. The excellent electrical and reliability properties of the small integrated ferroelectric capacitors prove the feasibility of the technology, while the verification of the potential 3D effect confirms the basic scaling potential of our concept beyond that of the single-mask capacitor. The paper outlines the different material and technological challenges, and working solutions are demonstrated. While some issues are specific to our own cell, many are applicable to different stacked FeRAM cell concepts, or will become more general concerns when more developments are moving into 3D structures.

  12. Effect of MnO doping on the structure, microstructure and electrical properties of the (K,Na,Li)(Nb,Ta,Sb)O3 lead-free piezoceramics

    International Nuclear Information System (INIS)

    Rubio-Marcos, F.; Marchet, P.; Vendrell, X.; Romero, J.J.; Remondiere, F.; Mestres, L.; Fernandez, J.F.

    2011-01-01

    Highlights: · MnO doping effects on structure and properties of (K,Na,Li)(Nb,Ta,Sb)O 3 piezoceramics. · The structure changes towards an orthorhombic symmetry for higher MnO concentrations. · High doping levels induce a tetragonal tungsten-bronze secondary phase. · Mn 2+ doping modifies the phase transition temperature and the piezoelectric properties. · Manganese doping increases the mechanical quality factor Q m . - Abstract: Mn 2+ -doped (K,Na,Li)(Nb,Ta,Sb)O 3 lead-free piezoelectric ceramics have been prepared by a conventional sintering technique. The effects of Mn 2+ doping on the phase structure, microstructure and ferro-piezoelectric properties of the ceramics have been evaluated. MnO doping modifies the (K,Na,Li)(Nb,Ta,Sb)O 3 structure, giving rise to the appearance of a TTB-like secondary phase and to changes on the orthorhombic to tetragonal phase transition temperature. The modification of this temperature induces a reduction of the piezoelectric constants, which is accompanied by an increase on the mechanical quality factor. Mn 2+ ions incorporate into the perovskite structure in different off ways depending on their concentration.

  13. Electrical properties of Sb and Cr-doped PbZrO3-PbTiO3-PbMg1/3Nb2/3O3 ceramics

    OpenAIRE

    Whatmore, Roger W.; Molter, O.; Shaw, Christopher P.

    2003-01-01

    The pyroelectric, dielectric and DC resistive properties of Sb and Cr-doped ceramics with a base composition of Pb(Mg1/3Nb2/3)0.025(Zr0.825Ti0.175)0.975O3 have been studied. Sb doping has been shown to produce a linear reduction in Curie temperature (TC=−22z+294 °C) with concentration (z) and to give an increase in pyroelectric coefficient from 250 to 310 μCm−2 K−1 for z increasing from 0 to 3 at.%. It also produces first a reduction and then an increase in both dielectric constant and loss, ...

  14. Synthesis and crystal structure of Mg{sub 0.5}NbO{sub 2}: An ion-exchange reaction with Mg{sup 2+} between trigonal [NbO{sub 2}]{sup -} layers

    Energy Technology Data Exchange (ETDEWEB)

    Miura, Akira, E-mail: amiura@yamanashi.ac.jp [Center for Crystal Science and Technology, University of Yamanashi (Japan); Takei, Takahiro; Kumada, Nobuhiro [Center for Crystal Science and Technology, University of Yamanashi (Japan)

    2013-01-15

    A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2} through a cation-exchange reaction with Mg{sup 2+} at 450-550 Degree-Sign C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO{sub 2}]{sup -} layers. It is proposed to be isostructural with LiNbO{sub 2} (space group; P6{sub 3}/mmc) with lattice parameters of a=2.9052(6) A, c=10.625(15) A. The lattice parameters and formation energy of Mg{sub 0.5}NbO{sub 2} crystallized in LiNbO{sub 2} form and other layered CaNb{sub 2}O{sub 4} one were calculated by density functional theory. - Graphical abstract: A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2} through a cation-exchange reaction with Mg{sup 2+} at 450-550 Degree-Sign C. It is isostructural with LiNbO{sub 2} with lattice parameters of a=2.9052(6) A, c=10.625(15) A. Mg{sup 2+} are described in spheres located between [NbO{sub 2}]{sup -} trigonal layers and its occupancy is 0.5. Highlights: Black-Right-Pointing-Pointer A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2}. Black-Right-Pointing-Pointer Cation-exchange reaction converted two monovalent Li{sup +} into one divalent Mg{sup 2+} at 450-550 Degree-Sign C. Black-Right-Pointing-Pointer Mg{sub 0.5}NbO{sub 2} was isostructural with LiNbO{sub 2} (space group; P6{sub 3}/mmc). Black-Right-Pointing-Pointer Its lattice parameters were a=2.9052(6) A and c=10.625(15) A. Black-Right-Pointing-Pointer Synthesized Mg{sub 0.5}NbO{sub 2} was calculated to be thermodynamically more favorable.

  15. Stress effects of the inter-level dielectric layer on the ferroelectric performance of integrated SrBi2Ta2O9 capacitors

    International Nuclear Information System (INIS)

    Hong, Suk-Kyoung; Yang, B.; Oh, Sang Hyun; Kang, Young Min; Kang, Nam Soo; Hwang, Cheol Seong; Kwon, Oh Seong

    2001-01-01

    The thermal stress effects of the inter-level dielectric (ILD) layer on the ferroelectric performance of integrated Pt/SrBi 2 Ta 2 O 9 (SBT)/Pt capacitors were investigated. Two different thin film materials, pure SiO 2 grown at 650 degree C and B- and P-doped SiO 2 grown at 400 degree C by chemical vapor deposition techniques, were tested as an ILD layer. The ILD layer encapsulated the SBT capacitor array. During high temperature thermal cycling (up to 800 degree C) after ILD deposition, which is used for both densifying the ILD and curing of the various damage imposed on the SBT capacitors, a large thermal stress occurred in the bottom Pt layer due to the thermal expansion mismatch between the various layers. In particular, the pure SiO 2 ILD layer between the capacitors did not allow thermal expansion of the Pt layers, which led to a large accumulation of compressive stress in the layer. This resulted in hillock formation in the bottom Pt layer and eventual capacitor failure. However, the B- and P-doped SiO 2 ILD layer contracted during thermal cycling by removing residual impurities, which allowed greater expansion of the Pt layer. Therefore, compressive stress accumulation did not occur and excellent ferroelectric properties were thus obtained from the integrated capacitor array. [copyright] 2001 American Institute of Physics

  16. Piezoelectric properties enhanced of Sr0.6(BiNa)0.2Bi2Nb2O9 ceramic by (LiCe) modification with charge neutrality

    International Nuclear Information System (INIS)

    Fang, Pinyang; Xi, Zengzhe; Long, Wei; Li, Xiaojuan; Li, Jin

    2013-01-01

    Graphical abstract: The oxygen vacancies were confirmed by the left figure. The role of oxygen vacancy on piezoelectric activities was obtained by comparing to the varieties of oxygen vacancy concentration and piezoelectric coefficient with (LiCe) modification. -- Highlights: • The Sr 0.6 (BiNa) 0.2 Bi 2 Nb 2 O 9 ceramic by (LiCe) modification with the charge neutrality was synthesized by the solid state reaction method. • The Curie temperature and piezoelectric coefficient were found to be T c ∼590 °C and d 33 ∼32 pC/N, respectively. • The mechanism of piezoelectric activities improved by (LiCe) modification was discussed. -- Abstract: Aurivillius-type ceramics, Sr 0.6−x (LiCe) x/2.5 (BiNa) 0.2 Bi 2 Nb 2 O 9 (SLCBNBNO) with the charge neutrality, were synthesized by using conventional solid-state processing. Phase analysis was performed by X-ray diffraction analyses (XRD) and Raman spectroscopy. Microstructural morphology was assessed by the scanning electron microscopy (SEM). Structural, dielectric, piezoelectric, ferroelectric, and electromechanical properties of the SLCBNBNO ceramics were investigated. Piezoelectric properties were significantly enhanced compared to Sr 0.6 (BiNa) 0.2 Bi 2 Nb 2 O 9 (SBNBN) ceramic and the maximum of piezoelectric coefficient d 33 of the SBNBN-LC6 ceramic was 32 pC/N with higher Curie temperature (T c ∼590 °C). In addition, mechanisms for the piezoelectric properties enhanced of the SBNBN-based ceramics were discussed

  17. Dielectric properties of the ternary TeO2/Nb2O5/ZnO glasses

    International Nuclear Information System (INIS)

    Ahmad, Mohamad M.; Yousef, El Sayed; Moustafa, El Sayed

    2006-01-01

    Glasses of the system TeO 2 /Nb 2 O 5 /ZnO containing different concentration of ZnO (ranging from 5 to 20 mol%) were prepared. The dielectric properties over wide ranges of frequencies and temperatures were investigated as a function of ZnO content by impedance spectroscopy measurements. The impedance spectra of the present glasses were modeled by appropriate equivalent circuit. The dielectric constant has a value of 66 for the 85TeO 2 /10Nb 2 O 5 /5ZnO glass, which is three times larger than that of pure TeO 2 glass and other binary, e.g. TeO 2 /ZnCl 2 , tellurite glassy systems. The results have been analyzed in light of varying NbO 6 octahedra and NbO 4 tetrahedra of niobium oxide as zinc oxide varies from 5 to 20 mol%. The relaxation properties of the investigated glasses are presented in the electric modulus formalism, where the relaxation time and the respective activation energy are determined

  18. Enhanced photorefractive properties in Hf, Ce and Cu co-doped LiNbO{sub 3} crystals for holographic application

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tao, E-mail: tzhang_hit02@yahoo.com [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China); Wang, Xin; Geng, Tao; Tong, Chengguo [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Kang, Chong [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China)

    2015-04-25

    Graphical abstract: Correlation spots of 200 holograms in a Hf, Ce and Cu co-doped LiNbO{sub 3}. - Highlights: • Several doped LiNbO{sub 3} crystals with various level of Hf doping were grown by Cz method. • IR peak shift is attributed to the complex defect change at different level of Hf. • Enhanced photorefractive properties have been got with higher Hf-doping level. • Reduced defect and increased photoconductivity are responsible for optical properties. • 200 holograms’ experiment is realized in a coherent volume 0.073 cm{sup 3}. - Abstract: Hf, Ce and Cu co-doped LiNbO{sub 3} crystals with various level of Hf doping were grown in air by a conventional Cz method. The infrared spectra were measured to discuss the defect structures and the mechanism of the absorption peak shift in these crystals. The light-induced scattering of the crystals was evaluated by the transmitted light method. The influence of the Hf-doping level on the photorefractive properties of Hf, Ce and Cu co-doped LiNbO{sub 3} crystals was studied via two-beam coupling. It is found that proper doping Hf is an efficient method to enhance the comprehensive photorefractive properties of the LiNbO{sub 3}. Using one of these crystals as medium, 200 holograms storage and correlation experiments based on angle fractal multiplexing have been realized in a coherent volume 0.073 cm{sup 3}. Moreover the diffraction efficiency is uniform and the storage density has reached 2.2 Gb/cm{sup 3}.

  19. Crystal growth, optical properties, and continuous-wave laser operation of Nd3+-doped CaNb2O6 crystal

    International Nuclear Information System (INIS)

    Cheng, Y; Xu, X D; Xiao, X D; Li, D Z; Zhao, C C; Zhou, S M; Xin, Z; Yang, X B; Xu, J

    2009-01-01

    Laser crystal Nd:CaNb 2 O 6 with excellent quality has been grown by Czochralski technique. The effective segregation coefficient of Nd 3+ was studied by X-ray fluorescence method. The polarized absorption spectra and the fluorescence spectra of Nd:CaNb 2 O 6 were measured at room temperature. The peak absorption cross section was calculated to be 6.202×10 -20 cm 2 with a broad FWHM of 7 nm at 808 nm for E ∥ a light polarization. The emission cross section at 1062 nm is 9.87×10 -20 cm 2 . We report what we believe to be the first demonstration of the continuous-wave Nd:CaNb 2 O 6 laser operation under diode pumping. Output power of 1.86 W at 1062 nm was obtained with a slope efficiency of 19% in the CW regime

  20. Crystal growth, optical properties, and continuous-wave laser operation of Nd3+-doped CaNb2O6 crystal

    Science.gov (United States)

    Cheng, Y.; Xu, X. D.; Xin, Z.; Yang, X. B.; Xiao, X. D.; Li, D. Z.; Zhao, C. C.; Xu, J.; Zhou, S. M.

    2009-10-01

    Laser crystal Nd:CaNb2O6 with excellent quality has been grown by Czochralski technique. The effective segregation coefficient of Nd3+ was studied by X-ray fluorescence method. The polarized absorption spectra and the fluorescence spectra of Nd:CaNb2O6 were measured at room temperature. The peak absorption cross section was calculated to be 6.202×10-20 cm2 with a broad FWHM of 7 nm at 808 nm for E ∥ a light polarization. The emission cross section at 1062 nm is 9.87×10-20 cm2. We report what we believe to be the first demonstration of the continuous-wave Nd:CaNb2O6 laser operation under diode pumping. Output power of 1.86 W at 1062 nm was obtained with a slope efficiency of 19% in the CW regime.

  1. Electronic parameters of Sr2Nb2O7 and chemical bonding

    DEFF Research Database (Denmark)

    Atuchin, V.V.; Grivel, Jean-Claude; Korotkov, A.S.

    2008-01-01

    /2)) and Delta(O-Sr) = BE(O 1s)-BE(Sr 3d(5/2)), were used to characterize the valence electron transfer on the formation of the Nb-O and Sr-O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and earlier published structural and XPS data for other Sr- or Nb...

  2. Neutron and X-ray study of stoichiometric and doped LiNbO3:Zn0.08

    International Nuclear Information System (INIS)

    Sulyanov, S.; Maximov, B.; Volk, T.; Boysen, H.; Schneider, J.; Rubinina, N.; Hansen, Th.

    2002-01-01

    LiNbO 3 (LN) crystals possess useful optical properties, which are strongly dependent on both the crystal stoichiometry and the content of dopants such as Mg 2+ , Zn 2+ , In 3+ , and Sc 3+ . Such elements drastically reduce photorefraction at a sufficiently high threshold concentration, which for Zn is in the range of 7-8 at. % and was supposed to be connected with the change of dopant-atom localisation in the lattice. We report the results of a single-crystal neutron study of stoichiometric, congruent, and doped (with 8.2 at. % Zn) LiNbO 3 at T=78 K and 298 K and also a multi-pattern powder neutron and X-ray Rietveld refinement of the doped material. Zn ions occupy both Li and Nb sites and there is no residual Nb on Li sites. LN single crystals are very perfect, and extinction problems are discussed. (orig.)

  3. B-site cation order/disorder and their valence states in Ba3MnNb2O9 perovskite oxide

    Science.gov (United States)

    Xin, Yan; Huang, Qing; Shafieizadeh, Zahra; Zhou, Haidong

    2018-06-01

    Polycrystalline samples Ba3MnNb2O9 synthesized by solid state reaction and single crystal samples grown by optical floating zone have been characterized using scanning transmission electron microscopy and electron energy loss spectroscopy. Three types of B-site Mn and Nb ordering phase are observed: fully ordered 1Mn:2Nb; fully disordered; nano-sized 1Mn:1Nb ordered. No electronic structure change for crystals with different ordering/disordering. The Mn valence is determined to be 2+, and Nb valence is 5+. Oxygen 2p orbitals hybridize with Mn 3d and Nb 4d orbitals. Factors that affect the electron energy loss near edge structures of transition metal white-lines in electron energy loss spectroscopy are explicitly illustrated and discussed.

  4. History-dependent thermal expansion in NbO{sub 2}F

    Energy Technology Data Exchange (ETDEWEB)

    Wilkinson, Angus P., E-mail: angus.wilkinson@chemistry.gatech.edu [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States); Josefsberg, Ryan E.; Gallington, Leighanne C.; Morelock, Cody R.; Monaco, Christopher M. [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States)

    2014-05-01

    Materials with cubic ReO{sub 3}-type structures are of interest for their low or negative thermal expansion characteristics. TaO{sub 2}F is known to display almost zero thermal expansion over a wide temperature range. On heating NbO{sub 2}F, its volume coefficient of thermal expansion decreases from ∼+45 ppm K{sup −1} at 100 K to almost zero at 400 K. NbO{sub 2}F is cubic between 100 and 500 K. Samples of “NbO{sub 2}F” prepared by the digestion of Nb{sub 2}O{sub 5} in aqueous HF followed by mild drying contain hydroxyl defects and metal vacancies. On heating, they can undergo irreversible chemical changes while maintaining a cubic ReO{sub 3}-type structure. The possibility of hydroxyl defect incorporation should be considered when preparing oxyfluorides for evaluation as battery materials. - Graphical abstract: “NbO{sub 2}F” prepared by the digestion of Nb{sub 2}O{sub 5} in HF contains cation vacancies and hydroxyl groups. It undergoes irreversible changes on heating to low temperatures, unlike NbO{sub 2}F prepared by the solid state reaction of Nb{sub 2}O{sub 5} and NbF{sub 5}. - Highlights: • The digestion of Nb{sub 2}O{sub 5} in aqueous HF followed by mild drying does not produce NbO{sub 2}F. • The ReO{sub 3}-type product from the HF digestion of Nb{sub 2}O{sub 5} contains metal vacancies and hydroxyl. • The thermal expansion coefficient of NbO{sub 2}F decreases on heating and approaches zero at ∼400 K.

  5. Nanocomposite dielectrics in PbO-BaO-Na2O-Nb2O5-SiO2 system with high breakdown strength for high voltage capacitor applications.

    Science.gov (United States)

    Zhang, Qingmeng; Luo, Jun; Tang, Qun; Han, Dongfang; Zhou, Yi; Du, Jun

    2012-11-01

    Nanocomposite dielectrics in 6PbO-4BaO-20Na2O-40Nb2O5-30SiO2 system were prepared via melt-quenching followed by controlled crystallization. X-ray diffraction studies reveal that Pb2Nb2O7, Ba,NaNb5O15, NaNbO3 and PbNb2O6 phases are formed from the as-quenched glass annealed in temperature range from 700 degrees C to 850 degrees C. Ba2NaNb5O15, Pb2Nb2O7 crystallizes at 700 degrees C and then Pb2Nb2O7 disappears at 850 degrees C, while PbNb2O6 and NaNbO3 are formed at 850 degrees C. Microstructural observation shows that the crystallized particles are nanometer-sized and randomly distributed with glass matrix being often found at grain boundaries. The dielectric constant of the nanocomposites formed at different crystallization temperatures shows good frequency and electric field stability. The breakdown strength is slightly decreased when the glass-ceramics thickness is varied from 1 mm to 4 mm. The corresponding energy density could reach 2.96 J/cm3 with a breakdown strength of 58 kV/mm for thickness of 1 mm.

  6. Anatase phase stability and doping concentration dependent refractivity in codoped transparent conducting TiO{sub 2} films

    Energy Technology Data Exchange (ETDEWEB)

    Chen, T L [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Furubayashi, Y [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Hirose, Y [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Hitosugi, T [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Shimada, T [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Hasegawa, T [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan)

    2007-10-07

    Nb{sub 0.06}Sn{sub x}Ti{sub 0.94-x}O{sub 2} (x {<=} 0.3) thin films were grown by a pulsed-laser deposition method with varying Sn concentration. Through a combinatorial technique, we find that Sn concentration can reach a maximum of about x = 0.3 while maintaining the stable anatase phase and epitaxy. A doping concentration dependence of the refractivity is revealed, in which refractivity reduction at a wavelength of {lambda} = 500 nm is estimated to be 12.4% for Nb{sub 0.06}Sn{sub 0.3} Ti{sub 0.64}O{sub 2} thin film. Sn doping induced band-gap blue shift can be contributed to the mixing of extended Sn 5s orbitals with the conduction band of TiO{sub 2}. Low resistivity on the order of 10{sup -4} {omega} cm at room temperature and high internal transmittance of more than 95% in the visible light region are exhibited for Nb{sub 0.06}Sn{sub x} Ti{sub 0.94-x}O{sub 2} thin films (x {<=} 0.2). Optical and transport analyses demonstrate that doping Sn into Nb{sub 0.06} Ti{sub 0.94}O{sub 2} can reduce the refractivity while maintaining low resistivity and high transparency.

  7. Non-stoichiometric disorder in α-Nb2O5 at elevated temperatures

    International Nuclear Information System (INIS)

    Balachandran, U.; Eror, N.G.

    1982-01-01

    The electrical conductivity of polycrystalline α-Nb 2 O 5 was determined for the oxygen partial pressure range of 10 0 to 10 -20 atm and temperature range 700 to 1150 0 C. The data were found to be proportional to the -1/6th power of the oxygen partial pressure for the oxygen pressure range 10 -20 to 10 -9 atm, and proportional to Psub(O 2 )sup(-1/4) for oxygen pressures greater than 10 -9 atm. The region of linearity where electrical conductivity varies as the -1/4th power of Psub(O 2 ) increased as the temperature was decreased. Thermogravimetric measurements were carried out in the temperature range 950 to 1250 0 C. The deviation from stoichiometry in α-Nb 2 O 5 (x in Nb 2 Osub(5-x)) as a function of partial pressure of oxygen showed two distinct regions, namely a region with an approximately -1/6th dependence on Psub(O 2 ) and a region where the deviation was nearly independent of oxygen partial pressure. The electrical conductivity and thermogravimetric data are consistent with the presence of small amounts of acceptor impurities in α-Nb 2 O 5 . (author)

  8. A study on the superconducting properties of YBa{sub 2}Cu{sub 9-x}Nb{sub x}O{sup y} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, S.; Bhatnagar, A.K. [Univ. of Hyderabad (India); Pinto, R. [Solid State Electronics Group, Bombay (India)] [and others

    1994-12-31

    Effect of niobium substitution at the copper site in YBa{sub 2}Cu{sub 9}O{sub 7-x} was studied in thin film form. The films were deposited by laser ablation technique using the targets of the YBa{sub 2}Cu{sub 3-x}Nb{sub x}O{sub y} where x = 0.0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8 and 1.0 under identical deposition conditions on SrTiO{sub 9} <100> substrates. Films were characterized by XRD, resistivity, I-V and J{sub c} measurements. Films made from x = 0.025 and 0.05 concentrations of Nb substituted targets showed relatively improved superconducting properties compared to that of undoped films. The best 7 realized for x = 0.025 Nb concentration was 1.8 x 10{sup {sigma}} A/cm{sup 2} and for 0.05 Nb concentration it was 3.2x10{sup {sigma}} A/cm{sup 2} at 77K. However, degradation of the superconducting properties, with the increase of x {ge} 0.1 Nb concentration and drastic suppression and complete loss of superconductivity was noticed for x {ge} 0.4. The growth of impurity phase YBa{sub 2}NbO{sub 6} for x = 0.1 and above of Nb concentration was noticed from XRD patterns. However, the site occupancy of Nb could not be confirmed from these studies.

  9. Influence of Nb content on the structural and optical properties of anatase TiO{sub 2} polycrystalline thin film by e-beam technique

    Energy Technology Data Exchange (ETDEWEB)

    Shah, A., E-mail: attaullah77@yahoo.com; Mahmood, Arshad; Aziz, Uzma; Rashid, Rashad; Raza, Qaiser; Ali, Zahid

    2016-09-01

    In this paper, we report the structural and optical properties of Nb-doped TiO{sub 2} thin films deposited by e-beam evaporation technique. After post annealing in air at 500 °C for 1 h, the samples were characterized by various techniques such as X-ray diffraction (XRD), Raman spectroscopy, UV–Vis spectrophotometry and spectroscopic Ellipsometer. Both XRD and Raman analyses indicate that the films were crystallized into the polycrystalline anatase TiO{sub 2} structure. However it was observed that the crystallinity of the films decreases with the addition of Nb atoms and tends to become amorphous at 20% Nb content in TiO{sub 2} film. Moreover, no new phases such as Nb{sub 2}O{sub 5}, NbO{sub 2} or Nb metal were observed. The band gap energy was found to decrease with the increasing of Nb concentration which was verified by ellipsometric study. Ellipsomtric measurements also indicate that refractive index (n) of the films decreases while extinction coefficient (k) increases with the increasing of Nb content. All these analyses elucidate that the incorporation of Nb atom into TiO{sub 2} may tune the structural and optical properties of TiO{sub 2} thin films. - Highlights: • The addition of Nb into TiO{sub 2} film has strongly influenced its physical properties. • Anatase polycrystalline Nb:TiO{sub 2} films were grown up to 15% Nb content. • The film becomes an amorphous at 20% Nb doping. • Band gap energy of TiO{sub 2} film was decreased with increasing of Nb content in the film. • The Optical constants (n, k) of Nb:TiO{sub 2} film were varied as a function of Nb content.

  10. Effect of MnO doping on the structure, microstructure and electrical properties of the (K,Na,Li)(Nb,Ta,Sb)O{sub 3} lead-free piezoceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rubio-Marcos, F., E-mail: fernando.rubio-marcos@unilim.fr [Laboratoire de Science des Procedes Ceramiques et de Traitements de Surface, UMR 6638 CNRS, Universite de Limoges, Centre Europeen de la Ceramique, 12, rue Atlantis, 87068 Limoges Cedex (France); Marchet, P. [Laboratoire de Science des Procedes Ceramiques et de Traitements de Surface, UMR 6638 CNRS, Universite de Limoges, Centre Europeen de la Ceramique, 12, rue Atlantis, 87068 Limoges Cedex (France); Vendrell, X. [Grup de Quimica de l' Estat Solid, Departament de Quimica Inorganica, Universitat de Barcelona, 08028 Barcelona (Spain); Romero, J.J. [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Remondiere, F. [Laboratoire de Science des Procedes Ceramiques et de Traitements de Surface, UMR 6638 CNRS, Universite de Limoges, Centre Europeen de la Ceramique, 12, rue Atlantis, 87068 Limoges Cedex (France); Mestres, L. [Grup de Quimica de l' Estat Solid, Departament de Quimica Inorganica, Universitat de Barcelona, 08028 Barcelona (Spain); Fernandez, J.F. [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain)

    2011-09-01

    Highlights: {center_dot} MnO doping effects on structure and properties of (K,Na,Li)(Nb,Ta,Sb)O{sub 3} piezoceramics. {center_dot} The structure changes towards an orthorhombic symmetry for higher MnO concentrations. {center_dot} High doping levels induce a tetragonal tungsten-bronze secondary phase. {center_dot} Mn{sup 2+} doping modifies the phase transition temperature and the piezoelectric properties. {center_dot} Manganese doping increases the mechanical quality factor Q{sub m}. - Abstract: Mn{sup 2+}-doped (K,Na,Li)(Nb,Ta,Sb)O{sub 3} lead-free piezoelectric ceramics have been prepared by a conventional sintering technique. The effects of Mn{sup 2+} doping on the phase structure, microstructure and ferro-piezoelectric properties of the ceramics have been evaluated. MnO doping modifies the (K,Na,Li)(Nb,Ta,Sb)O{sub 3} structure, giving rise to the appearance of a TTB-like secondary phase and to changes on the orthorhombic to tetragonal phase transition temperature. The modification of this temperature induces a reduction of the piezoelectric constants, which is accompanied by an increase on the mechanical quality factor. Mn{sup 2+} ions incorporate into the perovskite structure in different off ways depending on their concentration.

  11. Influence of different substrates on the ionic conduction in LiCoO{sub 2}/LiNbO{sub 3} thin-film bi-layers

    Energy Technology Data Exchange (ETDEWEB)

    Horopanitis, E.E.; Perentzis, G.; Papadimitriou, L. [Aristotle University of Thessaloniki, Department of Physics, Section of Solid State Physics, Thessaloniki (Greece)

    2008-07-01

    LiNbO{sub 3} thin films, deposited by e-gun evaporation, show lithium deficiency, which is cured by ''Li doping''. The ''Li doping'' of the films was achieved by preparing a structure of Li-Nb-O/Li/Li-Nb-O, which after annealing forms a homogenized LiNbO{sub 3} layer because of diffusion of Li in the two Li-Nb-O layers. The LiCoO{sub 2}/LiNbO{sub 3} bi-layers were prepared either on Stainless Steel/TiN or on Al{sub 2}O{sub 3}/Co/Pt substrates/ohmic-contacts by depositing first either the cathode LiCoO{sub 2} or the electrolyte LiNbO{sub 3}. The Nyquist plots of the AC impedance measurements of all structures showed that the interfaces prepared on Stainless-Steel/TiN consisted of two semicircles. The structures deposited on Al{sub 2}O{sub 3}/Co/Pt showed a third semicircle, which is probably due to the roughness of the substrate. It is important that the ionic properties of the bi-layers with the cathode material deposited first, a usual structure in a microbattery, are improved compared to the other structures. The quality of the LiNbO{sub 3} layer depends very much on the substrate. It can be evaluated from Arrhenius plots that the activation energy of this layer is considerably lower when the whole structure is deposited on Stainless Steel/TiN. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Enhancement of Dielectric Breakdown Strength and Energy Conversion Efficiency of Niobate Glass-Ceramics by Sc2O3 Doping

    Science.gov (United States)

    Xiao, Shi; Xiu, Shaomei; Yang, Ke; Shen, Bo; Zhai, Jiwei

    2018-01-01

    Niobate glass-ceramics K2O-SrO-Nb2O5-B2O3-Al2O3-SiO2 (KSN-BAS) doped with different amounts of Sc2O3 have been prepared through a melt quenching/controlled crystallization method, and the influence of the Sc2O3 content on their phase composition, microstructure, dielectric performance, and charge-discharge properties investigated. X-ray powder diffraction results showed that the peak positions of the KSr2Nb5O15 phase shifted to higher angle and the glass-ceramic microstructures were significantly improved by Sc2O3 addition. Based on these results, 0.5 mol.% Sc2O3 doping was found to achieve remarkable enhancement in energy storage density, which reached 9.63 ± 0.39 J/cm3 at dielectric breakdown strength of 1450.38 ± 29.01 kV/cm with high conversion efficiency of ˜ 92.1%. For pulsed power applications, discharge speed of 17 ns and power density of 0.48 MW/cm3 were obtained in the glass-ceramic with 0.5 mol.% Sc2O3. These results could provide a new design strategy for high-performance dielectric capacitors.

  13. Investigations on Raman and X-ray photoemission scattering patterns of vanadium-doped SrBi4Ti4O15 ferroelectric ceramics

    International Nuclear Information System (INIS)

    Zhu, Jun; Chen, Xiao-Bing; He, Jun-hui; Shen, Jian-Cang

    2007-01-01

    Vanadium incorporation in SrBi 4 Ti 4 O 15 results in an improvement of electric properties. Raman scattering reveals that V-addition brings about the local disorders of structure, charge, and internal stress. The chemical valence of Bi and Ti does not increase after V-doping. The electric property improvement is originated from the restraint of oxygen vacancies, mobility weakening of the defects, and the vacancies produced at A-site

  14. Transparent Conducting Nb-Doped TiO2 Electrodes Activated by Laser Annealing for Inexpensive Flexible Organic Solar Cells

    Science.gov (United States)

    Lee, Jung-Hsiang; Lin, Chia-Chi; Lin, Yi-Chang

    2012-01-01

    A KrF excimer laser (λ= 248 nm) has been adopted for annealing cost-effective Nb-doped TiO2 (NTO) films. Sputtered NTO layers were annealed on SiO2-coated flexible poly(ethylene terephthalate) (PET) substrates. This local laser annealing technique is very useful for the formation of anatase NTO electrodes used in flexible organic solar cells (OSCs). An amorphous NTO film with a high resistivity and a low transparency was transformed significantly into a conductive and transparent anatase NTO electrode by laser irradiation. The 210 nm anatase NTO film shows a sheet resistance of 50 Ω and an average optical transmittance of 83.5% in the wavelength range from 450 to 600 nm after annealing at 0.25 J/cm2. The activation of Nb dopants and the formation of the anatase phase contribute to the high conductivity of the laser-annealed NTO electrode. Nb activation causes an increase in the optical band gap due to the Burstein-Moss effect. The electrical properties are in agreement with the material characteristics determined by X-ray diffraction (XRD) analysis and secondary ion mass spectrometry (SIMS). The irradiation energy for the NTO electrode also affects the performance of the organic solar cell. The laser annealing technique provides good properties of the anatase NTO film used as a transparent electrode for flexible organic solar cells (OSCs) without damage to the PET substrate or layer delamination from the substrate.

  15. Enhanced magnetic and ferroelectric properties in scandium doped nano Bi{sub 2}Fe{sub 4}O{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Dimple P., E-mail: dimpled@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Sudakar, C.; Mocherla, Pavana S.V. [Department of Physics, IIT Madras, Chennai 600 036 (India); Mandal, Balaji P.; Jayakumar, Onnatu D. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Tyagi, Avesh K., E-mail: aktyagi@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2012-08-15

    In this study we report the synthesis of undoped and Sc{sup 3+} doped Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles using sonochemical technique. X-ray diffraction reveals that all samples are single phase with no impurities detected. EDS analysis was done to confirm the extent of Sc{sup 3+} doping in the samples. The size and morphology of the nanoparticles have been analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles show a weak ferromagnetic behavior at room temperature, which is quite different from the linear M-H relationship reported for bulk Bi{sub 2}Fe{sub 4}O{sub 9}. A magnetization of 0.144 {mu}B/f.u. is obtained at 300 K, which is mainly attributed to the uncompensated moments at the disordered particle surface resulting from the reduced coordination of the surface spins, arising due to lattice strain or oxygen deficiency. Addition of Sc{sup 3+} dopant in varying concentrations in these Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles, improves their magnetic as well as ferroelectric properties. The leakage current is considerably reduced and electric polarization increases significantly in case of Bi{sub 2}Fe{sub 4(1-x)}Sc{sub x}O{sub 9} (x = 0.1) nanoparticles. Thus it can be inferred that Sc{sup 3+} doped Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles shows promise as good multiferroic materials. -- Graphical abstract: Undoped and Sc{sup 3+} doped Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles have been synthesized using sonochemical technique. The bi-functionalities of Sc{sup 3+} doped Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles have been demonstrated. The Bi{sub 2}Fe{sub 4(1-x)}Sc{sub x}O{sub 9} (x = 0.1) nanoparticles showed enhanced magnetic and ferroelectric properties with considerably less lossy characteristics compared to the bulk Bi{sub 2}Fe{sub 4}O{sub 9}. Highlights: Black-Right-Pointing-Pointer Phase pure Bi{sub 2}Fe{sub 4}O{sub 9} nanostructures synthesized using a facile

  16. Nb and Pd co-doped La0.57Sr0.38Co0.19Fe0.665Nb0.095Pd0.05O3-δ as a stable, high performance electrode for barrier-layer-free Y2O3-ZrO2 electrolyte of solid oxide fuel cells

    Science.gov (United States)

    Chen, Kongfa; He, Shuai; Li, Na; Cheng, Yi; Ai, Na; Chen, Minle; Rickard, William D. A.; Zhang, Teng; Jiang, San Ping

    2018-02-01

    La0.6Sr0.2Co0.2Fe0.8O3-δ (LSCF) is the most intensively investigated high performance cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs), but strontium segregation and migration at the electrode/electrolyte interface is a critical issue limiting the electrocatalytic activity and stability of LSCF based cathodes. Herein, we report a Nb and Pd co-doped LSCF (La0.57Sr0.38Co0.19Fe0.665Nb0.095Pd0.05O3-δ, LSCFNPd) perovskite as stable and active cathode on a barrier-layer-free anode-supported yttria-stabilized zirconia (YSZ) electrolyte cell using direct assembly method without pre-sintering at high temperatures. The cell exhibits a peak power density of 1.3 W cm-2 at 750 °C and excellent stability with no degradation during polarization at 500 mA cm-2 and 750 °C for 175 h. Microscopic and spectroscopic analysis show that the electrochemical polarization promotes the formation of electrode/electrolyte interface in operando and exsolution of Pd/PdO nanoparticles. The Nb doping in the B-site of LSCF significantly reduces the Sr surface segregation, enhancing the stability of the cathode, while the exsoluted Pd/PdO nanoparticles increases the electrocatalytic activity for the oxygen reduction reaction. The present study opens up a new route for the development of cobaltite-based perovskite cathodes with high activity and stability for barrier-layer-free YSZ electrolyte based IT-SOFCs.

  17. Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO2: recovery of high conductivity

    International Nuclear Information System (INIS)

    Nakao, Shoichiro; Hirose, Yasushi; Hasegawa, Tetsuya

    2016-01-01

    We studied the effects of reductive annealing on insulating polycrystalline thin films of anatase Nb-doped TiO 2 (TNO). The insulating TNO films were intentionally fabricated by annealing conductive TNO films in oxygen ambient at 400 °C. Reduced free carrier absorption in the insulating TNO films indicated carrier compensation due to excess oxygen. With H 2 -annealing, both carrier density and Hall mobility recovered to the level of conducting TNO, demonstrating that the excess oxygen can be efficiently removed by the annealing process without introducing additional scattering centers. (paper)

  18. Crystal structures and electronic properties of UTixNb3-xO10 (x=0,1/3,1) and of the intercalation compound Li0.9UTiNb2O10

    International Nuclear Information System (INIS)

    Dickens, P.G.; Flynn, G.J.; Patat, S.; Stuttart, G.P.

    1997-01-01

    Complete crystal structures of the related phases UTi x Nb 3-x O 10 (x=0,1/3,1) and of the intercalation compound Li 0.9 UTiNb 2 O 10 have been determined by Rietveld analysis of room-temperature powder neutron diffraction data. The new structural data combined with magnetic susceptibility measurements made in the range 5 y 1 U V 1+y-x U VI x-y Ti IV x Nb V 3-x O 10 (y≤ x ≤1) with U V (f 1 ) being the only paramagnetic species present. (Author)

  19. A combined diffraction and dielectric properties investigation of Ba3MnNb2O9 complex perovskites

    International Nuclear Information System (INIS)

    Liu Yun; Withers, Ray L.; Whichello, A.P.; Noren, Lasse; Ting, Valeska; Brink, Frank; Fitz Gerald, John D.

    2005-01-01

    A combined synthesis, diffraction and dielectric properties investigation of the dependence (and effect) of Mn 2+ /Nb 5+ ordering in Ba 3 MnNb 2 O 9 (BMN) upon annealing atmosphere and processing conditions has been carried out. Annealing in different atmospheres was not found to significantly alter either nominal stoichiometry or structure type. The obtained structure type (disordered metrically cubic or ordered trigonal) as well as the measured electrical properties (in particular, the dielectric loss) were, however, found to be sensitive to the synthesis route. Samples obtained via solid-state reaction were found to be predominantly of 1:2 Mn 2+ /Nb 5+ ordered, P3-bar m1 trigonal structure type whereas samples obtained via an aqueous solution route were found to be of a Mn 2+ /Nb 5+ 'disordered', metrically cubic structure type. All solid-state synthesized samples showed reasonable dielectric properties. The microwave dielectric constant and dielectric quality factor, Q, at 8GHz of an as-synthesized BMN sample were 38 and 100, respectively. By contrast, the dielectric loss of the metrically cubic, Mn 2+ /Nb 5+ 'disordered' samples obtained via an aqueous solution synthesis process were significantly worse

  20. Performance evaluation of Mn and Fe doped SrCo0.9Nb0.1O3-δ cathode for IT-SOFC application

    Science.gov (United States)

    Bele, Lokesh; Lenka, R. K.; Patro, P. K.; Muhmood, L.; Mahata, T.; Sinha, P. K.

    2018-02-01

    Cathode materials of Mn and Fe doped SrCo0.9Nb0.1O3-δ, are synthesized by solid state route for intermediate temperature fuel cell applications. Phase pure material is obtained after calcining the precursors at 1100 °C. Phase compatibility is observed between this novel cathode material with gadolinia doped ceria (GDC) electrolyte material as reflected in the diffraction pattern. The state of art YSZ electrolyte is not compatible with this cathode material. Average thermal expansion coefficient of the material varies between 17 to 22 X 10-6 K-1 on doping, from room temperature to 800 °C. Increase in thermal expansion coefficient is observed with Mn and Fe doping associated with the loss of oxygen from the crystal. The electrical conductivity of the cathode material decreases with Fe and Mn doping. Mn doped samples show lowest conductivity. From the symmetric cell measurement lower area specific resistance (0.16 Ω-cm2) is obtained for un-doped samples, at 850 °C. From the initial results it can be inferred that Mn/Fe doping improves neither the thermal expansion co-efficient nor the electrochemical activity.

  1. Performance-Microstructure Relations in Ni/CGO Infiltrated Nb-doped SrTiO3 SOFC Anodes

    DEFF Research Database (Denmark)

    Ramos, Tania; Bernuy-Lopez, Carlos; Reddy Sudireddy, Bhaskar

    2012-01-01

    Nb-doped SrTiO3 solid oxide fuel cell (SOFC) anodes, infiltrated with CGO/Ni, were investigated by electrochemical impedance spectroscopy (EIS) and high resolution microscopy techniques, upon varying production and testing parameters. The electrochemical analysis involved a combination of distrib......Nb-doped SrTiO3 solid oxide fuel cell (SOFC) anodes, infiltrated with CGO/Ni, were investigated by electrochemical impedance spectroscopy (EIS) and high resolution microscopy techniques, upon varying production and testing parameters. The electrochemical analysis involved a combination...... of distribution of relaxation times (DRT) and complex non-linear least squares (CNLS) fitting routine. These electrodes were studied as singlephase or as composites with 8YSZ. Sr0.94Ti0.9Nb0.1O3-δ/ 10 vol.% 8YSZ composite infiltrated electrodes were the best overall performers, with enhanced performance stability...

  2. Phase relations, crystal structure, and phase transformation of In_1_−_xNb_1_−_xTi_2_xO_4 (0 ≤ x < 0.45) in In_2O_3–Nb_2O_5–TiO_2 system

    International Nuclear Information System (INIS)

    Su, Liumei; Fan, Xing; Cai, Gemei; Liu, Huashan; Jin, Zhanpeng

    2015-01-01

    Phase relations, crystal structures, and phase transformation of In_1_−_xNb_1_−_xTi_2_xO_4 (0 ≤ x < 0.45) in In_2O_3–Nb_2O_5–TiO_2 ternary system were investigated for the first time. A number of samples with different compositions were prepared by a solid-state reaction method, and phase assembles were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe micro-analysis (EPMA). Five three-phase regions, ten two-phase regions, and six single-phase solid solutions were determined in this system. The solid solution of In_1_−_xNb_1_−_xTi_2_xO_4 (0 ≤ x < 0.45) is composed of both ordered monoclinic wolframite-type structure (0 ≤ x < 0.35) and disordered orthorhombic α-PbO_2 type structure (0.35 < x < 0.45). Driving force for composition-driven phase transformation in In_1_−_xNb_1_−_xTi_2_xO_4 (0 ≤ x < 0.45) stems from the ordering of cations. The ever reported compound InNbTiO_6 with an orthorhombic α-PbO_2 type structure was amended to be a monoclinic wolframite-type structure. Present investigations will be useful for the whole ceramic community working with In_2O_3–Nb_2O_5–TiO_2 ternary system as well as for the development of functional materials. - Highlights: • Phase relations of In_2O_3–Nb_2O_5–TiO_2 ternary system were constructed. • Crystal structures of a novel solid solution In_1_−_xNb_1_−_xTi_2_xO_4 were determined. • Crystal structure of InNbTiO_6 was amended to be a wolframite-type structure. • Composition-driven phase transformation of In_1_−_xNb_1_−_xTi_2_xO_4 was investigated.

  3. Major enhancement of the thermoelectric performance in Pr/Nb-doped SrTiO3 under strain

    KAUST Repository

    Amin, B.

    2013-07-16

    The electronic structure and thermoelectric properties of strained (biaxially and uniaxially) Sr0.95Pr0.05TiO3 and SrTi0.95Nb0.05O3 are investigated in the temperature range from 300 K to 1200 K. Substitutions of Pr at the Sr site and Nb at the Ti site generate n-type doping and thus improve the thermoelectric performance as compared to pristine SrTiO3. Further enhancement is achieved by the application of strain, for example, of the Seebeck coefficient by 21% for Sr0.95Pr0.05TiO3 and 10% for SrTi0.95Nb0.05O3 at room temperature in the case of 5% biaxial strain. At 1200 K, we predict figures of merit of 0.58 and 0.55 for 2.5% biaxially strained Sr0.95Pr0.05TiO3 and SrTi0.95Nb0.05O3 , respectively, which are the highest values reported for rare earth doped SrTiO3.

  4. Single-Crystal X-Ray Diffraction Studies of Homologues in the Series nBa(Nb,Zr)O 3+3 mNbO with n=2, 3, 4, 5 and m=1

    Science.gov (United States)

    Nilsson, G.; Svensson, G.

    2001-01-01

    Single crystals of four homologues in the series nBa(Nb,Zr)O3+3mNbO, with n:m=2:1, 3:1, 4:1, and 5:1, were found in the reduced Ba-Nb-Zr-O system. Single-crystal X-ray diffraction data were collected for all the crystals. For all homologues the space group was found to be P4/mmm. The structures can be described as intergrowths of Ba(Nb,Zr)O3 perovskite and NbO slabs. The refined cell parameters and compositions of the 2:1, 3:1, and 4:1 homologues are a=4.1768(5) Å and c=12.269(2) Å for Ba2Nb4.5(1)Zr0.5(1)O9, a=4.1769(5) Å and c=16.493(3) Å for Ba3+δNb4.8(2)-δ Zr1.2(2)O12-δ (δ=0.098(4)), and a=4.1747(6) Å and c= 20.619(4) Å for Ba4+δNb5.1(4)-δZr1.9(4)O15-δ (δ=0.270(9)). The refined cell parameters of the 5:1 homologue are a=4.1727(3) Å and c=24.804(3) Å. Zr replaces Nb only in the NbO6 octahedra found in the perovskite slabs.

  5. Spectroscopic investigations of nanostructured LiNbO3 doped with Eu3+

    International Nuclear Information System (INIS)

    Hreniak, D.; Speghini, A.; Bettinelli, M.; Strek, W.

    2006-01-01

    Structural and optical properties of the sol-gel derived nanocrystalline lithium niobate (LiNbO 3 ) powders doped with Eu 3+ ions have been studied. In particular, the influence of the sizes of nanoparticles controlled by temperature on the structural and luminescence properties has been investigated. Emission bands corresponding to 5 D emission became more resolved with increasing nanocrystal size and changed to a typical Eu 3+ :LiNbO 3 single crystal spectrum for nanocrystals having an average size of more than 40 nm. Nonlinear optical properties of nanostructured LiNbO 3 have been confirmed by simple observation of second harmonic generation effect (SHG). The possibility of using nanostructured LiNbO 3 doped with rare-earth ions as self-doubling elements in integrated optoelectronic devices has been discussed

  6. Unusual broadening of the NIR luminescence of Er{sup 3+}-doped Nb{sub 2}O{sub 5} nanocrystals embedded in silica host: Preparation and their structural and spectroscopic study for photonics applications

    Energy Technology Data Exchange (ETDEWEB)

    Aquino, Felipe Thomaz; Pereira, Rafael R. [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, CEP 14040-901 Ribeirão Preto, SP (Brazil); Ferrari, Jefferson Luis [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, CEP 14040-901 Ribeirão Preto, SP (Brazil); Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, 36301-160 São João Del Rei, MG (Brazil); Ribeiro, Sidney José Lima [Laboratório de Materiais Fotônicos, Instituto de Química, UNESP, Caixa Postal 355, 14801-970 Araraquara, SP (Brazil); Ferrier, Alban; Goldner, Philippe [Chimie-Paristech, Laboratoire de Chimie de la Matière Condensée de Paris, CNRS-UMR 7574, UPMC Univ Paris 06, 11 Rue Pierre et Marie Curie, 75005 Paris (France); and others

    2014-10-15

    This paper reports on the preparation of novel sol-gel erbium-doped SiO{sub 2}-based nanocomposites embedded with Nb{sub 2}O{sub 5} nanocrystals fabricated using a bottom-up method and describes their structural, morphological, and luminescence characterization. To prepare the glass ceramics, we synthesized xerogels containing Si/Nb molar ratios of 90:10 up to 50:50 at room temperature, followed by annealing at 900, 1000, or 1100 °C for 10 h. We identified crystallization accompanying host densification in all the nanocomposites with orthorhombic (T-phase) or monoclinic (M-phase) Nb{sub 2}O{sub 5} nanocrystals dispersed in the amorphous SiO{sub 2} phase, depending on the niobium content and annealing temperature. A high-intensity broadband emission in the near-infrared region assigned to the {sup 4}I{sub 13/2} → {sup 4}I{sub 15/2} transition of the Er{sup 3+} ions was registered for all the nanocomposites. The shape and the bandwidth changed with the Nb{sub 2}O{sub 5} crystalline phase, with values achieving up to 81 nm. Er{sup 3+} ions were located mainly in Nb{sub 2}O{sub 5}-rich regions, and the complex structure of the different Nb{sub 2}O{sub 5} polymorphs accounted for the broadening in the emission spectra. The materials containing the T-phase, displayed higher luminescence intensity, longer {sup 4}I{sub 13/2} lifetime and broader bandwidth. In conclusion, these nanostructured materials are potential candidates for photonic applications like optical amplifiers and WDM devices operating in the S, C, and L telecommunication bands. - Highlights: • Rare earth doped Nb{sub 2}O{sub 5} nanocrystals prepared from a bottom-up approach. • Unusual broadband NIR emission in glass ceramic system. • Structural features tuning the luminescence properties. • Potential as optical amplifiers and WDM devices. • Photonic devices operating in the S, C, and L telecommunication.

  7. Structural and ferroelectric properties of Sr1−xBaxBi2Nb2O9 thin films obtained by dip-coating

    Directory of Open Access Journals (Sweden)

    Y. González-Abreu

    2017-10-01

    Full Text Available The paper presents the structural and ferroelectric results for Sr1−xBaxBi2Nb2O9(x=0.30; 0.85 thin films, which were obtained by using dip-coating. The solutions containing the desirable ions were prepared from the powders of the previous studied ceramic samples. The films were deposited at room temperature on Fluorine-doped Tin Oxide (FTO substrates and submitted to a heat treatment for crystallization. The films were characterized by using scanning microscopy electronic, energy dispersive spectroscopy and ellipsometry. Hysteresis ferroelectric loops were obtained, at room temperature, by using a Sawyer-Tower circuit at several frequencies. A well-defined grain structure was observed for both compositions. The energy dispersive spectroscopy (EDS measurements revealed the presence of the corresponding elements from the chemical composition of the ceramic systems. The band-gap energy was around 3.3eV for both samples. Typical hysteresis loops for normal and relaxor ferroelectrics were obtained for x=0.30 and 0.85, respectively.

  8. Pt-doped In{sub 2}O{sub 3} nanoparticles prepared by flame spray pyrolysis for NO{sub 2} sensing

    Energy Technology Data Exchange (ETDEWEB)

    Inyawilert, K. [Chiang Mai University, Department of Physics and Materials Science, Faculty of Science (Thailand); Channei, D. [Naresuan University, Department of Chemistry, Faculty of Science (Thailand); Tamaekong, N. [Maejo University, Program in Materials Science, Faculty of Science (Thailand); Liewhiran, C. [Chiang Mai University, Department of Physics and Materials Science, Faculty of Science (Thailand); Wisitsoraat, A.; Tuantranont, A. [National Electronics and Computer Technology Center (NECTEC), Nanoelectronics and MEMS Laboratory (Thailand); Phanichphant, S., E-mail: sphanichphant@gmail.com [Chiang Mai University, Faculty of Science, Materials Science Research Center (Thailand)

    2016-02-15

    Undoped In{sub 2}O{sub 3} and 0.25–1.00 wt% M (M=Pt, Nb, and Ru)-doped/loaded In{sub 2}O{sub 3} nanoparticles were successfully synthesized in a single-step flame spray pyrolysis technique using indium nitrate, platinum (II) acetylacetonate, niobium ethoxide, and ruthenium (III) acetylacetonate precursors. The undoped In{sub 2}O{sub 3} and M-doped In{sub 2}O{sub 3} nanoparticles were characterized by Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM & TEM). The BET average diameter of spherical nanoparticles was found to be in the range of 10.2–15.2 nm under 5/5 (precursor/oxygen) flame conditions. All XRD peaks were confirmed to correspond to the cubic structure of In{sub 2}O{sub 3}. TEM images showed that there is no Pt nanoparticle loaded on In{sub 2}O{sub 3} surface, suggesting that Pt should form solid solution with the In{sub 2}O{sub 3} lattice. Gas sensing studies showed that 0.5 wt% Pt doping in In{sub 2}O{sub 3} nanoparticles gave a significant enhancement of NO{sub 2} sensing performances in terms of sensor response and selectivity. 0.5 wt% Pt/In{sub 2}O{sub 3} exhibited a high NO{sub 2} response of ∼1904 to 5 ppm NO{sub 2} at 250 °C and good NO{sub 2} selectivity against NO, H{sub 2}S, H{sub 2}, and C{sub 2}H{sub 5}OH. In contrast, Nb and Ru loading resulted in deteriorated NO{sub 2} response. Therefore, Pt is demonstrated to be an effective additive to enhance NO{sub 2} sensing performances of In{sub 2}O{sub 3}-based sensors.

  9. Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

    Science.gov (United States)

    Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

    2016-02-01

    This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

  10. Rotational Symmetry Breaking in a Trigonal Superconductor Nb-doped Bi_{2}Se_{3}

    Directory of Open Access Journals (Sweden)

    Tomoya Asaba

    2017-01-01

    Full Text Available The search for unconventional superconductivity has been focused on materials with strong spin-orbit coupling and unique crystal lattices. Doped bismuth selenide (Bi_{2}Se_{3} is a strong candidate, given the topological insulator nature of the parent compound and its triangular lattice. The coupling between the physical properties in the superconducting state and its underlying crystal symmetry is a crucial test for unconventional superconductivity. In this paper, we report direct evidence that the superconducting magnetic response couples strongly to the underlying trigonal crystal symmetry in the recently discovered superconductor with trigonal crystal structure, niobium (Nb-doped Bi_{2}Se_{3}. As a result, the in-plane magnetic torque signal vanishes every 60°. More importantly, the superconducting hysteresis loop amplitude is enhanced along one preferred direction, spontaneously breaking the rotational symmetry. This observation indicates the presence of nematic order in the superconducting ground state of Nb-doped Bi_{2}Se_{3}.

  11. Nb-doped rutile TiO₂: a potential anode material for Na-ion battery.

    Science.gov (United States)

    Usui, Hiroyuki; Yoshioka, Sho; Wasada, Kuniaki; Shimizu, Masahiro; Sakaguchi, Hiroki

    2015-04-01

    The electrochemical properties of the rutile-type TiO2 and Nb-doped TiO2 were investigated for the first time as Na-ion battery anodes. Ti(1-x)Nb(x)O2 thick-film electrodes without a binder and a conductive additive were prepared using a sol-gel method followed by a gas-deposition method. The TiO2 electrode showed reversible reactions of Na insertion/extraction accompanied by expansion/contraction of the TiO2 lattice. Among the Ti(1-x)Nb(x)O2 electrodes with x = 0-0.18, the Ti(0.94)Nb(0.06)O2 electrode exhibited the best cycling performance, with a reversible capacity of 160 mA h g(-1) at the 50th cycle. As the Li-ion battery anode, this electrode also attained an excellent rate capability, with a capacity of 120 mA h g(-1) even at the high current density of 16.75 A g(-1) (50C). The improvements in the performances are attributed to a 3 orders of magnitude higher electronic conductivity of Ti(0.94)Nb(0.06)O2 compared to that of TiO2. This offers the possibility of Nb-doped rutile TiO2 as a Na-ion battery anode as well as a Li-ion battery anode.

  12. Structure of TeO2 - LiNbO3 glasses

    Science.gov (United States)

    Shinde, A. B.; Krishna, P. S. R.; Rao, Rekha

    2017-05-01

    Tellurite based lithium niobate glasses with composition (100-x)TeO2-xLiNbO3 (x=0.1,0.2 & 0.3) were prepared by conventional melt quenching method. The microscopic structural investigation of these glasses is carried out by means of neutron diffraction and Raman scattering measurements. It is found that the basic structural units in these glasses are TeO4 trigonal bipyramids(TBP), TeO3 trigonal pyramids(TP) and NbO6 Octahedra depending on the composition. It is evident from Raman studies that TBPs decreases, TPs increases and NbO6 Octahedra increases with increasing x. From Neutron diffraction studies it is found that network is comprised of TBPs and TPs along with TeO3+1 structural units. Distorted NbO6 octahedral units are present and also increase with the increase in x.

  13. Irradiation-induced amorphization of Cd2Nb2O7 pyrochlore

    International Nuclear Information System (INIS)

    Meldrum, A.; White, C. W.; Keppens, V.; Boatner, L. A.; Ewing, R. C.

    2001-01-01

    Several investigations have recently been undertaken in order to achieve a more complete understanding of the radiation-damage mechanisms in A 2 B 2 O 7 pyrochlore-structure compounds. The present work represents the first systematic study of the irradiation-induced amorphization of a pyrochlore with A- and B-site cation valences of +2 and +5, respectively. Relatively large single crystals of Cd 2 Nb 2 O 7 were grown for these experiments. In situ ion-irradiation experiments were carried out in a transmission electron microscope in conjunction with ex situ Rutherford backscattering measurements of ion-irradiated Cd 2 Nb 2 O 7 single crystals. Cd 2 Nb 2 O 7 can be amorphized in situ by Ne or Xe ions at temperatures up to 480 and 620 K, respectively. At room temperature, the amorphization fluence was 36 times higher for 280 keV Ne + than for 1200 keV Xe 2+ , corresponding to a displacement dose that was higher by a factor of 3. Disordering of Cd and Nb over the available cation sites occurs at intermediate ion doses prior to amorphization. The temperature dependence of the amorphization dose is modeled, and the results are compared to those of a previous model. The bulk-sample Rutherford backscattering spectroscopy (RBS) results were generally consistent with the in situ TEM measurements. Effects of crystallographic orientation and ion charge state had relatively little effect on the damage accumulation in bulk crystals. The RBS data are consistent with a defect-accumulation, cascade-overlap model of amorphization of Cd 2 Nb 2 O 7 , as are the in situ TEM observations

  14. Raman, dielectric and variable range hopping nature of Gd2O3-doped K0.5N0.5NbO3 piezoelectric ceramics

    Directory of Open Access Journals (Sweden)

    Mahesh Peddigari

    2015-10-01

    Full Text Available (K0.5Na0.5NbO3 (KNN + x wt% Gd2O3 (x = 0 -1.5 ceramics have been prepared by conventional solid state reaction method. The effect of Gd2O3 on the structural, microstructural and dielectric properties of KNN ceramics were studied systematically. The effect of Gd2O3 on phase transformation from orthorhombic to psuedocubic structure is explained interms of changes in the internal vibration modes of NbO6 octahedra. The Raman intensity of the stretching mode v1 enhanced and shifted toward higher wavenumber with Gd2O3 concentration, which is attributed to the increase in polarizability and change in the O-Nb-O bond angles. Microstructural analysis revealed that the grain size of the KNN ceramics decreases from 2.26 ± 1.07 μm to 0.35 ± 0.13 μm and becomes homogenous with an increase in Gd2O3 concentration. The frequency dependent dielectric spectra are analyzed by using Havriliak-Negami function. The fitted symmetry parameter and relaxation time (τ are found to be 0.914 and 8.78 × 10−10 ± 5.5 × 10−11 s, respectively for the sample doped with x = 1.0. The addition of Gd2O3 to the KNN shifted the polymorphic phase transition orthorhombic to tetragonal transition temperature (TO-T from 199oC to 85oC with enhanced dielectric permittivity (ε′ = 1139 at 1 MHz. The sample with x = 1.0, shown a high dielectric permittivity (ε′ = 879 and low dielectric loss (<5% in the broad temperature range (-140oC – 150oC with the Curie temperature 307 oC can have the potential for high temperature piezoelectric and tunable RF circuit applications. The temperature dependent AC-conductivity follows the variable range hopping conduction mechanism by obtaining the slope -0.25 from the ln[ln(ρac] versus ln(T graph in the temperature range of 133 K-308 K. The effect of Gd2O3 on the Mott’s parameters such as density of states (N(EF, hopping length (RH, and hopping energy (WH have been discussed.

  15. Preparation of orthophosphate glasses in the MgO-CaO-SiO2-Nb2O5-P2O5 system.

    Science.gov (United States)

    Lee, Sungho; Ueda, Kyosuke; Narushima, Takayuki; Nakano, Takayoshi; Kasuga, Toshihiro

    2017-01-01

    Niobia/magnesia-containing orthophosphate invert glasses were successfully prepared in our earlier work. Orthophosphate groups in the glasses were cross-linked by tetrahedral niobia (NbO4) and magnesia. The aim of this work is to prepare calcium orthophosphate invert glasses containing magnesia and niobia, incorporating silica, and to evaluate their structures and releasing behaviors. The glasses were prepared by melt-quenching, and their structures and ion-releasing behaviors were evaluated. 31P solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies showed the glasses consist of orthophosphate (PO4), orthosilicate (SiO4), and NbO4 tetrahedra. NbO4 and MgO in the glasses act as network formers. By incorporating SiO2 into the glasses, the chemical durability of the glasses was slightly improved. The glasses reheated at 800°C formed the orthophosphate crystalline phases, such as β-Ca3(PO4)2, Mg3(PO4)2 and Mg3Ca3(PO4)4 in the glasses. The chemical durability of the crystallized glasses was slightly improved. Orthosilicate groups and NbO4 in the glasses coordinated with each other to form Si-O-Nb bonds. The chemical durability of the glasses was slightly improved by addition of SiO2, since the field strength of Si is larger than that of Ca or Mg.

  16. Photoluminescence properties of Eu2+-activated Ca2Y2Si2O9 phosphor

    NARCIS (Netherlands)

    Zhang, Zhijun; Delsing, A.C.A.; Notten, P.H.L.; Zhao, Jingtai; Hintzen, H.T.J.M.

    2012-01-01

    Eu2+-activated Ca2Y2Si2O9 phosphors with different Eu2+ concentrations have been prepared by a solid-state reaction method at high temperature and their photoluminescence (PL) properties were investigated. Photoluminescence results show that Eu2+-doped Ca2Y2Si2O9 can be efficiently excited by

  17. Study of SBN films for dynamic memory devices

    International Nuclear Information System (INIS)

    Tulegulov, A.D.; Kuketaev, T.A.

    2006-01-01

    The analysis happens to in this work, was got on a concrete sample of the type Si-SnO 2 -SBN-Cr (sample 290787). The thickness SBN is ∼0.8 micron. SBN synthesized by frequency 13 MHz of HF-generator. In accordance with got results are made some findings and are determined dependencies to capacities and conductivities from frequency. (author)

  18. Thickness and Nb-doping effects on ferro- and piezoelectric properties of highly a-axis-oriented Nb-doped Pb(Zr0.3Ti0.7)O3 films

    Science.gov (United States)

    Zhu, Zhi-Xiang; Ruangchalermwong, C.; Li, Jing-Feng

    2008-09-01

    Tetragonal Nb-doped Pb(Zr0.3Ti0.7)O3 (PNZT) films with a lead oxide seeding layer were deposited on the Pt(111)/Ti/SiO2/Si(100) substrates by sol-gel processing. The as-grown PNZT films with thicknesses ranging from about 0.08 to 0.78 μm show highly a-axis preferential orientation, and their ferroelectric and piezoelectric properties improved with increasing film thickness. Due to the combined effects of Nb doping and a-axis texturing as well as reduced substrate constraint, a high d33 constant up to 196 pm/V was obtained for PNZT film at 0.78 μm in addition to a large remnant polarization of 69 μC/cm2. This well a-axis-oriented PNZT films on platinized Si with a high piezoresponse are suitable for the fabrication of microelectromechanical devices.

  19. Near-surface effects of transient oxidation and reduction on Nb-doped SrTiO3 epitaxial thin films

    Science.gov (United States)

    Chang, C. F.; Chen, Q. Y.; Wadekar, P. V.; Lozano, O.; Wong, M. S.; Hsieh, W. C.; Lin, W. Y.; Ko, H. H.; Lin, Q. J.; Huang, H. C.; Ho, N. J.; Tu, L. W.; Liao, H. H.; Chinta, P. V.; Chu, W. K.; Seo, H. W.

    2014-03-01

    We studied the effects of transient oxidation and reduction of Nb-doped epitaxial thin films through variations of PAr and PO2. The samples were prepared by co-sputtering of Nb and SrTiO3 on LaAlO3 substrates. The Nb-content were varied from 0-33.7%, as determined by PIXE. Contact resistance, sheet resistance, and optical properties are used to discriminate the effects.

  20. The effect of low platinum loading on the efficiency of PEMFC’s electrocatalysts supported on TiO2Nb, and SnO2Nb: An experimental comparison between active and stable conditions

    International Nuclear Information System (INIS)

    Shahgaldi, Samaneh; Hamelin, Jean

    2015-01-01

    Highlights: • SnO 2Nb, and TiO 2Nb thin films synthesized via sputtering. • SnO 2Nb, and TiO 2Nb thin films applied as a Pt support in PEMFC. • Low amount of Pt sputtered on supports as catalyst in cathode side. • Fabricate a single cell and plot I–V curves. - Abstract: Electrocatalyst supports have been demonstrated to strongly influence the cost, performance and durability of PEMFC systems, which have been among the heated research topics in the course of the past decades. However, the present support materials used in fuel cell stack are not adequately durable for commercialization. Development of active electrocatalyst with cost effectiveness and high durability is one of the main challenges. In this paper, titania and tin oxide nanoparticles doped nobidium were selected as thermo chemically stable and carbonless electrocatalyst supports. Low Pt loading (0.05 mg/cm 2 ) is deposited on supports through sputtering method, and the structure, the distribution of nanoparticles, and the electrical resistivity were systematically analyzed. To make the studies of oxygen reduction reaction activity, catalytic stability and performance of PEMFC more precise, rotation disk electrode (RDE), cyclic voltammetry (CV), and single cell test were utilized. The data analysis of this study highlighted that SnO 2 –Nb–Pt depicted higher stability and better fuel cell performance in comparison with TiO 2 –Nb–Pt

  1. Compounds of the type Ba/sub 3/Bsup(II)M/sub 2/sup(V)O/sub 9/ with Bsup(II) = Mg, Ca, Sr, Ba, and Msup(V) = Nb, Ta

    Energy Technology Data Exchange (ETDEWEB)

    Kemmler-Sack, S; Thumm, I; Herrmann, M [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

    1981-08-01

    The hexagonal perovskites Ba/sub 3/Bsup(II)M/sub 2/sup(V)O/sub 9/ (Msup(V) = Nb, Ta) crystallize with Bsup(II) = Mg, Ca in a 3 L structure (sequence (c)/sub 3/) and Bsup(II) = Sr in the hexagonal BaTiO/sub 3/ type (6 L; sequence (hcc)/sub 2/) with an 1:2 order for the B and M ions. Intensity calculations for Ba/sub 3/SrNb/sub 2/O/sub 9/ and Ba/sub 3/SrTa/sub 2/O/sub 9/ gave in the space group P6/sub 3//mmc a refined, intensity related R' value of 8.4% (Nb) and 9.0% (Ta) respectively. For Bsup(II) = Ba the perovskite Ba/sub 3/BaTa/sub 2/O/sub 9/ has an orthorhombic distorted 6 L structure and forms with Ba/sub 3/SrTa/sub 2/O/sub 9/ a continuous series of mixed crystals (Ba/sub 3/Srsub(1-x)Basub(x)Ta/sub 2/O/sub 9/). In the system Ba/sub 3/Srsub(1-x)Basub(x)Nb/sub 2/O/sub 9/ the range of existence of the hexagonal BaTiO/sub 3/ type is confined to the Sr richer end. The pure Ba compound posesses a proper structure type (5 L: Ba/sub 5/BaNb/sub 3/vacantOsub(13.5)vacantsub(1.5)).

  2. Effects of additives on the sintering of UO2.Gd2O3 nuclear fuel

    International Nuclear Information System (INIS)

    Pagano Junior, Luciano

    2009-01-01

    The addition of 0.5wt% TiO 2 , Nb 2 O 5 , SiO 2 , Fe 2 O 3 and Al(OH) 3 in the UO 2 ·7%Gd 2 O 3 nuclear fuel and the effect on its sintering kinetics under a 99.999% H 2 atmosphere were investigated by stepwise isothermal dilatometry. This fuel, used as burnable poison in nuclear power plants, presents a diffusion barrier around 1573 K that impairs densification. The aid of the sintering additives TiO 2 , Al(OH) 3 , Nb 2 O 5 and Fe 2 O 3 turned out to be effective to obtain the required final density, unlike the effect observed for the SiO 2 -doped composition. The activation energy for the intermediate sintering stage was calculated by stepwise isothermal dilatometry method and a positive correlation with the sintered body density was found. The method was valid for part of the intermediate sintering stage, in the range from 1200 K to 1700 K for the doped compositions and with no additive, except for the SiO 2 -doped one, whose validity range was between 1500 K and 1900 K. The energy-density correlation was not valid for the SiO 2 -doped composition, whose effect was to reduce the final density. This anomalous behavior may be attributed to the intense loss of Si mass, probably due to lower oxides volatilization, during the initial sintering stage at temperatures lower than 1173 K. Similar loss, but no so intense, was observed for the Al(OH) 3 -doped composition in the temperature interval from 1173 K to 1573 K. The Si concentration decrease to residual values of dozens of parts per million may explain its anomalous behavior. The positive correlation between activation energy and sintered body density may be explained by the inhibitor role played by the TiO 2 , Nb 2 O 5 , Fe 2 O 3 and Al(OH) 3 additives on the diffusion mechanisms that enhance the coarsening regime. As a consequence, the densification mechanisms are favored in the competition for the surface free energy. The coarsening-densification transition temperature model, originally suggested for the UO 2

  3. Effects of Sb-doping on the formation of (K, Na)(Nb, Sb)O3 solid solution under hydrothermal conditions

    International Nuclear Information System (INIS)

    Su Likui; Zhu Kongjun; Bai Lin; Qiu Jinhao; Ji Hongli

    2010-01-01

    (K, Na)(Nb, Sb)O 3 (KNNS) lead-free peizoceramic powders were successfully synthesized by hydrothermal treatment at 240 o C for 8 h using the KOH, NaOH, Nb 2 O 5 and Sb 2 O 3 as raw materials. Effects of Sb-doping on the crystal structure and morphology of the as-prepared powders were investigated by powder X-ray diffraction (XRD), Raman spectra (Raman), scanning electron microscope (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The Sb element was successfully doped into the alkaline niobate perovskite structure to form crystalline (K 0.7 Na 0.3 )(Nb 0.95 Sb 0.05 )O 3 lead-free piezoelectric ceramic powder, which has a hexagonal morphology due to the aggregation growth of small grains. Phase and morphology evolutions with the reaction time were also studied, and a possible formation mechanism was proposed.

  4. Intense 2.7 µm emission and structural origin in Er3+-doped bismuthate (Bi2O3-GeO2-Ga2O3-Na2O) glass.

    Science.gov (United States)

    Guo, Yanyan; Li, Ming; Hu, Lili; Zhang, Junjie

    2012-01-15

    The 2.7 μm emission properties in Er3+-doped bismuthate (Bi2O3-GeO2-Ga2O3-Na2O) glass were investigated in the present Letter. An intense 2.7 μm emission in Er3+-doped bismuthate glass was observed. It is found that Er3+-doped bismuthate glass possesses high spontaneous transition probability A (65.26 s(-1)) and large 2.7 μm emission cross section σ(em) (9.53×10(-21) cm2) corresponding to the stimulated emission of Er3+:4I11/2→4I13/2 transition. The emission characteristic and energy transfer process upon excitation of a conventional 980 nm laser diode in bismuthate glass were analyzed. Additionally, the structure of bismuthate glass was analyzed by the Raman spectrum. The advantageous spectroscopic characteristics of Er3+ single-doped bismuthate glass together with the prominent thermal property indicate that bismuthate glass might become an attractive host for developing solid-state lasers around 2.7 μm.

  5. Correlation of infrared spectra and phase transitions in annealed proton-exchanged MgO doped LiNbO3

    International Nuclear Information System (INIS)

    Sun, Jian; Xu, Chang-qing

    2015-01-01

    Infrared spectra of OH − groups in annealed proton-exchanged (APE) 5 mol. % MgO-doped LiNbO 3 (MgO:LiNbO 3 ) crystals were studied using the Fourier transform infrared spectroscopy technique. Samples were prepared by benzoic acid proton-exchange followed with thermal annealing in oxygen. Evolutions of absorption peaks in APE MgO:LiNbO 3 crystals were recorded and analyzed. Comparing with none-doped APE LiNbO 3 crystals, a different phase transition behavior was found during thermal annealing. A periodically poled MgO:LiNbO 3 slab waveguide was prepared using identical procedures, and the second harmonic generation (SHG) signals were measured. Comparing the obtained SHG results with the infrared spectra, relationships between the phase transitions and the recovery of second-order nonlinear coefficients during thermal annealing were investigated. Finally, a method for optimizing the performance of MgO:LiNbO 3 waveguides was proposed

  6. Synthesis and photocatalytic activity of hydrated layered perovskite K2-xLa2Ti3-xNb xO10 (0 ≤ x ≤ 1) and protonated derivatives

    International Nuclear Information System (INIS)

    Huang Yunfang; Wu Jihuai; Wei Yuelin; Hao Sancun; Huang Miaoliang; Lin Jianming

    2007-01-01

    A series of photocatalytic intercalated materials K 2-x La 2 Ti 3-x Nb x O 10 (0 ≤ x ≤ 1) and a series of its protonated derivatives H 2-x La 2 Ti 3-x Nb x O 10 were prepared by solid-state reaction and ion-exchange reaction. The photocatalytic activities of samples were evaluated using methanol as electron donor under UV irradiation. All H 2-x La 2 Ti 3-x Nb x O 10 samples possessed approximately twofold higher photocatalytic activity than the corresponding K 2-x La 2 Ti 3-x Nb x O 10 . This difference was most pronounced for the photocatalyst H 1.9 La 2 Ti 2.9 Nb 0.1 O 10 which showed the highest activity: 22 μmol H 2 /catalyst (g) for 5 h, more than three times the activity of K 1.9 La 2 Ti 2.9 Nb 0.1 O 10

  7. IR emission and electrical conductivity of Nd/Nb-codoped TiO{sub x} (1.5 < x < 2) thin films grown by pulsed-laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tchiffo-Tameko, C.; Cachoncinlle, C. [GREMI, UMR 7344 CNRS-Université Orléans, 45067 Orléans Cedex 2 (France); Perriere, J. [Sorbonne Universités, UPMC Université Paris 06, UMR 7588, INSP, 75005 Paris (France); CNRS, UMR 7588, INSP, 75005 Paris (France); Nistor, M. [NILPRP, L 22 P.O. Box MG-36, 77125 Bucharest-Magurele (Romania); Petit, A.; Aubry, O. [GREMI, UMR 7344 CNRS-Université Orléans, 45067 Orléans Cedex 2 (France); Pérez Casero, R. [Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Millon, E., E-mail: eric.millon@univ-orleans.fr [GREMI, UMR 7344 CNRS-Université Orléans, 45067 Orléans Cedex 2 (France)

    2016-12-15

    Highlights: • Nd/Nb-codoped TiO{sub 2} PLD films are electrically insulating and transparent in the UV visible NIR spectral domain. • Nd/Nb-codoped oxygen deficient TiO{sub x} (x ≈ 1.5) films are conductive and absorbent. • IR emission of Nd{sup 3+} in codoped TiO{sub x} films is quenched due to oxygen deficiency. • High Nb-doping rate decreases the IR emission of Nd{sup 3+} in Nd/Nb-codoped TiO{sub 2} films. - Abstract: The effect of the co-doping with Nd and Nb on electrical and optical properties of TiO{sub x} films is reported. The role of oxygen vacancies on the physical properties is also evidenced. The films are grown by pulsed-laser deposition onto (001) sapphire and (100) silicon substrates. The substrate temperature was fixed at 700 °C. To obtain either stoichiometric (TiO{sub 2}) or highly oxygen deficient (TiO{sub x} with x < 1.6) thin films, the oxygen partial pressure was adjusted at 10{sup −1} and 10{sup −6} mbar, respectively. 1%Nd-1%Nb, 1%Nd-5%Nb and 5%Nd-1%Nb co-doped TiO{sub 2} were used as bulk ceramic target. Composition, structural and morphological properties of films determined by Rutherford backscattering spectroscopy, X-ray diffraction and scanning electron microscopy, are correlated to their optical (UV–vis transmission and photoluminescence) and electrical properties (resistivity at room temperature). The most intense Nd{sup 3+} emission in the IR domain is obtained for stoichiometric films. Codoping Nd-TiO{sub x} films by Nb{sup 5+} ions is found to decrease the photoluminescence efficiency. The oxygen pressure during the growth allows to tune the optical and electrical properties: insulating and highly transparent (80% in the visible range) Nd/Nb codoped TiO{sub 2} films are obtained at high oxygen pressure, while conductive and absorbent films are grown under low oxygen pressure (10{sup −6} mbar).

  8. Solid Phase Equilibrium Relations in the CaO-SiO2-Nb2O5-La2O3 System at 1273 K

    Science.gov (United States)

    Qiu, Jiyu; Liu, Chengjun

    2018-02-01

    Silicate slag system with additions Nb and RE formed in the utilization of REE-Nb-Fe ore deposit resources in China has industrial uses as a metallurgical slag system. The lack of a phase diagram, theoretical, and thermodynamic information for the multi-component system restrict the comprehensive utilization process. In the current work, solid phase equilibrium relations in the CaO-SiO2-Nb2O5-La2O3 quaternary system at 1273 K (1000 °C) were investigated experimentally by the high-temperature equilibrium experiment followed by X-ray diffraction, scanning electron microscope, and energy dispersive spectrometer. Six spatial independent tetrahedron fields in the CaO-SiO2-Nb2O5-La2O3 system phase diagram were determined by the Gibbs Phase Rule. The current work combines the mass fraction of equilibrium phase and corresponding geometric relation. A determinant method was deduced to calculate the mass fraction of equilibrium phase in quaternary system according to the Mass Conservation Law, the Gibbs Phase Rule, the Lever's Rule, and the Cramer Law.

  9. Note: High-power piezoelectric transformer fabricated with ternary relaxor ferroelectric Pb(Mg(1/3)Nb(2/3))O3-Pb(In(1/2)Nb(1/2))O3-PbTiO3 single crystal.

    Science.gov (United States)

    Wang, Qing; Ma, Chuanguo; Wang, Feifei; Liu, Bao; Chen, Jianwei; Luo, Haosu; Wang, Tao; Shi, Wangzhou

    2016-03-01

    A plate-shaped piezoelectric transformer was designed and fabricated using ternary relaxor ferroelectric single crystal Pb(Mg(1/3)Nb(2/3))O3-Pb(In(1/2)Nb(1/2))O3-PbTiO3. Both the input and output sections utilized the transverse-extensional vibration mode. The frequency and load dependences of the electrical properties for the proposed transformer were systematically studied. Results indicated that under a matching load resistance of 14.9 kΩ, a maximum output power of 2.56 W was obtained with the temperature rise less than 5 °C. The corresponding power density reached up to 50 W/cm(3). This ternary single-crystal transformer had potential applications in compact-size converters requiring high power density.

  10. Effects of Nb doping level on the electronic transport, photoelectric effect and magnetoresistance across La0.5Ca0.5MnO3/Nb:SrTiO3 junctions

    Science.gov (United States)

    Wang, J. F.; Jiang, Y. C.; Chen, M. G.; Gao, J.

    2013-12-01

    Heterojunctions composed of La0.5Ca0.5MnO3 and Nb doped SrTiO3 were fabricated, and the effects of the Nb doping level on their electronic transport, photoelectric effect, and magnetoresistance were investigated. A lower doping concentration of Nb led to better rectifying properties and higher open circuit voltages. The I-V curves for La0.5Ca0.5MnO3/0.7 wt. % Nb-SrTiO3 showed a negligible response to magnetic fields for all temperatures, whereas La0.5Ca0.5MnO3/0.05 wt. % Nb-SrTiO3 exhibited distinct magnetoresistance, which depended on both the bias voltage and temperature. These results are discussed with the assistance of conventional semiconductor theories.

  11. Oxidation-resistant Ge-doped silicide coating on Cr-Cr2Nb alloys by pack cementation

    International Nuclear Information System (INIS)

    He Yirong

    1997-01-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on Cr-Cr 2 Nb alloys in a single processing step. The morphology and composition of the coating depended both on the pack composition and processing schedule and also on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi 2 and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. Under cyclic and isothermal oxidation conditions, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation and from pesting by the formation of a Ge-doped silica film. (orig.)

  12. Vibrational modes and Structure of Niobium(V) Oxosulfato Complexes in the Molten Nb2O5-K2S2O7-K2SO4 System Studied by Raman Spectroscopy

    DEFF Research Database (Denmark)

    Paulsen, Andreas L.; Borup, Flemming; Berg, Rolf W.

    2010-01-01

    The structural and vibrational properties of NbV oxosulfato complexes formed in Nb2O5-K2S2O7 and Nb2O5-K2S2O7-K2SO4 molten mixtures with 0 ... for the binary Nb2O5-K2S2O7 molten system indicate that the dissolution of Nb2O5 proceeds with consumption of S2O7 leading to the formation of a NbV oxosulfato complex according to Nb2O5 + nS2O7 --> C2n-; a simple formalism exploiting the relative Raman band intensities is used for determining the stoichiometric...... coefficient, n, pointing to n = 3 and to the following reaction: Nb2O5 + 3S2O7 --> 2NbO(SO4)3, which is consistent with the Raman spectra of the molten mixtures. Nb2O5 could be dissolved much easier when K2SO4 was present in an equimolar (1:1) SO4/Nb ratio; the incremental presence of K2SO4 in Nb2O5-K2S2O7...

  13. A Ruddlesden-Popper-type layered perovskite, Na2Ca2Nb4O13

    International Nuclear Information System (INIS)

    Chiba, K.; Ishizawa, N.; Oishi, S.

    1999-01-01

    Single crystals of disodium dicalcium tetraniobium tridecaoxide, Na 2 Ca 2 Nb 4 O 13 , were grown by the flux method. The structure was determined in space group Bb2 1 m. Perovskite-type layers with the formula [(Ca 2 Na)Nb 4 O 13 ] - are concatenated by Na + cations near the interlayer, forming a Ruddlesden-Popper-type structure. The interlayer structure, composed of Na and O atoms, can be regarded as a rocksalt-type. NbO 6 octahedra are tilted about [010] and [001]. The off-centre displacement of Nb atoms suggests a ferroelectric nature along [010], with a calculated magnitude of polarization of 0.12 C m -2 . (orig.)

  14. Piezoelectric properties and temperature stability of Mn-doped Pb(Mg1/3Nb2/3)-PbZrO3-PbTiO3 textured ceramics

    Science.gov (United States)

    Yan, Yongke; Cho, Kyung-Hoon; Priya, Shashank

    2012-03-01

    In this letter, we report the electromechanical properties of textured 0.4Pb(Mg1/3Nb2/3)O3-0.25PbZrO3-0.35PbTiO3 (PMN-PZT) composition which has relatively high rhombohedral to tetragonal (R-T) transition temperature (TR-T of 160 °C) and Curie temperature (TC of 234 °C) and explore the effect of Mn-doping on this composition. It was found that MnO2-doped textured PMN-PZT ceramics with 5 vol. % BaTiO3 template (T-5BT) exhibited inferior temperature stability. The coupling factor (k31) of T-5BT ceramic started to degrade from 75 °C while the random counterpart showed a very stable tendency up to 180 °C. This degradation was associated with the "interface region" formed in the vicinity of BT template. MnO2 doped PMN-PZT ceramics textured with 3 vol. % BT and subsequently poled at 140 °C (T-3BT140) exhibited very stable and high k31 (>0.53) in a wide temperature range from room temperature to 130 °C through reduction in the interface region volume. Further, the T-3BT140 ceramic exhibited excellent hard and soft combinatory piezoelectric properties of d33 = 720 pC/N, k31 = 0.53, Qm = 403, tan δ = 0.3% which are very promising for high power and magnetoelectric applications.

  15. Characterization and Comparison of Photocatalytic Activity Silver Ion doped on TiO2(TiO2/Ag+) and Silver Ion doped on Black TiO2(Black TiO2/Ag+)

    Science.gov (United States)

    Kim, Jin Yi; Sim, Ho Hyung; Song, Sinae; Noh, Yeoung Ah; Lee, Hong Woon; Taik Kim, Hee

    2018-03-01

    Titanium dioxide (TiO2) is one of the representative ceramic materials containing photocatalyst, optic and antibacterial activity. The hydroxyl radical in TiO2 applies to the intensive oxidizing agent, hence TiO2 is suitable to use photocatalytic materials. Black TiO2was prepared through reduction of amorphous TiO2 conducting under H2 which leads to color changes. Its black color is proven that absorbs 100% light across the whole-visible light, drawing enhancement of photocatalytic property. In this study, we aimed to compare the photocatalytic activity of silver ion doped on TiO2(TiO2/Ag+) and silver ion doped on black TiO2(black TiO2/Ag+) under visible light range. TiO2/Ag+ was fabricated following steps. 1) TiO2 was synthesized by a sol-gel method from Titanium tetraisopropoxide (TTIP). 2) Then AgNO3 was added during an aging process step for silver ion doping on the surface of TiO2. Moreover, Black TiO2/Ag+ was obtained same as TiO2/Ag+ except for calcination under H2. The samples were characterized X-ray diffraction (XRD), UV-visible reflectance (UV-vis DRS), and Methylene Blue degradation test. XRD analysis confirmed morphology of TiO2. The band gap of black TiO2/Ag+ was confirmed (2.6 eV) through UV-vis DRS, which was lower than TiO2/Ag+ (2.9 eV). The photocatalytic effect was conducted by methylene blue degradation test. It demonstrated that black TiO2/Ag+ had a photocatalytic effect under UV light also visible light.

  16. Reflectance of Co- and Nb-doped BaTiO3 for photon energies from 1.8 to 70 eV

    International Nuclear Information System (INIS)

    Goudonnet, J.P.; Godefroy, G.; Inagaki, T.; Moretti, P.; Williams, M.W.; Arakawa, E.T.

    1985-01-01

    The reflectance spectra of Co- and Nb-doped BaTiO 3 crystals have been measured for photon energies from 1.8 to 70 eV. For both types of crystal, structures observed in the 1.8 to 2.3 eV range can be attributed to the presence of residual impurities. Between 2.3 and 3.2 eV the peaks in the reflectance of the Co-doped crystal are found to be of an acceptor charge transfer type. For Nb-doped crystals structures appear at the bottom of the conduction band. For energies larger than 3.2 eV the spectra are characteristic of pure BaTiO 3 crystals, in reasonable agreement with those determined by Baeuerle et al. and calculated by Michel-Calendini and Moretti. 15 refs., 4 figs., 1 tab

  17. Enhancement of the catalytic activity of Pt nanoparticles toward methanol electro-oxidation using doped-SnO2 supporting materials

    Science.gov (United States)

    Merati, Zohreh; Basiri Parsa, Jalal

    2018-03-01

    Catalyst supports play important role in governing overall catalyst activity and durability. In this study metal oxides (SnO2, Sb and Nb doped SnO2) were electrochemically deposited on titanium substrate (Ti) as a new support material for Pt catalyst in order to electro-oxidation of methanol. Afterward platinum nanoparticles were deposited on metal oxide film via electro reduction of platinum salt in an acidic solution. The surface morphology of modified electrodes were evaluated by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDX) techniques. The electro-catalytic activities of prepared electrodes for methanol oxidation reaction (MOR) and oxidation of carbon monoxide (CO) absorbed on Pt was considered with cyclic voltammetry. The results showed high catalytic activity for Pt/Nb-SnO2/Ti electrode. The electrochemical surface area (ECSA) of a platinum electro-catalyst was determined by hydrogen adsorption. Pt/Nb-SnO2/Ti electrode has highest ECSA compared to other electrode resulting in high activity toward methanol electro-oxidation and CO stripping experiments. The doping of SnO2 with Sb and Nb improved ECSA and MOR activity, which act as electronic donors to increase electronic conductivity.

  18. Enhancing Piezoelectric Performance of CaBi2Nb2O9 Ceramics Through Microstructure Control

    Science.gov (United States)

    Chen, Huanbei; Zhai, Jiwei

    2012-08-01

    Calcium bismuth niobate (CaBi2Nb2O9, CBN) is a high-Curie-temperature ( T C) piezoelectric material with relatively poor piezoelectric performance. Attempts were made to enhance the piezoelectric and direct-current (DC) resistive properties of CBN ceramics by increasing their density and controlling their microstructural texture, which were achieved by combining the templated grain growth and hot pressing methods. The modified CBN ceramics with 97.5% relative density and 90.5% Lotgering factor had much higher piezoelectric constant ( d 33 = 20 pC/N) than those prepared by the normal sintering process ( d 33 = 6 pC/N). High-temperature alternating-current (AC) impedance spectroscopy of the CBN ceramics was measured by using an impedance/gain-phase analyzer. Their electrical resistivity was approximately 6.5 × 104 Ω cm at 600°C. Therefore, CBN ceramics can be used for high-temperature piezoelectric applications.

  19. Effect of the doping on the energy of direct and indirect optical gap of KSr{sub 2}Nb{sub 5}O{sub 15} nanopowders; Estudo da influencia da dopagem na energia de gap direto e indireto de nanopos de KSr{sub 2}Nb{sub 5}O{sub 15}

    Energy Technology Data Exchange (ETDEWEB)

    Lanfredi, S.; Silva, G.D.; Genova, D.H.M.; Bellucci, F.S.; Constantino, C.J.L.; Nobre, M.A.L., E-mail: silvania@fct.unesp.b [Universidade Estadual Paulista (LaCCeF/DFQB/UNESP), Presidente Prudente, SP (Brazil). Dept. de Fisica, Quimica e Biologia. Lab. de Compositos e Ceramicas Funcionais

    2009-07-01

    Lead-free ferroelectric oxides with tetragonal tungsten bronze TTB type structure have exhibited several applications in recent piezoelectric/dielectric technologies. In TTB niobates, the cationic specie and its distribution exhibit strong influence on the electrical and optical proprieties. Solid solution development from transition-metals cations doping occurs on the niobium site allowing an intrinsic-ferro electricity modulation. In this work, the effect of the concentration of nickel cations on the semiconductor properties of KSr{sub 2}Nb{sub 5}O{sub 15} nanoparticles was investigated by invisible spectroscopy via gap energy determination. Single phase and nanocrystalline powders of KSr{sub 2}NixNb{sub 5}-xO{sub 15}-{sigma} with x = 0.75 and 1 was prepared by high energy ball milling. Powders were characterized by x-ray diffraction. Increase in temperature of calcination leads to decreasing of the gap energy. The influence of concentration of Ni{sup 3+} in the semiconductor character of KSr{sub 2}NixNb{sub 5}-xO{sub 15}-{sigma} is discussed based on the thermal evolution of structural parameters. (author)

  20. Superconducting Nb{sub 3}Sn intermetallics made by electrochemical reduction of Nb{sub 2}O{sub 5}-SnO{sub 2} oxides

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, B A; Fray, D J; Yan, X-Y; Chen, G

    2003-05-01

    The article is focused on low temperature superconducting Nb{sub 3}Sn material manufactured by novel electrodeoxidizing method developed in Cambridge whereby the range of alloys and intermetallics are produced cheaply making potential superconducting wires more cost effective. The process of direct electrochemical reduction of Nb{sub 2}O{sub 5}-SnO{sub 2} mixtures and in situ formation of the Nb{sub 3}Sn is discussed in details.

  1. An ultrasonic therapeutic transducers using lead-free Na{sub 0.5}K{sub 0.5}NbO{sub 3}-CuNb{sub 2}O{sub 6} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ming-Ru [Department of Electrical Engineering, National Cheng Kung University, Taiwan (China); Chu, Sheng-Yuan, E-mail: chusy@mail.ncku.edu.t [Department of Electrical Engineering, National Cheng Kung University, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Nanotechnology and Microsystems Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Tsai, Cheng-Che [Department of Electronics Engineering and Computer Science, Tung-Fang Institute of Technology, Kaohsiung 829, Taiwan (China)

    2010-10-08

    Research highlights: {yields} In this paper, CN was added to NKN ceramics to decrease the sintering temperature and to improve the density and piezoelectric characteristics. The influence of CuNb{sub 2}O{sub 6} (CN) content on the microstructure, electrical properties, temperature stability, and mechanical properties of the synthesized samples was investigated. Results show that the samples synthesized with CN-doped not only improved the density but also exhibited superior piezoelectric characteristic, temperature stability of resonance frequency (TCF), and elastic stiffness coefficient than those of pure NKN piezoelectric ceramics. {yields} The bulk density (4.47 g/cm{sup 3}), k{sub p} (40%), k{sub t} (45%), Q{sub m} (1642), C{sub 33}{sup D} (19.64 x 10{sup 10} N/m{sup 2}), TCF (-0.011%/{sup o}C) and TCC (0.135%/{sup o}C) values for NKN-01CN ceramics obtained from experiments show excellent 'hard' piezoelectric properties. Furthermore, a lead-free NKN-01CN ultrasonic therapeutic transducer was successfully driven by a self-tuning circuit. - Abstract: In this work, we reports on the CuNb{sub 2}O{sub 6} (CN) modified lead-free Na{sub 0.5}K{sub 0.5}NbO{sub 3} (NKN) based piezoelectric ceramics were synthesized by solid-state reaction methods and sintered at 1075 {sup o}C for 3 h. A secondary phase of K{sub 4}CuNb{sub 8}O{sub 23} was found in the XRD pattern of NKN-based ceramics as the CN dopants is 1 mol%. Microstructural analyses of un-doped and CN-doped ceramics were performed in a scanning electron microscope. The influence of CN content on the microstructure, electrical properties, temperature stability, and mechanical properties of the synthesized ceramics was investigated. The results show that the synthesized ceramics with CN-doped not only had improved density but also exhibited superior piezoelectric characteristics, temperature stability of resonance frequency (TCF), and a better elastic stiffness coefficient than those of pure NKN piezoelectric

  2. Atomic Defects and Doping of Monolayer NbSe2.

    Science.gov (United States)

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J P; Lawlor, Sean; Sanchez, Ana M; Sloan, Jeremy; Gorbachev, Roman V; Grigorieva, Irina V; Krasheninnikov, Arkady V; Haigh, Sarah J

    2017-03-28

    We have investigated the structure of atomic defects within monolayer NbSe 2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe 2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

  3. Spectral evolution of Eu{sup 3+} doped Y{sub 3}NbO{sub 7} niobate induced by temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K-Y.; Durand, A. [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Heintz, J-M.; Veillere, A. [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Bordeaux INP, ICMCB, UPR 9048, F-33600 Pessac (France); Jubera, V., E-mail: veronique.jubera@u-bordeaux.fr [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France)

    2016-03-15

    A Eu{sup 3+} doped Y{sub 3}NbO{sub 7} niobate powder was synthetized using a polymerizable complex route. It gave rise to nanometric particles that crystallized in the fluorine structure, corresponding to the Y{sub 3}NbO{sub 7} phase. The thermal evolution of this powder was followed up to 1600 °C, using X-ray diffraction and optical characterizations. The fluorine structure was maintained in the whole temperature range. However, spectral evolution of the samples calcined above 900 °C showed a more complex situation. Emission spectra of powders heat treated at different temperatures showed an evolution of the emission lines that can be attributed first to a better crystallization of the niobate phase and second to its partial decomposition in favor of the formation of YNbO{sub 4} and Y{sub 2}O{sub 3}. Although the Y{sub 3}NbO{sub 7} phase appeared stable up to 1650 °C, from X-ray diffraction analysis, spectral analysis showed that the local environment of the doping element is modified from 1100 °C. - Graphical abstract: Spectral evolution of Eu{sup 3+} doped Y{sub 3}NbO{sub 7} niobate induced by temperature.

  4. Effects of Nb and Sr doping on crystal structure of epitaxial BaTiO3 thin films on MgO substrates

    International Nuclear Information System (INIS)

    Kim, Yongsam; Chen, Chunhua; Saiki, Atsushi; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

    2002-01-01

    Niobium (Nb) and strontium (Sr) doped barium titanate (BT) films were deposited by radio frequency (RF) magnetron sputtering with Nb and Sr doped BT ceramic targets, respectively. The effect of Nb and Sr doping on the crystal structure of epitaxial BaTiO 3 thin films on MgO substrates was investigated. The crystal structure of the films was examined using the reciprocal space mapping measurement. All the films exhibit a cube-on-cube relation with respect to the substrates. As the amount of doped Sr increased, both of the in-plane and out-of-plane lattice constants of Sr doped BT films slowly approached the BT bulk values. On the other hand, the lattice constants of Nb doped BT films were rapidly coming close to the bulk values. These indicated that the lattices of doped BT films were relaxed as the amount of doped elements increased. In addition, Nb doping had greater influence on the relaxation of the films than Sr doping for the same content of dopant. (author)

  5. Synthesis and characterization of Nb_2O_5 by a colloidal route

    International Nuclear Information System (INIS)

    Falk, G.S.; Borlaf, M.; Oliveira, A.P. Novaes de; Rodrigues Neto, J.B.; Hotza, D.; Moreno, R.

    2014-01-01

    The niobium pentoxide (Nb_2O_5) is known to be a polymorphic ceramic semiconductor and display features, which makes it a potential candidate in the field of photocatalysis. In this paper, we evaluate a colloidal route for the synthesis of Nb_2O_5. The properties of the suspension and the powder obtained were determined by analysis of particle size, zeta potential, thermogravimetric and differential thermal analysis (TG-DTA) and X-ray diffraction (XRD). The results indicated that the particle size was 0.3 μm and at pHs between 8 and 9, stable suspensions were obtained. Through the XRD results it was observed that the synthesized powder is amorphous and that at 300°C/1h niobic acid (HNbO_3) crystallizes, which after calcination at 450, 650, 850 and 1050 deg C/1h, turns into Nb_2O_5 with different crystalline structures. (author)

  6. Piezoelectric properties enhanced of Sr{sub 0.6}(BiNa){sub 0.2}Bi{sub 2}Nb{sub 2}O{sub 9} ceramic by (LiCe) modification with charge neutrality

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Pinyang, E-mail: fpy_2000@163.com [Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices, School of Materials and Chemical Engineering, Xi’an Technological University, Xi’an 710032 (China); Xi, Zengzhe; Long, Wei; Li, Xiaojuan [Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices, School of Materials and Chemical Engineering, Xi’an Technological University, Xi’an 710032 (China); Li, Jin [Northwest Institute For Non-ferrous Metal Research, Xi’an 710016 (China)

    2013-09-01

    Graphical abstract: The oxygen vacancies were confirmed by the left figure. The role of oxygen vacancy on piezoelectric activities was obtained by comparing to the varieties of oxygen vacancy concentration and piezoelectric coefficient with (LiCe) modification. -- Highlights: • The Sr{sub 0.6}(BiNa){sub 0.2}Bi{sub 2}Nb{sub 2}O{sub 9} ceramic by (LiCe) modification with the charge neutrality was synthesized by the solid state reaction method. • The Curie temperature and piezoelectric coefficient were found to be T{sub c} ∼590 °C and d{sub 33} ∼32 pC/N, respectively. • The mechanism of piezoelectric activities improved by (LiCe) modification was discussed. -- Abstract: Aurivillius-type ceramics, Sr{sub 0.6−x}(LiCe){sub x/2.5}(BiNa){sub 0.2}Bi{sub 2}Nb{sub 2}O{sub 9}(SLCBNBNO) with the charge neutrality, were synthesized by using conventional solid-state processing. Phase analysis was performed by X-ray diffraction analyses (XRD) and Raman spectroscopy. Microstructural morphology was assessed by the scanning electron microscopy (SEM). Structural, dielectric, piezoelectric, ferroelectric, and electromechanical properties of the SLCBNBNO ceramics were investigated. Piezoelectric properties were significantly enhanced compared to Sr{sub 0.6}(BiNa){sub 0.2}Bi{sub 2}Nb{sub 2}O{sub 9} (SBNBN) ceramic and the maximum of piezoelectric coefficient d{sub 33} of the SBNBN-LC6 ceramic was 32 pC/N with higher Curie temperature (T{sub c} ∼590 °C). In addition, mechanisms for the piezoelectric properties enhanced of the SBNBN-based ceramics were discussed.

  7. Structural investigation and luminescence of nanocrystalline lanthanide doped NaNbO{sub 3} and Na{sub 0.5}K{sub 0.5}NbO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Pin, Sonia [Paul Scherrer Institute, General Energy Research (ENE), Laboratory for Bioenergy and Catalysis, CH-5232 Villigen PSI (Switzerland); Piccinelli, Fabio [Dipartimento di Biotecnologie, Universita di Verona and INSTM, UdR Verona, Strada Le Grazie 15, I-37134 Verona (Italy); Upendra Kumar, Kagola [Grupo de Fotonica e Fluidos Complexos, Instituto de Fisica, Universidade Federal de Alagoas (UFAL), Maceio-AL (Brazil); Enzo, Stefano [Dipartimento di Chimica, Universita di Sassari, 07100 Sassari (Italy); Ghigna, Paolo [Dipartimento di Chimica, Universita di Pavia, V.le Taramelli 16, I-27100 Pavia (Italy); Cannas, Carla; Musinu, Anna [Dipartimento di Scienze Chimiche, Universita di Cagliari, Cittadella Universitaria Monserrato, I-09042 Cagliari (Italy); Mariotto, Gino [Dipartimento di Informatica, Universita di Verona, Strada Le Grazie 15, I-37134 Verona (Italy); Bettinelli, Marco [Dipartimento di Biotecnologie, Universita di Verona and INSTM, UdR Verona, Strada Le Grazie 15, I-37134 Verona (Italy); Speghini, Adolfo, E-mail: adolfo.speghini@univr.it [Dipartimento di Biotecnologie, Universita di Verona and INSTM, UdR Verona, Strada Le Grazie 15, I-37134 Verona (Italy)

    2012-12-15

    Nd{sup 3+} and Eu{sup 3+} doped NaNbO{sub 3} and Na{sub 0.5}K{sub 0.5}NbO{sub 3} nanostructured multiferroics (nanoparticles or nanorods) were prepared by a sol-gel route. X-Ray powder diffraction results evidence that the sodium and mixed sodium-potassium niobates show orthorhombic (Pmc2{sub 1} space group), and monoclinic structure (Pm space group), respectively, confirmed by the Raman spectra. The local structure around the trivalent lanthanides was investigated with Extended X-ray Absorption Fine Structure spectroscopy at the Ln-K edge and luminescence spectroscopy. The Ln{sup 3+} ions enter the structure by substituting the alkali metals, with a 12-fold oxygen coordination, and inducing a large amount of static disorder. The visible emission bands of the Eu{sup 3+} ions indicate that multiple sites exist for the lanthanide ions, in agreement with the EXAFS results showing the largest amount of static disorder in these samples. A possible indication of clustering of oxygen vacancies around the Ln{sub Na} Double-Prime defect is obtained by VBS calculations. - Graphical Abstract: Ln{sup 3+} doped NaNbO{sub 3} and Na{sub 0.5}K{sub 0.5}NbO{sub 3} nanoparticles or nanorods can be prepared by a simple sol-gel procedure. The synergy of X-ray diffraction, EXAFS and luminescence spectroscopy gives important information on the Ln{sup 3+} local environment. Highlights: Black-Right-Pointing-Pointer Nd{sup 3+} and Eu{sup 3+} doped NaNbO{sub 3} and Na{sub 0.5}K{sub 0.5}NbO{sub 3} nanoparticles or nanorods are prepared by sol-gel. Black-Right-Pointing-Pointer EXAFS indicates that the Ln{sup 3+} ions substitutes the Na{sup +} and K{sup +} ions, inducing a large amount of static disorder. Black-Right-Pointing-Pointer The visible emission bands of the Eu{sup 3+} ions confirm that multiple sites exist for the lanthanide ions.

  8. Optical temperature sensing by upconversion luminescence of Er doped Bi5TiNbWO15ferroelectric materials

    Directory of Open Access Journals (Sweden)

    Hua Zou

    2014-12-01

    Full Text Available The Er3+ doped Bi5TiNbWO15 ceramics have been synthesized using conventional solid-state reaction techniques. The crystal structure, ferroelectric properties, UC emission properties and especially the temperature sensing behaviors were systematically studied. With increasing Er3+ content, the investigation of XRD pattern, the ferroelectric loop and the UC emission indicated that the Er3+ ions dopants preferentially substituted the A sites of Bi3TiNbO9 and then Bi2WO6. Based on fluorescence intensity ratio (FIR technique, the observed results implied the ceramics were promising candidates for temperature sensors in the temperature range of 175 K −550 K. More importantly, this study provided a contrast of temperature sensitivity between emission from the same part (Bi3TiNbO9 in bismuth layered-structure and emission from the different part (Bi3TiNbO9 and Bi2WO6 in bismuth layered-structure for the first time.

  9. The effect of Nd and Mg doping on the micro-Raman spectra of LiNbO3 single-crystals

    International Nuclear Information System (INIS)

    Quispe-Siccha, R; Villagran-Muniz, M; MejIa-Uriarte, E V; Jaque, D; GarcIa Sole, J; Jaque, F; Sato-Berru, R Y; Camarillo, E; Hernandez A, J; Murrieta S, H

    2009-01-01

    The LiNbO 3 congruent crystals doped with small Nd concentrations, 1 (TO 1 ) and A 1 (TO 2 ) modes, the half-width composition and the area ratio of the A 1 (TO 4 ) and E(TO 8 ) bands, we reached several conclusions about the incorporation mechanism of the Nd and Mg ions into the LiNbO 3 lattice. Likewise the Raman shift and half-width of the E(TO 1 ) and E(TO 7 ) modes were investigated in the Z direction. Results indicate that Mg and Nd ions are located in the Li site for low doping concentrations and for larger concentrations there is a replacement in both Li and Nb ion sites.

  10. Efficiency of Nb-Doped ZnO Nanoparticles Electrode for Dye-Sensitized Solar Cells Application

    Science.gov (United States)

    Anuntahirunrat, Jirapat; Sung, Youl-Moon; Pooyodying, Pattarapon

    2017-09-01

    The technological of Dye-sensitized solar cells (DSSCs) had been improved for several years. Due to its simplicity and low cost materials with belonging to the part of thin films solar cells. DSSCs have numerous advantages and benefits among the other types of solar cells. Many of the DSSC devices had use organic chemical that produce by specific method to use as thin film electrodes. The organic chemical that widely use to establish thin film electrodes are Zinc Oxide (ZnO), Titanium Dioxide (TiO2) and many other chemical substances. Zinc oxide (ZnO) nanoparticles had been used in DSSCs applications as thin film electrodes. Nanoparticles are a part of nanomaterials that are defined as a single particles 1-100 nm in diameter. From a few year ZnO widely used in DSSC applications because of its optical, electrical and many others properties. In particular, the unique properties and utility of ZnO structure. However the efficiency of ZnO nanoparticles based solar cells can be improved by doped various foreign impurity to change the structures and properties. Niobium (Nb) had been use as a dopant of metal oxide thin films. Using specification method to doped the ZnO nanoparticles thin film can improved the efficiencies of DSSCs. The efficiencies of Nb-doped ZnO can be compared by doping 0 at wt% to 5 at wt% in ZnO nanoparticles thin films that prepared by the spin coating method. The thin film electrodes doped with 3 at wt% represent a maximum efficiencies with the lowest resistivity of 8.95×10-4 Ω·cm.

  11. Measurements of defect structures by positron annihilation lifetime spectroscopy of the tellurite glass TeO2-P2O5-ZnO-LiNbO3 doped with ions of rare earth elements: Er3+, Nd3+ and Gd3+

    Science.gov (United States)

    Golis, E.; Yousef, El. S.; Reben, M.; Kotynia, K.; Filipecki, J.

    2015-12-01

    The objective of the study was the structural analysis of the TeO2-P2O5-ZnO-LiNbO3 tellurite glasses doped with ions of the rare-earth elements: Er3+, Nd3+ and Gd3+ based on the PALS (Positron Annihilation Lifetime Spectroscopy) method of measuring positron lifetimes. Values of positron lifetimes and the corresponding intensities may be connected with the sizes and number of structural defects, such as vacancies, mono-vacancies, dislocations or pores, the sizes of which range from a few angstroms to a few dozen nanometres. Experimental positron lifetime spectrum revealed existence of two positron lifetime components τ1 and τ2. Their interpretation was based on two-state positron trapping model where the physical parameters are the annihilation velocity and positron trapping rate.

  12. Nonohmic behavior of SnO2.MnO2-based ceramics

    Directory of Open Access Journals (Sweden)

    Marcelo O. Orlandi

    2003-06-01

    Full Text Available The present paper describes the nonohmic behavior of the SnO2.MnO-based system and analyzes the influence of the sintering time and the Nb2O5 concentration on this system's electrical properties. A nonlinear coefficient of ~7 was obtained for a 0.2 mol%-doped Nb2O5 composition, which is comparable to other values reported in the literature for the ternary SnO2-based systems. A recent barrier formation model proposed in the literature to explain the nonlinear electrical behavior of SnO2-based systems is used to clarify the role of the MnO constituent in the formation of the barrier, taking into account the influence of segregated atoms, precipitated phase and oxygen species in the grain boundary region.

  13. Superparamagnetic behavior of Fe-doped SnO2 nanoparticles

    International Nuclear Information System (INIS)

    Hachisu, M.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Mori, K.; Ichiyanagi, Y.

    2014-01-01

    SnO 2 is an n-type semiconductor with a wide band gap of 3.62 eV, and SnO 2 nanoparticles doped with magnetic ions are expected to realized new diluted magnetic semiconductors (DMSs). Realizing ferromagnetism at room temperature is important for spintronics device applications, and it is interesting that the magnetic properties of these DMS systems can be varied significantly by modifying the preparation methods or conditions. In this study, the magnetic properties of Fe-doped (3% and 5%) SnO 2 nanoparticles, prepared using our novel chemical preparation method and encapsulated in amorphous SiO 2 , were investigated. The particle size (1.8–16.9 nm) and crystal phase were controlled by the annealing temperature. X-ray diffraction confirmed a rutile SnO 2 single-phase structure for samples annealed at 1073–1373 K, and the composition was confirmed using X-ray fluorescence analysis. SQUID magnetometer measurements revealed superparamagnetic behavior of the 5%-Fe-doped sample at room temperature, although SnO 2 is known to be diamagnetic. Magnetization curves at 5 K indicated that the 3%-Fe-doped has a larger magnetization than that of the 5%-Fe-doped sample. We conclude that the magnetization of the 5%-Fe-doped sample decreased at 5 K due to the superexchange interaction between the antiferromagnetic coupling in the nanoparticle system

  14. Superparamagnetic behavior of Fe-doped SnO2 nanoparticles

    Science.gov (United States)

    Hachisu, M.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Mori, K.; Ichiyanagi, Y.

    2014-02-01

    SnO2 is an n-type semiconductor with a wide band gap of 3.62 eV, and SnO2 nanoparticles doped with magnetic ions are expected to realized new diluted magnetic semiconductors (DMSs). Realizing ferromagnetism at room temperature is important for spintronics device applications, and it is interesting that the magnetic properties of these DMS systems can be varied significantly by modifying the preparation methods or conditions. In this study, the magnetic properties of Fe-doped (3% and 5%) SnO2 nanoparticles, prepared using our novel chemical preparation method and encapsulated in amorphous SiO2, were investigated. The particle size (1.8-16.9 nm) and crystal phase were controlled by the annealing temperature. X-ray diffraction confirmed a rutile SnO2 single-phase structure for samples annealed at 1073-1373 K, and the composition was confirmed using X-ray fluorescence analysis. SQUID magnetometer measurements revealed superparamagnetic behavior of the 5%-Fe-doped sample at room temperature, although SnO2 is known to be diamagnetic. Magnetization curves at 5 K indicated that the 3%-Fe-doped has a larger magnetization than that of the 5%-Fe-doped sample. We conclude that the magnetization of the 5%-Fe-doped sample decreased at 5 K due to the superexchange interaction between the antiferromagnetic coupling in the nanoparticle system.

  15. The effect of La2O3 in Tm3+-doped germanate-tellurite glasses for ~2 μm emission

    OpenAIRE

    Peng, Ya-Pei; Yuan, Xinqiang; Zhang, Junjie; Zhang, Long

    2014-01-01

    A germanate-tellurite glass (GeO2-TeO2-K2O-Nb2O5-La2O3) with thulium doping has been investigated for application as a laser material around 2.0 μm regions. Under the 808 nm laser diode pumped, intense 1.8 μm emission is obtained. Based on the absorption spectra, radiative properties are predicted using Judd-Ofelt theory. The maximum value of emission cross-section of Tm3+ around 1.8 μm can reach 1.46 × 10−20 cm2, which indicated that the germanate-tellurite glass may provide high gain as a g...

  16. Electric Properties of Pb(Sb1/2Nb1/2)O3 PbTiO3 PbZrO3 Ceramics

    Science.gov (United States)

    Kawamura, Yasushi; Ohuchi, Hiromu

    1994-09-01

    Solid-solution ceramics of ternary system xPb(Sb1/2Nb1/2)O3 yPbTiO3 zPbZrO3 were prepared by the solid-state reaction of powder materials. Ceramic, electric, dielectric and piezoelectric properties and crystal structures of the system were studied. Sintering of the system xPb(Sb1/2Nb1/2)O3 yPbTiO3 zPbZrO3 is much easier than that of each end composition, and well-sintered high-density ceramics were obtained for the compositions near the morphotropic transformation. Piezoelectric ceramics with high relative dielectric constants, high radial coupling coefficient and low resonant resistance were obtained for the composition near the morphotropic transformation. The composition Pb(Sb1/2Nb1/2)0.075Ti0.45Zr0.475O3 showed the highest dielectric constant (ɛr=1690), and the composition Pb(Sb1/2Nb1/2)0.05Ti0.45Zr0.5O3 showed the highest radial coupling coefficient (kp=64%).

  17. Molten salt synthesis of ZnNb2O6 powder

    International Nuclear Information System (INIS)

    Guo Liangzhai; Dai Jinhui; Tian Jintao; Zhu Zhibin; He Tian

    2007-01-01

    Pure ZnNb 2 O 6 powder was successfully prepared by the molten salt synthesis method using Nb 2 O 5 and ZnO as raw materials and a mixture of NaCl and KCl as the solvent. The phase form and morphology of the prepared powder were characterized by X-ray diffraction and scanning electron microscopy. The effect of reacting temperature on phase formation was investigated. The results indicated that the single phase ZnNb 2 O 6 powder can be obtained by the molten salt synthesis method at 600 deg. C, and the SEM photographs show that the grains of the powder are rod-like particles

  18. Synthesis and photocatalytic property for H{sub 2} production of H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} nanosheets

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bing [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi, 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Yingxuan, E-mail: yxli@ms.xjb.ac.cn [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi, 830011 (China); Luo, Jianmin [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi, 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xinjiang Uygur Autonomous Region Academy of Instrument Analysis, Urumqi, 830011 (China); Zhao, He [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi, 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, Jie; Dong, Guohui; Zhu, Yunqing [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi, 830011 (China); Wang, Chuanyi, E-mail: cywang@ms.xjb.ac.cn [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi, 830011 (China)

    2017-01-01

    Highlights: • Ultrathin HSN Ns were first synthesized based on molten salt synthesis method. • HSN Ns Exhibit 5.5 times higher activity than that of the HSN Ps. • The enhanced photocatalytic activity of HSN Ns is due to the reduction in thickness. - Abstract: The SrBi{sub 2}Nb{sub 2}O{sub 9} platelets with a thickness of about 600 nm were synthesized by molten salt synthesis method. The treatment of the SrBi{sub 2}Nb{sub 2}O{sub 9} platelets with hydrochloric acid resulted in the formation of the protonated H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} platelets. Through a top–down approach in ethylamine solution, the H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} platelets were exfoliated into H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} nanosheets with a thickness of about 2.6 nm. The evolution of the structure, composition, morphology, optical, and photocatalytic properties of SrBi{sub 2}Nb{sub 2}O{sub 9} platelets was studied as it is converted into H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} platelets and subsequently exfoliated into H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} nanosheets. The absorption edge shifts to a lower wavelength accompanied by the protonation and exfoliation. The photocatalytic H{sub 2} evolution of the three samples were evaluated under the irradiation of a 300 W Xenon lamp from CH{sub 3}OH/H{sub 2}O solution, indicating that H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} nanosheets Exhibit 5.5 and 26.2 times higher activity than that of the H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} and SrBi{sub 2}Nb{sub 2}O{sub 9} platelets, respectively. The enhanced activity for the H{sub 1.78}Sr{sub 0.78}Bi{sub 0.22}Nb{sub 2}O{sub 7} nanosheets is mainly attributed to the higher separation efficiency of the photogenerated carriers and the larger specific surface area caused by the significant reduction in thickness.

  19. Ultrasonic, photocatalytic and sonophotocatalytic degradation of Basic Red-2 by using Nb2O5 nano catalyst

    Directory of Open Access Journals (Sweden)

    Gunvant H. Sonawane

    2016-09-01

    Full Text Available The ultrasonic, photocatalytic and sonophotocatalytic degradation of Basic Red-2 accompanied by Nb2O5 nano catalysts were studied. The structure and morphology of synthesized Nb2O5 nano catalyst was investigated using scanning election microscopy (SEM, Electron dispersive X-ray spectroscopy (EDS and X-ray diffraction (XRD.The effects of various experimental parameters such as the Basic Red-2 concentration, catalyst dose, pH and addition of H2O2 on the ultrasonic, photocatalytic and sonophotocatalytic degradation were investigated. Photocatalytic and sonophotocatalytic degradation of Basic Red-2 was strongly affected by initial dye concentration, catalyst dose, H2O2 addition and pH. Basic pH (pH-10 was favored for the ultrasonic (US, photocatalytic (UV + Nb2O5 and sonophotocatalytic (US + UV + Nb2O5 degradation of Basic Red-2 by using Nb2O5 nano catalyst. The ultrasonic degradation of Basic Red-2 was enhanced by the addition of photocatalyst. Then, the effect of Nb2O5 dose on photocatalytic and sonophotocatalytic degradation were studied, and it was found that increase in catalyst dose increase in the percentage degradation of Basic Red-2. In addition, the effects of H2O2 on ultrasonic, photolytic, photocatalytic and sonophotocatalytic degradation was also investigated, and it was found that H2O2 enhances the % degradation of Basic Red-2. The possible mechanism of ultrasonic, photocatalytic and sonophotocatalytic degradation of Basic Red-2 reported by LC-MS shows generation of different degradation products

  20. Improvement of the phase diagram for the pseudobinary PbNb2O6-BaNb2O6 system

    International Nuclear Information System (INIS)

    Venet, M.; Zabotto, F. L.; Eiras, J. A.; Garcia, D.

    2009-01-01

    Characteristics of phase transitions of lead barium niobate compositions around the morphotropic phase boundary were investigated. Using structural characterizations, it was found that the morphotropic phase boundary extends toward a wide composition range, in which both tetragonal (4mm) and orthorhombic (m2m) tungsten bronze phases coexist. In addition, on heating, two phase transitions were observed for all the studied compositions. First, the fraction with m2m symmetry phase transforms into the 4mm symmetry one and, second, the 4mm symmetry phase, which represents the whole material, transforms into the paraelectric phase (4/mmm symmetry). The phase transition temperatures were determined from dielectric characterizations. These results helped to improve the phase diagram of the pseudobinary PbNb 2 O 6 -BaNb 2 O 6 system around the morphotropic phase boundary region.

  1. Phase Content and Equilibrium Relationships in Ternary Systems MOx/VO2,5/PO2,5 (M = TiIV, ZrIV, NbV; x = 2 or 2,5) with Additions for Four-Component System Ti/Cr/P/O

    International Nuclear Information System (INIS)

    Titlbach, Sven

    2014-01-01

    In the systems TiO 2 / V 2 O 5 / P 2 O 5 , ZrO 2 / V 2 O 5 / P 2 O 5 and Nb 2 O 5 / V 2 O 5 / P 2 O 5 studies on phase composition and the equilibrium relations were performed in the context of the heterogeneously catalyzed gas-phase oxidation of n-butane to maleic anhydride. Here is a selection of the research findings: in the system TiO 2 / V 2 O 5 / P 2 O 5 the hitherto unknown orthophosphate (VO)Ti 6 (PO 4 ) 9 and the mixed crystal series Ti(P 1-x V x ) 2 O 7 (0 ≤ x ≤ 0,24; 0,30 ≤ x ≤ 0,43) with miscibility gap was detected. In the quasi-ternary system ZrO 2 / V 2 O 5 / P 2 O 5 the literature well described gapless solid solution Zr(P 1-x V x ) 2 O 7 was confirmed and investigated radiographically and by NMR spectroscopy. In the system Nb 2 O 5 / V 2 O 5 / P 2 O 5 the mixed crystal series Nb 1-x V x O(PO 4 ) (0 ≤ x ≤ 0,36), P 1-x V x Nb 9 O 25 (0 ≤ x ≤ 1) and NbOP 1-x V x O 4 (0 ≤ x ≤ 0,20) were found.

  2. Theoretical and experimental study of NbO2 nanoslice formation

    International Nuclear Information System (INIS)

    Music, Denis; Geyer, Richard W

    2015-01-01

    We have used reactive magnetron sputtering to form NbO 2 nanoslices. These unique nanostructures with the dominating diffractions peaks related to low surface energy NbO 2 planes are self-assembled into two different populations: aligned and random nanoslices. To provide an explanation for the formation of these NbO 2 nanoslices with respect to competitive growth of nanorods, we employed density functional theory based molecular dynamics. (1 1 0) and (0 0 1) surfaces together with the related nanoslices and nanorods were considered, corresponding to low and high surface energy configurations, respectively. For the (1 1 0) configuration, nanoslices are more stable at all temperatures (0 K–900 K), which is consistent with experimental observations. On the other hand, for the (0 0 1) configuration nanorods are more stable at and above room temperature. We suggest that the texture modulation is the physical origin of NbO 2 nanostructure formation. (paper)

  3. The effect of La2O3 in Tm3+-doped germanate-tellurite glasses for ~2 μm emission

    Science.gov (United States)

    Peng, Ya-Pei; Yuan, Xinqiang; Zhang, Junjie; Zhang, Long

    2014-06-01

    A germanate-tellurite glass (GeO2-TeO2-K2O-Nb2O5-La2O3) with thulium doping has been investigated for application as a laser material around 2.0 μm regions. Under the 808 nm laser diode pumped, intense 1.8 μm emission is obtained. Based on the absorption spectra, radiative properties are predicted using Judd-Ofelt theory. The maximum value of emission cross-section of Tm3+ around 1.8 μm can reach 1.46 × 10-20 cm2, which indicated that the germanate-tellurite glass may provide high gain as a good medium for efficient 1.8 μm laser system.

  4. Development and application of graphite-SiO2/Al2O3/Nb2O5-methylene blue (GRP-SiAlNb-MB composite for electrochemical determination of dopamine

    Directory of Open Access Journals (Sweden)

    Juliana de Fátima Giarola

    2017-03-01

    Full Text Available In the present paper an amperometric sensor based on graphite-SiO2/Al2O3/Nb2O5-methylene blue (GRP-SiAlNb-MB composite has been successfully prepared for dopamine (DA determination in real samples. The electrochemical behavior of DA at the GRP-SiAlNb-MB has been evaluated by employing cyclic voltammetry. The best ratio (m/m of GRP-SiAlNb-MB composite was found to be 1:0.54. Under optimized conditions (pH 7.5 in 0.15 mol L−1 phosphate buffer the amperometry method responds linearly to DA from 5.0 up to 500.0 μmol L−1 (r = 0.995 with limits of detection and quantification of 1.49 and 4.97 μmol L−1, respectively. The developed method was successfully applied for DA determination in real samples of pharmaceutical formulations and can be used for routine quality control analysis of pharmaceutical formulations containing DA. The use of inorganic matrix SiAlNb was found to be very useful to adsorb MB in the composite material with further improvement of the anodic peak current of DA.

  5. Efficient conversion from UV light to near-IR emission in Yb{sup 3+}-doped triple-layered perovskite CaLaNb{sub 3}O{sub 10}

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yuting; Li, Yuze; Qin, Lin; Huang, Yanlin [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Qin, Chuanxiang, E-mail: qinchuanxiang@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Tsuboi, Taiju [Jiangsu-Singapore Joint Research Center for Organic/Bio-Electronics & Information Displays and Institute of Advanced Materials (IAM), Nanjing Tech University, Nanjing 211816 (China); Huang, Wei, E-mail: wei-huang@njtech.edu.cn [Jiangsu-Singapore Joint Research Center for Organic/Bio-Electronics & Information Displays and Institute of Advanced Materials (IAM), Nanjing Tech University, Nanjing 211816 (China)

    2015-04-15

    Graphical abstract: CaRNb{sub 3}O{sub 10} is a self-activated oxide due to charge transfer transition in octahedral NbO{sub 6} groups. CaLaNb{sub 3}O{sub 10}:Yb{sup 3+} presents intense IR emission due to the cooperative energy transfer from host (NbO{sub 6}) to Yb{sup 3+} is responsible. It could be expected to be potentially applicable for enhancing photovoltaic conversion efficiency of Si-based solar cells. - Abstract: Yb{sup 3+}-doped triple-layered perovskite CaLaNb{sub 3}O{sub 10} micro-particles were synthesized via the solid-state reaction method. The crystal structure and morphology of the polycrystalline samples were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) measurements, respectively. The reflectance spectra, photoluminescence (PL) excitation and emission spectra, the decay curves, and the absolute quantum efficiency (QE) of the near-infrared (NIR) emission (910–1100 nm) were measured. Under excitation of UV light, Yb{sup 3+}-doped perovskite shows an intense NIR emission attributed to the {sup 2}F{sub 5/2} → {sup 2}F{sub 7/2} transitions of Yb{sup 3+} ions, which could match maximum spectral response of a Si-based solar cell. This is beneficial for its possible application in an enhancement of the photovoltaic conversion efficiency of solar energy utilization. The efficient energy transfer in Yb{sup 3+}-doped CaLaNb{sub 3}O{sub 10} from NbO{sub 6} groups into Yb{sup 3+} ions was confirmed by the spectra and fluorescent decay measurements. Cooperative energy transfer (CET) was supposed to be the NIR emission mechanism.

  6. Enhanced Photocatalytic Activity of ZrO2-SiO2 Nanoparticles by Platinum Doping

    Directory of Open Access Journals (Sweden)

    Mohammad W. Kadi

    2013-01-01

    Full Text Available ZrO2-SiO2 mixed oxides were prepared via the sol-gel method. Photo-assisted deposition was utilized for doping the prepared mixed oxide with 0.1, 0.2, 0.3, and 0.4 wt% of Pt. XRD spectra showed that doping did not result in the incorporation of Pt within the crystal structure of the material. UV-reflectance spectrometry showed that the band gap of ZrO2-SiO2 decreased from 3.04 eV to 2.48 eV with 0.4 wt% Pt doping. The results show a specific surface area increase of 20%. Enhanced photocatalysis of Pt/ZrO2-SiO2 was successfully tested on photo degradation of cyanide under illumination of visible light. 100% conversion was achieved within 20 min with 0.3 wt% of Pt doped ZrO2-SiO2.

  7. Sorption properties and reversibility of Ti(IV) and Nb(V)-fluoride doped-Ca(BH4)2-MgH2 system

    International Nuclear Information System (INIS)

    Bonatto Minella, Christian; Garroni, Sebastiano; Pistidda, Claudio; Baró, Maria Dolors; Gutfleisch, Oliver; Klassen, Thomas; Dornheim, Martin

    2015-01-01

    Highlights: • Faster desorption reaction for doped materials vs. the pure composite system. • Kinetic improvement concerning re-hydrogenation reaction showed by the addition of NbF 5 . • Full characterization of the de-hydrogenation reaction pathway by means of both SR-PXD and 11 B{ 1 H} MAS-NMR. • Study of the evolution of the chemical state of the additives upon both milling and sorption reactions. - Abstract: In the last decade, alkaline and alkaline earth metal tetrahydroborates have been the focuses of the research due to their high gravimetric and volumetric hydrogen densities. Among them, Ca(BH 4 ) 2 and the Ca(BH 4 ) 2 + MgH 2 reactive hydride composites (RHC), were calculated to have the ideal thermodynamic properties which fall within the optimal range for mobile applications. In this study, the addition of NbF 5 or TiF 4 to the Ca(BH 4 ) 2 + MgH 2 reactive hydride composite system was attempted aiming to obtain a full reversible system with the simultaneous suppression of CaB 12 H 12 . Structural characterization of the specimens was performed by means of in-situ Synchrotron Radiation Powder X-ray diffraction (SR-PXD) and 11 B{ 1 H} Solid State Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). The evolution of the chemical state of the Nb- and Ti-based additives was monitored by X-ray Absorption Near Edge Structure (XANES). The addition of NbF 5 or TiF 4 to the Ca(BH 4 ) 2 + MgH 2 system have not suppressed completely the formation of CaB 12 H 12 and only a slight improvement concerning the reversible reaction was displayed just in the case of Nb-doped composite material

  8. Novel transparent conducting oxide: Anatase Ti1-xNb xO2

    International Nuclear Information System (INIS)

    Furubayashi, Yutaka; Hitosugi, Taro; Yamamoto, Yukio; Hirose, Yasushi; Kinoda, Go; Inaba, Kazuhisa; Shimada, Toshihiro; Hasegawa, Tetsuya

    2006-01-01

    Single-crystalline Ti 1-x Nb x O 2 (x = 0.2) films of 40 nm thickness were deposited on SrTiO 3 (100) substrates by the pulsed laser deposition (PLD) technique. X-ray diffraction measurement confirmed epitaxial growth of anatase (001) film. The resistivity of Ti 1-x Nb x O 2 films with x ≥ 0.03 is 2-3 x 10 -4 Ω cm at room temperature. The carrier density of Ti 1-x Nb x O 2 , which is almost proportional to the Nb concentration, can be controlled in a range of 1 x 10 19 to 2 x 10 21 cm -3 . Optical measurements revealed that internal transmittance in the visible and near-infrared region for films with x = 0.03 was more than 97%. These results demonstrate that the presently developed anatase Ti 1-x Nb x O 2 is one of the promising candidates for the practical TCOs

  9. Electronic parameters of Sr2M2O7 (M = V, Nb, Ta) and Sr-O chemical bonding

    DEFF Research Database (Denmark)

    Atuchin, Victor V.; Grivel, Jean-Claude; Zhang, Zhaoming

    2010-01-01

    XPS measurements were carried out on Sr2Nb2O7 and Sr2Ta2O7 powder samples, which were synthesized using standard solid state method. The binding energy differences between the O 1s and cation core level, Δ(O-Sr) = BE(O 1s) - BE(Sr 3d5/2), was used to characterize the valence electron transfer...... on the formation of the Sr-O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and Sr2Ta2O7 and the previously published structural and XPS data for other Sr-oxide compounds. A new empirical relationship between Δ(O-Sr) and L(Sr-O) was obtained. Possible applications...

  10. Andreev Reflection Spectroscopy of Nb-doped Bi2Se3 Topological Insulator

    Science.gov (United States)

    Kurter, C.; Finck, A. D. K.; Qiu, Y.; Huemiller, E.; Weis, A.; Atkinson, J.; Medvedeva, J.; Hor, Y. S.; van Harlingen, D. J.

    2015-03-01

    Doped topological insulators are speculated to realize p-wave superconductivity with unusual low energy quasiparticles, such as surface Andreev bound states. We present point contact spectroscopy of thin exfoliated flakes of Nb-doped Bi2Se3 where superconductivity persists up to ~ 1 K, compared to 3.2 K in bulk crystals. The critical magnetic field is strongly anisotropic, consistent with quasi-2D behavior. Andreev reflection measurements of devices with low resistance contacts result in prominent BTK-like behavior with an enhanced conductance plateau at low bias. For high resistance contacts, we observe a split zero bias conductance anomaly and additional features at the superconducting gap. Our results suggest that this material is a promising platform for studying topological superconductivity. We acknowledge support from Microsoft Project Q.

  11. Influence of oxygen annealing on the dielectric properties of SrBi{sub 2}(V{sub 0.1}Nb{sub 0.9}){sub 2}O{sub 9} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Y.; Forbess, M.; Seraji, S.; Limmer, S.; Chou, T.; Cao, G.Z. [University of Washington, Materials Science and Engineering, Seattle, WA (United States)]. E-mail: gzcao@u.washington.edu

    2001-09-07

    The influences of O{sub 2} and N{sub 2} annealing on the dielectric properties of SrBi{sub 2}(V{sub 0.1}Nb{sub 0.9}){sub 2}O{sub 9} (SBVN) ferroelectrics were studied. Ceramic samples were prepared by reaction sintering a powder mixture of constituent oxides at 950 deg. C for 2 h in air. Some samples were also subsequently annealed at 800 deg. C for 3 h in O{sub 2} or N{sub 2}. With O{sub 2} annealing, the Curie point of the SBVN ferroelectrics changed from {approx}433 to {approx}438 deg. C and the peak dielectric constant increased from {approx}760 to {approx}1010 (at 100 kHz). However, no change in the Curie point was found with N{sub 2} annealing. Furthermore, O{sub 2} annealing was found to reduce significantly both the dielectric constant and loss tangent of the SBVN ferroelectrics at frequencies below 1000 Hz. XRD results revealed a small reduction in the lattice constants with O{sub 2} annealing, but no appreciable change with N{sub 2} annealing. In addition, no detectable change in the microstructure of the SBVN samples was found with annealing. These results imply that some V{sup 4+} ions, which are compensated by the formation of oxygen vacancies, existed in the SBVN ferroelectrics prior to O{sub 2} annealing. V{sup 4+} ions were oxidized to V{sup 5+} with O{sub 2} annealing, which resulted in improved dielectric properties. (author)

  12. Structure of 3 at.% and 9 at.% Si-doped HfO{sub 2} from combined refinement of X-ray and neutron diffraction patterns

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Lili [Department of Materials Science and Engineering, North Carolina State University, NC 27695 (United States); School of Information Science and Technology, Northwest University, Xi' an 710127 (China); Hou, Dong; Usher, Tedi-Marie; Iamsasri, Thanakorn; Fancher, Chris M.; Forrester, Jennifer S. [Department of Materials Science and Engineering, North Carolina State University, NC 27695 (United States); Nishida, Toshikazu [Department of Electrical and Computer Engineering, University of Florida, FL 32611 (United States); Moghaddam, Saeed [Department of Mechanical and Aerospace Engineering, University of Florida, FL 32611 (United States); Jones, Jacob L., E-mail: jacobjones@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, NC 27695 (United States)

    2015-10-15

    The crystal structure of 3 at.% and 9 at.% Si-doped HfO{sub 2} powder was determined through refinements using X-ray and neutron diffraction patterns. The lattice parameters, atomic positions, dopant occupancy, and the second phase fraction were determined with high precision using a combined full pattern fitting via the Rietveld method. The results show that both 3 at.% and 9 at.% Si-doped HfO{sub 2} powder exhibit the monoclinic crystal structure with P 1 2{sub 1}/c 1 space group. Through the combined refinement, the crystal structure parameters, especially for the positions and occupancies of the lighter atoms, were more precisely determined compared to independent X-ray diffraction refinement. Although the ionic radius of Si{sup 4+} is smaller than Hf{sup 4+}, with increasing Si occupancy, the unit cell volume slightly increases; possible mechanisms for this effect are discussed. Moreover, the refined results provide evidence of the existence of a non-equilibrium phase of Hf{sub x}Si{sub 1−x}O{sub 2}. The second phase (SiO{sub 2}) fraction is determined as 0.17 at.% for 3 at.% Si-doped HfO{sub 2} powders and 1.7 at.% for 9 at.% Si-doped HfO{sub 2} powders. - Highlights: • X-ray and neutron diffraction patterns were used to determine crystal structure. • Results from independent refinements and a combined refinement were compared. • Highly precise structural parameters were obtained by the combined refinement. • Structural data of 3 at.% and 9 at.% Si-doped HfO{sub 2} are provided. • The unit cell volume slightly increases with Si concentration from 3 to 9 at.%.

  13. Raman, FTIR, thermal and optical properties of TeO2-Nb2O5-B2O3-V2O5 quaternary glass system

    Directory of Open Access Journals (Sweden)

    Swapna

    2017-07-01

    Full Text Available A series of quaternary glass systems with the composition 79TeO2-(20−xNb2O5-xB2O3-1V2O5 was prepared using the melt quench technique. Such studies as optical absorption, Raman, FTIR spectroscopy, EPR and DSC were carried out on the glass system. The physical properties, such as density (ρ and molar volume (VM, were determined. The Urbach energy (ΔE, optical band gap (Eopt, optical basicity (Λ, refractive index (n and electron polarizability (α of the glasses were determined from optical absorption data. Spin-Hamiltonian parameters of VO2+ ions were calculated from the EPR data. With the gradual substitution of B2O3 at the expense of Nb2O5, the density and optical band gap of the glasses decreased, and the electronic polarizability increased. EPR spectra revealed that VO2+ occupies an octahedral site with tetrahedral compression. Spin-Hamiltonian parameters g|| and g⊥ increased as B2O3 content increased in the glass. The glass transition temperature (Tg also decreased as the B2O3 content in the glass increased.

  14. Superparamagnetic behavior of Fe-doped SnO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hachisu, M.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Mori, K.; Ichiyanagi, Y. [Department of Physics, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama, Kanagawa 240-8501 (Japan)

    2014-02-20

    SnO{sub 2} is an n-type semiconductor with a wide band gap of 3.62 eV, and SnO{sub 2} nanoparticles doped with magnetic ions are expected to realized new diluted magnetic semiconductors (DMSs). Realizing ferromagnetism at room temperature is important for spintronics device applications, and it is interesting that the magnetic properties of these DMS systems can be varied significantly by modifying the preparation methods or conditions. In this study, the magnetic properties of Fe-doped (3% and 5%) SnO{sub 2} nanoparticles, prepared using our novel chemical preparation method and encapsulated in amorphous SiO{sub 2}, were investigated. The particle size (1.8–16.9 nm) and crystal phase were controlled by the annealing temperature. X-ray diffraction confirmed a rutile SnO{sub 2} single-phase structure for samples annealed at 1073–1373 K, and the composition was confirmed using X-ray fluorescence analysis. SQUID magnetometer measurements revealed superparamagnetic behavior of the 5%-Fe-doped sample at room temperature, although SnO{sub 2} is known to be diamagnetic. Magnetization curves at 5 K indicated that the 3%-Fe-doped has a larger magnetization than that of the 5%-Fe-doped sample. We conclude that the magnetization of the 5%-Fe-doped sample decreased at 5 K due to the superexchange interaction between the antiferromagnetic coupling in the nanoparticle system.

  15. Modulation-doped β-(Al0.2Ga0.8)2O3/Ga2O3 field-effect transistor

    Science.gov (United States)

    Krishnamoorthy, Sriram; Xia, Zhanbo; Joishi, Chandan; Zhang, Yuewei; McGlone, Joe; Johnson, Jared; Brenner, Mark; Arehart, Aaron R.; Hwang, Jinwoo; Lodha, Saurabh; Rajan, Siddharth

    2017-07-01

    Modulation-doped heterostructures are a key enabler for realizing high mobility and better scaling properties for high performance transistors. We report the realization of a modulation-doped two-dimensional electron gas (2DEG) at the β-(Al0.2Ga0.8)2O3/Ga2O3 heterojunction by silicon delta doping. The formation of a 2DEG was confirmed using capacitance voltage measurements. A modulation-doped 2DEG channel was used to realize a modulation-doped field-effect transistor. The demonstration of modulation doping in the β-(Al0.2Ga0.8)2O3/Ga2O3 material system could enable heterojunction devices for high performance electronics.

  16. Growth and electrical properties of (Mn,F) co-doped 0.92Pb(Zn 1/3Nb 2/3)O 3-0.08PbTiO 3 single crystal

    Science.gov (United States)

    Zhang, Shujun; Lebrun, Laurent; Randall, Clive A.; Shrout, Thomas R.

    2004-06-01

    The growth and characterization of (Mn,F) doped Pb(Zn 1/3Nb 2/3)O 3-PbTiO 3 (PZNT) single crystals are reported in this paper. The typical single crystal obtained is up to 30 mm size with dark brown color. The crystal lattice parameters of doped PZNT crystal are slightly decreased compared to the pure one. The room temperature dielectric permittivity along direction is about 6000, which is lower than that of the pure PZNT8 because of the dopants. The Curie temperature of the doped crystal is about 180°C while the ferroelectric phase transition temperature is around 100°C, which are higher than those of the pure PZNT8 single crystal. The remnant polarization and coercive field of oriented doped crystal measured at 1 Hz and 10 kV/cm field are about 27 μC/cm 2 and 4.2 kV/cm, respectively. The room temperature mechanical quality factor is ˜300. Piezoelectric coefficient of oriented doped crystal is higher than 3500 pC/N and the longitudinal electromechanical coupling factor is larger than 93%. The piezoelectric properties of doped PZNT single crystal with temperature and orientations are also reported in this paper. The valence state of the manganese dopant was determined by electron spin resonance, indicating no Mn 4+ in the crystals, suggesting the valence of manganese ions in PZNT crystals may be 2+, which acts as a hardener, stabilizes the domain wall and pins the domain wall motion, on the other hand, the dopant will enter Ti 4+ position, shifting the crystal composition to higher PT content.

  17. Preparation and electrical properties of (1 - x)Sr(Fe1/2Nb1/2)O3-xPbTiO3 ferroelectric ceramics

    International Nuclear Information System (INIS)

    Fang Bijun; Cheng Zhenquan; Sun Renbing; Ding Chenlu

    2009-01-01

    (1 - x)Sr(Fe 1/2 Nb 1/2 )O 3 -xPbTiO 3 (SFN-PT) ferroelectric ceramics were prepared by conventional solid-state reaction method via the wolframite precursor route. X-ray diffraction (XRD) measurement confirmed that the synthesized SFN-PT ceramics are of pure perovskite structure. With the increase of the concentration of PbTiO 3 (PT), crystal structure of the sintered SFN-PT ceramics changes from rhombohedral phase to tetragonal phase. Dielectric response of the SFN-PT ceramics changes from diffused and broad dielectric peaks to relatively sharp ones accompanied by the increase of the temperature of dielectric maximum (T m ). Small content of MnO 2 or Li 2 CO 3 doping can greatly decrease the dielectric loss of the SFN-PT ceramics, furthermore, the abnormal increase of dielectric constant and loss tangent in the paraelectric phase is suppressed accordingly. Typical P-E hysteresis loops are observed in the SFN-PT ceramics, however, the saturate polarization (P s ) is small. MnO 2 or Li 2 CO 3 doping can greatly decrease the coercive field (E c ) of the SFN-PT ceramics accompanied by large increase of P s . Piezoelectric constant d 33 of the SFN-PT ceramics is small except for SFN30-PT70 ceramics, which reaches 22pC/N

  18. Investigation into self-pumped and mutually pumped phase conjugation with beams entering the negative c face of doped (K0.5Na0.5)0.2(Sr0.75 Ba0.25)0.9Nb2O6 crystals

    International Nuclear Information System (INIS)

    Zhang, J.; Liu, H.; Jia, W.

    1997-01-01

    We investigated some novel geometries of self-pumped phase conjugation (SPPC) and mutually pumped phase conjugation (MPPC), relying on total internal reflection both from the a face and from corners, with beams entering the negative c face of doped (K 0.5 Na 0.5 ) 0.2 (Sr 0.75 Ba 0.25 ) 0.9 Nb 2 O 6 crystals. The different situations for internal light paths and their direct transformation at the same incident wavelength were observed. Similarities and differences between SPPC and MPPC are discussed. The dynamic features of SPPC and MPPC in different situations were also observed. Three or more four-wave-mixing interaction regions were clearly observed inside the phase conjugators. The multistep interaction and its influence on the response rate and conjugation fidelity are analyzed. The large size of the samples seems necessary to ensure an optical path that is long enough for multistep bifurcation. The stability of the light channels is discussed based on the fanning effect. copyright 1997 Optical Society of America

  19. Optical properties of nanocrystalline potassium lithium niobate in the glass system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5).

    Science.gov (United States)

    Ahamad, M Niyaz; Varma, K B R

    2009-08-01

    Optically clear glasses of various compositions in the system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5) (2 glasses comprising potassium lithium niobate (K3Li2Nb5O15) microcrystallites on the surface and nanocrystallites within the glass were obtained by controlled heat-treatment of the as-quenched glasses just above the glass transition temperature (T(g)). The optical transmission spectra of these glasses and glass-crystal composites of various compositions were recorded in the 200-2500 nm wavelength range. Various optical parameters such as optical band gap, Urbach energy, refractive index were determined. Second order optical non-linearity was established in the heat-treated samples by employing the Maker-Fringe method.

  20. Synthesis of TiO2-doped SiO2 composite films and its applications

    Indian Academy of Sciences (India)

    Wintec

    structure of the titanium oxide species in the TiO2-doped SiO2 composite films and the photocatalytic reactiv- ity in order to ... gaku D-max γA diffractometer with graphite mono- chromized ... FT–IR absorption spectra of TiO2-doped SiO2 com-.

  1. The effect of La2O3 in Tm3+-doped germanate-tellurite glasses for ~2 μm emission

    Science.gov (United States)

    Peng, Ya-Pei; Yuan, Xinqiang; Zhang, Junjie; Zhang, Long

    2014-01-01

    A germanate-tellurite glass (GeO2-TeO2-K2O-Nb2O5-La2O3) with thulium doping has been investigated for application as a laser material around 2.0 μm regions. Under the 808 nm laser diode pumped, intense 1.8 μm emission is obtained. Based on the absorption spectra, radiative properties are predicted using Judd-Ofelt theory. The maximum value of emission cross-section of Tm3+ around 1.8 μm can reach 1.46 × 10−20 cm2, which indicated that the germanate-tellurite glass may provide high gain as a good medium for efficient 1.8 μm laser system. PMID:24918516

  2. Quadruple-layered perovskite (CuCl)Ca2NaNb4O13

    International Nuclear Information System (INIS)

    Kitada, A.; Tsujimoto, Y.; Yamamoto, T.; Kobayashi, Y.; Narumi, Y.; Kindo, K.; Aczel, A.A.; Luke, G.M.; Uemura, Y.J.; Kiuchi, Y.; Ueda, Y.; Yoshimura, K.; Ajiro, Y.; Kageyama, H.

    2012-01-01

    We will present the synthesis, structure and magnetic properties of a new quadruple-layered perovskite (CuCl)Ca 2 NaNb 4 O 13 . Through a topotactic ion-exchange reaction with CuCl 2 , the precursor RbCa 2 NaNb 4 O 13 presumably having an incoherent octahederal tliting changes into (CuCl)Ca 2 NaNb 4 O 13 with a 2a p ×2a p ×2c p superstructure (tetragonal; a=7.73232(5) Å, c=39.2156(4) Å). The well-defined superstructure for the ion-exchanged product should be stabilized by the inserted CuCl 4 O 2 octahedral layers that firmly connect with neighboring perovskite layers. Magnetic studies show the absence of long-range magnetic ordering down to 2 K despite strong in-plane interactions. Aleksandrov′s group theory and Rietveld refinement of synchrotron X-ray diffraction data suggest the structure to be of I4/mmm space group with in-phase tilting along the a and b axes, a two-tilt system (++0). - Graphical Abstract: We present a quadruple-layered copper oxyhalide (CuCl)Ca 2 NaNb 4 O 13 synthesized through a topotactic ion-exchange reaction of RbCa 2 NaNb 4 O 13 with CuCl 2 . The compound has a well-defined superstructure. Magnetic studies suggest the absence of magnetic order even at 2 K. Highlights: ► (CuCl)Ca 2 NaNb 4 O 13 was prepared by ion-exchange reaction of RbCa 2 NaNb 4 O 13 with CuCl 2 . ► Compound has a 2a p ×2a p ×2c p superstructure (tetragonal; a=7.73 Å, c=39.21 Å). ► Such a well-defined superstructure was not observed in the precursor compound. ► Aleksandrov′s theory and Rietveld study suggest a (++0) octahedral tilting (I4/mmm). ► Magnetic studies revealed the absence of magnetic order down to 2 K.

  3. Metal-metal bonding and aromaticity in [M2(NHCHNH)3]2 (μ-E)2 (E = O, S; M = Nb, Mo, Tc, Ru, Rh).

    Science.gov (United States)

    Yan, Xiuli; Meng, Lingpeng; Sun, Zheng; Li, Xiaoyan

    2016-02-01

    The nature of M-M bonding and aromaticity of [M2(NHCHNH)3]2(μ-E)2 (E = O, S; M = Nb, Mo, Tc, Ru, Rh) was investigated using atoms in molecules (AIM) theory, electron localization function (ELF), natural bond orbital (NBO) and molecular orbital analysis. These analyses led to the following main conclusions: in [M2(NHCHNH)3]2(μ-E)2 (E = O, S; M = Nb, Mo, Tc, Ru, Rh), the Nb-Nb, Ru-Ru, and Rh-Rh bonds belong to "metallic" bonds, whereas Mo-Mo and Tc-Tc drifted toward the "dative" side; all these bonds are partially covalent in character. The Nb-Nb, Mo-Mo, and Tc-Tc bonds are stronger than Ru-Ru and Rh-Rh bonds. The M-M bonds in [M2(NHCHNH)3]2(μ-S)2 are stronger than those in [M2(NHCHNH)3]2(μ-O)2 for M = Nb, Mo, Tc, and Ru. The NICS(1)ZZ values show that all of the studied molecules, except [Ru2(NHCHNH)3]2(μ-O)2, are aromaticity molecules. O-bridged compounds have more aromaticity than S-bridged compounds. Graphical Abstract Left Molecular graph, and right electron localization function (ELF) isosurface of [M2(NHCHNH)3]2(μ-E)2(E = O, S; M = Nb, Mo, Tc, Ru, Rh).

  4. Epitaxial growth of Er, Ti doped LiNbO3 films prepared by sol-gel method

    International Nuclear Information System (INIS)

    Takahashi, Makoto; Yoshiga, Tsuyoshi; Kajitani, Naofumi; Takeda, Yuki; Sato, Shoji; Wakita, Koichi; Ohnishi, Naoyuki; Hotta, Kazutoshi; Kurachi, Masato

    2006-01-01

    Erbium (Er 3+ ) doped lithium niobate (LiNbO 3 ) thick films were deposited on z-cut congruent LiNbO 3 (LN) substrate by the sol-gel method from the 0.20 mol/dm 3 precursor solution containing various Er 3+ concentration and 0.10 mol/dm 3 poly(vinyl alcohol) (PVA), and their crystal characteristics were evaluated. The Er 3+ concentration in the LN film was controlled by the Er 3+ concentration in the starting solution. The orientation relationships between Er doped LN films and substrates were determined by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy, and (006) oriented Er doped LN epitaxial layers with parallel epitaxial relationships could be grown on the z-cut LN wafer. Moreover, it was made clear from the electron beam diffraction measurements that the film came to be polycrystalline, when the Er concentration was over 3 mol%. The refractive index of Er-doped LN films decreased with increasing Er concentration. 1.5 mol% Ti: 1.0 mol% Er LN films, which acted as a waveguide, were prepared by our so-gel method. It showed the 1530 nm emission by 980 nm excitation, which was considered to be due to the Er 3+ corresponding to the 4 I 13/2 → 4 I 15/2 transition. (author)

  5. Superconductivity induced by oxygen doping in Y{sub 2}O{sub 2}Bi

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Xiyue; Deng, Shuiquan [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter (FJIRSM), Chinese Academy of Sciences (CAS), Fuzhou (China); Gordon, Elijah E. [Department of Chemistry, North Carolina State University, Raleigh, NC (United States); Whangbo, Myung-Hwan [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter (FJIRSM), Chinese Academy of Sciences (CAS), Fuzhou (China); Department of Chemistry, North Carolina State University, Raleigh, NC (United States)

    2017-08-14

    When doped with oxygen, the layered Y{sub 2}O{sub 2}Bi phase becomes a superconductor. This finding raises questions about the sites for doped oxygen, the mechanism of superconductivity, and practical guidelines for discovering new superconductors. We probed these questions in terms of first-principles calculations for undoped and O-doped Y{sub 2}O{sub 2}Bi. The preferred sites for doped O atoms are the centers of Bi{sub 4} squares in the Bi square net. Several Bi 6p x/y bands of Y{sub 2}O{sub 2}Bi are raised in energy by oxygen doping because the 2p x/y orbitals of the doped oxygen make antibonding possible with the 6p x/y orbitals of surrounding Bi atoms. Consequently, the condition necessary for the ''flat/steep'' band model for superconductivity is satisfied in O-doped Y{sub 2}O{sub 2}Bi. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Properties of Nb-doped ZnO transparent conductive thin films ...

    Indian Academy of Sciences (India)

    Administrator

    by rf magnetron sputtering using a high quality ceramic target ... Guangxi Key Laboratory of Information Materials, Guilin University of Electronic ... films are highly textured along the c axis and perpendicular to the surface of the substrate. ... ZnO films; Nb-doped; magnetron sputtering; optical and electrical properties. 1.

  7. Growth and physical properties of highly oriented La-doped (K,Na)NbO3 ferroelectric thin films

    International Nuclear Information System (INIS)

    Vendrell, X.; Raymond, O.; Ochoa, D.A.; García, J.E.; Mestres, L.

    2015-01-01

    Lead-free (K,Na)NbO 3 (KNN) and La doped (K,Na)NbO 3 (KNN-La) thin films are grown on SrTiO 3 substrates using the chemical solution deposition method. The effect of adding different amounts of Na and K excess (0–20 mol%) is investigated. The results confirm the necessity of adding 20 mol% excess amounts of Na and K precursor solutions in order to avoid the formation of the secondary phase, K 4 Nb 6 O 17 , as confirmed by X-ray diffraction and Raman spectroscopy. Moreover, when adding a 20 mol% of alkaline metal excess, the thin films are highly textured with out-of-plane preferential orientation in the [100] direction of the [100] orientation of the substrate. Doping with lanthanum results in a decrease of the leakage current density at low electric field, and an increase in the dielectric permittivity across the whole temperature range (80–380 K). Although the (100)-oriented KNN and KNN-La films exhibited rounded hysteresis loops, at low temperatures the films show the typical ferroelectric hysteresis loops. - Highlights: • (K 0.5 Na 0.5 )NbO 3 and [(K 0.5 Na 0.5 ) 0.985 La 0.005 ]NbO 3 thin films have been prepared. • The obtained thin films show an excellent (100) preferred orientation. • Doping with lanthanum results in a decrease of the leakage current density. • The dielectric properties are enhanced when doping with lanthanum

  8. Controlling the reaction between boron-containing sealing glass and a lanthanum-containing cathode by adding Nb2O5

    Science.gov (United States)

    Zhao, Dandan; Fang, Lihua; Tang, Dian; Zhang, Teng

    2016-09-01

    In solid oxide fuel cell (SOFC) stacks, the volatile boron species present in the sealing glass often react with the lanthanum-containing cathode, degrading the activity of the cathode (this phenomenon is known as boron poisoning). In this work, we report that this detrimental reaction can be effectively reduced by doping bismuth-containing borosilicate sealing glass-ceramic with a niobium dopant. The addition of Nb2O5 not only condenses the [SiO4] structural units in the glass network, but also promotes the conversion of [BO3] to [BO4]. Moreover, the Nb2O5 dopant enhances the formation of boron-containing phases (Ca3B2O6 and CaB2Si2O8), which significantly reduces the volatility of boron compounds in the sealing glass, suppressing the formation of LaBO3 in the reaction couple between the glass and the cathode. The reported results provide a new approach to solve the problem of boron poisoning.

  9. Preparation and characterization of Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} composite oxide formed by cathodic electroplating and anodizing

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Joo-Hee; Kim, Tae-Yoo; Kim, Nam-Jeong; Lee, Chang-Hyoung; Park, Eun-Mi [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Chan [Division of Materials Science and Engineering, Pukyong National University, Busan 608-739 (Korea, Republic of); Suh, Su-Jeong, E-mail: suhsj@skku.ac.kr [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Advanced Materials and Process Research Center for IT, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2011-11-15

    Highlights: > We fabricate Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3}/Al film for high performance thin film capacitor. > The optimum condition of electrolyte composition will coat NbO{sub x} on Al without corrosion of Al during the cathodic electroplating. > Increasing annealing temperature will form Nb{sub 2}O{sub 5} crystalline. > The Al{sub 2}O{sub 3} layer will form between Nb{sub 2}O{sub 5} layer and metal Al after anodizing and the thin film capacitor with Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3}/Al improve dielectric properties. - Abstract: Al foil was coated with niobium oxide by cathodic electroplating and anodized in a neutral boric acid solution to achieve high capacitance in a thin film capacitor. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) revealed the niobium oxide layer on Al to be a hydroxide-rich amorphous phase. The film was crystalline and had stoichiometric stability after annealing at temperatures up to 600 deg. C followed by anodizing at 500 V, and the specific capacitance of the Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} composite oxide was approximately 27% higher than that of Al{sub 2}O{sub 3} without a Nb{sub 2}O{sub 5} layer. The capacitance was quite stable to the resonance frequency. Overall, the Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} composite oxide film is a suitable material for thin film capacitors.

  10. Photocatalysis with chromium-doped TiO2: Bulk and surface doping

    KAUST Repository

    Ould-Chikh, Samy

    2014-04-15

    The photocatalytic properties of TiO2 modified by chromium are usually found to depend strongly on the preparation method. To clarify this problem, two series of chromium-doped titania with a chromium content of up to 1.56 wt % have been prepared under hydrothermal conditions: the first series (Cr:TiO2) is intended to dope the bulk of TiO2, whereas the second series (Cr/TiO2) is intended to load the surface of TiO2 with Cr. The catalytic properties have been compared in the photocatalytic oxidation of formic acid. Characterization data provides evidence that in the Cr/TiO2 catalysts chromium is located on the surface of TiO2 as amorphous CrOOH clusters. In contrast, in the Cr:TiO 2 series, chromium is mostly dissolved in the titania lattice, although a minor part is still present on the surface. Photocatalytic tests show that both series of chromium-doped titania demonstrate visible-light-driven photo-oxidation activity. Surface-doped Cr/TiO2 solids appear to be more efficient photocatalysts than the bulk-doped Cr:TiO2 counterparts. It\\'s classified! The photocatalytic properties of TiO2 modified by chromium depend strongly on the preparation method. To clarify this problem, two types of modified titania are discussed: one with CrIII doped in the bulk and one with CrOOH clusters on the TiO2 surface (see picture). Both series show visible-light-driven photo-oxidation activity. However, surface modification appears to be a more efficient strategy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. A comparative study of the magnetization in transition metal ion doped CeO2, TiO2 and SnO2 nanoparticles

    Science.gov (United States)

    Apostolov, A. T.; Apostolova, I. N.; Wesselinowa, J. M.

    2018-05-01

    Using the microscopic s-d model taking into account anharmonic spin-phonon interactions we have studied the magnetic properties of Co and Cu ion doped CeO2 and TiO2 nanoparticles and compared them with those of SnO2. By Co-doping there is a maximum in the magnetization M(x) curve for all nanoparticles observed in the most transition metal doped ones. The s-d interaction plays an important role by the decrease of M at higher dopant concentration. We have discussed the magnetization in dependence of different model parameters. By small Cu-ion doping there are some differences. In CeO2M decreases with the Cu-concentration, whereas in TiO2 and SnO2M increases. For higher Cu dopant concentrations M(X) decreases in TiO2 nanoparticles. We obtain room temperature ferromagnetism also in Zn doped CeO2, TiO2 and SnO2 nanoparticles, i.e. in non-transition metal ion doped ones. The different behavior of M in Co and Cu doped nanoparticles is due to a combination effect of multivalent metal ions, oxygen vacancies, different radius of cation dopants, connection between lattice and magnetism, as well as competition between the s-d and d-d ferromagnetic or antiferromagnetic interactions.

  12. Photoelectrochemical oxidation of ibuprofen via Cu_2O-doped TiO_2 nanotube arrays

    International Nuclear Information System (INIS)

    Sun, Qiannan; Peng, Yen-Ping; Chen, Hanlin; Chang, Ken-Lin; Qiu, Yang-Neng; Lai, Shiau-Wu

    2016-01-01

    Highlights: • A p–n junction material was synthesized to enhance photocatalytic ability. • Cu_2O-doped TiO_2 nanotube arrays works as a photoanode in a PEC system. • Recombination of photo-generated holes and electrons were greatly reduced. • Synergetic effect was quantified in PEC degradation. • Recombination of photogenerated holes and electrons was greatly enhanced. - Abstract: A p–n junction based Cu_2O-doped TiO_2 nanotube arrays (Cu_2O-TNAs) were synthesized and used as a working anode in a photoelectrochemical (PEC) system. The results revealed that the Cu_2O-TNAs were dominated by the anatase phase and responded significantly to visible light. XPS analyses indicated that with an amount of 24.79% Cu doping into the structure, the band gap of Cu_2O-TNAs was greatly reduced. SEM images revealed that the supported TiO_2 nanotubes had diameters of approximately 80 nm and lengths of about 2.63 μm. Upon doping with Cu_2O, the TiO_2 nanotubes maintained their structural integrity, exhibiting no significant morphological change, favoring PEC applications. Under illumination, the photocurrent from Cu_2O/TNAs was 2.4 times larger than that from TNAs, implying that doping with Cu_2O significantly improved electron mobility by reducing the rate of recombination of electron-hole pairs. The EIS and Bode plot revealed that the estimated electron lifetimes, τ_e_l, of TNAs and Cu_2O/TNAs were 6.91 and 26.26 ms, respectively. The efficiencies of degradation of Ibuprofen by photoelectrochemical, photocatalytic (PC), electrochemical (EC) and photolytic (P) methods were measured.

  13. Effects of laser light confinement in periodically poled orthorhombic non-centrosymmetric Ba2NaNb5O15 crystals

    International Nuclear Information System (INIS)

    Lamela, J; Ródenas, A; Lifante, G; Jaque, D; Jaque, F; Kaminskii, A A

    2008-01-01

    In this paper we report on experimental evidence of laser light confinement between ferroelectric domains in the neodymium doped Ba 2 NaNb 5 O 15 ferroelectric crystal. High contrast near field optical microscopy images have been obtained as a consequence of the periodic modulation in the refractive index caused by the presence of 2D antiparallel ferroelectric domains

  14. Phase transitions and electrical properties of Bi2W1−xNbxO6−y and Bi2W1−xTaxO6−y

    International Nuclear Information System (INIS)

    Kharitonova, E.P.; Voronkova, V.I.; Gagor, A.B.; Pietraszko, A.P.; Alekseeva, O.A.

    2013-01-01

    Highlights: •The limit of Bi 2 W 1−x Me x O 6−y solid solutions is at x = 0.1, 0.15 for Me = Nb, Ta. •Ta and Nb substitutions for W suppress the reconstructive phase transition. •Bi 2 W 0.9 Nb 0.1 O 6−y samples belong to Aurivillius-type structure up to their melting. •Nb and Ta doping shifts ferroelectric transition to low temperatures up to 200 °C. •The highest conductivity reaches 10 −1 S/cm at 800 °C (x = 0.05, 0.1; Me = Nb, Ta). -- Abstract: Polycrystalline samples of Bi 2 W 1−x Me x O 6−y (Me = Nb, Ta) solid solutions have been prepared by solid-state reactions, and the influence of Nb and Ta substitutions for W on the polymorphism and electrical properties of Bi 2 WO 6 has been studied. The limit of the solid solutions is at x = 0.1 for Me = Nb and at x = 0.15 for Me = Ta. The distinctive features of the polymorphism of the Nb- and Ta-doped materials have been identified. According to differential scanning calorimetry data, tantalum and niobium substitutions for tungsten increase the temperature of the high-temperature, orthorhombic-to-monoclinic reconstructive phase transition and suppress the transition starting at x = 0.05 for Me = Nb and x = 0.10 for Me = Ta. As a result, the Bi 2 W 1−x Nb x O 6−y samples have an orthorhombic Aurivillius-type structure up to their melting point. The Bi 2 W 1−x Ta x O 6−y solid solutions at high temperatures consist of a mixture of an orthorhombic and a monoclinic phase. Nb and Ta doping shifts the ferroelectric phase transition to lower temperatures by more than 200 °C, thus markedly extending the stability range of the nonpolar orthorhombic paraelectric phase, which exists in a temperature range as narrow as 930–960 °C in the case of undoped Bi 2 WO 6 . The increase in oxygen vacancy concentration due to heterovalent substitutions of Nb 5+ and Ta 5+ for W 6+ leads to an increase in conductivity by two orders of magnitude relative to the unsubstituted compound

  15. Organometallic Trinuclear Niobium Cluster Complex in Aqueous Solution: Synthesis and Characterization of Niobium Complexes Containing Nb-3(mu-eta(2):eta(2) (perpendicular to)-NCCH3)(mu(2)-O)(3)(6+) Cluster Core

    DEFF Research Database (Denmark)

    Joensen, H.A.N.; Hansson, G. K.; Kozlova, S.G.

    2010-01-01

    ) and a broad peak at 565 nm (epsilon similar to 335 M-1 cm(-1)) in the UV-visible region. It is electron paramagnetic resonance (EPR)-active (g = 1.98), but no hyperfine interaction with the Nb-93 nuclear spin (I = 9/2) was observed. The cyclic voltammogram of [Nb-3(mu-eta(2):eta(2)-NCCH3)O-3(H2O)(9)](6+) in 4...

  16. Caging Nb2 O5 Nanowires in PECVD-Derived Graphene Capsules toward Bendable Sodium-Ion Hybrid Supercapacitors.

    Science.gov (United States)

    Wang, Xiangguo; Li, Qiucheng; Zhang, Li; Hu, Zhongli; Yu, Lianghao; Jiang, Tao; Lu, Chen; Yan, Chenglin; Sun, Jingyu; Liu, Zhongfan

    2018-05-14

    Sodium-ion hybrid supercapacitors (Na-HSCs) by virtue of synergizing the merits of batteries and supercapacitors have attracted considerable attention for high-energy and high-power energy-storage applications. Orthorhombic Nb 2 O 5 (T-Nb 2 O 5 ) has recently been recognized as a promising anode material for Na-HSCs due to its typical pseudocapacitive feature, but it suffers from intrinsically low electrical conductivity. Reasonably high electrochemical performance of T-Nb 2 O 5 -based electrodes could merely be gained to date when sufficient carbon content was introduced. In addition, flexible Na-HSC devices have scarcely been demonstrated by far. Herein, an in situ encapsulation strategy is devised to directly grow ultrathin graphene shells over T-Nb 2 O 5 nanowires (denoted as Gr-Nb 2 O 5 composites) by plasma-enhanced chemical vapor deposition, targeting a highly conductive anode material for Na-HSCs. The few-layered graphene capsules with ample topological defects would enable facile electron and Na + ion transport, guaranteeing rapid pseudocapacitive processes at the Nb 2 O 5 /electrolyte interface. The Na-HSC full-cell comprising a Gr-Nb 2 O 5 anode and an activated carbon cathode delivers high energy/power densities (112.9 Wh kg -1 /80.1 W kg -1 and 62.2 Wh kg -1 /5330 W kg -1 ), outperforming those of recently reported Na-HSC counterparts. Proof-of-concept Na-HSC devices with favorable mechanical robustness manifest stable electrochemical performances under different bending conditions and after various bending-release cycles. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Thermoluminescence and optically stimulated luminescence properties of Dy3+-doped CaO-Al2O3-B2O3-based glasses

    Science.gov (United States)

    Yahaba, T.; Fujimoto, Y.; Yanagida, T.; Koshimizu, M.; Tanaka, H.; Saeki, K.; Asai, K.

    2017-02-01

    We developed Dy3+-doped CaO-Al2O3-B2O3 based glasses with Dy concentrations of 0.5, 1.0, and 2.0 mol% using a melt-quenching technique. The as-synthesized glasses were applicable as materials exhibiting thermoluminescence (TL) and optically stimulated luminescence (OSL). The optical and radiation response properties of the glasses were characterized. In the photoluminescence (PL) spectra, two emission bands due to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ were observed at 480 and 580 nm. In the OSL spectra, the emission band due to the 4F9/2 → 6H15/2 transition of Dy3+ was observed. Excellent TL and OSL responses were observed for dose ranges of 0.1-90 Gy. In addition, TL fading behavior was better than that of OSL in term of the long-time storage. These results indicate that the Dy3+-doped CaO-Al2O3-B2O3-based glasses are applicable as TL materials.

  18. Bottom-up synthesis of up-converting submicron-sized Er3+-doped LiNbO3 particles

    International Nuclear Information System (INIS)

    Jardiel, T.; Caballero, A.C.; Marín-Dobrincic, M.; Cantelar, E.; Cussó, F.

    2012-01-01

    A new and simple wet chemical synthesis method is proposed to prepare submicron-sized Erbium-doped LiNbO 3 powders. The synthesis procedure comprises the co-precipitation of lithium and erbium ions from common precursors and their subsequent reaction with niobium ethoxide. A systematic characterization by means of X-Ray Diffraction (XRD), X-ray Fluorescence (XRF), Inductively Coupled Plasma (ICP-OES), Atomic Absorption (AAS), Field Emission Scanning Electron Microscopy (FE-SEM), as well as by the examination of the luminescence properties, evidence that with this method a congruent Er 3+ -doped LiNbO 3 single phase material can be obtained without using complex and time-consuming processing steps. The synthesized powders exhibit efficient IR to VIS up-conversion emissions under 974 nm pumping. -- Highlights: ► A novel chemical route to the preparation of LiNbO 3 powders has been developed. ► This process avoids complex and time-consuming processing steps. ► A congruent Er 3+ -doped LiNbO 3 single phase material can be obtained by this way. ► The luminescence properties are the expected for this composition.

  19. Dielectric, ferroelectric and piezoelectric properties of Nb{sup 5+} doped BCZT ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Parjansri, Piewpan [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, 50200 Chiang Mai (Thailand); Intatha, Uraiwan [School of Science, Mae Fah Luang University, 57100 Chiang Rai (Thailand); Eitssayeam, Sukum, E-mail: sukum99@yahoo.com [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, 50200 Chiang Mai (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, 50200 Chiang Mai (Thailand)

    2015-05-15

    Highlights: • Average grain size of BCZT ceramic decreased with the increasing Nb{sup 5+} doping. • Dielectric constant value is enhanced with Nb{sup 5+} doping. • Dielectric loss of BCZT − x Nb{sup 5+} ceramics was less than 0.03 at room temperature (1 kHz). • Piezoelectric coefficient decreased with the increasing Nb{sup 5+} doping. • The relaxation behavior is enhanced with the doping of Nb{sup 5+}. - Abstract: This work investigated the electrical properties of Nb{sup 5+} (0.0–1.0 mol%) doped with Ba{sub 0.90}Ca{sub 0.10}Zr{sub 0.10}Ti{sub 0.90}O{sub 3} while adding 1 mol% of Ba{sub 0.90}Ca{sub 0.10}Zr{sub 0.10}Ti{sub 0.90}O{sub 3} seeds. The mixed powder was ball milled for 24 h, calcined and sintered at 1200 °C for 2 h and 1450 °C for 4 h, respectively. The XRD patterns of the ceramic samples were investigated by X-ray diffraction. The electrical properties of ceramics were measured and the results indicated that all samples show a pure perovskite phase with no secondary phase. Density and average grain size values were in the range of 5.60–5.71 g/cm{sup 3} and 12.62–1.86 μm, respectively. The highest dielectric constant, ϵ{sub r} at room temperature (1 kHz) was 4636 found at 1.0 mol% Nb. The dielectric loss, tan δ was less than 0.03 for all samples at room temperature (1 kHz). Other electrical properties, P{sub r}, d{sub 33} and k{sub p} values were decreased with Nb doped relates to the decreasing grain size in BCZT ceramics. Moreover, the degrees of phase transition diffuseness and relaxation behavior were observed in the higher Nb doping.

  20. Ionic conductivity of co-doped Sc2O3-ZrO2 ceramics

    DEFF Research Database (Denmark)

    Omar, Shobit; bin Najib, Waqas; Chen, Weiwu

    2012-01-01

    The oxide ionic conductivity of Sc0.18Zr0.82O1.91 doped with 0.5 mol.% of both Yb2O3 and In2O3 is evaluated at various temperatures in air. Among various co-doped compositions, In0.02Sc0.18Zr0.80O1.90 exhibits the highest grain ionic conductivity followed by Yb0.02Sc0.18Zr0.80O1.90 at 500°C....... However, it also possesses phase transformation from c- to β-phase at 475°C on cooling. In the present work, an attempt is made to completely stabilize the cphase in In0.02Sc0.18Zr0.80O1.90 by substituting 0.5 mol.% of In2O3 with Yb2O3, which can enhance the ionic conductivity in co-doped compositions....

  1. High-quality single crystal growth and magnetic property of Mn4Ta2O9

    Science.gov (United States)

    Cao, Yiming; Xu, Kun; Yang, Ya; Yang, Wangfan; Zhang, Yuanlei; Kang, Yanru; He, Xijia; Zheng, Anmin; Liu, Mian; Wei, Shengxian; Li, Zhe; Cao, Shixun

    2018-06-01

    A large-size single crystal of Mn4Ta2O9 with ∼3.5 mm in diameter and ∼65 mm in length was successfully grown for the first time by a newly designed one-step method based on the optical floating zone technique. Both the clear Laue spots and sharp XRD Bragg reflections suggest the high quality of the single crystal. In Mn4Ta2O9 single crystal, an antiferromagnetic phase transition was observed below Néel temperature 102 K along c axis, which is similar to the isostructural compound Mn4Nb2O9, but differs from the isostructural Co4Nb2O9. Relative dielectric constant at 30 kOe suggests that no magnetoelectric coupling exists in Mn4Ta2O9.

  2. Effects of B site doping on electronic structures of InNbO4 based on hybrid density functional calculations

    Science.gov (United States)

    Lu, M. F.; Zhou, C. P.; Li, Q. Q.; Zhang, C. L.; Shi, H. F.

    2018-01-01

    In order to improve the photocatalytic activity under visible-light irradiation, we adopted first principle calculations based on density functional theory (DFT) to calculate the electronic structures of B site transition metal element doped InNbO4. The results indicated that the complete hybridization of Nb 4d states and some Ti 3d states contributed to the new conduction band of Ti doped InNbO4, barely changing the position of band edge. For Cr doping, some localized Cr 3d states were introduced into the band gap. Nonetheless, the potential of localized levels was too positive to cause visible-light reaction. When it came to Cu doping, the band gap was almost same with that of InNbO4 as well as some localized Cu 3d states appeared above the top of VB. The introduction of localized energy levels benefited electrons to migrate from valence band (VB) to conduction band (CB) by absorbing lower energy photons, realizing visible-light response.

  3. Effects of PbO-B2O3 Glass Doping on the Sintering Temperature and Piezoelectric Properties of 0.35Pb (Ni1/3Nb2/3)O3-0.65Pb(Zr0.41Ti0.59)O3 Ceramics

    Science.gov (United States)

    Yi, Jinqiao; Shen, Meng; Liu, Sisi; Jiang, Shenglin

    2015-12-01

    0.35Pb(Ni1/3Nb2/3)O3-0.65Pb(Zr0.41Ti0.59)O3 (PNN-PZT) ceramics doped with 0.5PbO-0.5B2O3 glass have been synthesized by the conventional solid-state sintering technique. The effects of 0.5PbO-0.5B2O3 glass on the sintering temperature and piezoelectric properties of PNN-PZT ceramics were studied. The results indicated that the sintering temperature of PNN-PZT was significantly reduced due to the incorporation of 0.5PbO-0.5B2O3 glass dopant. When the content of 0.5PbO-0.5B2O3 glass was 0.5 wt.%, the sintering temperature of PNN-PZT was observed to reduce from above 1200°C to 920°C while the samples maintained high density (7.91 g/cm3), excellent piezoelectric constant ( d 33 = 479 pC/N), large electromechanical coupling coefficient ( K p = 0.55), and relatively low electromechanical quality factor ( Q m = 79). Moreover, large dielectric constant ( ɛ 33 T / ɛ 0 = 2904) and low dielectric loss (tan δ = 0.0166) were obtained in this work.

  4. Effect of concurrent Mg/Nb-doping on dielectric properties of Ba0.45Sr0.55TiO3 thin films

    Science.gov (United States)

    Alema, Fikadu; Reich, Michael; Reinholz, Aaron; Pokhodnya, Konstantin

    2013-08-01

    Composition, microstructure, and dielectric properties of undoped and Ba(Mg1/3Nb2/3)O3 (BMN) doped Ba0.45Sr0.55TiO3 (BST) thin films deposited via rf. magnetron sputtering on platinized alumina substrates have been investigated. The analysis of microstructure has shown that despite the sizable effect of doping on the residual stress, the latter is partially compensated by the thermal expansion coefficient mismatch, and its influence on the BST film crystal structure is insignificant. It was revealed that BMN doped film demonstrated an average (over 2000 devices) of 52.5% tunability at 640 kV/cm, which is ˜8% lower than the value for the undoped film. This drop is associated with the presence of Mg ions in BMN; however, the effect of Mg doping is partially compensated by that of Nb ions. The decrease in grain size upon doping may also contribute to the tunability drop. Doping with BMN allows achievement of a compensation concentration yielding no free carriers and resulting in significant leakage current reduction when compared with the undoped film. In addition, the presence of large amounts of empty shallow traps related to NbTi• allows localizing free carriers injected from the contacts thus extending the device control voltage substantially above 10 V.

  5. Effects of MnO{sub 2} doping on structure, dielectric and piezoelectric properties of 0.825NaNbO{sub 3}-0.175Ba{sub 0.6}(Bi{sub 0.5}K{sub 0.5}){sub 0.4}TiO{sub 3} lead-free ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Ximing; Lin, Dunmin; Zheng, Qiaoji; Sun, Hailing; Wan, Yang; Wu, Xiaochun [College of Chemistry and Materials Science, and Visual Computing and Virtual Reality Key Laboratory of Sichuan Province, Sichuan Normal University, Chengdu 610066 (China); Wu, Lang [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China)

    2012-12-15

    Lead-free ceramics 0.825NaNbO{sub 3}-0.175Ba{sub 0.6}(Bi{sub 0.5}K{sub 0.5}){sub 0.4}TiO{sub 3} + xmol% MnO{sub 2} were prepared by an ordinary sintering technique and the effects of MnO{sub 2} doping on the structure, dielectric, and piezoelectric properties of the ceramics were studied. The ceramics with perovskite structure are transformed from tetragonal to pseudocubic phases by increasing the doping level of MnO{sub 2}. After the addition of MnO{sub 2}, the Curie temperature T{sub C} of the ceramics decreases and the ferroelectric-paraelectric phase transition at T{sub C} becomes more diffusive. Because of the donor and acceptor doping effects of Mn ions simultaneously, the piezoelectric constant d{sub 33}, electromechanical coupling coefficient k{sub p}, relative permittivity {epsilon}{sub r}, and mechanical quality factor Q{sub m} are enhanced considerably after the addition of 1 mol% MnO{sub 2}. The ceramic with 1 mol% MnO{sub 2} doping possesses the optimum piezoelectricity (d{sub 33} = 131 pC/N and k{sub p} = 21.8%) and relatively high Q{sub m} = 627. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Photocatalytic activity of TiO2 doped with boron and vanadium

    International Nuclear Information System (INIS)

    Bettinelli, M.; Dallacasa, V.; Falcomer, D.; Fornasiero, P.; Gombac, V.; Montini, T.; Romano, L.; Speghini, A.

    2007-01-01

    Boron (B)- and vanadium (V)-doped TiO 2 photocatalysts were synthesized using modified sol-gel reaction processes and characterized by X-ray diffraction (XRD), Raman spectroscopy and N 2 physisorption (BET). The photocatalytic activities were evaluated by monitoring the degradation of methylene blue (MB). The results showed that the materials possess high surface area. The addition of B favored the transformation of anatase to rutile, while in the presence of V, anatase was the only phase detected. The MB degradation on V-doped TiO 2 was significantly affected by the preparation method. In fact while the presence of V in the bulk did not influence strongly the photoreactivity under visible irradiation, an increase of surface V doping lead to improved photodegradation of MB. The degradation of MB dye indicated that the photocatalytic activities of TiO 2 increased as the boron doping increased, with high conversion efficiency for 9 mol% B doping

  7. Pd/Nb2O5/SiO2 catalyst for the direct hydrodeoxygenation of biomass-related compounds to liquid alkanes under mild conditions.

    Science.gov (United States)

    Shao, Yi; Xia, Qineng; Liu, Xiaohui; Lu, Guanzhong; Wang, Yanqin

    2015-05-22

    A simple Pd-loaded Nb2 O5 /SiO2 catalyst was prepared for the hydrodeoxygenation of biomass-related compounds to alkanes under mild conditions. Niobium oxide dispersed in silica (Nb2 O5 /SiO2 ) as the support was prepared by the sol-gel method and characterized by various techniques, including N2 adsorption, XRD, NH3 temperature-programmed desorption (TPD), TEM, and energy-dispersive X-ray spectroscopy (EDAX) atomic mapping. The characterization results showed that the niobium oxide species were amorphous and well dispersed in silica. Compared to commercial Nb2 O5 , Nb2 O5 /SiO2 has significantly more active niobium oxide species exposed on the surface. Under mild conditions (170 °C, 2.5 MPa), Pd/10 %Nb2 O5 /SiO2 was effective for the hydrodeoxygenation reactions of 4-(2-furyl)-3-buten-2-one (aldol adduct of furfural with acetone), palmitic acid, tristearin, and diphenyl ether (model compounds of microalgae oils, vegetable oils, and lignin), which gave high yields (>94 %) of alkanes with little CC bond cleavage. More importantly, owing to the significant promotion effect of NbOx species on CO bond cleavage and the mild reaction conditions, the CC cleavage was considerably restrained, and the catalyst showed an excellent activity and stability for the hydrodeoxygenation of palmitic acid with almost no decrease in hexadecane yield (94-95 %) in a 150 h time-on-stream test. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Ti2Nb10O29-x mesoporous microspheres as promising anode materials for high-performance lithium-ion batteries

    Science.gov (United States)

    Deng, Shengjue; Luo, Zhibin; Liu, Yating; Lou, Xiaoming; Lin, Chunfu; Yang, Chao; Zhao, Hua; Zheng, Peng; Sun, Zhongliang; Li, Jianbao; Wang, Ning; Wu, Hui

    2017-09-01

    Ti2Nb10O29 has recently been reported as a promising anode material for lithium-ion batteries. However, its poor electronic conductivity and insufficient Li+-ion diffusion coefficient significantly limit its rate capability. To tackle this issue, a strategy combining nanosizing and crystal-structure modification is employed. Ti2Nb10O29-x mesoporous microspheres with a sphere-size range of 0.5-4 μm are prepared by a one-step solvothermal method followed by thermal treatment in N2. These Ti2Nb10O29-x mesoporous microspheres exhibit primary nanoparticles, a large specific surface area (22.9 m2 g-1) and suitable pore sizes, leading to easy electron/Li+-ion transport and good interfacial reactivity. Ti2Nb10O29-x shows a defective shear ReO3 crystal structure with O2- vacancies and an increased unit cell volume, resulting in its increased Li+-ion diffusion coefficient. Besides Ti4+ and Nb5+ ions, Ti2Nb10O29-x comprises Nb4+ ions with unpaired 4d electrons, which significantly increase its electronic conductivity. As a result of these improvements, the Ti2Nb10O29-x mesoporous microspheres reveal superior electrochemical performances in term of large reversible specific capacity (309 mAh g-1 at 0.1 C), outstanding rate capability (235 mAh g-1 at 40 C) and durable cyclic stability (capacity retention of 92.1% over 100 cycles at 10 C).

  9. Temperature compensation effects of TiO2 on Ca[(Li1/3Nb2/3)0.8Sn0.2]O3-δ microwave dielectric ceramic

    Science.gov (United States)

    Hu, Mingzhe; Wei, Huanghe; Xiao, Lihua; Zhang, Kesheng; Hao, Yongde

    2017-10-01

    The crystal structure and dielectric properties of TiO2-modified Ca[(Li1/3Nb2/3)0.8Sn0.2]O3-δ microwave ceramics are investigated in the present paper. The crystal structure is probed by XRD patterns and their Rietveld refinement, results show that a single perovskite phase is formed in TiO2-modified Ca[(Li1/3Nb2/3)0.8Sn0.2]O3-δ ceramics with the crystal structure belonging to the orthorhombic Pbnm 62 space group. Raman spectra results indicate that the B-site order-disorder structure transition is a key point to the dielectric loss of TiO2-modified Ca[(Li1/3Nb2/3)0.8Sn0.2]O3-δ ceramics at microwave frequencies. After properly modified by TiO2, the large negative temperature coefficient of Ca[(Li1/3Nb2/3)0.8Sn0.2]O3-δ ceramic can be compensated and the optimal microwave dielectric properties can reach 𝜀r = 25.66, Qf = 18,894 GHz and TCF = -6.3 ppm/∘C when sintered at 1170∘C for 2.5 h, which manifests itself for potential use in microwave dielectric devices for modern wireless communication.

  10. Dielectric properties of Li doped Li-Nb-O thin films

    Energy Technology Data Exchange (ETDEWEB)

    Perentzis, G.; Horopanitis, E.E.; Papadimitriou, L. [Aristotle University of Thessaloniki, Department of Physics, 54124 Thessaloniki (Greece); Durman, V.; Saly, V.; Packa, J. [Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, 81219 Bratislava (Slovakia)

    2007-03-15

    Lithium niobate LiNbO{sub 3} was prepared as a thin film layered structure deposited on stainless steel substrate using e-gun evaporation. The Li doping was provided for by the formation of Li-Nb-O/Li/LiNb-O sandwich structure and annealing at about 250 C. AC impedance spectroscopy measurements were performed on the samples at temperatures from the interval between 28 and 165 C and in a frequency range of 10{sup -3} to 10{sup 6} Hz. Using the values Z' and Z'' at different frequencies, the dielectric parameters - parts of the complex permittivity {epsilon}' and {epsilon}'' and loss tangent tan {delta} were calculated. The results prove validity of the proposed equivalent circuit containing parallel RC elements connected in series where the first RC element represents the bulk of material and the second RC element belongs to the double layer at the metal interface. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Synthesis and Characterization of Yttria-Stabilized Zirconia Nanoparticles Doped with Ytterbium and Gadolinium: ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3

    Science.gov (United States)

    Bahamirian, M.; Hadavi, S. M. M.; Rahimipour, M. R.; Farvizi, M.; Keyvani, A.

    2018-06-01

    Defect cluster thermal barrier coatings (TBCs) are attractive alternatives to Yttria-stabilized zirconia (YSZ) in advanced applications. In this study, YSZ nanoparticles doped with ytterbium and gadolinium (ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3 (ZGYbY)) were synthesized through a chemical co-precipitation and calcination method, and characterized by in situ high-temperature X-ray diffraction analysis in the temperature range of 25 °C to 1000 °C (HTK-XRD), thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Precise cell parameters of t-prime phase and the best zirconia phase for TBC applications were calculated by Cohen's and Rietveld refinement methods. Optimum crystallization temperature of the precursor powder was found to be 1000 °C. Furthermore, FE-SEM results for the calcined ZGYbY powders indicated orderly particles of uniform shape and size with a small tendency toward agglomeration. Average lattice thermal expansion coefficient in the temperature range of 25 °C to 1000 °C was determined to be 31.71 × 10-6 K-1.

  12. Synthesis and Characterization of Yttria-Stabilized Zirconia Nanoparticles Doped with Ytterbium and Gadolinium: ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3

    Science.gov (United States)

    Bahamirian, M.; Hadavi, S. M. M.; Rahimipour, M. R.; Farvizi, M.; Keyvani, A.

    2018-03-01

    Defect cluster thermal barrier coatings (TBCs) are attractive alternatives to Yttria-stabilized zirconia (YSZ) in advanced applications. In this study, YSZ nanoparticles doped with ytterbium and gadolinium (ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3 (ZGYbY)) were synthesized through a chemical co-precipitation and calcination method, and characterized by in situ high-temperature X-ray diffraction analysis in the temperature range of 25 °C to 1000 °C (HTK-XRD), thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Precise cell parameters of t-prime phase and the best zirconia phase for TBC applications were calculated by Cohen's and Rietveld refinement methods. Optimum crystallization temperature of the precursor powder was found to be 1000 °C. Furthermore, FE-SEM results for the calcined ZGYbY powders indicated orderly particles of uniform shape and size with a small tendency toward agglomeration. Average lattice thermal expansion coefficient in the temperature range of 25 °C to 1000 °C was determined to be 31.71 × 10-6 K-1.

  13. The role of the Mg sup 2 sup + ions in Cr sup 3 sup + spectroscopy for near-stoichiometric LiNbO sub 3 crystals

    CERN Document Server

    Han, T P J; Bermudez, V; Diéguez, E

    2003-01-01

    The optical spectroscopy of Cr sup 3 sup + ions doped into near-stoichiometric LiNbO sub 3 crystals, pure and co-doped with MgO, has been investigated. In the near-stoichiometric LiNbO sub 3 :Cr(0.2 mol%):Mg(2 mol%) crystal, the optical spectra resemble those previously observed for congruent LiNbO sub 3 :Cr:MgO samples when the total MgO content exceeds the 4.6 mol% threshold. The coexistence of two types of Cr sup 3 sup + centre ([Cr] sub L sub i and [Cr] sub N sub b) characterized the optical and luminescence spectra of this sample. The concentration equilibrium between the two types of centre is strongly displaced towards the [Cr sup 3 sup + ] sub N sub b centre, permitting us to obtain with accuracy the parameters of the broad bands. The R-line associated with the [Cr] sub N sub b centre is only observable in the low-temperature emission spectrum. The Fano anti-resonance lines present have been observed to be more pronounced for the near-stoichiometric samples than for congruent ones.

  14. The effect of Mg doping on the Raman spectra of LiNbO3 crystals

    International Nuclear Information System (INIS)

    Lengyel, K.; Kovacs, L.; Peter, A.; Polgar, K.; Corradi, G.; Bourson, P.

    2007-01-01

    LiNbO 3 :Mg crystals doped with 0-8 mol% Mg with stoichiometric, intermediate and congruent compositions were systematically investigated by Raman spectroscopy in backscattering y(zx)y and y(zz)y geometries. The halfwidths of E(TO 3 ) - E(TO 9 ) and A 1 (TO 1 ) - A 1 (TO 4 ) bands, which have a significant composition dependence for undoped LiNbO 3 crystals, show only weak Mg-concentration dependence below the photorefractive threshold. This is a consequence of the counteracting effect of the decreasing amount of Nb ions at Li-ion sites (Nb Li ) and increasing amount of Mg ions at Li-ion sites (Mg Li ). The halfwidths of these bands, however, increase linearly with growing Mg content for samples above the threshold, irrespective of the Li/Nb ratio. The same effect was observed in the Mg dependence of the position and halfwidth of the two-phonon band at about 689 - 705 cm -1 . The change in the Mg concentration dependence of these parameters at a given Li/Nb ratio determines the same threshold value as that concluded from IR and UV spectroscopic measurements. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Substitution of Nb doping on the structural, microstructural and electrical properties in PZT films

    International Nuclear Information System (INIS)

    Haccart, T.; Remiens, D.; Cattan, E.

    2003-01-01

    Undoped and niobium (Nb) doped Pb 1-y (Zr 0.54 Ti 0.46 ) 1-y Nb y O 3 have been deposited by sputtering on Pt metallized silicon substrates. The niobium concentration, y, was varied from 1 to 7 at.% by 1 at.%. The Zr/Ti ratio was fixed to 54/46 corresponding to the Morphotropic Phase Boundary. Structural, microstructural, and electrical properties were evaluated depending on Nb content. The films (doped and undoped) present a (1 1 1)-preferred orientation. The Nb doping induces an increase of the grain size and as it was observed in bulk materials the dielectric constant (ε r ) and the piezoelectric coefficients (e 31 and d 33 ) reach their maximum for low Nb concentration (2 at.%). The remnant and the maximum polarizations increase as the coercive field decreased slightly with the Nb concentration. The internal electric field increases with Nb content; as a result, the 'self-polarization' of the films (polarization measured without poling treatment) is enhanced with niobium substitution. In term of fatigue behavior, it was found that switching endurance characteristics are maximum for low Nb doping level

  16. Substitution of Nb doping on the structural, microstructural and electrical properties in PZT films

    Energy Technology Data Exchange (ETDEWEB)

    Haccart, T.; Remiens, D.; Cattan, E

    2003-01-15

    Undoped and niobium (Nb) doped Pb{sub 1-y}(Zr{sub 0.54}Ti{sub 0.46}){sub 1-y}Nb{sub y}O{sub 3} have been deposited by sputtering on Pt metallized silicon substrates. The niobium concentration, y, was varied from 1 to 7 at.% by 1 at.%. The Zr/Ti ratio was fixed to 54/46 corresponding to the Morphotropic Phase Boundary. Structural, microstructural, and electrical properties were evaluated depending on Nb content. The films (doped and undoped) present a (1 1 1)-preferred orientation. The Nb doping induces an increase of the grain size and as it was observed in bulk materials the dielectric constant ({epsilon}{sub r}) and the piezoelectric coefficients (e{sub 31} and d{sub 33}) reach their maximum for low Nb concentration (2 at.%). The remnant and the maximum polarizations increase as the coercive field decreased slightly with the Nb concentration. The internal electric field increases with Nb content; as a result, the 'self-polarization' of the films (polarization measured without poling treatment) is enhanced with niobium substitution. In term of fatigue behavior, it was found that switching endurance characteristics are maximum for low Nb doping level.

  17. Tailoring the surface chemical bond states of the NbN films by doping Ag: Achieving hard hydrophobic surface

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Ping; Zhang, Kan; Du, Suxuan [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Meng, Qingnan [College of Construction Engineering, Jilin University, Changchun, 130026 (China); He, Xin [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Wang, Shuo [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Wen, Mao, E-mail: wenmao225@jlu.edu.cn [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China); Zheng, Weitao, E-mail: WTZheng@jlu.edu.cn [Department of Materials Science, State Key Laboratory of Superhard Materials, and Key Laboratory of Automobile Materials, MOE, Jilin University, Changchun, 130012 (China)

    2017-06-15

    Highlights: • Intrinsically hydrophilic NbN films can transfer to hydrophobic Nb-Ag-N films by doping Ag atoms into NbN sublattice. • Solute Ag can promote that the hydrophobic Ag{sub 2}O groups formed on the Nb-Ag-N film surface through self-oxidation. • The present work may provide a straightforward approach for the production of robust hydrophobic ceramic surfaces. - Abstract: Robust hydrophobic surfaces based on ceramics capable of withstanding harsh conditions such as abrasion, erosion and high temperature, are required in a broad range of applications. The metal cations with coordinative saturation or low electronegativity are commonly chosen to achieve the intrinsically hydrophobic ceramic by reducing Lewis acidity, and thus the ceramic systems are limited. In this work, we present a different picture that robust hydrophobic surface with high hardness (≥20 GPa) can be fabricated through doping Ag atoms into intrinsically hydrophilic ceramic film NbN by reactive co-sputtering. The transition of wettability from hydrophilic to hydrophobic of Nb-Ag-N films induced by Ag doping results from the appearance of Ag{sub 2}O groups on the films surfaces through self-oxidation, because Ag cations (Ag{sup +}) in Ag{sub 2}O are the filled-shell (4d{sup 10}5S{sup 0}) electronic structure with coordinative saturation that have no tendency to interact with water. The results show that surface Ag{sub 2}O benefited for hydrophobicity comes from the solute Ag atoms rather than precipitate metal Ag, in which the more Ag atoms incorporated into Nb-sublattice are able to further improve the hydrophobicity, whereas the precipitation of Ag nanoclusters would worsen it. The present work opens a window for fabricating robust hydrophobic surface through tailoring surface chemical bond states by doping Ag into transition metal nitrides.

  18. Structures and electrical properties of Mn- and Co-doped lead-free ferroelectric K0.5Na0.5NbO3 films prepared by a chemical solution deposition method

    International Nuclear Information System (INIS)

    Wang, Lingyan; Ren, Wei; Goh, Phoi Chin; Yao, Kui; Shi, Peng; Wu, Xiaoqing; Yao, Xi

    2013-01-01

    The un-doped, 2 mol% Mn- and 2 mol% Co-doped K 0.5 Na 0.5 NbO 3 (KNN) films were prepared by a chemical solution deposition method. The crystalline phase and surface morphologies of KNN films hardly changed after Mn- and Co-doping. X-ray photoelectron spectrocopy analysis indicates that the introduction of both Mn and Co promoted the formation of KNN perovskite structure, and the most Mn 2+ and Co 2+ ions were oxidized into high-valence ions during thermal process. As a result, the leakage current density of the KNN films was decreased and the electrical properties were enhanced after the doping. - Highlights: • The leakage current density of K 0.5 Na 0.5 NbO 3 (KNN) films decreased after doping • The introduction of dopant promoted the formation of KNN perovskite structure • A portion of introduced doping ions became high-valent after heat-treatment

  19. The preparation and testing of Nb-Zr and Nb-ZrO2 single crystals for deformation studies

    International Nuclear Information System (INIS)

    Botta Filho, W.J.; Christian, J.W.; Taylor, G.

    1987-01-01

    The difficulties to obtain adequate single crystals of Nb-Zr and Nb-ZrO 2 alloys for deformation studies are discussed. Low-temperature internal oxidation of Nb-Zr alloys followed by ageing at higher temperatures resulted in the precipitation of ZrO 2 particles. However, the effect of this treatment on the particles size and distribution and on the crystallographic structure of the particle was not completely understood. Compression tests in the temperature range 4.2K to 373K showed a small effect of zirconia particles on the mechanical properties of Nb-Zr solid solutions and a significative effect of the amount of oxygen remaining in solid solution after the oxidation treatment. (author) [pt

  20. Free-anchored Nb2O5@graphene networks for ultrafast-stable lithium storage

    Science.gov (United States)

    Deng, Qinglin; Li, Mengjiao; Wang, Junyong; Jiang, Kai; Hu, Zhigao; Chu, Junhao

    2018-05-01

    Orthorhombic Nb2O5 (T-Nb2O5) has structural merit but poor electrical conductivity, limiting their applications in energy storage. Although graphene is frequently adopted to effectively improve its electrochemical properties, the ordinary modified methods cannot meet the growing demands for high-performance. Here, we demonstrate that different graphene modified routes play a vital role in affecting the electrochemical performances of T-Nb2O5. By only manual shaking within one minute, Nb2O5 nano-particles can be rapidly adsorbed onto graphene, then the free-anchored T-Nb2O5@graphene three-dimensional networks can be successfully prepared based on hydrogel method. As for the application in lithium-ion batteries, it performs outstanding rate character (129 mA h g-1 (25C rate), 110 mA h g-1 (50C rate) and 90 mA h g-1 (100C rate), correspond to 79%, 67% and 55% capacity of 0.5C rate, respectively) and excellent long-term cycling feature (˜70% capacity retention after 20000 cycles). Moreover, it still maintains similar ultrafast-stable lithium storage performances when Cu foil is substituted by Al foil as current collector. In addition, relevant kinetics mechanisms are also expounded. This work provides a versatile strategy for the preparation of graphene modified Nb2O5 or other types of nanoparticles.

  1. Preparation and near-infrared absorption of nano-SnO{sub 2}/SiO{sub 2} assemblies with doping and without doping

    Energy Technology Data Exchange (ETDEWEB)

    Hai Shujie [Faculty of Material Science and Chemical Engineering, China University of Geosciences, Lu Mo Road 388, Wuhan 430074 (China); Yan Chunjie, E-mail: chjyan2005@126.co [Engineering Research Center of Nano-Geomaterials, Ministry of Education, China University of Geosciences, Lu Mo Road 388, Wuhan 430074 (China); Yu Hongjie; Xiao Guoqi; Wang Duo [Faculty of Material Science and Chemical Engineering, China University of Geosciences, Lu Mo Road 388, Wuhan 430074 (China)

    2009-11-20

    The assemblies of nano-SnO{sub 2}/SiO{sub 2} and Sb- or Pd-doped nano-SnO{sub 2}/SiO{sub 2}, in which the nano-SnO{sub 2} particles are located in the pores of mesoporous SiO{sub 2} dry gels, were synthesized. Only for the Sb-doped nano-SnO{sub 2}/SiO{sub 2} assemblies, a broad near-infrared absorption step occurs in the optical absorption spectrum of the wavelength range from 300 to 1500 nm. The near-infrared absorption phenomenon is attributed to electronic transitions from the ground states to the excitation states of the impurity energy levels, which are formed by Sb doping in SnO{sub 2}. With increasing the weight ratio of SnO{sub 2}:SiO{sub 2} or the annealing temperature, the near-infrared absorption step slope side exhibits 'red shift', which is caused by the quantum confinement effect weakening due to the increased SnO{sub 2} crystalline diameter.

  2. Dielectric properties of Ga2O3-doped barium iron niobate ceramics

    International Nuclear Information System (INIS)

    Sanjoom, Kachaporn; Pengpat, Kamonpan; Eitssayeam, Sukum; Tunkasiri, Tawee; Rujijanagul, Gobwute

    2014-01-01

    Ga-doped BaFe 0.5 Nb 0.5 O 3 (Ba(Fe 1-x Ga x ) 0.5 Nb 0.5 O 3 ) ceramics were fabricated and their properties were investigated. All ceramics showed perovskite structure with cubic symmetry and the solubility of Ga in BFN ceramics had a limit at x = 0.2. Examination of the dielectric spectra indicated that all ceramic samples presented high dielectric constants that were frequency dependent. The x = 0.2 ceramic showed a very high dielectric constant (ε r > 240 000 at 1 kHz) while the x = 0.4 sample exhibited high thermal stability of dielectric constant with low loss tangent from room temperature (RT) to 100 C with ε r > 28 000 (at 1 kHz) when compared to other samples. By using a complex impedance analysis technique, bulk grain, grain boundary, and electrode response were found to affect the dielectric behavior that could be related to the Maxwell-Wagner polarization mechanism. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Sorption properties and reversibility of Ti(IV) and Nb(V)-fluoride doped-Ca(BH{sub 4}){sub 2}-MgH{sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Bonatto Minella, Christian, E-mail: christian.minella@kit.edu [Institute for Metallic Materials, IFW Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany); Technische Universität Dresden, D-01062 Dresden (Germany); Garroni, Sebastiano [Dipartimento di Chimica e Farmacia, Universitá di Sassari and INSTM, Via Vienna 2, I-07100 Sassari (Italy); Pistidda, Claudio [Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH, Max Planck Str. 1, D-21502 Geesthacht (Germany); Baró, Maria Dolors [Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Gutfleisch, Oliver [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt (Germany); Klassen, Thomas; Dornheim, Martin [Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH, Max Planck Str. 1, D-21502 Geesthacht (Germany)

    2015-02-15

    Highlights: • Faster desorption reaction for doped materials vs. the pure composite system. • Kinetic improvement concerning re-hydrogenation reaction showed by the addition of NbF{sub 5}. • Full characterization of the de-hydrogenation reaction pathway by means of both SR-PXD and {sup 11}B{"1H} MAS-NMR. • Study of the evolution of the chemical state of the additives upon both milling and sorption reactions. - Abstract: In the last decade, alkaline and alkaline earth metal tetrahydroborates have been the focuses of the research due to their high gravimetric and volumetric hydrogen densities. Among them, Ca(BH{sub 4}){sub 2} and the Ca(BH{sub 4}){sub 2} + MgH{sub 2} reactive hydride composites (RHC), were calculated to have the ideal thermodynamic properties which fall within the optimal range for mobile applications. In this study, the addition of NbF{sub 5} or TiF{sub 4} to the Ca(BH{sub 4}){sub 2} + MgH{sub 2} reactive hydride composite system was attempted aiming to obtain a full reversible system with the simultaneous suppression of CaB{sub 12}H{sub 12}. Structural characterization of the specimens was performed by means of in-situ Synchrotron Radiation Powder X-ray diffraction (SR-PXD) and {sup 11}B{"1H} Solid State Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). The evolution of the chemical state of the Nb- and Ti-based additives was monitored by X-ray Absorption Near Edge Structure (XANES). The addition of NbF{sub 5} or TiF{sub 4} to the Ca(BH{sub 4}){sub 2} + MgH{sub 2} system have not suppressed completely the formation of CaB{sub 12}H{sub 12} and only a slight improvement concerning the reversible reaction was displayed just in the case of Nb-doped composite material.

  4. Synthesis of La2O3 doped Zn2SnO4 hollow fibers by electrospinning method and application in detecting of acetone

    Science.gov (United States)

    Yang, H. M.; Ma, S. Y.; Yang, G. J.; Chen, Q.; Zeng, Q. Z.; Ge, Q.; Ma, L.; Tie, Y.

    2017-12-01

    Hollow porous pure and La2O3 doped Zn2SnO4 fibers were synthesized via single capillary electrospinning technology and used for obtaining of gas sensors. The as-prepared samples were characterized by microscopy, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy and UV-vis absorption spectra. The newly obtained gas sensors were investigated for acetone detection. Compared with pure Zn2SnO4 hollow fibers, the La2O3 doped Zn2SnO4 hollow fibers not only exhibited perfect sensing performance toward acetone with excellent selectivity, high response and fast response/recovery capability (7 s for adsorption and 9 s for desorption), but also the operating temperature was reduced from 240 °C to 200 °C. These results demonstrated that the special hollow porous La doped Zn2SnO4 fibers structures were used as the sensing material for fabricating high performance acetone sensors. The acetone sensing mechanism of La2O3 doped Zn2SnO4 hollow fibers was discussed too.

  5. Disk-type piezoelectric transformer of a Na0.5K0.5NbO3–CuNb2O6 lead-free ceramic for driving T5 fluorescent lamp

    International Nuclear Information System (INIS)

    Yang, Ming-Ru; Chu, Sheng-Yuan; Chan, I.-Hao; Yang, Song-Ling

    2012-01-01

    Highlights: ► CuNb 2 O 6 dopants were doped into NKN ceramics not only improved the density but also exhibited superior piezoelectric characteristic, temperature stability of resonance frequency. ► Lead-free NKN-01CN piezoelectric transformer was simplified as an equivalent circuit and analyzed using MATLAB. ► An 8W T5 fluorescent lamp was successfully driven by the NKN-01CN piezoelectric transformer. - Abstract: Lead-free (Na 0.5 K 0.5 )NbO 3 (NKN) ceramics doped with 1 mol% CuNb 2 O 6 (CN) ceramics were prepared using the conventional mixed oxide method, with a sintering temperature of 1075 °C. Microstructural analyses of the NKN–01CN ceramics were carried out and compared, using X-ray diffraction (XRD). NKN–01CN ceramics sintered at 1075 °C not only exhibited excellent ‘hard’ piezoelectric properties of k p = 40%, k t = 45%, k 33 = 57%, a ferroelectric property of E c = 23 kV/cm, and an extraordinarily high mechanical quality factor (Q m ) of 1933 but also showed excellent stability with temperature (TCF = −154 ppm/°C). The piezoelectric transformer was simplified, using an equivalent circuit, and analyzed, using MATLAB; the simulation data agreed well with the experimental results. An efficiency of 95.7% was achieved for the NKN–01CN piezoelectric transformer with load resistance of 20 kΩ. An 8 W T5 fluorescent lamp was successfully driven by the NKN–01CN piezoelectric transformer.

  6. Near infrared emission and multicolor tunability of enhanced upconversion emission from Er{sup 3+}–Yb{sup 3+} co-doped Nb{sub 2}O{sub 5} nanocrystals embedded in silica-based nanocomposite and planar waveguides for photonics

    Energy Technology Data Exchange (ETDEWEB)

    Aquino, Felipe Thomaz [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo. Av. Bandeirantes, 3900, CEP 14040-901 Ribeirão Preto, SP (Brazil); Ferrari, Jefferson Luis [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo. Av. Bandeirantes, 3900, CEP 14040-901 Ribeirão Preto, SP (Brazil); Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, 36301-160 São João Del Rei, MG (Brazil); Maia, Lauro June Queiroz [Grupo Física de Materiais, Instituto de Física, Universidade Federal de Goiás, Campus II, C.P. 131, CEP 74001-970, Goiânia, GO (Brazil); Ribeiro, Sidney José Lima [Institute of Chemistry- São Paulo State University- UNESP, Araraquara, SP 14800-900 (Brazil); Ferrier, Alban [PSL Research University, Chimie ParisTech - CNRS, Institut de Recherche de Chimie Paris, 75005 Paris (France); Sorbonne Universités, UPMC Univ Paris 06, 75005 Paris (France); and others

    2016-02-15

    This work reports on the Yb{sup 3+} ion addition effect on the near infrared emission and infrared-to-visible up conversion from planar waveguides based on Er{sup 3+}–Yb{sup 3+} co-doped Nb{sub 2}O{sub 5} nanocrystals embedded in SiO{sub 2}-based nanocomposite prepared by a sol–gel process with controlled crystallization in situ. Planar waveguides and xerogels containing Si/Nb molar ratio of 90:10 up to 50:50 were prepared. Spherical-like orthorhombic or monoclinic Nb{sub 2}O{sub 5} nanocrystals were grown in the amorphous SiO{sub 2}-based host depending on the niobium content and annealing temperature, resulting in transparent glass ceramics. Crystallization process was intensely affected by rare earth content increase. Enhancement and broadening of the NIR emission has been achieved depending on the rare earth content, niobium content and annealing temperature. Effective Yb{sup 3+}→Er{sup 3+} energy transfer and a high-intensity broad band emission in the near infrared region assigned to the Er{sup 3+} ions {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition, and longer {sup 4}I{sub 13/2} lifetimes were observed for samples containing orthorhombic Nb{sub 2}O{sub 5} nanocrystals. Intense green and red emissions were registered for all Er{sup 3+}–Yb{sup 3+} co-doped waveguides under 980 nm excitation, assigned to {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} (525 nm),{sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} (545nm) and {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} (670 nm) transitions, respectively. Different relative green and red intensities emissions were observed, depending upon niobium oxide content and the laser power. Upconversion dynamics were determined by the photons number, evidencing that ESA or ETU mechanisms are probably occurring. The 1931 CIE chromaticity diagrams indicated interesting color tunability based on the waveguides composition and pump power. The nanocomposite waveguides are promising materials for photonic applications as optical amplifiers and

  7. Temperature stability of c-axis oriented LiNbO3/SiO2/Si thin film layered structures

    International Nuclear Information System (INIS)

    Tomar, Monika; Gupta, Vinay; Mansingh, Abhai; Sreenivas, K.

    2001-01-01

    Theoretical calculations have been performed for the temperature stability of the c-axis oriented LiNbO 3 thin film layered structures on passivated silicon (SiO 2 /Si) substrate with and without a non-piezoelectric SiO 2 overlayer. The phase velocity, electromechanical coupling coefficient and temperature coefficient of delay (TCD) have been calculated. The thicknesses of various layers have been determined for optimum SAW performance with zero TCD. The presence of a non-piezoelectric SiO 2 overlayer on LiNbO 3 film is found to significantly enhance the coupling coefficient. The optimized results reveal that a high coupling coefficient of K 2 =3.45% and a zero TCD can be obtained in the SiO 2 /LiNbO 3 /SiO 2 /Si structure with a 0.235λ thick LiNbO 3 layer sandwiched between 0.1λ thick SiO 2 layers. (author)

  8. Hexagonal-like Nb2O5 Nanoplates-Based Photodetectors and Photocatalyst with High Performances

    Science.gov (United States)

    Liu, Hui; Gao, Nan; Liao, Meiyong; Fang, Xiaosheng

    2015-01-01

    Ultraviolet (UV) photodetectors are important tools in the fields of optical imaging, environmental monitoring, and air and water sterilization, as well as flame sensing and early rocket plume detection. Herein, hexagonal-like Nb2O5 nanoplates are synthesized using a facile solvothermal method. UV photodetectors based on single Nb2O5 nanoplates are constructed and the optoelectronic properties have been probed. The photodetectors show remarkable sensitivity with a high external quantum efficiency (EQE) of 9617%, and adequate wavelength selectivity with respect to UV-A light. In addition, the photodetectors exhibit robust stability and strong dependence of photocurrent on light intensity. Also, a low-cost drop-casting method is used to fabricate photodetectors based on Nb2O5 nanoplate film, which exhibit singular thermal stability. Moreover, the hexagonal-like Nb2O5 nanoplates show significantly better photocatalytic performances in decomposing Methylene-blue and Rhdamine B dyes than commercial Nb2O5.

  9. Effect of Li2O-doping of nanocrystalline CoO/Fe2O3 on isopropanol conversion

    International Nuclear Information System (INIS)

    El-Shobaky, Hala G.; Ali, Suzan A.H.; Hassan, Neven A.

    2007-01-01

    The catalytic conversion of isopropanol was carried out over pure and Li 2 O-doped (0.75-4.5 mol%) cobalt ferrite prepared by heating Fe/Co mixed hydroxides at 400 and 600 deg. C. The techniques employed were XRD, N 2 adsorption at -196 deg. C and conversion of isopropanol at 200-400 deg. C using a flow method. The results showed that Li 2 O-doping and increasing the heating temperature of the system investigated from 400 to 600 deg. C stimulated CoFe 2 O 4 formation also. Pure and variously doped solids were moderately crystallized CoFe 2 O 4 phase having a crystallite size varying between 5 and 15 nm. The S BET of various solids was found to decrease by increasing their calcination temperature and also by doping with 4.5 mol% Li 2 O. However, this treatment, resulted in a significant increase in their catalytic activities which much increased by doping. The presence of 1.5 mol% Li 2 O brought about an increase in the catalytic activity, measured at 300 deg. C, of 97% and 63% for the solids being calcined at 400 and 600 deg. C, respectively. All solids investigated behaved as dehydrogenation catalysts (having selectivities to acetone formation above 95%). The doping process did not alter the mechanism of dehydrogenation of isopropanol, but increased the concentration of active sites involved in the catalyzed reaction

  10. Synthesis and characterization of Al2O3NbC composite and the effect of Y2O3 addition on its sintering

    International Nuclear Information System (INIS)

    Pasotti, Rosa Maria da Rocha

    1999-01-01

    Alumina composites containing ceramic particles have been intensively studied because they show improved mechanical properties and some advantages over fibres and whiskers based composites mainly for processing. The embedment of NbC particles in an Al 2 O 3 matrix has been investigated in this work. Composite materials were obtained by the conventional ceramic processing with compositions Al 2 O 3 -x NbC where x=10, 20, and 40 weight %. Materials were sintered in argon at 1650 deg C/30 min, and at 1750 deg C/15min using a graphite resistance furnace. Three sets of samples were processed: containing NbC powder as received; containing NbC powder milled for 30 h; and containing 3 weight % of Y 2 O 3 added to the Al 2 O 3 matrix. After sintering samples were analysed to evaluate the densification grade. Phases were determined by X-ray diffraction, and samples were analysed by optical microscopy, scanning electron microscopy and transmission electron microscopy to observe the microstructure features. Hardness and fracture toughness at room temperature were also determined by the indentation method, and the sintering kinetic was evaluated by dilatometry. The present work shows that Al 2 O 3 -NbC composite can be produced by using pressureless sintering, leading to materials with densities higher than 95% of the theoretical density for all composites containing NbC and sintered at 1750 deg C. The same result can be obtained for composites containing 10 and 20 weight % of NbC, and sintered at temperatures as low as 1650 deg C. Higher concentration of NbC in the Al 2 O 3 matrix promotes an improvement of fracture toughness. Samples with 40-wt % of NbC show K IC equals to 4.5 MPa.m 1/2 . This value is compared to the ones previously determined for Al 2 O 3 - TiC composites, available commercially and used in ceramic cutting-tools. (author)

  11. Anomalous enhancement of the thermoelectric figure of merit by V co-doping of Nb-SrTiO3

    KAUST Repository

    Ozdogan, K.

    2012-05-10

    The effect of V co-doping of Nb-SrTiO3 is studied by full-potential density functional theory. We obtain a stronger increase of the carrier density for V than for Nbdopants. While in Nb-SrTiO3 a high carrier density counteracts a high thermoelectric figure of merit, the trend is inverted by V co-doping. The mechanism leading to this behavior is explained in terms of a local spin-polarization introduced by the V ions. Our results indicate that magnetic co-doping can be a prominent tool for improving the thermoelectric figure of merit.

  12. Anomalous enhancement of the thermoelectric figure of merit by V co-doping of Nb-SrTiO3

    KAUST Repository

    Ozdogan, K.; Alshareef, Husam N.; Schwingenschlö gl, Udo; Upadhyay Kahaly, M.

    2012-01-01

    The effect of V co-doping of Nb-SrTiO3 is studied by full-potential density functional theory. We obtain a stronger increase of the carrier density for V than for Nbdopants. While in Nb-SrTiO3 a high carrier density counteracts a high thermoelectric figure of merit, the trend is inverted by V co-doping. The mechanism leading to this behavior is explained in terms of a local spin-polarization introduced by the V ions. Our results indicate that magnetic co-doping can be a prominent tool for improving the thermoelectric figure of merit.

  13. Dimerization of A-[alpha]-[SiNb3W9O40]7- by pH-controlled formation of individual Nb−µ-O−Nb linkages

    Science.gov (United States)

    Gyu-Shik Kim; Huadong Zeng; Wade A. Neiwert; Jennifer J. Cowan; Donald VanDerveer; Craig L. Hill; Ira A. Weinstock

    2003-01-01

    The reversible, stepwise formation of individual Nb−µ-O−Nb linkages during acid condensation of 2 equiv of A-[alpha]-[SiNb3W9O40]7- (1) to the tri-µ-oxo-bridged structure A-[alpha]-[Si2Nb6W18O77]8- (4) is demonstrated by a combination of X-ray crystallography and variable-pD solution 183W and 29Si NMR spectroscopy. Addition of DCl to a pD 8.4...

  14. Spectroscopic properties and energy transfer analysis of Tm3+-doped BaF2-Ga2O3-GeO2-La2O3 glass.

    Science.gov (United States)

    Yu, Shenglei; Yang, Zhongmin; Xu, Shanhui

    2010-05-01

    This paper reports on the spectroscopic properties and energy transfer analysis of Tm(3+)-doped BaF(2)-Ga(2)O(3)-GeO(2)-La(2)O(3) glasses with different Tm(2)O(3) doping concentrations (0.2, 0.5, 2.0, 2.5, 3.0, 3.5, 3.5, 4.0 wt%). Mid-IR fluorescence intensities in the range of 1,300 nm-2,200 nm have been measured when excited under an 808 nm LD for all the samples with the same pump power. Energy level structure and Judd-Ofelt parameters have been calculated based on the absorption spectra of Tm(3+), cross-relaxation rates and multi-phonon relaxation rates have been estimated with different Tm(2)O(3) doping concentrations. The maximum fluorescence intensity at around 1.8 mum has been obtained in Tm(2)O(3)-3 wt% sample and the maximum value of calculated stimulated emission cross-section of Tm(3+) in this sample is about 0.48 x 10(-20) cm(2) at 1,793 nm, and there is not any crystallization peak in the DSC curve of this sample, which indicate the potential utility of Tm(3+)-doped BaF(2)-Ga(2)O(3)-GeO(2)- La(2)O(3) glass for 2.0-microm optical fiber laser.

  15. Internal friction and Young's modulus measurements in Zr-2.5Nb alloy doped with hydrogen

    International Nuclear Information System (INIS)

    Ritchie, I.G.; Pan, Z.-L.

    1992-01-01

    The presence of hydrides is an important factor in assessing the potential for delayed hydride cracking in Zr-2.5Nb alloys, and consequently, the terminal solid solubility (TSS) of hydrogen in the material is an important parameter. In pure zirconium doped with hydrogen, the TSS is marked by a dissolution peak of internal friction on heating and a truncated precipitation peak associated with hydride nucleation on cooling. These phenomena occur only at low frequencies and are accompanied in torsion pendulum studies by autotwisting of the sample (or zero-point drift) that stops abruptly at the TSS. Neither the dissolution/precipitation peaks nor the autotwisting phenomena are observed in Zr-2.5Nb. However, the TSS is also marked by an abrupt change in the slope of Young's modulus as a function of temperature. This phenomenon is observed regardless of the frequency (in the range 1 Hz to 120 kHz) and in both pure zirconium and Zr-2.5Nb alloys. The reasons for the absence of the dissolution/precipitation peak in Zr-2.5Nb alloys are discussed and the use of Young's modulus changes to investigate the TSS of hydrogen and the hysteresis between heat-up and cool-down TSS curves is demonstrated. (author)

  16. Potential thermoelectric performance of hole-doped Cu2O

    International Nuclear Information System (INIS)

    Chen, Xin; Parker, David; Du, Mao-Hua; Singh, David J

    2013-01-01

    High thermoelectric performance in oxides requires stable conductive materials that have suitable band structures. Here we show, based on an analysis of the thermopower and related properties using first-principles calculations and Boltzmann transport theory in the relaxation time approximation, that hole-doped Cu 2 O may be such a material. We find that hole-doped Cu 2 O has a high thermopower of above 200 μV K −1 even with doping levels as high as 5.2 × 10 20 cm −3 at 500 K, mainly attributed to the heavy valence bands of Cu 2 O. This is reminiscent of the cobaltate family of high-performance oxide thermoelectrics and implies that hole-doped Cu 2 O could be an excellent thermoelectric material if suitably doped. (paper)

  17. Synthesis of green emission upconversion phosphor nanosheets (LaNb{sub 2}O{sub 7}) doped with Er{sup 3+} and Yb{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Takasugi, Soichi [Course of Science and Technology, Graduate School of Science and Technology, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Iida, Riku [Department of Chemistry, School of Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Tomita, Koji, E-mail: tomita@keyaki.cc.u-tokai.ac.jp [Department of Chemistry, School of Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Iwaoka, Michio [Course of Science and Technology, Graduate School of Science and Technology, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Department of Chemistry, School of Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Katagiri, Kiyofumi [Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527 (Japan); Osada, Minoru [International Center for Materials Nano architectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Kakihana, Masato [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2016-05-15

    LaNb{sub 2}O{sub 7}:Er{sup 3+},Yb{sup 3+} upconversion (UPC) phosphor nanosheets were prepared by exfoliating a KLaNb{sub 2}O{sub 7}:Er{sup 3+},Yb{sup 3+} layered compound. Highly crystalline nanosheets with a thickness and lateral size of 3.91 nm and approximately 300 nm, respectively, were obtained. The UPC emission intensity of the nanosheets was 7.6 times greater than that of mechanically milled particles (100–500 nm) of bulk KLaNb{sub 2}O{sub 7}:Er{sup 3+},Yb{sup 3+}. The UPC emission intensities of the nanosheets dispersed in different solvents (H{sub 2}O, D{sub 2}O, CH{sub 3}OH, CH{sub 2}Cl{sub 2}, and CCl{sub 4}) were measured, and the intensities were observed to decrease in the order CCl{sub 4}>CH{sub 2}Cl{sub 2}>D{sub 2}O>CH{sub 3}OH>H{sub 2}O. Because of the large surface area of the nanosheets, their emission intensity was decreased depending on the solvent's vibrational energy. - Highlights: • La{sub 0.45}Er{sub 0.05}Yb{sub 0.5}Nb{sub 2}O{sub 7} nanosheets were synthesized by a soft breakdown method (exfoliation). • The lateral size and thickness of the nanosheets were approximately 300 nm and approximately 3.91 nm, respectively. • The exfoliated nanosheets exhibited bright upconversion emission 7.6 times more intense than that of the milled sample (100–500 nm). • The nanosheets dispersed in solvents exhibited greatly different upconversion emission intensities depending on the solvent's vibrational energy.

  18. Self-diffusion of Er and Hf inpure and HfO2-doped polycrystalline Er2O3

    International Nuclear Information System (INIS)

    Scheidecker, R.W.

    1979-01-01

    Using a tracer technique, self-diffusion of Er and Hf was measured over the approximate temperature interval of 1600 to 1970 0 C in pure and HfO 2 -doped polycryatalline Er 2 O 3 . Up to about 10 m/o HfO 2 dopant level, the Er self-diffusion coefficients followed a relationship based on cation vacancies. Above 10 m/o HfO 2 , deviation from this relationship occurred, apparently due to clustering of cation vacancies and oxygen interstitials around the dopant hafnia ion. The activation energy for the self-diffusion of Er in pure Er 2 O 3 was 82.2 Kcal/mole and increased with the HfO 2 dopant level present. Self-diffusion of Hf was measured in pure Er 2 O 3 having two impurity levels, and a separation of the grain boundary. The volume diffusion of Hf showed both extrinsic and intrinsic behavior with the transition temperature increasing with the impurity level present in Er 2 O 3 . The activation energy for Hf volume diffusion in the intrinsic region was high, i.e. 235 -+ 9.5 Kcal/mole. The grain boundary diffusion was apparently extrinsic over the entire temperature interval Very low Hf self diffusion rates were found in both pure and HfO 2 doped Er 2 O 3 compositions. Despite a clustering effect, the HfO 2 dopant increased the Hf volume diffusion coefficients

  19. Photoelectrochemical oxidation of ibuprofen via Cu{sub 2}O-doped TiO{sub 2} nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Qiannan [College of Environment and Energy, South China University of Technology, Guangzhou (China); Peng, Yen-Ping, E-mail: yppeng@thu.edu.tw [Department of Environmental Science and Engineering, Tunghai University, Taichung, Taiwan (China); Chen, Hanlin [College of Environment and Energy, South China University of Technology, Guangzhou (China); Chang, Ken-Lin [School of Environmental Science and Engineering and Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 51006 China (China); Qiu, Yang-Neng; Lai, Shiau-Wu [Department of Environmental Science and Engineering, Tunghai University, Taichung, Taiwan (China)

    2016-12-05

    Highlights: • A p–n junction material was synthesized to enhance photocatalytic ability. • Cu{sub 2}O-doped TiO{sub 2} nanotube arrays works as a photoanode in a PEC system. • Recombination of photo-generated holes and electrons were greatly reduced. • Synergetic effect was quantified in PEC degradation. • Recombination of photogenerated holes and electrons was greatly enhanced. - Abstract: A p–n junction based Cu{sub 2}O-doped TiO{sub 2} nanotube arrays (Cu{sub 2}O-TNAs) were synthesized and used as a working anode in a photoelectrochemical (PEC) system. The results revealed that the Cu{sub 2}O-TNAs were dominated by the anatase phase and responded significantly to visible light. XPS analyses indicated that with an amount of 24.79% Cu doping into the structure, the band gap of Cu{sub 2}O-TNAs was greatly reduced. SEM images revealed that the supported TiO{sub 2} nanotubes had diameters of approximately 80 nm and lengths of about 2.63 μm. Upon doping with Cu{sub 2}O, the TiO{sub 2} nanotubes maintained their structural integrity, exhibiting no significant morphological change, favoring PEC applications. Under illumination, the photocurrent from Cu{sub 2}O/TNAs was 2.4 times larger than that from TNAs, implying that doping with Cu{sub 2}O significantly improved electron mobility by reducing the rate of recombination of electron-hole pairs. The EIS and Bode plot revealed that the estimated electron lifetimes, τ{sub el}, of TNAs and Cu{sub 2}O/TNAs were 6.91 and 26.26 ms, respectively. The efficiencies of degradation of Ibuprofen by photoelectrochemical, photocatalytic (PC), electrochemical (EC) and photolytic (P) methods were measured.

  20. Experimental study on microstructure development of binary system Zn-O-Nb2O5 sintered at 1100 deg C-1400 deg C

    International Nuclear Information System (INIS)

    Syarif, Dani Gustaman; Sukirman, Engkir; Handayani, Ari; Hidayat, Saeful

    2000-01-01

    In order to find effective (simple) varistor, in this work effect of Nb 2 O 5 addition on microstructure development and it's mechanism was studied experimentally. The study was conducted by sintering Zn-O added with 0-1% mole Nb 2 O 5 at 1100 o C-1400 o C in air for 1 hour and analyzing the sintered pellets using optical and electromicroscope (SEM) and x-ray diffractometer. The x-ray diffraction analysis showed that in Nb 2 O 5 added -ZnO (Zn-O-Nb 2 O 5 ) pellets sintered at 1100 o C-1400 o C, second phase of Zn 3 Nb 2 O 8 existed. On the other hand, the metallographic analysis showed that at sintering temperature of 1100 o C-1400 o C, grain size of Zn-O-Nb 2 O 5 pellets increased with increasing of Nb 2 O 5 , however, the grain size decreased again after the concentration of Nb 2 O 5 exceeding certain value. From this data it was know also, that there was solid solution area in Zn-O-Nb 2 O 5 phase diagram. At sintering temperature ≥ 1300 o C, there was liquid phase sintering that make grains become rounded

  1. Optical Properties and Photoactivity of The Pigmentary TiO2 Doped with P2O5, K2O, Al2O3 and Sb2O3

    International Nuclear Information System (INIS)

    Glen, M; Grzmil, B

    2011-01-01

    The influence of the increasing content of antimony calculated to Sb 2 O 3 (0.08-0.57 mol%) with the constant amount of the other additives (calculated to P 2 O 5 , K 2 O, Al 2 O 3 ) on the optical properties and photostability of doped rutile has been investigated. The properties of the obtained TiO 2 -PKAlSb samples were compared to the commercial TiO 2 -PKAl composition. The starting material was the concentrated suspension of technical-grade hydrated titanium dioxide (HTD). The dopant agents' solutions were introduced to HTD. Prepared samples were calcined with gradually increasing process temperature. The XRD analysis was used to determine the rutile content in the TiO 2 samples. Optical properties of modified titanium dioxide have been determined spectrophotometrically by measuring the colour in the white (brightness, white tone) and grey system (relative lightening power, grey tone). Photostability was characterized by the white lead-glycerin test with UV-Vis light. It was observed that with the increasing content of antimony in rutile TiO 2 , doped with phosphates, potassium and aluminium, the brightness and grey tone were increasing but white tone decreased. The changes of the relative lightening power values were insignificant. Comparing the samples of TiO 2 -PKAlSb with the TiO 2 -PKAl composition it was observed that titanium dioxide doped with antimony had better white and grey tone. The increasing Sb 2 O 3 content in the TiO 2 caused the improvement of the photostability.

  2. Rectifying characteristics and magnetoresistance in La0.9Sr0.1MnO3/Nb-doped SrTiO3 heterojunctions

    International Nuclear Information System (INIS)

    Luo, Z.; Gao, J.

    2007-01-01

    Manganite-based heterojunctions have attracted lots of attention as one of the most promising practical applications of colossal magnetoresistance materials. In this work, heterojunctions were fabricated by depositing La 0.9 Sr 0.1 MnO 3 (LSMO) films on substrates of 0.7 wt.% Nb-doped SrTiO 3 using pulsed laser deposition technique. X-ray diffraction spectra confirmed that the grown films are of single phase and have an orientation with the c-axis perpendicular to the substrate surface. As temperature decreases, the resistivity of LSMO films first increases gradually and then increases abruptly at temperature lower than 150 K. These junctions showed clear rectifying characteristics and strong temperature dependent current-voltage relation. Diffusion voltage decreases as temperature increases. Under forward bias, current is proportion to exp(eV/nkT). Ideal factor increases quickly and tunneling current plays more and more important role as temperature decreases. At 50 K, tunneling current becomes nearly dominant. Large magnetoresistance was observed. The sign and value of such magnetoresistance depends on the direction and value of current

  3. First-principles calculation of the effects of Li-doping on the structure and piezoelectricity of (K0.5Na0.5)NbO3 lead-free ceramics.

    Science.gov (United States)

    Yang, D; Wei, L L; Chao, X L; Yang, Z P; Zhou, X Y

    2016-03-21

    The crystal structures of the lead-free piezoelectric ceramics (K0.5Na0.5)NbO3 and (K0.5Na0.5)0.94Li0.06NbO3 prepared by a solid-state method were investigated using first-principles calculations. The calculated values of piezoelectricity were in good agreement with the experimental data. We found that the primary contribution to piezoelectricity in this material comes from the hybridization of the O 2p and Nb 4d orbitals, which causes a change in the Nb-O bond length and the distortion of the Nb-O octahedral structure. Analysis of the band structure and the total density of states revealed that Li-doped (K0.5Na0.5)NbO3 enhances hybridization of the O 2p and Nb 4d orbitals. This hybridization enhancement further reduces the Nb-O1 bond length and enhances the distortion of the Nb-O octahedron along the [001] direction, which may be the main reason for the improvement of the piezoelectric properties. In addition, the piezoelectric coefficients are calculated here, which show the same trend as the experimental results.

  4. Insertion of lithium in Nb2O5

    International Nuclear Information System (INIS)

    Alves, M.C.M.; Bulhoes, L.O.S.; Castro, S.C.

    1990-01-01

    The electrode process during the reduction and oxidation of Nb sub(2) O sub(5) by cyclic voltametry was characterized. The surface analysis by X-ray photo electronic spectroscopy allowed characterize the surface processes, that happening during the insertion reaction. (author)

  5. Electrochemical conversion of solid Nb{sub 2}O{sub 5} to Nb in sodium chloride melt as proof of oxygen ionisation mechanism of electrodeoxidation

    Energy Technology Data Exchange (ETDEWEB)

    Sri Maha Vishnu, D., E-mail: smvd2@cam.ac.uk [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India); Presently with Materials Chemistry Group, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS (United Kingdom); Sanil, N.; Mohandas, K.S. [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India)

    2016-08-25

    The direct electrochemical reduction of a solid metal oxide (MO{sub x}) to metal (M) in calcium chloride melt (FFC Cambridge process) has been proposed to take place via. oxygen ionisation mechanism, MO{sub x} + 2xe{sup −} → M + xO{sup 2−}. However, generation of calcium metal and reduction of the oxide with it too becomes possible under the applied potential condition (3.1 V) of an FFC cell. The unique chemistry of calcium chloride melt, upon cathodic polarisation, makes it difficult to distinguish between the reduction by electrons and calcium metal. Hence in order to confirm the oxygen ionisation theory of electro-deoxidation, electrochemical deoxidation experiments were carried out with sintered Nb{sub 2}O{sub 5} pellet electrodes in molten sodium chloride at 1173 K. The pellets were found reduced to Nb metal. Sodiothermic reduction of Nb{sub 2}O{sub 5} is thermodynamically not feasible (Nb{sub 2}O{sub 5} + 10Na → 5Na{sub 2}O + 2Nb, ΔG°{sub 1173K} = 102.1 kJ) and hence the observed reduction of the oxide is attributed to electrons. This study, for the first time, gives reliable experimental evidence to the oxygen ionisation mechanism of electro-reduction of solid oxides in the FFC process. The experimental results also prove that the electro-reduction of oxides can occur in melts, which otherwise were considered unsuitable from thermodynamic considerations. - Highlights: • In NaCl melt: Negligible O{sup 2−} ion solubility & Na reduction of Nb{sub 2}O{sub 5} to Nb – absent. • Nb{sub 2}O{sub 5} could be electrochemically reduced to spongy Nb in NaCl melt at 1173 K. • Mechanism: Nb{sub 2}O{sub 5} → Na−Nb−O compounds + suboxides of Nb → Na{sub x}NbO{sub y} → Nb. • Metallothermic reduction of oxide in melt - not mandatory for electrodeoxidation. • In FFC Cambridge process: Metallothermic reduction is not essential but desirable.

  6. Application of nanostructured Ca doped CeO2 for ultraviolet filtration

    International Nuclear Information System (INIS)

    Truffault, Laurianne; Ta, Minh-Tri; Devers, Thierry; Konstantinov, Konstantin; Harel, Valerie; Simmonard, Cyriaque; Andreazza, Caroline; Nevirkovets, Ivan P.; Pineau, Alain; Veron, Olivier; Blondeau, Jean-Philippe

    2010-01-01

    Calcium doped CeO 2 nanoparticles with doping concentrations between 0 and 50 mol% were synthesized by a co-precipitation method for ultraviolet filtration application. Below 20 mol% doping concentration, the samples were single-phase. From 30 mol%, CaCO 3 appears as a secondary phase. The calculated CeO 2 mean crystallite size was 9.3 nm for the pure and 5.7 nm for the 50 mol% Ca-doped sample. Between 250 and 330 nm, the absorbance increased for the 10, 30, and 40 mol% Ca-doped samples compared to the pure one. The band-gap was found to be 3.20 eV for the undoped, and between 3.36 and 3.51 eV for the doped samples. The blue shifts are attributed to the quantum confinement effect. X-ray photoelectron spectroscopy showed that the Ce 3+ atomic concentration in the pure sample was higher than that of the 20 mol% Ca-doped sample.

  7. Investigation of the La2O3-Nb2O5-WO3 ternary phase diagram: Isolation and crystal structure determination of the original La3NbWO10 material

    KAUST Repository

    Vu, T.D.; Vu, T.D.; Barre, M.; Adil, Karim; Jouanneaux, A.; Suard, E.; Goutenoire, F.

    2015-01-01

    In the course of the exploration of the La2O3-WO3-Nb2O5 ternary phase diagram, a new compound with the formula La3NbWO10 was discovered. Its structure was determined from a combination of powder X-ray and neutron diffraction data. It crystallizes

  8. Photoluminescence of Er-doped Si-SiO2 and Al-Si-SiO2 sputtered thin films

    International Nuclear Information System (INIS)

    Rozo, C.; Fonseca, L.F.; Jaque, D.; Sole, J.Garcia

    2008-01-01

    Er-doped Si-SiO 2 and Al-Si-SiO 2 films have been deposited by rf-sputtering being annealed afterwards. Annealing behavior of the Er 3+ : 4 I 13/2 → 4 I 15/2 emission of Er-doped Si-SiO 2 yields a maximum intensity for annealing at 700-800 deg. C. 4 I 13/2 → 4 I 15/2 peak emission for Er-doped Al-Si-SiO 2 at 1525 nm is shifted from that for Er-doped Si-SiO 2 at 1530 nm and the bandwidth increases from 29 to 42 nm. 4 I 13/2 → 4 I 15/2 emission decays present a fast decaying component related to Er ions coupled to Si nanoparticles, defects, or other ions, and a slow decaying component related to isolated Er ions. Excitation wavelength dependence and excitation power dependence for the 4 I 13/2 → 4 I 15/2 emission correspond with energy transfer from Si nanoparticles. Populating of the 4 I 11/2 level in Er-doped Si-SiO 2 involves branching and energy transfer upconversion involving two or more Er ions. Addition of Al reduces the populating of this level to an energy transfer upconversion involving two ions

  9. Laachite, (Ca,Mn){sub 2}Zr{sub 2}Nb{sub 2}TiFeO{sub 14}, a new zirconolite-related mineral from the Eifel volcanic region, Germany

    Energy Technology Data Exchange (ETDEWEB)

    Chukanov, Nikita V. [Institute of Problems of Chemical Physics, Chernogolovka (Russian Federation); Krivovichev, Sergey V.; Pakhomova, Anna S. [St. Petersburg State Univ. (Russian Federation). Faculty of Crystallography; Pekov, Igor V.; Vigasina, Marina F. [Moscow State Univ. (Russian Federation). Faculty of Geology; Schaefer, Christof [Suedwestdeutsche Salzwerke AG, Heilbronn (Germany); Van, Konstantin V. [Russian Academy of Sciences, Chernogolovka (Russian Federation). Inst. of Experimental Mineralogy

    2014-02-15

    The new mineral laachite was discovered in a sanidinite specimen from the Laach Lake (Laacher See) volcano, Eifel region, Rheinland-Pfalz, Germany. Associated minerals are sanidine, allanite-(Ce), baddeleyite, hau¨yne, hedenbergite, intermediate members of the jacobsite-magnetite series, phlogopite, rhodonite, spessartine, tephroite, thorite, zircon, and a pyrochlore-group mineral. Laachite is deep brownish-red, has an adamantine lustre, and is translucent; the streak is brownish red. It forms longprismatic crystals up to 0.02 x 0.04 x 0.5 mm, which are present as random intergrowths and twins in cavities within sanidinite. The density calculated from the empirical formula is 5.417 g/cm{sup 3}. The mean refractive index calculated from the Gladstone-Dale relationship is 2.26. The Raman spectrum shows the absence of hydrogen-bearing groups. The chemical composition is (electron microprobe, mean of 5 analyses, wt. %): CaO 4.29, MnO 9.42, FeO 5.73, Y{sub 2}O{sub 3} 2.56, La{sub 2}O{sub 3} 2.00, Ce{sub 2}O{sub 3} 6.37, Nd{sub 2}O{sub 3} 2.22, Al{sub 2}O{sub 3} 0.99, ThO{sub 2} 7.75, TiO{sub 2} 10.98, ZrO{sub 2} 19.39, Nb{sub 2}O{sub 5} 27.82, total 99.52. The empirical formula based on 14 O atoms is: (Ca{sub 0.66}Mn{sub 0.37}Th{sub 0.25}Y{sub 0.20}La{sub 0.11}Ce{sub 0.34}Nd{sub 0.11})(Zr{sub 1.3} {sub 6}Mn{sub 0.64})(Nb{sub 1.81}Ti{sub 1.19})(Fe{sub 0.69}Al{sub 0.17}Mn{sub 0.14})O{sub 14.00}. The simplified formula, taking into account the structural data, is: (Ca,Mn){sub 2}(Zr,Mn){sub 2}Nb{sub 2}TiFeO{sub 14}. Laachite is monoclinic, space group C2/c, a = 7.3119(5), b = 14.1790(10), c = 10.1700(7)Aa, β = 90.072(2), V = 1054.38(1) Aa{sup 3}, Z = 4. The crystal structure was solved using single-crystal X-ray diffraction data. Laachite is a monoclinic analogue of zirconolite-3O, CaZrTi{sub 2}O{sub 7}, with Nb dominant over Ti in the octahedral sites Nb1 and Nb2 and Fe dominant in a site with four-fold coordination. The strongest lines of the powder X-ray diffraction

  10. Effects of the co-addition of LiSbO3-LiTaO3 on the densification of (Na1/2K1/2)NbO3 lead free ceramics by atmosphere sintering

    International Nuclear Information System (INIS)

    Jiang Na; Fang Bijun; Wu Jian; Du Qingbo

    2011-01-01

    Research highlights: → This manuscript shows a synthesis method that can easily obtain excellent lead-free samples, which is valuable for industrial production. → Pure phase perovskite 0.94(Na 1/2 K 1/2 )NbO 3 -0.03LiSbO 3 -0.03LiTaO 3 (0.94NKN-0.03LS-0.03LT) lead-free piezoelectric ceramics with high relative density, being 94.73%, and excellent integral electrical properties, piezoelectric constant d 33 being 228 pC/N, were prepared by atmosphere sintering method. Which can be attributed to the co-doping of LiSbO 3 -LiTaO 3 . - Abstract: Pure phase perovskite 0.94(Na 1/2 K 1/2 )NbO 3 -0.03LiSbO 3 -0.03LiTaO 3 (0.94NKN-0.03LS-0.03LT) lead-free piezoelectric ceramics were prepared by the conventional solid-state reaction method. Due to the co-addition of LiSbO 3 -LiTaO 3 , the 0.94NKN-0.03LS-0.03LT ceramics prepared by atmosphere sintering at 1040 deg. C exhibit high relative density, being 94.73%, and rather homogenous microstructure. X-ray diffraction (XRD) measurement confirmed that the sintered ceramics exhibit pure tetragonal perovskite structure. The 0.94NKN-0.03LS-0.03LT ceramics exhibit excellent integral electrical properties, in which the value of piezoelectric constant d 33 is 228 pC/N, the electromechanical coupling factors K p and K t are 0.220 and 0.230, respectively, the mechanical quality factor Q m is 32.19, and the remnant polarization P r is 23.06 μC/cm 2 . Such excellent electrical properties are considered as correlating with the high relative density of the synthesized ceramics induced by the co-doping of LiSbO 3 -LiTaO 3 .

  11. Photoluminescence and thermoluminescence properties of Eu2+ doped and Eu2+ ,Dy3+ co-doped Ba2 MgSi2 O7 phosphors.

    Science.gov (United States)

    Sao, Sanjay Kumar; Brahme, Nameeta; Bisen, D P; Tiwari, Geetanjali

    2016-11-01

    In this work, we report the preparation, characterization, comparison and luminescence mechanisms of Eu 2 + -doped and Eu 2 + ,Dy 3 + -co-doped Ba 2 MgSi 2 O 7 (BMSO) phosphors. Prepared phosphors were synthesized via a high temperature solid-state reaction method. All prepared phosphors appeared white. The phase structure, particle size, and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) analysis. The luminescence properties of the phosphors were investigated by thermoluminescence (TL) and photoluminescence (PL). The PL excitation and emission spectra of Ba 2 MgSi 2 O 7 :Eu 2 + showed the peak to be around 381 nm and 490 nm respectively. The PL excitation spectrum of Ba 2 MgSi 2 O 7 :Eu 2 + Dy 3 + showed the peak to be around 341 nm and 388 nm, and the emission spectrum had a broad band around 488 nm. These emissions originated from the 4f 6 5d 1 to 4f 7 transition of Eu 2 + . TL analysis revealed that the maximum TL intensity was found at 5 mol% of Eu 2 + doping in Ba 2 MgSi 2 O 7 phosphors after 15 min of ultraviolet (UV) light exposure. TL intensity was increased when Dy 3 + ions were co-doped in Ba 2 MgSi 2 O 7 :Eu 2 + and maximum TL intensity was observed for 2 mol% of Dy 3 + . TL emission spectra of Ba 1.95 MgSi 2 O 7 :0.05Eu 2 + and Ba 1.93 MgSi 2 O 7 :0.05Eu 2 + ,0.02Dy 3 + phosphors were found at 500 nm. TL intensity increased with UV exposure time up to 15 min, then decreased for the higher UV radiation dose for both Eu doping and Eu,Dy co-doping. The trap depths were calculated to be 0.54 eV for Ba 1.95 MgSi 2 O 7 :0.05Eu 2 + and 0.54 eV and 0.75 eV for Ba 1.93 MgSi 2 O 7 :0.05Eu 2 + ,0.02Dy 3 + phosphors. It was observed that co-doping with small amounts of Dy 3 + enhanced the thermoluminescence properties of Ba 2 MgSi 2 O 7 phosphor. Copyright © 2016 John Wiley & Sons, Ltd. [Correction added on 5 April 2016, after first online publication: The

  12. Current-Voltage Characteristics of Nb2O5 nanoporous via light illumination

    Science.gov (United States)

    Samihah Khairir, Nur; Rani, Rozina Abdul; Fazlida Hanim Abdullah, Wan; Hafiz Mamat, Mohamad; Kadir, Rosmalini Abdul; Rusop, M.; Sabirin Zoolfakar, Ahmad

    2018-03-01

    This work discussed the effect of light on I-V characteristics of anodized niobium pentoxide (Nb2O5) which formed nanoporous structure film. The structure was synthesized by anodizing niobium foils in glycerol based solution with 10 wt% supplied by two different voltages, 5V and 10V. The anodized foils that contained Nb2O5 film were then annealed to obtain an orthorhombic phase for 30 minutes at 450°C. The metal contact used for I-V testing was platinum (Pt) and it was deposited using thermal evaporator at 30nm thickness. I-V tests were conducted under different condition; dark and illumination to study the effect of light on I-V characteristics of anodized nanoporous Nb2O5. Higher anodization voltage and longer anodization time resulted in higher pore dispersion and larger pore size causing the current to increase. The increase of conductivity in I-V behaviour of Nb2O5 device is also affected by the illumination test as higher light intensity caused space charge region width to increase, thus making it easier for electron transfer between energy band gap.

  13. ZnO doped SnO2 nanoparticles heterojunction photo-catalyst for environmental remediation

    International Nuclear Information System (INIS)

    Lamba, Randeep; Umar, Ahmad; Mehta, S.K.; Kansal, Sushil Kumar

    2015-01-01

    ZnO doped SnO 2 nanoparticles were synthesized by facile and simple hydrothermal technique and used as an effective photocatalyst for the photocatalytic degradation of harmful and toxic organic dye. The prepared nanoparticles were characterized in detail using different techniques for morphological, structural and optical properties. The characterization results revealed that the synthesized nanoparticles possess both crystal phases of tetragonal rutile phase of pure SnO 2 and wurtzite hexagonal phase of ZnO. In addition, the nanoparticles were synthesized in very high quantity with good crystallinity. The photocatalytic activity of prepared nanoparticles was evaluated by the photocatalytic degradation of methylene blue (MB) dye. Detailed photocatalytic experiments based on the effects of irradiation time, catalyst dose and pH were performed and presented in this paper. The detailed photocatalytic experiments revealed that the synthesized ZnO doped SnO 2 nanoparticles heterojunction photocatalyst exhibit best photocatalytic performance when the catalyst dose was 0.25 g/L and pH = 10. ZnO doped SnO 2 nanoparticles heterojunction photocatalyst was also compared with commercially available TiO 2 (PC-50), TiO 2 (PC-500) and SnO 2 and interestingly ZnO doped SnO 2 nanoparticles exhibited superior photocatalytic performance. The presented work demonstrates that the prepared ZnO doped SnO 2 nanoparticles are promising material for the photocatalytic degradation of organic dyes and toxic chemicals. - Highlights: • Synthesis of well-crystalline ZnO-doped SnO 2 nanoparticles. • Excellent morphological, crystalline and photoluminescent properties. • Efficient environmental remediation using ZnO-doped SnO 2 nanoparticles.

  14. High Temperature Thermoelectric Oxides Engineered At Multiple Length Scales For Energy Harvesting

    Energy Technology Data Exchange (ETDEWEB)

    Ohuchi, Fumio [Univ. of Washington, Seattle, WA (United States); Bordia, Rajendra [Clemson Univ., SC (United States)

    2014-12-20

    Thermoelectric aspects of the processing parameters the n-type relaxors, including SrxBa1-xNb2O6 (SBN100x), Sr2Nb2O7 (SN) and SrBi2Nb2O9 (SBiN), were investigated. A solution combustion synthesis (SCS) route was devised to fabricate SBN, SN and SBiN nanoparticles with excellent phase purity. X-ray photoelectron spectroscopy (XPS) was used to deduce the local cation site occupancy, and detailed thermoelectric transport processes were investigated. Based on the identified behavior, effectiveness of pore formers on the thermoelectric performance was investigated with the goal of decreasing κ through enhanced phonon scattering while preserving the electron transport characteristics.

  15. Nanocrystal in Er3+-doped SiO2-ZrO2 Planar Waveguide with Yb3+ Sensitizer

    International Nuclear Information System (INIS)

    Razaki, N. Iznie; Jais, U. Sarah; Abd-Rahman, M. Kamil; Bhaktha, S. N. B.; Chiasera, A.; Ferrari, M.

    2010-01-01

    Higher doping of Er 3+ in glass ceramic waveguides would cause concentration and pair-induced quenching which lead to inhomogeneous line-width of luminescence spectrum thus reduce output intensity. Concentration quenching can be overcome by introducing ZrO 2 in the glass matrix while co-doping with Yb 3+ which acts as sensitizer would improve the excitation efficiency of Er 3+ . In this study, SiO 2 -ZrO 2 planar waveguides having composition in mol percent of 70SiO 2 -30ZrO 2 doped with Er 3+ and co-doped with Yb 3+ , were prepared via sol-gel route. Narrower and shaper peaks of PL and XRD shows the formation of nanocrystals. Intensity is increase with addition amount of Yb 3+ shows sensitizing effect on Er 3+ .

  16. Optical properties of Er{sup 3+}-doped strontium barium niobate nanocrystals obtained by thermal treatment in glass

    Energy Technology Data Exchange (ETDEWEB)

    Haro-Gonzalez, P. [Dep. of Fisica Fundamental Experimental, Electronica y Sistemas, Universidad de La Laguna Avda Astrofisico Franscisco Sanchez, 38206 La Laguna, S/C de Tenerife (Spain)], E-mail: patharo@ull.es; Lahoz, F. [Dep. of Fisica Fundamental Experimental, Electronica y Sistemas, Universidad de La Laguna Avda Astrofisico Franscisco Sanchez, 38206 La Laguna, S/C de Tenerife (Spain); Gonzalez-Platas, J. [Dep. of Fisica Fundamental II, Universidad de La Laguna, 38206 La Laguna, S/C de Tenerife (Spain); Caceres, J.M. [Dep. of Edafologia y Geologia, Universidad de La Laguna, 38206 La Laguna, S/C de Tenerife (Spain); Gonzalez-Perez, S. [Dep. of Fisica Fundamental Experimental, Electronica y Sistemas, Universidad de La Laguna Avda Astrofisico Franscisco Sanchez, 38206 La Laguna, S/C de Tenerife (Spain); Marrero-Lopez, D. [Dep. of Quimica Inorganica, Universidad de La Laguna, 38206 La Laguna, S/C de Tenerife (Spain); Capuj, N. [Dep. of Fisica Basica, Universidad de La Laguna, 38206 La Laguna, S/C de Tenerife (Spain); Martin, I.R. [Dep. of Fisica Fundamental Experimental, Electronica y Sistemas, Universidad de La Laguna Avda Astrofisico Franscisco Sanchez, 38206 La Laguna, S/C de Tenerife (Spain)

    2008-05-15

    Measurements of the optical properties of Er{sup 3+} ions in strontium barium niobate glass and glass ceramics have been carried out. The glasses have been fabricated using a melt-quenching method, and the glass ceramic samples have been obtained from the glass precursor by a thermal treatment. The ceramic samples formed by a glassy phase, and a crystalline phase contains nanocrystals of Sr{sub 1-x}Ba{sub x}Nb{sub 2}O{sub 6} (SBN) doped with Er{sup 3+} ions with a mean size of {approx}50 nm, as confirmed with XRD. Green up-conversion emission has been obtained under excitation at 800 nm, and the temporal evolution of this emission has been reported with the purpose of determining the involved up-conversion mechanism. These optical measures have confirmed that the Er{sup 3+} ions have been incorporated into the SBN matrix, after a thermal treatment, which produced an increment of the up-conversion efficiency.

  17. Bottom-up synthesis of up-converting submicron-sized Er{sup 3+}-doped LiNbO{sub 3} particles

    Energy Technology Data Exchange (ETDEWEB)

    Jardiel, T., E-mail: jardiel@icv.csic.es [Departamento de Electroceramica, Instituto de Ceramica y Vidrio-CSIC, Kelsen 5, 28049 Madrid (Spain); Caballero, A.C. [Departamento de Electroceramica, Instituto de Ceramica y Vidrio-CSIC, Kelsen 5, 28049 Madrid (Spain); Marin-Dobrincic, M.; Cantelar, E.; Cusso, F. [Departamento de Fisica de Materiales, C-04, Facultad de Ciencias, Universidad Autonoma de Madrid, Avda. Francisco Tomas y Valiente 7, 28049 Madrid (Spain)

    2012-08-15

    A new and simple wet chemical synthesis method is proposed to prepare submicron-sized Erbium-doped LiNbO{sub 3} powders. The synthesis procedure comprises the co-precipitation of lithium and erbium ions from common precursors and their subsequent reaction with niobium ethoxide. A systematic characterization by means of X-Ray Diffraction (XRD), X-ray Fluorescence (XRF), Inductively Coupled Plasma (ICP-OES), Atomic Absorption (AAS), Field Emission Scanning Electron Microscopy (FE-SEM), as well as by the examination of the luminescence properties, evidence that with this method a congruent Er{sup 3+}-doped LiNbO{sub 3} single phase material can be obtained without using complex and time-consuming processing steps. The synthesized powders exhibit efficient IR to VIS up-conversion emissions under 974 nm pumping. -- Highlights: Black-Right-Pointing-Pointer A novel chemical route to the preparation of LiNbO{sub 3} powders has been developed. Black-Right-Pointing-Pointer This process avoids complex and time-consuming processing steps. Black-Right-Pointing-Pointer A congruent Er{sup 3+}-doped LiNbO{sub 3} single phase material can be obtained by this way. Black-Right-Pointing-Pointer The luminescence properties are the expected for this composition.

  18. Anomalous behavior of soft mode attenuation in the incommensurate phase in Cd2Nb2O7, K2SeO4 and Rb2ZnBr4

    International Nuclear Information System (INIS)

    Smolenskij, G.A.; Kolpakova, N.N.; Sher, E.S.; Brzhezina, B.

    1986-01-01

    Moderation of soft mode attenuation in the incommensurate phase in Cd 2 Nb 2 O 7 , K 2 SeO 4 and Rb 2 ZnBr 4 is observed at temperature drop and anomalous jump-like decrease of integral intensity of the soft mode under transition to the low-temperature commensurate phase. Anomalous behaviour of the soft mode is explained by wave amplitudon contribution (q=0) in Raman spectrum of the first order and composite tone (wave amplitudon (q=0) +- wave phase (q=K i )) in Raman spectrum of the second order. Relative contribution of the phase wave (q=K i ) to soft mode attenuation can be estimated supposing that wave amplitudon attenuation is G A ∼ (T i -T) -1 . ΔG f max makes up approximately 6 cm -1 in Cd 2 Nb 2 O 7 and approximately 3 cm -1 in K 2 SeO 4 and Rb 2 ZnBr 4 at temperatures above T c . In the low-temperature phase the soft mode corresponds to the wave amplitudon (q=0) in the Raman spectrum of the first order at T c - 26 K) in Cd 2 Nb 2 O 7 , T c - 13 K) in K 2 SeO 4 and T c - 163 K) in Rb 2 ZnBr 4

  19. Crystal structure and ion conducting properties of La5NbMo2O16

    KAUST Repository

    Vu, T.D.

    2016-01-29

    The new compound La5NbMo2O16 with high ionic conduction has been discovered during the study of the ternary phase diagram of La2O3-MoO3-Nb2O5. The material crystallizes in the cubic space group Pn 3n (no 222) with the unit cell parameter a=11.2250(1) Å. La5NbMo2O16 is a new analogue of the R5Mo3O16 series (R=Pr, Nd). The structure was refined from a combined data X-ray and neutron powder diffraction. The ionic conductivity of the compound is then measured on sintered pellets, by means of complex impedance spectroscopy. © 2016 Elsevier Inc. All rights reserved.

  20. Anomalous behavior of B1g mode in highly transparent anatase nano-crystalline Nb-doped Titanium Dioxide (NTO thin films

    Directory of Open Access Journals (Sweden)

    Subodh K. Gautam

    2015-12-01

    Full Text Available The effect of Niobium doping and size of crystallites on highly transparent nano-crystalline Niobium doped Titanium Dioxide (NTO thin films with stable anatase phase are reported. The Nb doping concentration is varied within the solubility limit in TiO2 lattice. Films were annealed in controlled environment for improving the crystallinity and size of crystallites. Elemental and thickness analysis were carried out using Rutherford backscattering spectrometry and cross sectional field emission scanning electron microscopy. Structural characteristics reveal a substitutional incorporation of Nb+5 in the TiO2 lattice which inhibits the anatase crystallites growth with increasing the doping percentage. The micro-Raman (MR spectra of films with small size crystallites shows stiffening of about 4 cm−1 for the Eg(1 mode and is ascribed to phonon confinement and non-stoichiometry. In contrast, B1g mode exhibits a large anomalous softening of 20 cm−1 with asymmetrical broadening; which was not reported for the case of pure TiO2 crystallites. This anomalous behaviour is explained by contraction of the apical Ti-O bonds at the surface upon substitutional Nb5+ doping induced reduction of Ti4+ ions also known as hetero-coordination effect. The proposed hypotheses is manifested through studying the electronic structure and phonon dynamics by performing the near edge x-ray absorption fine structure (NEXAFS and temperature dependent MR down to liquid nitrogen temperature on pure and 2.5 at.% doped NTO films, respectively.

  1. Preparation of Pb(Mg1/3Nb2/3)O3 by simultaneous precipitations

    International Nuclear Information System (INIS)

    Juiz, S.A.; Varela, J.A.; Santilli, C.V.; Pulcinelli, S.H.; Longo, E.

    1990-01-01

    Pb(Mg 1/3 Nb 2/3 )O 3 was obtained by simultaneous precipitation of Pb(NO 3 ) 2' Mg(NO 3 ) 2 . 6H 2 O and NH 4 H 2 /NbO(C 2 O 4 ) 3 ./3H 2 O in alkaline medium. DTA of the precipitates show the PMN formation between 700 and 750 0 C. XRD on powder calcined at 750 0 C indicates on other phases basiders PMN. Measurements of dielectric constants shows a Curie temperature shifted to -80 0 C. (author) [pt

  2. Modulation-Doped In2O3/ZnO Heterojunction Transistors Processed from Solution

    KAUST Repository

    Khim, Dongyoon

    2017-03-15

    This paper reports the controlled growth of atomically sharp In2 O3 /ZnO and In2 O3 /Li-doped ZnO (In2 O3 /Li-ZnO) heterojunctions via spin-coating at 200 °C and assesses their application in n-channel thin-film transistors (TFTs). It is shown that addition of Li in ZnO leads to n-type doping and allows for the accurate tuning of its Fermi energy. In the case of In2 O3 /ZnO heterojunctions, presence of the n-doped ZnO layer results in an increased amount of electrons being transferred from its conduction band minimum to that of In2 O3 over the interface, in a process similar to modulation doping. Electrical characterization reveals the profound impact of the presence of the n-doped ZnO layer on the charge transport properties of the isotype In2 O3 /Li-ZnO heterojunctions as well as on the operating characteristics of the resulting TFTs. By judicious optimization of the In2 O3 /Li-ZnO interface microstructure, and Li concentration, significant enhancement in both the electron mobility and TFT bias stability is demonstrated.

  3. Modulation-Doped In2O3/ZnO Heterojunction Transistors Processed from Solution

    KAUST Repository

    Khim, Dongyoon; Lin, Yen-Hung; Nam, Sungho; Faber, Hendrik; Tetzner, Kornelius; Li, Ruipeng; Zhang, Qiang; Li, Jun; Zhang, Xixiang; Anthopoulos, Thomas D.

    2017-01-01

    This paper reports the controlled growth of atomically sharp In2 O3 /ZnO and In2 O3 /Li-doped ZnO (In2 O3 /Li-ZnO) heterojunctions via spin-coating at 200 °C and assesses their application in n-channel thin-film transistors (TFTs). It is shown that addition of Li in ZnO leads to n-type doping and allows for the accurate tuning of its Fermi energy. In the case of In2 O3 /ZnO heterojunctions, presence of the n-doped ZnO layer results in an increased amount of electrons being transferred from its conduction band minimum to that of In2 O3 over the interface, in a process similar to modulation doping. Electrical characterization reveals the profound impact of the presence of the n-doped ZnO layer on the charge transport properties of the isotype In2 O3 /Li-ZnO heterojunctions as well as on the operating characteristics of the resulting TFTs. By judicious optimization of the In2 O3 /Li-ZnO interface microstructure, and Li concentration, significant enhancement in both the electron mobility and TFT bias stability is demonstrated.

  4. Effects of Bi(Zn2/3Nb1/3)O3 Modification on the Relaxor Behavior and Piezoelectricity of Pb(Mg1/3Nb2/3)O3-PbTiO3 Ceramics.

    Science.gov (United States)

    Liu, Zenghui; Wu, Hua; Paterson, Alisa; Ren, Wei; Ye, Zuo-Guang

    2017-10-01

    Relaxor lead magnesium niobate (PMN)-based materials exhibit complex structures and unusual properties that have been puzzling researchers for decades. In this paper, a new ternary solid solution of Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 -Bi(Zn 2/3 Nb 1/3 )O 3 (PMN-PT-BZN) is prepared in the form of ceramics, and the effects of the incorporation of BZN into the PMN-PT binary system are investigated. The crystal structure favors a pseudocubic symmetry and the relaxor properties are enhanced as the concentration of BZN increases. The relaxor behavior and the related phase transformations are studied by dielectric spectroscopy. A phase diagram mapping out the characteristic temperatures and various states is established. Interestingly, the piezoelectricity of the PMN-PT ceramics is significantly enhanced by the BZN substitution, with an optimal value of d 33 reaching 826 pC/N for 0.96[0.7Pb(Mg 1/3 Nb 2/3 )O 3 -0.3PbTiO 3 ]-0.04Bi(Zn 2/3 Nb 1/3 )O 3 . This paper provides a better understanding of the relaxor ferroelectric behavior, and unveils a new relaxor-based ternary system as piezoelectric materials potentially useful for electromechanical transducer applications.

  5. Preparation and electrical properties of (1 - x)Sr(Fe{sub 1/2}Nb{sub 1/2})O{sub 3}-xPbTiO{sub 3} ferroelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fang Bijun [School of Materials Science and Engineering, Jiangsu Polytechnic University, Changzhou, Jiangsu 213164 (China)], E-mail: fangbj@em.jpu.edu.cn; Cheng Zhenquan; Sun Renbing; Ding Chenlu [School of Materials Science and Engineering, Jiangsu Polytechnic University, Changzhou, Jiangsu 213164 (China)

    2009-03-05

    (1 - x)Sr(Fe{sub 1/2}Nb{sub 1/2})O{sub 3}-xPbTiO{sub 3} (SFN-PT) ferroelectric ceramics were prepared by conventional solid-state reaction method via the wolframite precursor route. X-ray diffraction (XRD) measurement confirmed that the synthesized SFN-PT ceramics are of pure perovskite structure. With the increase of the concentration of PbTiO{sub 3} (PT), crystal structure of the sintered SFN-PT ceramics changes from rhombohedral phase to tetragonal phase. Dielectric response of the SFN-PT ceramics changes from diffused and broad dielectric peaks to relatively sharp ones accompanied by the increase of the temperature of dielectric maximum (T{sub m}). Small content of MnO{sub 2} or Li{sub 2}CO{sub 3} doping can greatly decrease the dielectric loss of the SFN-PT ceramics, furthermore, the abnormal increase of dielectric constant and loss tangent in the paraelectric phase is suppressed accordingly. Typical P-E hysteresis loops are observed in the SFN-PT ceramics, however, the saturate polarization (P{sub s}) is small. MnO{sub 2} or Li{sub 2}CO{sub 3} doping can greatly decrease the coercive field (E{sub c}) of the SFN-PT ceramics accompanied by large increase of P{sub s}. Piezoelectric constant d{sub 33} of the SFN-PT ceramics is small except for SFN30-PT70 ceramics, which reaches 22pC/N.

  6. Experimental and theoretical study of pure and doped crystals: Gd2O2S, Gd2O2S:Eu3+ and Gd2O2S:Tb3+

    Science.gov (United States)

    Wang, Fei; Chen, Xiumin; Liu, Dachun; Yang, Bin; Dai, Yongnian

    2012-08-01

    Quantum chemistry and experimental method were used to study on pure and doped Gd2O2S crystals in this paper. The band structure and DOS diagrams of pure and doped Gd2O2S crystals which calculated by using DFT (Density Functional Theory) method were illustrated to explain the luminescent properties of impurities in crystals. The calculations of the crystal structure were finished by using the program of CASTEP (Cambridge Sequential Total Energy Package). The samples showed the characteristic emissions of Tb3+ ions with 5D4-7FJ transitions and Eu3+ ions with 5D0-7FJ transitions which emit pure green luminescence and red luminescence respectively. The experimental excitation spectra of Tb3+ and Eu3+ doped Gd2O2S are in agreement of the DOS diagrams over the explored energy range, which has allowed a better understanding of different luminescence mechanisms of Tb3+ and Eu3+ in Gd2O2S crystals.

  7. Photoresponse in La0.9Hf0.1MnO3/0.05wt%Nb-doped SrTiO3 heteroepitaxial junctions

    Science.gov (United States)

    Qi, Yaping; Ni, Hao; Zheng, Ming; Zeng, Jiali; Jiang, Yucheng; Gao, Ju

    2018-05-01

    Excellent photo detectors need to have the rapid response and good repeatability from the requirement of industrial applications. In this paper, transport behavior and opto-response of heterostructures made with La0.9Hf0.1MnO3 and 0.05wt%Nb-doped SrTiO3 were investigated. The heterojunctions exhibited an excellent rectifying feature with very low leakage in a broad temperature region (from 40 to 300 K). These thin films presented persistent and stable photovoltages upon light illumination. Rapid shift between small and large voltages corresponding to "light OFF" and "light ON" states, respectively, was observed, demonstrating reliable photo detection behavior. A semiconductor laser with a wavelength of 650 nm was used as the light source. It is also noted that the observed photovoltages are strongly determined by light intensity. The injection of photoexcited charge carriers (electrons) could be responsible for the appearance of the observed opto-response. Such manipulative features by light irradiation exhibit great potential for light detectors for visible light.

  8. Photoresponse in La0.9Hf0.1MnO3/0.05wt%Nb-doped SrTiO3 heteroepitaxial junctions

    Directory of Open Access Journals (Sweden)

    Yaping Qi

    2018-05-01

    Full Text Available Excellent photo detectors need to have the rapid response and good repeatability from the requirement of industrial applications. In this paper, transport behavior and opto-response of heterostructures made with La0.9Hf0.1MnO3 and 0.05wt%Nb-doped SrTiO3 were investigated. The heterojunctions exhibited an excellent rectifying feature with very low leakage in a broad temperature region (from 40 to 300 K. These thin films presented persistent and stable photovoltages upon light illumination. Rapid shift between small and large voltages corresponding to “light OFF” and “light ON” states, respectively, was observed, demonstrating reliable photo detection behavior. A semiconductor laser with a wavelength of 650 nm was used as the light source. It is also noted that the observed photovoltages are strongly determined by light intensity. The injection of photoexcited charge carriers (electrons could be responsible for the appearance of the observed opto-response. Such manipulative features by light irradiation exhibit great potential for light detectors for visible light.

  9. 926 nm laser operation in Nd:GdNbO4 crystal based on 4F3/2 → 4I9/2 transition

    Science.gov (United States)

    Yan, Renpeng; Li, Xudong; Yao, Wenming; Shen, Yingjie; Zhou, Zhongxiang; Peng, Fang; Zhang, Qingli; Dou, Renqing; Gao, Jing

    2018-05-01

    926 nm laser operation in a Nd:GdNbO4 crystal based on quasi-three-level 4F3/2 → 4I9/2 transition is reported, for the first time to our best knowledge. An average output power of 393 mW at 926 nm under 879 nm LD pumping is obtained with a slope efficiency of 33.3% and an optical-to-optical efficiency of 26.0%. The slope efficiency with respect to absorbed pump power is estimated to be 47.7%. Comparison between output characters of 926 nm laser under direct and indirect pumping is conducted. The average output power at 926 nm under 808 nm LD pumping reaches 305 mW with an optical-to-optical efficiency of 16.1%.

  10. Synthesis and structure of nanomaterials in the system K2O-Nb2O5-SiO2

    Directory of Open Access Journals (Sweden)

    Georgi Chernev

    2009-06-01

    Full Text Available The aim of the present work is synthesis of ferroelectric nanomaterials, in the K2O-Nb2O5-SiO2 system via solgel method and studying the processes of formation and structure of the synthesized ferroelectric nanomaterials. The structure of synthesized materials has been studied by means of the following methods: EDS, XRD, FT-IR, SEM and AFM. The results obtained showed that the structure of the investigated compositions does not depend on the niobium content and all the samples keep their amorphous nature at room temperature. The surface structure shows random distribution of different kinds of aggregates with dimensions about 200–500 nm. The presence of a hybrid nanostructure with well-defi ned nanounits having special geometry is clearly observed.

  11. Neutron investigation of Ru-doped Nd1/2Ca1/2MnO3. Comparison with Cr-doped Nd1/2Ca1/2MnO3

    International Nuclear Information System (INIS)

    Moritomo, Yutaka; Nonobe, Toshihiko; Machida, Akihiko; Ohoyama, Kenji

    2002-01-01

    Lattice and magnetic properties are investigated for 3% Ru- and Cr-doped Nd 1/2 Ca 1/2 MnO 3 . The parent Nd 1/2 Ca 1/2 MnO 3 is a charge-ordered insulator (T CO =250K). With decreasing temperature below ≅210K, these compounds are separated into two perovskite phases, that is, the long-c and short-c phases. The long-c region shows a ferromagnetic transition at T C ≅210K for the Ru-doped compound and ≅130K for the Cr-doped compound, while the short-c region shows antiferromagnetic transition at T N ≅150K for Ru and ≅110K for Cr. We discuss the origin of the enhanced T C for the Ru-doped compound in terms of the effective one-electron bandwidth W of the e g -band. (author)

  12. Synthesis, Characterization, and Photocatalytic Activity of Zn-Doped SnO2/Zn2SnO4 Coupled Nanocomposites

    Directory of Open Access Journals (Sweden)

    Tiekun Jia

    2014-01-01

    Full Text Available Zn-doped SnO2/Zn2SnO4 nanocomposites were prepared via a two-step hydrothermal synthesis method. The as-prepared samples were characterized by X-ray diffraction (XRD, field-emission scanning electron microscopy (FESEM, transmission electron microscopy (TEM, UV-vis diffuse reflection spectroscopy, and adsorption-desorption isotherms. The results of FESEM and TEM showed that the as-prepared Zn-doped SnO2/Zn2SnO4 nanocomposites are composed of numerous nanoparticles with the size ranging from 20 nm to 50 nm. The specific surface area of the as-prepared Zn-doped SnO2/Zn2SnO4 nanocomposites is estimated to be 71.53 m2/g by the Brunauer-Emmett-Teller (BET method. The photocatalytic activity was evaluated by the degradation of methylene blue (MB, and the resulting showed that Zn-doped SnO2/Zn2SnO4 nanocomposites exhibited excellent photocatalytic activity due to their higher specific surface area and surface charge carrier transfer.

  13. Study of dielectric property on ZrO2 and Al doped ZrO2 nanoparticles

    International Nuclear Information System (INIS)

    Catherine Siriya Pushpa, K.; Mangayarkarasi, K.; Ravichandran, A.T.; Xavier, A. Robert; Nagabushana, B.M.

    2014-01-01

    A solution combustion process was used to synthesize ZrO 2 and Al doped ZrO 2 nanoparticles by using Zirconium nitrate and aluminium nitrate as the oxidizer and glycine as fuel. The prepared samples were characterized by several techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-visible spectroscopy (UV-vis). The dielectric values of the pelletized samples were examined at room temperature as the function of frequency. XRD shows the structure of the prepared and doped samples. The SEM shows the surface morphology of the pure and doped ZrO 2 nanoparticles. The dielectric property enhances with increase of Al concentration, which is useful in dielectric gates. (author)

  14. Enhanced photovoltaic performance of fully flexible dye-sensitized solar cells based on the Nb{sub 2}O{sub 5} coated hierarchical TiO{sub 2} nanowire-nanosheet arrays

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wenwu; Hong, Chengxun; Wang, Hui-gang; Zhang, Mei; Guo, Min, E-mail: guomin@ustb.edu.cn

    2016-02-28

    Graphical abstract: Nb{sub 2}O{sub 5} coated hierarchical TiO{sub 2} nanowire-sheet arrays photoanode was synthesized on Ti-mesh substrate by using a hydrothermal approach for fully flexible dye-sensitized solar cells which exhibited well photovoltaic efficiency of 4.55%. - Highlights: • Nb{sub 2}O{sub 5} coated hierarchical TiO{sub 2} nanowire-nanosheet arrays were prepared on Ti-mesh. • Nb{sub 2}O{sub 5} coated TiO{sub 2} HNWAs/Pt-ITO-PEN flexible DSSC was constructed. • The fully flexible DSSC exhibited an enhanced photovoltaic performance of 4.55%. • The reasons for the improved conversion efficiency of the DSSC were discussed. - Abstract: Nb{sub 2}O{sub 5} coated hierarchical TiO{sub 2} nanowire-sheet arrays photoanode was synthesized on flexible Ti-mesh substrate by using a hydrothermal approach. The effect of TiO{sub 2} morphology and Nb{sub 2}O{sub 5} coating layer on the photovoltaic performance of the flexible dye sensitized solar cells (DSSCs) based on Ti-mesh supported nanostructures were systematically investigated. Compared to the TiO{sub 2} nanowire arrays (NWAs), hierarchical TiO{sub 2} nanowire arrays (HNWAs) with enlarged internal surface area and strong light scattering properties exhibited higher overall conversion efficiency. The introduction of thin Nb{sub 2}O{sub 5} coating layers on the surface of the TiO{sub 2} HNWAs played a key role in improving the photovoltaic performance of the flexible DSSC. By separating the TiO{sub 2} and electrolyte (I{sup –}/I{sub 3}{sup –}), the Nb{sub 2}O{sub 5} energy barrier decreased the electron recombination rate and increased electron collection efficiency and injection efficiency, resulting in improved J{sub sc} and V{sub oc}. Furthermore, the influence of Nb{sub 2}O{sub 5} coating amounts on the power conversion efficiency were discussed in detail. The fully flexible DSSC based on Nb{sub 2}O{sub 5} coated TiO{sub 2} HNWAs films with a thickness of 14 μm displayed a well photovoltaic property

  15. Study and fabrication of ZnNb2O6 thin films by sol-gel method

    International Nuclear Information System (INIS)

    Hsu, Cheng-Hsing; Yang, Pai-Chuan; Yang, Hsi-Wen; Yan, Shu-Fong; Tung, Hsin-Han

    2011-01-01

    Zinc niobium oxide (ZnNb 2 O 6 ) thin films were grown on ITO/glass substrate by sol-gel process. Microstructure and surface morphology of the ZnNb 2 O 6 thin films have been studied by X-ray diffraction and scanning electron microscopy. Optical properties of the ZnNb 2 O 6 thin films were obtained by UV-visible recording spectrophotometer. The dependence of the microstructure, optical transmittance spectra, optical band gap on annealing temperature was also investigated.

  16. Optimization of Nb{sub 2}O{sub 5}/Ag/Nb{sub 2}O{sub 5} multilayers as transparent composite electrode on flexible substrate with high figure of merit

    Energy Technology Data Exchange (ETDEWEB)

    Dhar, Aritra [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); Alford, T. L. [School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287 (United States)

    2012-11-15

    Different multilayer structures of Nb{sub 2}O{sub 5}/Ag/Nb{sub 2}O{sub 5} have been deposited onto flexible substrates by sputtering at room temperature to develop an indium free transparent composite electrode. The effect of Ag thickness on the electrical and optical properties of the multilayer stack has been studied in accordance with the Ag morphology. The critical thickness of Ag to form a continuous conducting layer is found to be 9.5 nm. A new conduction mechanism has been proposed to describe the conduction before and after the critical thickness. The effective Hall resistivity of the optimized films is as low as 6.44 Multiplication-Sign 10{sup -5} Ohm-Sign -cm with a carrier concentration and mobility of 7.4 Multiplication-Sign 10{sup 21} cm{sup -3} and 13.1 cm{sup 2} /V-s, respectively, at the critical Ag layer thickness. The multilayer stack has been optimized to obtain a sheet resistance of 7.2 Ohm-Sign /sq and an average optical transmittance of 86% at 550 nm without any substrate heating or post-annealing process. The Haacke figure of merit (FOM) has been calculated for the films, and the multilayer with a 9.5 nm thick Ag layer has the highest FOM at 31.5 Multiplication-Sign 10-3 {Omega}{sup -1}, which is one of the highest FOM values reported for TCE deposited at room temperature on a flexible substrate.

  17. High temperature oxidation-sulfidation behavior of Cr-Al2O3 and Nb-Al2O3 composites densified by spark plasma sintering

    International Nuclear Information System (INIS)

    Saucedo-Acuna, R.A.; Monreal-Romero, H.; Martinez-Villafane, A.; Chacon-Nava, J.G.; Arce-Colunga, U.; Gaona-Tiburcio, C.; De la Torre, S.D.

    2007-01-01

    The high temperature oxidation-sulfidation behavior of Cr-Al 2 O 3 and Nb-Al 2 O 3 composites prepared by mechanical alloying (MA) and spark plasma sintering (SPS) has been studied. These composite powders have a particular metal-ceramic interpenetrating network and excellent mechanical properties. Oxidation-sulfidation tests were carried out at 900 deg. C, in a 2.5%SO 2 + 3.6%O 2 + N 2 (balance) atmosphere for 48 h. The results revealed the influence of the sintering conditions on the specimens corrosion resistance, i.e. the Cr-Al 2 O 3 and Nb-Al 2 O 3 composite sintered at 1310 deg. C/4 min showed better corrosion resistance (lower weight gains) compared with those found for the 1440 deg. C/5 min conditions. For the former composite, a protective Cr 2 O 3 layer immediately forms upon heating, whereas for the later pest disintegration was noted. Thus, under the same sintering conditions the Nb-Al 2 O 3 composites showed the highest weight gains. The oxidation products were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy

  18. Synthesis and microwave absorption enhancement of Fe-doped NiO@SiO2@graphene nanocomposites

    International Nuclear Information System (INIS)

    Wang, Lei; Huang, Ying; Ding, Xiao; Liu, Panbo; Zong, Meng; Wang, Yan

    2013-01-01

    Highlights: • Fe-doped NiO@SiO 2 @graphene composites have excellent microwave performance. • The reflection loss of Fe doped NiO@SiO 2 @graphene was below −10 dB in 7–11 GHz. • The maximum absorption of Fe-doped NiO@SiO 2 @graphene was −51.2 dB at 8.6 GHz. -- Abstract: Fe-doped NiO@SiO 2 @graphene nanocomposites have been successfully fabricated for the first time, in which Fe-doped NiO nanoparticles are about 3 nm in diameter. In order to measure their electromagnetic properties, Fe-doped NiO@SiO 2 @graphene (25 wt%) wax composites were then prepared. The experimental results show that Fe-doped NiO@SiO 2 @graphene nanocomposites exhibit significantly enhanced microwave absorption performance in terms of both the maximum reflection loss value and the absorption bandwidth in comparison with NiO@SiO 2 @graphene. The maximum reflection loss of Fe-doped NiO@SiO 2 @graphene nanocomposites can reach −51.2 dB at 8.6 GHz with a thickness of 4 mm, and the absorption bandwidth with the reflection loss below −10 dB is 4 GHz (from 7 to 11 GHz). Therefore, this kind of nanocomposites may have the potential as high-efficient absorbers for microwave absorption applications

  19. 1887 nm lasing in Tm3+-doped TeO2-BaF2-Y2O3 glass microstructured fibers

    Science.gov (United States)

    Wang, Shunbin; Yao, Chuanfei; Jia, Zhixu; Qin, Guanshi; Qin, Weiping

    2017-04-01

    In this paper, we demonstrate ∼2 μm lasing in Tm3+-doped fluorotellurite microstructured fibers. The Tm3+-doped fibers are based on TeO2-BaF2-Y2O3 glasses and fabricated by using a rod-in-tube method. Under the pump of a 1570 nm Er3+-doped fiber laser, lasing at 1887 nm is obtained in a ∼42.5 cm long Tm3+-doped fiber with a threshold pump power of 94 mW. As the pump power increases to 780 mW, the obtained maximum unsaturated power reaches up to ∼408 mW with a slop efficiency of ∼58.1%. This result indicates that the Tm3+-doped fluorotellurite fibers are promising gain media for ∼2 μm fiber lasers.

  20. Eu2+-doped Ba2GaB4O9Cl blue-emitting phosphor with high color purity for near-UV-pumped white light-emitting diodes

    Science.gov (United States)

    Gao, Zhiwen; Deng, Huajuan; Xue, Na; Jeong, Jung Hyun; Yu, Ruijin

    2018-01-01

    Eu2+-doped borate fluoride Ba2GaB4O9Cl was synthesized by the conventional high-temperature solid-state reaction. The crystal structure and luminescence properties of the phosphors, as well as their thermal luminescence quenching capabilities and CIE chromaticity coordinates were systematically investigated. Under the excitation at 340 nm, the phosphor exhibited an asymmetric broad-band blue emission with a peak at 445 nm, which is ascribed to the 4f-5d transition of Eu2+. It was further proved that energy transfer among the nearest neighbor ions is the major mechanism for concentration quenching of Eu2+ in Ba2-xGaB4O9Cl:xEu2+ phosphors. The luminescence quenching temperature is 432 K. The CIE color coordinates are very close to those of BaMgAl10O17:Eu2+ (BAM). All the properties indicated that the blue-emitting Ba2GaB4O9Cl:Eu2+ phosphor has potential application in white LEDs.

  1. Emission analysis of Tb3+ -and Sm3+ -ion-doped (Li2 O/Na2 O/K2 O) and (Li2 O + Na2 O/Li2 O + K2 O/K2 O + Na2 O)-modified borosilicate glasses.

    Science.gov (United States)

    Naveen Kumar Reddy, B; Sailaja, S; Thyagarajan, K; Jho, Young Dahl; Sudhakar Reddy, B

    2018-05-01

    Four series of borosilicate glasses modified by alkali oxides and doped with Tb 3+ and Sm 3+ ions were prepared using the conventional melt quenching technique, with the chemical composition 74.5B 2 O 3 + 10SiO 2 + 5MgO + R + 0.5(Tb 2 O 3 /Sm 2 O 3 ) [where R = 10(Li 2 O /Na 2 O/K 2 O) for series A and C, and R = 5(Li 2 O + Na 2 O/Li 2 O + K 2 O/K 2 O + Na 2 O) for series B and D]. The X-ray diffraction (XRD) patterns of all the prepared glasses indicate their amorphous nature. The spectroscopic properties of the prepared glasses were studied by optical absorption analysis, photoluminescence excitation (PLE) and photoluminescence (PL) analysis. A green emission corresponding to the 5 D 4 → 7 F 5 (543 nm) transition of the Tb 3+ ions was registered under excitation at 379 nm for series A and B glasses. The emission spectra of the Sm 3+ ions with the series C and D glasses showed strong reddish-orange emission at 600 nm ( 4 G 5/2 → 6 H 7/2 ) with an excitation wavelength λ exci = 404 nm ( 6 H 5/2 → 4 F 7/2 ). Furthermore, the change in the luminescence intensity with the addition of an alkali oxide and combinations of these alkali oxides to borosilicate glasses doped with Tb 3+ and Sm 3+ ions was studied to optimize the potential alkali-oxide-modified borosilicate glass. Copyright © 2017 John Wiley & Sons, Ltd.

  2. Dielectric properties of Ga{sub 2}O{sub 3}-doped barium iron niobate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sanjoom, Kachaporn [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand); Pengpat, Kamonpan; Eitssayeam, Sukum; Tunkasiri, Tawee [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Rujijanagul, Gobwute [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand)

    2014-08-15

    Ga-doped BaFe{sub 0.5}Nb{sub 0.5}O{sub 3} (Ba(Fe{sub 1-x}Ga{sub x}){sub 0.5}Nb{sub 0.5}O{sub 3}) ceramics were fabricated and their properties were investigated. All ceramics showed perovskite structure with cubic symmetry and the solubility of Ga in BFN ceramics had a limit at x = 0.2. Examination of the dielectric spectra indicated that all ceramic samples presented high dielectric constants that were frequency dependent. The x = 0.2 ceramic showed a very high dielectric constant (ε{sub r} > 240 000 at 1 kHz) while the x = 0.4 sample exhibited high thermal stability of dielectric constant with low loss tangent from room temperature (RT) to 100 C with ε{sub r} > 28 000 (at 1 kHz) when compared to other samples. By using a complex impedance analysis technique, bulk grain, grain boundary, and electrode response were found to affect the dielectric behavior that could be related to the Maxwell-Wagner polarization mechanism. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Thermal, defects, mechanical and spectral properties of Nd-doped GdNbO{sub 4} laser crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Shoujun [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China); University of Science and Technology of China, Hefei (China); Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Wang, Xiaofei; Sun, Guihua; Li, Xiuli; Sun, Dunlu [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China)

    2017-05-15

    A Nd-doped GdNbO{sub 4} crystal was grown successfully by Czochralski method. Its monoclinic structure was determined by X-ray diffraction; the unit-cell parameters are a = 5.38 Aa, b = 11.09 Aa, c = 5.11 Aa, and β = 94.56 . The morphological defects of Nd:GdNbO{sub 4} crystal were investigated using the chemical etching with the phosphoric acid etchant. For a new crystal, the physical properties are of great importance. The hardness and density of Nd:GdNbO{sub 4} were investigated first. Thermal properties of Nd:GdNbO{sub 4}, including thermal expansion coefficient and specific heat, were measured along a-, b-, and c-crystalline axes. Thermal properties indicate that the Nd:GdNbO{sub 4} pumped along c-axis can reduce the thermal lensing effect effectively. The specific heat is 0.53 J g{sup -1} K{sup -1} at 300 K, indicating a relatively high damage threshold of Nd:GdNbO{sub 4}. The transmission and emission spectrum of Nd:GdNbO{sub 4} were measured, and the absorption peaks were assigned. The strongest emission peak of Nd:GdNbO{sub 4} is located at 1065.3 nm in the spectral range of 850-1420 nm excited by 808 nm laser. The refractive index of Nd:GdNbO{sub 4} was calculated with the transmission spectrum and fitted with Sellmeier equation. All these obtained results is of great significance for the further research of Nd:GdNbO{sub 4}. (orig.)

  4. Ag+ implantation in Al2O3, LiNbO3 and quartz

    International Nuclear Information System (INIS)

    Rahmani, M.; Townsend, P.D.

    1989-01-01

    Silver implantation in insulators produces colloids whose growth is a function of ion dose, ion energy, implant temperature and crystal orientation. Data for three materials are compared. Colloid growth is favoured by higher energy implants at temperatures where the silver is mobile. Preferential diffusion along the Z axis of Al 2 O 3 , LiNbO 3 and quartz results in a higher fraction of the implanted silver ions appearing in the form of colloids for Y cut crystals than for those of Z cut. Annealing characteristics also show a strong dependence on crystal cut. For the LiNbO 3 the colloids in Z cut crystals anneal most rapidly whereas for Al 2 O 3 those in Y cut material are least stable, their loss being accompanied by a reduction in F centres. (author)

  5. Debye’s temperature and heat capacity for Sr0.15Ba0.85Bi2Nb2O9 relaxor ferroelectric ceramic

    Directory of Open Access Journals (Sweden)

    A. Peláiz-Barranco

    2016-03-01

    Full Text Available A lead-free relaxor ferroelectric, Sr0.15Ba0.85Bi2Nb2O9, was synthesized via solid-state reaction and the temperature-dependence of the heat capacity was measured in a wide temperature range. The dielectric permittivity was also measured between 500Hz and 5MHz in the same temperature range. No anomaly has been detected in the heat capacity curve for the whole temperature range covered in the present experiments, while broad peaks have been observed in the dielectric permittivity with high frequency dispersion. A typical relaxor behavior has been observed from the dielectric analysis. The Debye’s temperature has showed a minimum value near the freezing temperature. The results are discussed considering the spin-glass model and the high frequency dispersion, which has been observed for the studied relaxor system.

  6. Temperature stability of c-axis oriented LiNbO{sub 3}/SiO{sub 2}/Si thin film layered structures

    Energy Technology Data Exchange (ETDEWEB)

    Tomar, Monika [Department of Physics and Astrophysics, University of Delhi, Delhi (India)]. E-mail: mtomar@physics.du.ac.in; monikatomar@rediffmail.com; Gupta, Vinay; Mansingh, Abhai; Sreenivas, K. [Department of Physics and Astrophysics, University of Delhi, Delhi (India)

    2001-08-07

    Theoretical calculations have been performed for the temperature stability of the c-axis oriented LiNbO{sub 3} thin film layered structures on passivated silicon (SiO{sub 2}/Si) substrate with and without a non-piezoelectric SiO{sub 2} overlayer. The phase velocity, electromechanical coupling coefficient and temperature coefficient of delay (TCD) have been calculated. The thicknesses of various layers have been determined for optimum SAW performance with zero TCD. The presence of a non-piezoelectric SiO{sub 2} overlayer on LiNbO{sub 3} film is found to significantly enhance the coupling coefficient. The optimized results reveal that a high coupling coefficient of K{sup 2}=3.45% and a zero TCD can be obtained in the SiO{sub 2}/LiNbO{sub 3}/SiO{sub 2}/Si structure with a 0.235{lambda} thick LiNbO{sub 3} layer sandwiched between 0.1{lambda} thick SiO{sub 2} layers. (author)

  7. Flexible Nb2O5 nanowires/graphene film electrode for high-performance hybrid Li-ion supercapacitors

    Science.gov (United States)

    Song, Hao; Fu, Jijiang; Ding, Kang; Huang, Chao; Wu, Kai; Zhang, Xuming; Gao, Biao; Huo, Kaifu; Peng, Xiang; Chu, Paul K.

    2016-10-01

    The hybrid Li-ion electrochemical supercapacitor (Li-HSC) combining the battery-like anode with capacitive cathode is a promising energy storage device boasting large energy and power densities. Orthorhombic Nb2O5 is a good anode material in Li-HSCs because of its large pseudocapacitive Li-ion intercalation capacity. Herein, we report a high-performance, binder-free and flexible anode consisting of long Nb2O5 nanowires and graphene (L-Nb2O5 NWs/rGO). The paper-like L-Nb2O5 NWs/rGO film electrode has a large mass loading of Nb2O5 of 93.5 wt% as well as short solid-state ion diffusion length, and enhanced conductivity (5.1 S cm-1). The hybrid L-Nb2O5 NWs/rGO paper electrode shows a high reversible specific capacity of 160 mA h g-1 at a current density of 0.2 A g-1, superior rate capability with capacitance retention of 60% when the current density increases from 0.2 to 5 A g-1, as well as excellent cycle stability. The Li-HSC device based on the L-Nb2O5/rGO anode and the cathode of biomass-derived carbon nanosheets delivers an energy density of 106 Wh kg-1 at 580 W kg-1 and 32 Wh kg-1 at a large power density of 14 kW kg-1. Moreover, the Li-HSC device exhibits excellent cycling performance without obvious capacitance decay after 1000 cycles.

  8. Electron irradiation response on Ge and Al-doped SiO 2 optical fibres

    Science.gov (United States)

    Yaakob, N. H.; Wagiran, H.; Hossain, I.; Ramli, A. T.; Bradley, D. A.; Hashim, S.; Ali, H.

    2011-05-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  9. Electron irradiation response on Ge and Al-doped SiO2 optical fibres

    International Nuclear Information System (INIS)

    Yaakob, N.H.; Wagiran, H.; Hossain, I.; Ramli, A.T.; Bradley, D.A; Hashim, S.; Ali, H.

    2011-01-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  10. Structural, optical and ferromagnetic properties of Cr doped TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Choudhury, Biswajit; Choudhury, Amarjyoti

    2013-01-01

    Graphical abstract: Doping of Cr 3+ distorts the lattice of TiO 2 , generate oxygen vacancies and create d-band states in the mid band gap of TiO 2 . Incorporation of Cr 3+ also imparts magnetism in non-magnetic TiO 2 by undergoing coupling with the neighboring oxygen vacancies. -- Highlights: • Incorporation of Cr 3+ increases the concentration of oxygen vacancies in TiO 2 nanoparticles. • Doped TiO 2 nanoparticles contain absorption peaks corresponding to d–d transition of Cr 3+ into TiO 2 . • Pure and doped TiO 2 nanoparticles contain emission peaks related to oxygen vacancies. • Pure TiO 2 shows diamagnetism while Cr doped TiO 2 shows ferromagnetism. • The ferromagnetism is due to the interaction of Cr 3+ ions via oxygen vacancies. -- Abstract: Cr doped TiO 2 nanoparticles are prepared with three different concentrations of chromium, 1.5%, 3.0% and 4.5 mol% respectively. Doping decreases the crystallinity and increases the width of the X-ray diffraction peak. The Raman active E g peak of TiO 2 nanoparticles become asymmetric and shifted to higher energy on doping of 4.5% chromium. Electron paramagnetic resonance spectra reveal the presence of Cr 3+ in the host TiO 2 matrix. The absorption spectra of Cr doped TiO 2 nanoparticles contain absorption peaks corresponding to d–d transition of Cr 3+ in octahedral coordination. Most of the visible emission peaks are due to the electrons trapped in the oxygen vacancy centers. Undoped TiO 2 nanoparticles show diamagnetism at room temperature while all chromium doped samples show ferromagnetism. The magnetization of the doped samples increases at 1.5% and 3.0% and decreases at 4.5%. The ferromagnetism arises owing to the interaction of the neighboring Cr 3+ ions via oxygen vacancies. The decrease of magnetization at the highest doping is possibly due to the antiferromagnetic interactions of Cr 3+ pairs or due to Cr 3+ -O 2− -Cr 3+ superexchange interaction in the lattice

  11. Nano-phases of ZrO2 doped with Y2O3

    International Nuclear Information System (INIS)

    Duteanu, Narcis; Monty, Claude

    2001-01-01

    This work reports the method of obtaining oxygen sensors by using nano-phases of ZrO 2 doped with Y 2 O 3 95% molar in thin layers. In the first phase it is necessary to prepare a substratum based on La 1-x Sr 30 MnO 3 . This substratum is obtained by grinding powders of base, followed by mixing and then by baking of the product. The nano-phases of ZrO 2 doped with Y 2 O 3 95% molar are obtained using solar energy in a solar furnace; in the focus the temperature has value of 3000 deg. C. Such temperatures are enough to realize the process of vapor condensation. The nano-phases obtained will have used in thin layers, representing the active element. This layers are obtained directly through the process of vapor condensation in solar focus or using the spray method. The goal of this work was obtaining oxygen sensors which function at low temperatures (below 300 deg. C), because the sensors which are found on market, operate at a temperature of 800 deg. C. Those sensors are used to obtain a good combustion with engines with internal combustion. (authors)

  12. Micro-nanocomposites Al2O3/ NbC/ WC and Al2O3/ NbC/ TaC

    International Nuclear Information System (INIS)

    Santos, Thais da Silva

    2014-01-01

    Alumina based ceramics belong to a class of materials designated as structural, which are widely used in cutting tools. Although alumina has good properties for application as a structural ceramics, composites with different additives have been produced with the aim of improving its fracture toughness and mechanical strength. New studies point out micro-nanocomposites, wherein the addition of micrometric particles should enhance mechanical strength, and nano-sized particles enhance fracture toughness. In this work, alumina based micro nanocomposites were obtained by including nano-sized NbC and micrometer WC particles at 2:1, 6:4, 10:5 and 15:10 vol% proportions, and also with the inclusion of nano-sized NbC and micrometer TaC particles at 2:1 vol% proportion. For the study of densification, micro-nanocomposites were sintered in a dilatometer with a heating rate of 20°C/min until a temperature of 1800°C in argon atmosphere. Based on the dilatometry results, specimens were sintered in a resistive graphite furnace under argon atmosphere between 1500°C and 1700°C by holding the sintering temperature for 30 minutes. Densities, crystalline phases, hardness and tenacity were determined, and micro-nanocomposites microstructures were analyzed. The samples Al 2 O 3 : NbC: TaC sintered at 1700 ° C achieved the greater apparent density (~ 95% TD) and the sample sintered at 1600 ° C showed homogeneous microstructure and increased hardness value (15.8 GPa) compared to the pure alumina . The compositions with 3% inclusions are the most promising for future applications. (author)

  13. Thermal stability test of UO{sub 2}-doped pellet manufactured at INB

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Diogo R., E-mail: diogoribeiro@inb.gov.br [Indústrias Nucleares do Brasil S.A. (FCN/INB), Resende, RJ (Brazil). Fábrica de Combustível Nuclear; Freitas, Artur C., E-mail: artur.freitas@ipen.br [Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

    2017-07-01

    The thermal stability test of UO{sub 2}-doped pellet manufactured at INB was carried out in order to analyze the resintering behavior. This analysis is fundamental for predicting dimensional behavior during irradiation. INB commonly performs resintering test to qualify its production lots, and the same methodology was applied to UO{sub 2}-doped pellets. In this preliminary study, three sets of experiments have been made: 1) without any chemical additive (Z test, the standard UO{sub 2} pellets - undoped); 2) UO{sub 2} pellets doped with 0.1, 0.2 and 0.3 wt% of Al{sub 2}O{sub 3}; and 3) 0.1, 0.2 and 0.3 wt% of Nb{sub 2}O{sub 5}. The preliminary results showed an increase in sintered density in all resintering experiments. So as to obtain the percentage increase, the theoretical densities (g/cm{sup 3} and %TD) were calculated based on the undoped UO{sub 2} pellets. All samples increased in a range of 0.27 to 0.32 %TD the out-pile densification during the resintering process. However, the Z(Nb)3 test showed the lowest value of 0.08 %TD, which is not in agreement with the INB specification limits. The sintered density of this test (0.3 wt% niobia) was 96.15% TD. This fact might be related to the competitive mechanism between Kirkendall effect, forming porosity owing to niobium solubilization on UO{sub 2} matrix, and densification process as a result of uranium diffusivity. Thus, the densification was only 0.08 %TD in Z(Nb)3 sample. All the other samples were in agreement with INB specification. (author)

  14. Crystal growth and optical properties of Sm:CaNb2O6 single crystal

    International Nuclear Information System (INIS)

    Di Juqing; Xu Xiaodong; Xia Changtai; Zeng Huidan; Cheng Yan; Li Dongzhen; Zhou Dahua; Wu Feng; Cheng Jimeng; Xu Jun

    2012-01-01

    Highlights: ► Sm:CaNb 2 O 6 single crystal was grown by the Czochralski method. ► Thermal expansion coefficients and J–O parameters were calculated. ► We found that this crystal had high quantum efficiency of 97%. - Abstract: Sm:CaNb 2 O 6 single crystal has been grown by the Czochralski method. Its high-temperature X-ray powder diffraction, optical absorption, emission spectroscopic as well as lifetime have been studied. Thermal expansion coefficients (α), J–O parameters (Ω i ), radiative lifetime (τ rad ), branching ratios (β) and stimulated emission cross-sections (σ e ) were calculated. The quantum efficiency (η) was calculated to be 97%. The intense peak emission cross section at 610, 658 nm were calculated to be 2.40 × 10 −21 , 2.42 × 10 −21 cm 2 . These results indicate that Sm:CaNb 2 O 6 crystal has potential use in visible laser and photonic devices area.

  15. Effect of Te doping on superconductivity and charge-density wave in dichalcogenides 2H-NbSe2-χTeχ(χ=0,0.1,0.2)

    Institute of Scientific and Technical Information of China (English)

    Wang Hong-Tao; Li Lin-Jun; Ye De-shu; Cheng Xin-Hong; Xu Zhu-An

    2007-01-01

    Single crystals of Te-doped dichalcogenides 2H-NbSe2-χTeχ(χ=0,0.10,0.20)were grown by vapour transport method.The effect of Te doping on the superconducting and charge-density wave(CDW)transitions has been investigated.The sharp decrease of residual resistance ratio,RRR=R(300K)/R(8K),with increasing Te content was observed,indicating that the disorder in the conducting plane is induced by Te doping.Meanwhile the superconducting transition temperature,Tc,decreases monotonically with Te content.However,the CDW transition temperature,TCDW,shown by a small jump in the temperature dependence of the resistivity near 30 K,increases slightly.The results show that the suppression of superconductivity might be caused by the enhancement of CDW ordering.The disorder has little influence on the CDW ordering.

  16. Investigation of Mn Implanted LiNbO3 applying electron paramagnetic resonance technique

    International Nuclear Information System (INIS)

    Darwish, A.; Ila, D.; Poker, D.B.; Hensley, D.K.

    1997-10-01

    The effect of ion implantation on the LiNbO 3 crystal is studied using electron paramagnetic resonance spectroscopy (EPR). EPR measurements on these crystals were performed as a function of ion species Mn and Fe and fluence at room temperature. Also the effect of the laser illumination on the EPR signal was determined by illuminating the crystal in situ and measuring the decay and growth of the EPR signal. LiNbO 3 :Mn 2+ at a depth of approximately 200 nm was formed by implantation of 2.5 x 10 14 Mncm 2 and 1 x 10 17 Mn/cm 2 at 2 MeV. The implanted samples were compared with bulk doped crystals. It was found that the decay and growth of Mn EPR for the implanted crystal is very small compared with the bulk doped LiNbO 3 :Mn crystal. This was found to be primarily due to the spin concentration on the crystals. On the other, hand the decay time of the high fluence is about 40% slower than the decay of the low fluence implanted crystal

  17. Synthesis and photocatalytic activity of graphene based doped TiO2 nanocomposites

    International Nuclear Information System (INIS)

    Gu, Yongji; Xing, Mingyang; Zhang, Jinlong

    2014-01-01

    Graphical abstract: - Highlights: • Graphene based doped TiO 2 nanocomposites were prepared. • The intimate contact between doped TiO 2 and graphene is achieved simultaneously. • These nanocomposites showed higher photocatalytic activity than TiO 2 and doped TiO 2 . • Photocatalytic mechanism was explained thoroughly. - Abstract: The nanocomposites of reduced graphene oxide based nitrogen doped TiO 2 (N–TiO 2 –RGO) and reduced graphene oxide based nitrogen and vanadium co-doped TiO 2 (N, V–TiO 2 –RGO) were prepared via a facile hydrothermal reaction of graphene oxide and TiO 2 in a water solvent. In this hydrothermal treatment, the reduction of graphene oxide and the intimate contact between nitrogen doped TiO 2 (N–TiO 2 ) or nitrogen and vanadium co-doped TiO 2 (N,V–TiO 2 ) and the RGO sheet is achieved simultaneously. Both N–TiO 2 –RGO and N,V–TiO 2 –RGO nanocomposites exhibit much higher visible light photocatalytic activity than N–TiO 2 and N,V–TiO 2 , and the order of visible light photocatalytic activity is N,V–TiO 2 –RGO > N–TiO 2 –RGO > N,V–TiO 2 > N–TiO 2 > TiO 2 . According to the characterization, the enhanced photocatalytic activity of the nanocomposites is attributed to reasons, such as enhancement of adsorption of pollutants, light absorption intensity, minimizing the recombination of photoinduced electrons and holes and more excited states of these nanocomposites under visible light irradiation. Overall, this work provides a more marked contrast of graphene based semiconductor nanocomposites and a more comprehensive explanation of the mechanism

  18. Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics.

    Science.gov (United States)

    Ferluccio, Daniella A; Smith, Ronald I; Buckman, Jim; Bos, Jan-Willem G

    2018-02-07

    The half-Heuslers NbCoSn and NbCoSb have promising thermoelectric properties. Here, an investigation of the NbCo 1+y Sn 1-z Sb z (y = 0, 0.05; 0 ≤ z ≤ 1) solid-solution is presented. In addition, the p-type doping of NbCoSn using Ti and Zr substitution is investigated. Rietveld analysis reveals the gradual creation of Nb vacancies to compensate for the n-type doping caused by the substitution of Sb in NbCoSn. This leads to a similar valence electron count (∼18.25) for the NbCo 1+y Sn 1-z Sb z samples (z > 0). Mass fluctuation disorder due to the Nb vacancies strongly decreases the lattice thermal conductivity from 10 W m -1 K -1 (z = 0) to 4.5 W m -1 K -1 (z = 0.5, 1). This is accompanied by a transition to degenerate semiconducting behaviour leading to large power factors, S 2 /ρ = 2.5-3 mW m -1 K -2 and figures of merit, ZT = 0.25-0.33 at 773 K. Ti and Zr can be used to achieve positive Seebeck values, e.g. S = +150 μV K -1 for 20% Zr at 773 K. However, the electrical resistivity, ρ 323K = 27-35 mΩ cm, remains too large for these materials to be considered useful p-type materials.

  19. Electrochemical sensing property of Mn doped V2O5 nanoparticles

    International Nuclear Information System (INIS)

    Suresh, R.; Giribabu, K.; Manigandan, R.; Narayanan, V.; Vijayalakshmi, L.; Stephen, A.

    2012-01-01

    In this study, pure V 2 O 5 and Mn doped V 2 O 5 nanoparticles were synthesized by thermal decomposition method. The FT-IR spectrum of Mn doped V 2 O 5 shows the bands at 822 and 1027 cm -1 which essentiaIIy of crystalline V 2 O 5 . Further, the bands observed in Mn doped V 2 O 5 are all shifted to lower wave number than the V 2 O 5 . The optical property of the nanocomposite was studied using UV-Visible absorption spectroscopy. The XRD data also revealed that the Mn doped V 2 O 5 obtained had an orthorhombic structure. The diffraction peaks in Mn doped V 2 O 5 nanoparticles are similar to that of V 2 O 5 . There was no indication of any other impurities in the sample. However, all the peaks of V 2 O 5 are slightly shifted to tower 2θ values. The FE-SEM image of V 2 O 5 shows that the particles adopt ellipse-like particles with different sizes due to aggregation. The synthesized nanoparticles were used to modify glassy carbon electrode (GCE) and the modified electrode was used to detect uric acid (UA) by voltammetric techniques. The effects of Mn on the optical, morphological and electrochemical detecting property of V 2 O 5 have also been studied. (author)

  20. Effect of zinc doping on the bandgap and photoluminescence of Zn2+-doped TiO2 nanowires

    Science.gov (United States)

    Loan, Trinh Thi; Huong, Vu Hoang; Tham, Vu Thi; Long, Nguyen Ngoc

    2018-03-01

    This study was focused on the effect of Zn2+ dopant concentration on the absorption edge and photoluminescence of anatase TiO2 nanowires synthesized by hydrothermal technique. For the undoped anatase TiO2 nanowires, the indirect band gap of 3.26 eV and the direct band gap of 3.58 eV are assigned to the indirect Γ3 → X1b and direct X2b → X1b transitions, respectively. The Zn2+-doping makes the absorption edge of TiO2:Zn2+ nanowires shift towards the lower energy side (red shift). On the other hand, the replacing Ti4+ ions with Zn2+ ions creates oxygen vacancies (VO) and shallow defects associated with VO. Just these defects are responsible for the enhanced luminescence of Zn2+-doped TiO2 nanowires.

  1. Tuning electronic structure and optical properties of SrTiO{sub 3} by site-specific doping by Nb with N/B from hybrid functional calculations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yanyu; Zhou, Wei; Wu, Ping, E-mail: pingwu@tju.edu.cn

    2017-07-01

    In this study, the extensive density functional theory calculations are performed to modify the electronic structure of perovskite SrTiO{sub 3} by doping with Nb and N/B. The unoccupied states induced by the Nb monodoping at the Sr or Ti site, which were passivated in the codoped systems (the substitution of Nb at Ti site with the replacement of N at O site: Nb@Ti/N@O and the substitution of Nb at Sr site with the replacement of B at O site: Nb@Sr/B@O). The charge-compensated donor-acceptor pair codoping creates the new occupied states within the band gap, which yields the absorption edge extend to visible light. And the calculated defect formation energy implies that the codoped systems are energetically favorable under the O-rich condition. Moreover, the band-edge alignment confirmed that the Nb@Ti/N@O system is desirable for the spontaneous water splitting under visible light and the Nb@Sr/B@O system can split water into hydrogen in presence of sacrificial agent. - Highlights: • A systematical study has been employed on SrTiO{sub 3} with the donor-acceptor codoping. • The donor-acceptor pair codoping yields the absorption edge extend to visible light. • The formation energy implies that the codoped systems are favorable under the O-rich condition. • The Nb@Ti/N@O system is desirable for the spontaneous water splitting under visible light. • The Nb@Sr/B@O system can split water into hydrogen in presence of sacrificial agent.

  2. Luminescence and energy transfer of Tb3+-doped BaO-Gd2O3-Al2O3-B2O3-SiO2 glasses.

    Science.gov (United States)

    Zuo, Chenggang; Huang, Jinze; Liu, Shaoyou; Xiao, Anguo; Shen, Youming; Zhang, Xiangyang; Zhou, Zhihua; Zhu, Ligang

    2017-12-05

    Transparent Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses with the greater than 4g/cm 3 were prepared by high temperature melting method and its luminescent properties have been investigated by measured UV-vis transmission, excitation, emission and luminescence decay spectra. The transmission spectrum shows there are three weak absorption bands locate at about 312, 378 and 484nm in the glasses and it has good transmittance in the visible spectrum region. Intense green emission can be observed under UV excitation. The effective energy transfer from Gd 3+ ion to Tb 3+ ion could occur and sensitize the luminescence of Tb 3+ ion. The green emission intensity of Tb 3+ ion could change with the increasing SiO 2 /B 2 O 3 ratio in the borosilicate glass matrix. With the increasing concentration of Tb 3+ ion, 5 D 4 → 7 F J transitions could be enhanced through the cross relaxation between the two nearby Tb 3+ ions. Luminescence decay time of 2.12ms from 546nm emission is obtained. The results indicate that Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses would be potential scintillating material for applications in X-ray imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Investigation of the La2O3-Nb2O5-WO3 ternary phase diagram: Isolation and crystal structure determination of the original La3NbWO10 material

    KAUST Repository

    Vu, T.D.

    2015-05-23

    In the course of the exploration of the La2O3-WO3-Nb2O5 ternary phase diagram, a new compound with the formula La3NbWO10 was discovered. Its structure was determined from a combination of powder X-ray and neutron diffraction data. It crystallizes in the tetragonal space group P42/nmc (no. 137) with the lattice parameters: a=10.0807(1) Å; c=12.5540(1) Å. The structure is built up from infinite ribbons of octahedra (W/Nb)O5 which are perpendicular to each other, lanthanum ions being distributed around these ribbons. The electrical properties of this compound were investigated on sintered pellets by means of complex impedance spectroscopy. © 2015 Elsevier Inc. All rights reserved.

  4. The influence of AlCrN coating on the high-temperature corrosion resistance of Ti-46Al-7Nb alloy in an atmosphere containing 9% O{sub 2} + 0.2% HCl + 0.08% SO{sub 2} + N{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Malecka, Joanna [Opole Univ. of Technology (Poland). Faculty of Mechanical Engineering

    2013-09-15

    The results of investigation of the isothermal oxidation wear mechanism of Ti-46Al-7Nb-0.7Cr-0.1Si-0.2Ni intermetallic alloy with AlCrN coating are presented. Tests in 9% O{sub 2} + 0.2% HCl + 0.08% SO{sub 2} + N{sub 2} atmosphere were performed at a temperature of 700 C. The structure of the specimen and chemical composition of the oxidation products were analysed using scanning electron microscopy and energy dispersive X-ray analysis. In addition, mass changes were investigated.

  5. Electrochemical Behavior of TiO2 Nanoparticle Doped WO3 Thin Films

    Directory of Open Access Journals (Sweden)

    Suvarna R. Bathe

    2014-01-01

    Full Text Available Nanoparticle TiO2 doped WO3 thin films by pulsed spray pyrolysis technique have been studied on fluorine tin doped (FTO and glass substrate. XRD shows amorphous nature for undoped and anatase phase of TiO2 having (101 plane for nanoparticle TiO2 doped WO3 thin film. SEM shows microfibrous reticulated porous network for WO3 with 600 nm fiber diameter and nanocrystalline having size 40 nm for TiO2 nanoparticle doped WO3 thin film. TiO2 nanoparticle doped WO3 thin film shows ~95% reversibility due to may be attributed to nanocrystalline nature of the film, which helpful for charge insertion and deinsertion process. The diffusion coefficient for TiO2 nanoparticle doped WO3 film is less than undoped WO3.

  6. Highly active Ni/Y-doped ZrO{sub 2} catalysts for CO{sub 2} methanation

    Energy Technology Data Exchange (ETDEWEB)

    Takano, H., E-mail: takano_hi@hitachizosen.co.jp [Hitachi Zosen Corporation, Kashiwa, 277-8515 (Japan); Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, 060-8628 (Japan); Kirihata, Y.; Izumiya, K.; Kumagai, N. [Hitachi Zosen Corporation, Kashiwa, 277-8515 (Japan); Habazaki, H., E-mail: habazaki@eng.hokudai.ac.jp [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, 060-8628 (Japan); Division of Applied Chemistry & Frontier Chemistry Center, Faculty of Engineering, Hokkaido University, Sapporo, 060-8628 (Japan); Hashimoto, K. [Tohoku Institute of Technology, Sendai, 277-8515 (Japan)

    2016-12-01

    Highlights: • The Ni/Y-doped ZrO{sub 2} catalysts show highly catalytic activity for CO{sub 2} methanation. • Bidentate carbonate is a major adsorption spice on the Ni/Y-doped ZrO{sub 2} catalysts. • The oxide support of t-ZrO{sub 2} and/or c-ZrO{sub 2} with oxygen vacancies plays a key role. - Abstract: The catalytic methanation of CO{sub 2} was carried out on Ni catalysts supported on Y-doped ZrO{sub 2} with various Y{sup 3+} concentrations and Ni/(Zr + Y) molar ratio = 1. The catalysts were characterized by X-ray diffraction, scanning transmission electron microscopy, specific surface area, temperature-programmed desorption of CO{sub 2}, and temperature-programmed reaction. In addition, operando diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFT) was used to identify the adsorbed reaction intermediate. Catalysts supported on Y-doped ZrO{sub 2} show higher catalytic activity than the catalyst on Y-free ZrO{sub 2} with a monoclinic ZrO{sub 2} phase. The catalytic activity is also dependent upon the Y{sup 3+} concentration, and the highest activity was obtained for the catalyst with a Y/(Zr + Y) molar ratio of 0.333, which consists mainly of fcc Ni and cubic ZrO{sub 2} phase. Y{sup 3+} doping into ZrO{sub 2} introduces oxygen vacancies, which play an important role in enhancing the catalytic activity. The operando DRIFT study reveals that a CO adsorption intermediate is absent, and bidentate carbonate is an important intermediate for CH{sub 4} formation.

  7. Facile preparation of C, N co-modified Nb2O5 nanoneedles with enhanced visible light photocatalytic activity

    KAUST Repository

    Xue, Jiao

    2016-09-28

    C, N co-modified niobium pentoxide (Nb2O5) nanoneedles have been successfully synthesized via a facile hydrothermal method with Niobium Chloride (NbCl5) as a precursor and triethylamine as both the carbon and nitrogen source. The formation process of Nb2O5 nanoneedles has been presented in detail by investigating the effect of the crystallization temperature, the amount of triethylamine and the calcination temperature. The as-prepared Nb2O5 nanoneedles exhibit more efficient photocatalytic activity than commercial Degussa P25 and commercial Nb2O5 towards photodegradation of Rhodamine B (RhB) at a concentration of 10 mg L−1 under visible light. Special chemical species, such as carbonate species and NOX species, that exist on the surface of the as-prepared catalyst could extend the absorption into the visible region and thus enhance the photocatalytic activity of the Nb2O5 nanoneedles. At the same time, the obtained Nb2O5 nanoneedles exhibit excellent stability even after three successive cycles. A possible photodegradation mechanism was proposed and the corresponding photodecomposition process of RhB over the Nb2O5 nanoneedles was elucidated by a reactive species trapping experiment, suggesting that h+ and O2˙− play a major role in the photodegradation of RhB in aqueous solution.

  8. Growth and in-plane magnetic anisotropy of inverse spinel Co{sub 2}MnO{sub 4} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Taeyeong; Kim, Jaeyeong [Pohang University of Science and Technology, Pohang (Korea, Republic of); Song, Jonghyun [Chungnam National University, Daejeon (Korea, Republic of)

    2014-11-15

    Epitaxial Co{sub 2}MnO{sub 4} thin films were grown on Nb(0.1wt.)-doped SrTiO{sub 3} single-crystal substrates with (100) and (110) crystal orientations by using pulsed laser deposition. Their crystal structures and magnetic properties were investigated. Both samples exhibited ferrimagnetic transitions with enhanced transition temperatures. Isotropic M-H loops were observed on the in-plane surface of Co{sub 2}MnO{sub 4}(00l) grown on Nb(0.1wt)-doped SrTiO{sub 3}(100). Strong magnetic anisotropy was observed on the in-plane surface for Co{sub 2}MnO{sub 4} (ll0) grown on Nb(0.1wt)-doped SrTiO{sub 3}(110). A magnetic easy axis existed along the elongated tetragonal direction. This was attributed to the strong interplay between the spin and lattice degrees of freedom in the Co{sub 2}MnO{sub 4} thin film.

  9. Light up conversion effects in Erbium doped CaBi4Ti4O15 ceramics

    International Nuclear Information System (INIS)

    Bokolia, Renuka; Sreenivas, K.

    2013-01-01

    In recent years the rare earth doped bismuth layered structured ferroelectric (BLSF) compositions such as CaBi 4 Ti 4 O 15 , SrBi 4 Ti 4 O 15 and BaBi 4 Ti 4 O 15 ceramics have shown interesting light up-conversion emission effects. The observation of such novel effects has generated a lot of scientific interest, and there is a need to further improve their dielectric, piezoelectric and light up-conversion properties. In the present study, Erbium doped CaBi 4 Ti 4 O 15 (CBT), and SrBi 4 Ti 4 O 15 (SBT) ferroelectric ceramic have been prepared by the conventional solid state reaction method. Formation of single phase material is confirmed by X-Ray Diffraction (XRD), and changes occurring in the lattice parameters with Erbium dopant are analysed. Room temperature dielectric studies and ferroelectric studies will be discussed. (author)

  10. Preparation and Characteristics of Ultrasonic Transducers for High Temperature Using PbNb2O6

    Science.gov (United States)

    Soejima, Junichiro; Sato, Kokichi; Nagata, Kunihiro

    2000-05-01

    The substance PZT(Pb(Zr, Ti)O3) is chiefly used for piezoceramic transducers in many ultrasonic flow meters. It is difficult to use PZT transducers for flow meters for automobile exhaust gas at high temperatures over 350°C. Lead niobate (PbNb2O6) has a high Curie temperature of 540°C and a low mechanical quality factor, and is the most suitable as the sensor element in flow meters for automobile exhaust gas. However, it is difficult to fabricate dense PbNb2O6 ceramics that have good piezoelectric properties. In this study, ceramics with high density and a high piezoelectric effect were fabricated by adding various elements such as Mn and Ca to PbNb2O6 and by examining the sintering process. A Langevin transducer with a resonance frequency of 80 kHz was made for measuring automobile exhaust gas flow using PbNb2O6 ceramics.

  11. Fe-N co-doped SiO2@TiO2 yolk-shell hollow nanospheres with enhanced visible light photocatalytic degradation

    Science.gov (United States)

    Wan, Hengcheng; Yao, Weitang; Zhu, Wenkun; Tang, Yi; Ge, Huilin; Shi, Xiaozhong; Duan, Tao

    2018-06-01

    SiO2@TiO2 yolk@shell hollow nanospheres (STNSs) is considered as an outstanding photocatalyst due to its tunable structure and composition. Based on this point, we present an unprecedentedly excellent photocatalytic property of STNSs toward tannic acid via a Fe-N co-doped strategy. Their morphologies, compositions, structure and properties are characterized. The Fe-N co-doped STNSs formed good hollow yolk@shell structure. The results show that the energy gap of the composites can be downgraded to 2.82 eV (pure TiO2 = 3.2 eV). Photocatalytic degradation of tannic acid (TA, 30 mg L-1) under visible light (380 nm TiO2 nanospheres, non-doped STNSs and N-doped STNSs, the Fe-N co-doped STNSs exhibits the highest activity, which can degrade 99.5% TA into CO2 and H2O in 80 min. The probable degradation mechanism of the composites is simultaneously proposed, the band gap of STNSs becomes narrow by co-doping Fe-N, so that the TiO2 shell can stimulate electrons under visible light exposure, generate the ions of radOH and radO2- with a strong oxidizing property. Therefore this approach works is much desired for radioactive organic wastewater photocatalytic degradation.

  12. Zirconium doped TiO{sub 2} thin films deposited by chemical spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Juma, A. [Laboratory of Thin Film Chemical Technologies, Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Department of Physics and Astronomy, Botswana International University of Science and Technology, Private bag 16, Palapye (Botswana); Oja Acik, I., E-mail: ilona.oja@ttu.ee [Laboratory of Thin Film Chemical Technologies, Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Oluwabi, A.T.; Mere, A. [Laboratory of Thin Film Chemical Technologies, Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Mikli, V.; Danilson, M. [Chair of Semiconductor Materials Technology, Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Krunks, M. [Laboratory of Thin Film Chemical Technologies, Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia)

    2016-11-30

    Highlights: • Mean crystallite size of TiO{sub 2}:Zr film decreases with increasing [Zr] in the solution. • Zr doping supresses the anatase to rutile transformation process in TiO{sub 2} films. • Band gap of TiO{sub 2}:Zr film is 3.4 eV irrespective of the annealing temperature. - Abstract: Chemical spray pyrolysis (CSP) is a flexible deposition technique that allows for mixing of the precursor solutions in different proportions suitable for doping thin films. The CSP method was used to dope TiO{sub 2} thin films with Zr by adding zirconium(IV) acetylacetonate into a solution of titanium(IV) isopropoxide in ethanol stabilized by acetylacetone at [Zr]/[Ti] of 0, 5, 10 and 20 at%. The Zr-doped TiO{sub 2} thin films were uniform and homogeneous showing much smaller grains than the undoped TiO{sub 2} films. Zr stabilized the anatase phase to temperatures above 800 °C depending on Zr concentration in the spray solution. The concentration of Zr determined by XPS was 6.4 at% for the thin film deposited from the 20 at% solution. According to AFM studies, Zr doping decreased the root mean square roughness of TiO{sub 2} film from 5.9 to 1.1 nm. An XRD study of samples with the highest Zr amount showed the ZrTiO{sub 4} phase started forming after annealing at 800 °C. The optical band gap for TiO{sub 2} decreased from 3.3 eV to 3.0 eV after annealing at 800 °C but for the TiO{sub 2}:Zr(20) film it remained at 3.4 eV. The dielectric constant increased by more than four times with Zr-doping and this was associated with the change in the bond formations caused by substitution of Ti by Zr in the lattice.

  13. Damped soft phonons and diffuse scattering in 40%Pb(Mg1/3Nb2/3)O3-60%PbTiO3

    International Nuclear Information System (INIS)

    Stock, C.; Ellis, D.; Swainson, I. P.; Xu, Guangyong; Hiraka, H.; Shirane, G.; Zhong, Z.; Luo, H.; Zhao, X.; Viehland, D.; Birgeneau, R. J.

    2006-01-01

    Using neutron elastic and inelastic scattering and high-energy x-ray diffraction, we present a comparison of 40% Pb(Mg 1/3 Nb 2/3 )O 3 -60% PbTiO 3 (PMN-60PT) with pure Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) and PbTiO 3 (PT). We measure the structural properties of PMN-60PT to be identical to pure PT, however, the lattice dynamics are exactly that previously found in relaxors PMN and Pb(Zn 1/3 Nb 2/3 )O 3 (PZN). PMN-60PT displays a well-defined macroscopic structural transition from a cubic to tetragonal unit cell at 550 K. The diffuse scattering is shown to be weak indicating that the structural distortion is long-range in PMN-60PT and short-range polar correlations (polar nanoregions) are not present. Even though polar nanoregions are absent, the soft optic mode is short-lived for wave vectors near the zone center. Therefore PMN-60PT displays the same waterfall effect as prototypical relaxors PMN and PZN. We conclude that it is random fields resulting from the intrinsic chemical disorder which is the reason for the broad transverse optic mode observed in PMN and PMN-60PT near the zone center and not due to the formation of short-ranged polar correlations. Through our comparison of PMN, PMN-60PT, and pure PT, we interpret the dynamic and static properties of the PMN-xPT system in terms of a random field model in which the cubic anisotropy term dominates with increasing doping of PbTiO 3

  14. Study and characterization of the BBT (BaBi4Ti4O15) ceramic added with 1 wt. % Nb2O5

    International Nuclear Information System (INIS)

    Silva, P.M.O.; Sales, A.J.M.; Freitas, D.B.; Oliveira, R.G.M.; Sombra, A.S.B.; Sales, J.C.

    2012-01-01

    This study aims to synthesize and characterize the ceramic BBT (BaBi 4 TI 4 O 15 ) doped with 1% by mass of the densification Nb2O5 to improve the products. The phase of the BBT has been found by solid state reaction. The mixed oxides starting processed by high-energy milling in planetary mill reactor polymer and spheres of zirconia and calcined at 850°C/3h. Later, 'bulks' prepared with the calcined powder were sintered at 950°C/3h. The calcined powder was characterized by X-ray diffraction data and refined by the beta 3.2 DBWSTools program using the Rietveld method. The grain morphology and distribution of pores on the surface of the 'bulks' were analyzed by Scanning Electron Microscopy. The result confirmed the refined to obtain the single phase with tetragonal structure BaBi 4 TI 4 O 15 density of 5.088 g/cm3 calculated in the unit cell. SEM analysis by SEM showed improved densification of the doped. (author)

  15. Properties of TiO2-based transparent conducting oxide thin films on GaN(0001) surfaces

    International Nuclear Information System (INIS)

    Kasai, J.; Nakao, S.; Yamada, N.; Hitosugi, T.; Moriyama, M.; Goshonoo, K.; Hoang, N. L. H.; Hasegawa, T.

    2010-01-01

    Anatase Nb-doped TiO 2 transparent conducting oxide has been formed on GaN(0001) surfaces using a sputtering method. Amorphous films deposited at room temperature were annealed at a substrate temperature of 500 deg. C in vacuum to form single-phase anatase films. Films with a thickness of 170 nm exhibited a resistivity of 8x10 -4 Ω cm with absorptance less than 5% at a wavelength of 460 nm. Furthermore, the refractive index of the Nb-doped TiO 2 was well matched to that of GaN. These findings indicate that Nb-doped TiO 2 is a promising material for use as transparent electrodes in GaN-based light emitting diodes (LEDs), particularly since reflection at the electrode/GaN boundary can be suppressed, enhancing the external quantum efficiency of blue LEDs.

  16. Selectivity enhancement of indium-doped SnO2 gas sensors

    International Nuclear Information System (INIS)

    Salehi, A.

    2002-01-01

    Indium doping was used to enhance the selectivity of SnO 2 gas sensor. Both indium-doped and undoped SnO 2 gas sensors fabricated with different deposition techniques were investigated. The changes in the sensitivity of the sensors caused by selective gases (hydrogen and wood smoke) ranging from 500 to 3000 ppm were measured at different temperatures from 50 to 300 deg. C. The sensitivity peaks of the samples exhibit different values for selective gases with a response time of approximately 0.5 s. Thermally evaporated indium-doped SnO 2 gas sensor shows a considerable increase in the sensitivity peak of 27% in response to wood smoke, whereas it shows a sensitivity peak of 7% to hydrogen. This is in contrast to the sputter deposited indium-doped SnO 2 gas sensor, which exhibits a much lower sensitivity peak of approximately 2% to hydrogen and wood smoke compared to undoped SnO 2 gas sensors fabricated by chemical vapor deposition and spray pyrolysis. Scanning electron microscopy shows that different deposition techniques result in different porosity of the films. It is observed that the thermally evaporated indium-doped SnO 2 gas sensor shows high porosity, while the sputtered sample exhibits almost no porosity

  17. Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO_2-ZrO_2 nanocomposite

    International Nuclear Information System (INIS)

    Tomar, Laxmi J.; Bhatt, Piyush J.; Desai, Rahul K.; Chakrabarty, B. S.; Panchal, C. J.

    2016-01-01

    TiO_2-ZrO_2 and Zn doped TiO_2-ZrO_2 nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X –ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO_2, TiO_2-ZrO_2 and Zn doped TiO_2-ZrO_2 nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphite coated conducting glass plate was used as counter electrode. The I – V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO_2, TiO_2-ZrO_2 and Zn doped TiO_2-ZrO_2 nanocomposites were found 0.71%, 1.97% and 4.58% respectively.

  18. Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO2-ZrO2 nanocomposite

    Science.gov (United States)

    Tomar, Laxmi J.; Bhatt, Piyush J.; Desai, Rahul K.; Chakrabarty, B. S.; Panchal, C. J.

    2016-05-01

    TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X -ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO2, TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphite coated conducting glass plate was used as counter electrode. The I - V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO2, TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites were found 0.71%, 1.97% and 4.58% respectively.

  19. Reduction Mechanisms of Cu2+-Doped Na2O-Al2O3-SiO2 Glasses during Heating in H2 Gas.

    Science.gov (United States)

    Nogami, Masayuki; Quang, Vu Xuan; Ohki, Shinobu; Deguchi, Kenzo; Shimizu, Tadashi

    2018-01-25

    Controlling valence state of metal ions that are doped in materials has been widely applied for turning optical properties. Even though hydrogen has been proven effective to reduce metal ions because of its strong reducing capability, few comprehensive studies focus on practical applications because of the low diffusion rate of hydrogen in solids and the limited reaction near sample surfaces. Here, we investigated the reactions of hydrogen with Cu 2+ -doped Na 2 O-Al 2 O 3 -SiO 2 glass and found that a completely different reduction from results reported so far occurs, which is dominated by the Al/Na concentration ratio. For Al/Na glass body. For Al/Na > 1, on the other hand, the reduction of Cu 2+ ions occurred simultaneously with the formation of OH bonds, whereas the reduced Cu metal moved outward and formed a metallic film on glass surface. The NMR and Fourier transform infrared results indicated that the Cu 2+ ions were surrounded by Al 3+ ions that formed AlO 4 , distorted AlO 4 , and AlO 5 units. The diffused H 2 gas reacted with the Al-O - ···Cu + units, forming Al-OH and metallic Cu, the latter of which moved freely toward glass surface and in return enhanced H 2 diffusion.

  20. Ho3+/Yb3+ co-doped TeO2-BaF2-Y2O3 glasses for ∼1.2 μm laser applications

    Science.gov (United States)

    Wang, Shunbin; Li, Chengzhi; Yao, Chuanfei; Jia, Shijie; Jia, Zhixu; Qin, Guanshi; Qin, Weiping

    2017-02-01

    Intense ∼1.2 μm fluorescence is observed in Ho3+/Yb3+ co-doped TeO2-BaF2-Y2O3 glasses under 915 nm laser diode excitation. The 1.2 μm emission can be ascribed to the transition 5I6→5I8 of Ho3+. With the introducing of BaF2, the content of OH in the glasses drops markedly, and the 1.2 μm emission intensity increases gradually as increasing the concentration percentage of BaF2. Furthermore, microstructured fibers based on the TeO2-BaF2-Y2O3 glasses are fabricated by using a rod-in-tube method, and a relative positive gain of ∼9.42 dB at 1175.3 nm is obtained in a 5 cm long fiber.

  1. Effect of Ga2O3 addition on the properties of Y2O3-doped AlN ceramics

    Directory of Open Access Journals (Sweden)

    Shin H.

    2015-01-01

    Full Text Available Effect Ga2O3 addition on the densification and properties of Y2O3-doped AlN ceramics was investigated under the constraint of total sintering additives (Y2O3 and Ga2O3 of 4.5 wt%. Ga was detected in the AlN grain as well as the grain boundary phases. YAlO3 and Y4Al2O9 were observed as the secondary crystalline phases in all of the investigated compositions. As the substitution of Ga2O3 for Y2O3 increased, the quantity of the Y4Al2O9 phase decreased while that of YAlO3 was more or less similar. Neither additional secondary phases was identified, nor was the sinterability inhibited by the Ga2O3 addition; the linear shrinkage and apparent density were above 20 percent and 3.34-3.37 g/cm3, respectively. However, the optical reflectance and the elastic modulus generally decreased whereas the Poisson ratio increased significantly. The dielectric constant and the loss tangent of 4.0Y2O3-0.5Ga2O3-95.5Y2O3 at the resonant frequency of 8.22 GHz were 8.63 and 0.003, respectively.

  2. Avaliação da atividade fotocatalítica de Nb2O5 - DOI: 10.4025/actascitechnol.v32i1.3923

    Directory of Open Access Journals (Sweden)

    Veronice Slusarski Santana

    2009-12-01

    Full Text Available Como a fotocatálise heterogênea é um dos métodos de tratamento de efluentes mais promissores, o estudo da atividade fotocatalítica de novos catalisadores é de primordial interesse. Assim, testes de degradação de solução de sacarose parcialmente caramelizada foram realizados empregando 2 g de Nb2O5 e TiO2 mássicos e Nb2O5 impregnado em microesferas de vidro (5,0, 10 e 15%Nb2O5 vidro-1 sob radiação UV durante 168h. TiO2 e Nb2O5 foram submetidos a processo de aglomeração (tamanho de partícula: 0,210 e 0,297 mm e calcinados a 500ºC por 5h. Nb2O5 foi solubilizado em ácido oxálico (0,5 mol L-1 a 70ºC por 8h, misturado com as microesferas de vidro, seco a 110ºC por 12h e calcinado a 500ºC por 5h. A eficiência do processo fotocatalítico foi avaliada por espectrofotometria UV-VIS e método DNS. Os resultados mostraram que catalisadores de Nb2O5 são promissores para aplicação em fotocatálise, principalmente o 15% Nb2O5 vidro-1, o qual apresentou resultados semelhantes ao do TiO2.

  3. Highly Stable and Active Pt/Nb-TiO2 Carbon-Free Electrocatalyst for Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Shuhui Sun

    2012-01-01

    Full Text Available The current materials used in proton exchange membrane fuel cells (PEMFCs are not sufficiently durable for commercial deployment. One of the major challenges lies in the development of an inexpensive, efficient, and highly durable and active electrocatalyst. Here a new type of carbon-free Pt/Nb-TiO2 electrocatalyst has been reported. Mesoporous Nb-TiO2 hollow spheres were synthesized by the sol-gel method using polystyrene (PS sphere templates. Pt nanoparticles (NPs were then deposited onto mesoporous Nb-TiO2 hollow spheres via a simple wet-chemical route in aqueous solution, without the need for surfactants or potentiostats. The growth densities of Pt NPs on Nb-TiO2 supports could be easily modulated by simply adjusting the experimental parameters. Electrochemical studies of Pt/Nb-TiO2 show much enhanced activity and stability than commercial E-TEK Pt/C catalyst. PtNP/Nb-TiO2 is a promising new cathode catalyst for PEMFC applications.

  4. Room temperature ferromagnetism in Fe-doped CeO2 nanoparticles.

    Science.gov (United States)

    Maensiri, Santi; Phokha, Sumalin; Laokul, Paveena; Seraphin, Supapan

    2009-11-01

    RT ferromagnetism was observed in nanoparticles of Fe-doped CeO2 (i.e., Ce(0.97)Fe(0.03)O2) synthesized by a sol-gel method. The undoped and Fe-doped CeO2 were characterized by XRD, Raman spectroscopy, TEM, and VSM. The undoped samples and Ce(0.97)Fe(0.03)O2 precursor exhibit a diamagnetic behavior. The 673 K-calcined Ce(0.97)Fe(0.03)O2 sample is paramagnetic whereas 773 and 873 K-calcined Ce(0.97)Fe(0.03)O2 samples are ferromagnetism having the magnetizations of 4.65 x 10(-3) emu/g and 6.20 x 10(-3) emu/g at 10 kOe, respectively. Our results indicate that the ferromagnetic property is intrinsic to the Fe-doped CeO2 system and is not a result of any secondary magnetic phase or cluster formation.

  5. Structural Modification of Sol-Gel Synthesized V2O5 and TiO2 Thin Films with/without Erbium Doping

    Directory of Open Access Journals (Sweden)

    Fatma Pınar Gökdemir

    2014-01-01

    Full Text Available Comparative work of with/without erbium- (Er- doped vanadium pentoxide (V2O5 and titanium dioxide (TiO2 thin films were carried out via sol-gel technique by dissolving erbium (III nitrate pentahydrate (Er(NO33·5H2O in vanadium (V oxoisopropoxide (OV[OCH(CH32]3 and titanium (IV isopropoxide (Ti[OCH(CH32]4. Effect of Er doping was traced by Fourier transform IR (FTIR, thermogravimetric/differential thermal (TG/DTA, and photoluminescence measurements. UV-Vis transmission/absorption measurement indicated a blue shift upon Er doping in V2O5 film due to the softening of V=O bond while appearance of typical absorption peaks in Er-doped TiO2 film. Granule size of the films increased (reduced upon Er substitution on host material compared to undoped V2O5 and TiO2 films, respectively.

  6. Beam-Mode Piezoelectric Properties of Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals for Medical Linear Array Applications

    Science.gov (United States)

    Wang, Wei; Wang, Sheng; Zhang, Yaoyao; Zhao, Xiangyong; Luo, Haosu

    2011-11-01

    In this work, the dielectric and beam-mode piezoelectric properties of ternary 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PIMNT35/35/30) piezoelectric single crystals were investigated. The Curie temperature ( T C) and rhombohedral-to-tetragonal phase-transition temperature ( T rt) are 187°C and 127°C, about 30°C higher than those of PMNT crystals. The beam-mode coupling coefficient k {33/ w } was found to be 90.3%. Furthermore, 3.5-MHz linear arrays based on PIMNT35/35/30 crystals and Pb(Zr1- x Ti x )O3 ceramic (PZT-5H) were simulated using PiezoCAD software. The results indicate that the sensitivity and -6 dB bandwidth of a PIMNT35/35/30 transducer would be approximately 4 dB and 20% higher, respectively, compared with a traditional PZT transducer.

  7. Ga2O3 doping and vacancy effect in KNN—LT lead-free piezoceramics

    Science.gov (United States)

    Tan, Zhi; Xing, Jie; Jiang, Laiming; Zhu, Jianguo; Wu, Bo

    2017-12-01

    Ga2O3 was doped into 0.95(K0.48Na0.52)NbO3—0.05LiTaO3 (KNN—LT) ceramics and its influences on the sintering behavior, phase structure and electrical properties of ceramics were studied. Firstly, SEM observation exhibits that more and more glass phase appears in ceramics with the gradual addition of Ga2O3, which determines the continuous decrease in sintering temperatures. And the addition of Ga2O3 is also found to increase the orthorhombic—tetragonal transition temperature ( T O—T) of system to a higher level. Secondly, both the density and the coercive field ( E C) of ceramics increase firstly and then decrease with increasing the Ga2O3 content, and the KNN—LT— xGa sample at x = 0.004 shows a pinched P— E hysteresis loop. Finally, the impedance characteristics of KNN—LT— xGa ceramics were investigated at different temperatures, revealing a typical vacancy related conduction mechanism. This work demonstrates that Ga2O3 is a good sintering aid for KNN-based ceramics, and the vacancy plays an important role in the sintering and electrical behaviors of ceramics.

  8. Al2O3 doping of TiO2 electrodes and applications in dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Eom, Tae Sung; Kim, Kyung Hwan; Bark, Chung Wung; Choi, Hyung Wook

    2014-01-01

    Dye-sensitized solar cells (DSSCs) have been intensively studied since their discovery in 1991. DSSCs have been extensively researched over the past decades as cheaper alternatives to silicon solar cells due to their high energy-conversion efficiency and their low production cost. However, some problems need to be solved in order to enhance the efficiency of DSSCs. In particular, the electron recombination that occurs due to the contact between the transparent conductive oxide (TCO) and a redox electrolyte is one of the main limiting factors of efficiency. In this work, we report for the first time the improvement of the photovoltaic characteristics of DSSCs by doping TiO 2 with Al 2 O 3 . DSSCs were constructed using composite particles of Al 2 O 3 -doped TiO 2 and TiO 2 nanoparticles. The DSSCs using Al 2 O 3 showed the maximum conversion efficiency of 6.29% due to effective electron transport. DSSCs based on Al 2 O 3 -doped TiO 2 films showed better photovoltaic performance than cells fabricated with only TiO 2 nanoparticles. This result is attributed to the prevention of electron recombination between electrons in the TiO 2 conduction band with holes in the dye or the electrolyte. There mechanism is suggested based on impedance results, which indicated improved electron transport at the TiO 2 /dye/electrolyte interface.

  9. Surface passivation of n-type doped black silicon by atomic-layer-deposited SiO2/Al2O3 stacks

    Science.gov (United States)

    van de Loo, B. W. H.; Ingenito, A.; Verheijen, M. A.; Isabella, O.; Zeman, M.; Kessels, W. M. M.

    2017-06-01

    Black silicon (b-Si) nanotextures can significantly enhance the light absorption of crystalline silicon solar cells. Nevertheless, for a successful application of b-Si textures in industrially relevant solar cell architectures, it is imperative that charge-carrier recombination at particularly highly n-type doped black Si surfaces is further suppressed. In this work, this issue is addressed through systematically studying lowly and highly doped b-Si surfaces, which are passivated by atomic-layer-deposited Al2O3 films or SiO2/Al2O3 stacks. In lowly doped b-Si textures, a very low surface recombination prefactor of 16 fA/cm2 was found after surface passivation by Al2O3. The excellent passivation was achieved after a dedicated wet-chemical treatment prior to surface passivation, which removed structural defects which resided below the b-Si surface. On highly n-type doped b-Si, the SiO2/Al2O3 stacks result in a considerable improvement in surface passivation compared to the Al2O3 single layers. The atomic-layer-deposited SiO2/Al2O3 stacks therefore provide a low-temperature, industrially viable passivation method, enabling the application of highly n- type doped b-Si nanotextures in industrial silicon solar cells.

  10. Computational Study of Nb-Doped-SnO2/Pt Interfaces: Dopant Segregation, Electronic Transport, and Catalytic Properties

    DEFF Research Database (Denmark)

    Fu, Qiang; Halck, Niels Bendtsen; Hansen, Heine Anton

    2017-01-01

    functional theory and non equilibrium Green's function study, we investigate the Nb segregation at Pt/NTO interfaces under operational electrochemical conditions, and reveal the resulting effects on the electronic transport, as well as the catalytic properties. We find that the Nb dopants tend to aggregate......Carbon black, a state-of-the-art cathode material for proton exchange membrane fuel cells (PEMFCs), suffers from severe corrosion in practical applications. Niobium-doped tin dioxide (NTO) is a promising alternative to support the Pt catalysts at the cathodes. Here, through a combined density....... The electronic conductivities of the Pt/NTO systems are not particularly sensitive to the distance of the Nb dopants relative to the interface, but depend explicitly on the Nb concentration and configuration. Through a dopant induced ligand effect, the NTO substrates can improve the catalytic activity of the Pt...

  11. Defect phase diagram for doping of Ga2O3

    Science.gov (United States)

    Lany, Stephan

    2018-04-01

    For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2) conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

  12. Double perovskite Ca2GdNbO6:Mn4+ deep red phosphor: Potential application for warm W-LEDs

    Science.gov (United States)

    Lu, Zuizhi; Huang, Tianjiao; Deng, Ruopeng; Wang, Huan; Wen, Lingling; Huang, Meixin; Zhou, Liya; Yao, Chunying

    2018-05-01

    A novel Mn4+-doped Ca2GdNbO6 (CGN) phosphor was prepared by high-temperature solid-state reaction. The crystal structure was investigated by X-ray diffraction patterns and unit cell structure. Mn4+ replaced the location of Nb5+ in the CGN lattice, and the value of energy gap (Egap) decreased from 2.16 eV to 1.13 eV, indicating that Mn4+ ions play a great influence on the absorption of CGN hosts. The broad excitation band from 250 nm to 550 nm matches well with commercial near-UV light emitting diodes, and the emission peak centered at 680 nm is due to 2E→4A2g transition in Mn4+ ions. The CIE chromaticity coordinates (0.698, 0.303) of CGN:Mn4+ phosphor was close to standard red color coordinates (0.666, 0.333). These investigations demonstrate CGN:Mn4+ phosphor as an efficient red phosphor for potential applications.

  13. Enhanced separation efficiency of photoinduced charges for antimony-doped tin oxide (Sb-SnO{sub 2})/TiO{sub 2} heterojunction semiconductors with varied Sb doping concentration

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhen-Long [School of Physics and Electronics, Henan University, Kaifeng 475004 (China); Ma, Wen-Hai [School of Physical Education, Henan University, Kaifeng 475004 (China); Mao, Yan-Li, E-mail: ylmao1@163.com [School of Physics and Electronics, Henan University, Kaifeng 475004 (China); Institute for Computational Materials Science, Henan University, Kaifeng 475004 (China)

    2014-09-07

    In this paper, antimony-doped tin oxide (Sb-SnO{sub 2}) nanoparticles were synthesized with varied Sb doping concentration, and the Sb-SnO{sub 2}/TiO{sub 2} heterojunction semiconductors were prepared with Sb-SnO{sub 2} and TiO{sub 2}. The separation efficiency of photoinduced charges was characterized with surface photovoltage (SPV) technique. Compared with Sb-SnO{sub 2} and TiO{sub 2}, Sb-SnO{sub 2}/TiO{sub 2} presents an enhanced separation efficiency of photoinduced charges, and the SPV enhancements were estimated to be 1.40, 1.43, and 1.99 for Sb-SnO{sub 2}/TiO{sub 2} composed of Sb-SnO{sub 2} with the Sb doping concentration of 5%, 10%, and 15%, respectively. To understand the enhancement, the band structure of Sb-SnO{sub 2} and TiO{sub 2} in the heterojunction semiconductor was determined, and the conduction band offsets (CBO) between Sb-SnO{sub 2} and TiO{sub 2} were estimated to be 0.56, 0.64, and 0.98 eV for Sb-SnO{sub 2}/TiO{sub 2} composed of Sb-SnO{sub 2} with the Sb doping concentration of 5%, 10%, and 15%, respectively. These results indicate that the separation efficiency enhancement is resulting from the energy level matching, and the increase of enhancement is due to the rising of CBO.

  14. Collinear Order in Frustrated Quantum Antiferromagnet on Square Lattice (CuBr)LaNb2O7

    Science.gov (United States)

    Oba, Noriaki; Kageyama, Hiroshi; Kitano, Taro; Yasuda, Jun; Baba, Yoichi; Nishi, Masakazu; Hirota, Kazuma; Narumi, Yasuo; Hagiwara, Masayuki; Kindo, Koichi; Saito, Takashi; Ajiro, Yoshitami; Yoshimura, Kazuyoshi

    2006-11-01

    Magnetic susceptibility, heat capacity, high-field magnetization and neutron diffraction measurements have been performed on a two-dimensional S = 1/2 square-lattice system (CuBr)LaNb2O7, prepared by a topotactic ion-exchange reaction of a nonmagnetic double-layered perovskite RbLaNb2O7. (CuBr)LaNb2O7 exhibits a second-order magnetic transition at 32 K, in marked contrast to a spin-singlet nature for its Cl-based counterpart (CuCl)LaNb2O7, despite nearly identical structural parameters. The magnetic structure is a novel collinear antiferromagnetic (CAF) ordering characterized by a modulation vector q = (π, 0, π) with a reduced moment of 0.6μB. Mixed ferromagnetic nearest-neighbor (J1) and antiferromagnetic second-nearest-neighbor (J2) interactions are of comparable strength (J1/kB = -35.6 K and J2/kB = 41.3 K), placing the system in a more frustrated region of the CAF phase than ever reported.

  15. Electron irradiation response on Ge and Al-doped SiO{sub 2} optical fibres

    Energy Technology Data Exchange (ETDEWEB)

    Yaakob, N.H.; Wagiran, H. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Hossain, I., E-mail: imamhossain@utm.m [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Ramli, A.T. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Bradley, D.A [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Hashim, S. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Ali, H. [Department of Radiotherapy and Oncology, Hospital Sultan Ismail, Johor Darul Takzim (Malaysia)

    2011-05-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO{sub 2} optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO{sub 2} optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  16. Hexagonal perovskites with cationic vacancies. 28. Structure of rhombohedral 9 L stacking polytypes Ba/sub 3/Wsub(2-x)sup(VI)Nbsub(x)sup(V)vacantOsub(9-x/2)vacantsub(x/2)

    Energy Technology Data Exchange (ETDEWEB)

    Kemmler-Sack, S; Treiber, U [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

    1981-07-01

    According to the intensity calculations for Ba/sub 3/Wsub(4/3)Nbsub(2/3)vacantOsub(26/3)vacantsub(1/3) and Ba/sub 3/Nb/sub 2/vacantO/sub 8/vacant(II) these rhombohedral 9 L compounds crystallize in the space group R-3m, sequence (hhc)/sub 3/. The refined, intensity related R' values are 6.9% (Ba/sub 3/Wsub(4/3)Nbsub(2/3)vacantOsub(26/3)vacantsub(1/3)) and 7.2% (Ba/sub 3/Nb/sub 2/vacantO/sub 8/vacant(II)). The relations between the rhombohedral 9 L structure (A/sub 3/M/sub 2/vacantO/sub 9/) and the palmierite type (A/sub 3/M/sub 2/vacantO/sub 8/vacant) are discussed.

  17. CoO-doped MgO-Al2O3-SiO2-colored transparent glass-ceramics with high crystallinity

    Science.gov (United States)

    Tang, Wufu; Zhang, Qian; Luo, Zhiwei; Yu, Jingbo; Gao, Xianglong; Li, Yunxing; Lu, Anxian

    2018-02-01

    To obtain CoO-doped MgO-Al2O3-SiO2 (MAS)-colored transparent glass-ceramics with high crystallinity, the glass with the composition 21MgO-21Al2O3-54SiO2-4B2O3-0.2CoO (in mol %) was prepared by conventional melt quenching technique and subsequently thermal treated at several temperatures. The crystallization behavior of the glass, the precipitated crystalline phases and crystallinity were analyzed by X-ray diffraction (XRD). The microstructure of the glass-ceramics was characterized by field emission scanning electron microscopy (FSEM). The transmittance of glass-ceramic was measured by UV spectrophotometer. The results show that a large amount of α-cordierite (indianite) with nano-size was precipitated from the glass matrix after treatment at 1020 °C for 3 h. The crystallinity of the transparent glass-ceramic reached up to 97%. Meanwhile, the transmittance of the glass-ceramic was 74% at 400 nm with a complex absorption band from 450 nm to 700 nm. In addition, this colored transparent glass-ceramic possessed lower density (2.469 g/cm3), lower thermal expansion coefficient (1.822 × 10-6 /℃), higher Vickers hardness (9.1 GPa) and higher bending strength (198 MPa) than parent glass.

  18. Surface activation of MnNb{sub 2}O{sub 6} nanosheets by oxalic acid for enhanced photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Junshu; Wang, Jinshu, E-mail: wangjsh@bjut.edu.cn; Li, Hongyi; Li, Yongli; Du, Yucheng; Yang, Yilong; Jia, Xinjian

    2017-05-01

    Graphical abstract: Visible light driven photoreduction of Cr(VI) over MnNb{sub 2}O{sub 6} nanosheets is enhanced via oxalic acid surface complex to generate activation layer. - Highlights: • MnNb{sub 2}O{sub 6} nanosheets are crystallized by a surface capping route of sulfonate groups. • Oxalic acid on MnNb{sub 2}O{sub 6} nanosheets forms an excited surface complex hybrid layer. • Surface activation enhances visible-light induced reduction of Cr(VI) into Cr(III). - Abstract: MnNb{sub 2}O{sub 6} nanosheets (P-MNOs) is selectively crystallized by using surface capping ligand with functional sulfonate group (sodium dodecyl benzene sulphonate), which binds to the (131) surface of MnNb{sub 2}O{sub 6} inducing the morphology-controlled crystallization of MnNb{sub 2}O{sub 6} materials. Surface modification of photoactive P-MNOs with electron-rich oxalic acid ligands establishes an excited surface complex layer on phase-pure P-MNO as evidenced by spectroscopic analyses (FT-IR, UV–vis, Raman, PL, etc.), and thus more efficiently photocatalyzes the reduction of Cr(VI) into Cr(III) than solely P-MNOs or oxalic acid under visible light (λ > 420 nm) via a ligand-to-metal interfacial electron transfer pathway. However, the interaction between oxalic acid and MnNb{sub 2}O{sub 6} is highly dependent upon the morphology of solid MnNb{sub 2}O{sub 6} substrate due to the higher surface-area-to-volume ratio and higher surface activity of (131) planes in the sheet-like morphology. This study could assist the construction of stable niobate material systems to allow a versatile solid surface activation for establishing more energy efficient and robust catalysis process under visible light.

  19. Ab initio study of thermoelectric properties of doped SnO_2 superlattices

    International Nuclear Information System (INIS)

    Borges, P.D.; Silva, D.E.S.; Castro, N.S.; Ferreira, C.R.; Pinto, F.G.; Tronto, J.; Scolfaro, L.

    2015-01-01

    Transparent conductive oxides, such as tin dioxide (SnO_2), have recently shown to be promising materials for thermoelectric applications. In this work we studied the thermoelectric properties of Fe-, Sb- and Zn-uniformly doping and co-doping SnO_2, as well as of Sb and Zn planar (or delta)-doped layers in SnO_2 forming oxide superlattices (SLs). Based on the semiclassical Boltzmann transport equations (BTE) in conjunction with ab initio electronic structure calculations, the Seebeck coefficient (S) and figure of merit (ZT) are obtained for these systems, and are compared with available experimental data. The delta doping approach introduces a remarkable modification in the electronic structure of tin dioxide, when compared with the uniform doping, and colossal values for ZT are predicted for the delta-doped oxide SLs. This result is a consequence of the two-dimensional electronic confinement and the strong anisotropy introduced by the doped planes. In comparison with the uniformly doped systems, our predictions reveal a promising use of delta-doped SnO_2 SLs for enhanced S and ZT, which emerge as potential candidates for thermoelectric applications. - Graphical abstract: Band structure and Figure of merit for SnO2:Sb superlattice along Z direction, P. D. Borges, D. E. S. Silva, N. S. Castro, C. R. Ferreira, F. G. Pinto, J. Tronto and L. Scolfaro, Ab initio study of thermoelectric properties of doped SnO2 superlattices. - Highlights: • Thermoelectric properties of SnO_2-based alloys and superlattices. • High figure of merit is predicted for planar-doped SnO_2 superlattices. • Nanotechnology has an important role for the development of thermoelectric devices.

  20. Electromagnetic and optical characteristics of Nb5+-doped double-crossover and salmon DNA thin films

    Science.gov (United States)

    Babu Mitta, Sekhar; Reddy Dugasani, Sreekantha; Jung, Soon-Gil; Vellampatti, Srivithya; Park, Tuson; Park, Sung Ha

    2017-10-01

    We report the fabrication and physical characteristics of niobium ion (Nb5+)-doped double-crossover DNA (DX-DNA) and salmon DNA (SDNA) thin films. Different concentrations of Nb5+ ([Nb5+]) are coordinated into the DNA molecules, and the thin films are fabricated via substrate-assisted growth (DX-DNA) and drop-casting (SDNA) on oxygen plasma treated substrates. We conducted atomic force microscopy to estimate the optimum concentration of Nb5+ ([Nb5+]O = 0.08 mM) in Nb5+-doped DX-DNA thin films, up to which the DX-DNA lattices maintain their structures without deformation. X-ray photoelectron spectroscopy (XPS) was performed to probe the chemical nature of the intercalated Nb5+ in the SDNA thin films. The change in peak intensities and the shift in binding energy were witnessed in XPS spectra to explicate the binding and charge transfer mechanisms between Nb5+ and SDNA molecules. UV-visible, Raman, and photoluminescence (PL) spectra were measured to determine the optical properties and thus investigate the binding modes, Nb5+ coordination sites in Nb5+-doped SDNA thin films, and energy transfer mechanisms, respectively. As [Nb5+] increases, the absorbance peak intensities monotonically increase until ˜[Nb5+]O and then decrease. However, from the Raman measurements, the peak intensities gradually decrease with an increase in [Nb5+] to reveal the binding mechanism and binding sites of metal ions in the SDNA molecules. From the PL, we observe the emission intensities to reduce them at up to ˜[Nb5+]O and then increase after that, expecting the energy transfer between the Nb5+ and SDNA molecules. The current-voltage measurement shows a significant increase in the current observed as [Nb5+] increases in the SDNA thin films when compared to that of pristine SDNA thin films. Finally, we investigate the temperature dependent magnetization in which the Nb5+-doped SDNA thin films reveal weak ferromagnetism due to the existence of tiny magnetic dipoles in the Nb5+-doped SDNA

  1. Contribution to the identification and the evaluation of a doped UO2 fuel with controlled oxygen potential

    International Nuclear Information System (INIS)

    Pennisi, Vanessa

    2015-01-01

    Temperature and oxygen partial pressure (PO 2 ) of nuclear oxide fuels are the main parameters governing both their thermochemical evolution in reactor and the speciation of volatile fission products such as Cs, I or Te. An innovative way to limit the risk of cladding rupture by corrosion under irradiation consists in buffering the oxygen partial pressure of the fuel under operation in a PO 2 domain where the fission gas are harmless towards Zr clad, by using solid redox buffers as additives. Niobium, with its NbO 2 /NbO and Nb 2 O 5 /NbO 2 redox couples has been found to be a promising candidate to this end. A manufacturing process of a buffered UO 2 fuel, doped with niobium has been optimized, in order to fulfill usual specifications (density, microstructure). The experimental study of the UO 2 -NbO x system has shown the existence of a liquid phase between UO 2 and NbO x at 810 C, which was not reported in the literature. The characterization of Nb containing phases present in UO 2 both in solid solution and as precipitates has lead us to propose a solubility thermodynamic model of niobium in UO 2 at 1700 C. An extensive study of the niobium precipitates shows the co-existence in the fuel of NbO 2 and NbO as major phases, together with small amounts of metallic Nb. The coexistence of niobium under two oxidation states inside the fuel is a key element of demonstration of a possible in-situ buffering effect, which is likely to impact some properties of the material that are dependent upon PO 2 , such as densification. These results confirm the promising potential of oxygen buffered fuels as regard to their performance in reactor. (author) [fr

  2. Hexagonal perovskites with cationic vacancies. 24. Rhombohedral 9 L stacking polytypes in the systems Ba/sub 3/Wsub(2-x)sup(VI)Msub(x)sup(V)vacantOsub(9-x/2)vacantsub(x/2) with Msup(V) = Nb, Ta

    Energy Technology Data Exchange (ETDEWEB)

    Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

    1980-12-01

    In the system Ba/sub 3/Wsub(2-x)sup(VI)Nbsub(x)sup(V)vacantOsub(9-x/2)vacantsub(x/2) stacking polytypes of rhombohedral 9 L type (sequence (hhc)/sub 3/; space group R-3m) can be prepared with approximately 1/3 <= x <= 2. For x = 2(Ba/sub 3/Nb/sub 2/vacantO/sub 8/vacant) two modifications are formed. In the corresponding Ta system the phase width is reduced to a smaller region with x approximately 1/3.

  3. Optical evidences for an intermediate phase in relaxor ferroelectric Pb(In1/2Nb1/2O3-Pb(Mg1/3Nb2/3O3-PbTiO3 single crystals

    Directory of Open Access Journals (Sweden)

    Xiaolong Zhang

    2016-02-01

    Full Text Available The mechanism of low-temperature structural transformation and evolution of polar nano-structures in relaxor ferroelectric Pb(In1/2Nb1/2O3-Pb(Mg1/3Nb2/3O3-xPbTiO3 (x = 0.33, 0.35, and 0.42 single crystals have been investigated with the aid of temperature dependent low-wavenumber Raman scattering (LWRS and photoluminescence (PL spectra. The E(TO1 phonon mode reveals the characteristic relaxational polarization fluctuations associated with the reorientation of either polar nano-regions or polar nano-domains. It was found that these mechanisms are not independent and they can be ascribed to the phonon localization. In addition, a short-range monoclinic phase (Mc can be found below 250 K in the tetragonal phase region by LWRS, which is always associated with the morphotropic phase boundary (MPB and excellent electromechanical properties. It is interesting that PL spectra confirm these results. The present work indicates that external field modulation and change of composition can result in the monoclinic phase and co-existence of multi-phase.

  4. Doped titanium dioxide nanocrystalline powders with high photocatalytic activity

    International Nuclear Information System (INIS)

    Castro, A.L.; Nunes, M.R.; Carvalho, M.D.; Ferreira, L.P.; Jumas, J.-C.; Costa, F.M.; Florencio, M.H.

    2009-01-01

    Doped titanium dioxide nanopowders (M:TiO 2 ; M=Fe, Co, Nb, Sb) with anatase structure were successfully synthesized through an hydrothermal route preceded by a precipitation doping step. Structural and morphological characterizations were performed by powder XRD and TEM. Thermodynamic stability studies allowed to conclude that the anatase structure is highly stable for all doped TiO 2 prepared compounds. The photocatalytic efficiency of the synthesized nanopowders was tested and the results showed an appreciable enhancement in the photoactivity of the Sb:TiO 2 and Nb:TiO 2 , whereas no photocatalytic activity was detected for the Fe:TiO 2 and Co:TiO 2 nanopowders. These results were correlated to the doping ions oxidation states, determined by Moessbauer spectroscopy and magnetization data. - Graphical abstract: Doped titanium dioxide nanopowders (M:TiO 2 ; M=Fe, Co, Nb, Sb) with highly stable anatase structure were successfully synthesized through an hydrothermal route. The photocatalytic efficiencies of the synthesized nanopowders were tested and the results show an appreciable enhancement in the photoactivity of the Sb:TiO 2 and Nb:TiO 2 .

  5. Electric-field gradients at the $^{111}In$ and $^{111m}Cd$ sites in undoped and Mg-doped $LiNbO_{3}$

    CERN Document Server

    Hauer, B; Marques, J G; Barradas, N P; Correia, J G; Agulló-López, F; Diéguez, E

    1995-01-01

    The quadrupole interaction of 111Cd in undoped (congruent) and Mg-doped LiNbO3 single crystals has been studied using the perturbed angular correlation technique after implantation of 111In and 111mCd. A stepwise-annealing procedure shows the lattice to be fully reconstructed at 773 K. Our results show that both In and Cd are in the Li position. Mg doping at 6 mol % does not have any effect on the lattice location of these impurities in LiNbO3.

  6. Ultrasound assisted synthesis of iron doped TiO2 catalyst.

    Science.gov (United States)

    Ambati, Rohini; Gogate, Parag R

    2018-01-01

    The present work deals with synthesis of Fe (III) doped TiO 2 catalyst using the ultrasound assisted approach and conventional sol-gel approach with an objective of establishing the process intensification benefits. Effect of operating parameters such as Fe doping, type of solvent, solvent to precursor ratio and initial temperature has been investigated to get the best catalyst with minimum particle size. Comparison of the catalysts obtained using the conventional and ultrasound assisted approach under the optimized conditions has been performed using the characterization techniques like DLS, XRD, BET, SEM, EDS, TEM, FTIR and UV-Vis band gap analysis. It was established that catalyst synthesized by ultrasound assisted approach under optimized conditions of 0.4mol% doping, irradiation time of 60min, propan-2-ol as the solvent with the solvent to precursor ratio as 10 and initial temperature of 30°C was the best one with minimum particle size as 99nm and surface area as 49.41m 2 /g. SEM analysis, XRD analysis as well as the TEM analysis also confirmed the superiority of the catalyst obtained using ultrasound assisted approach as compared to the conventional approach. EDS analysis also confirmed the presence of 4.05mol% of Fe element in the sample of 0.4mol% iron doped TiO 2 . UV-Vis band gap results showed the reduction in band gap from 3.2eV to 2.9eV. Photocatalytic experiments performed to check the activity also confirmed that ultrasonically synthesized Fe doped TiO 2 catalyst resulted in a higher degradation of Acid Blue 80 as 38% while the conventionally synthesized catalyst resulted in a degradation of 31.1%. Overall, the work has clearly established importance of ultrasound in giving better catalyst characteristics as well as activity for degradation of the Acid Blue 80 dye. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. First-principles investigation of U doping in ZrO2

    International Nuclear Information System (INIS)

    Huang, H.W.; Pan, Y.; Yu, C.; Yang, J.; Wang, H.; Yi, W.; Peng, J.C.

    2014-01-01

    Highlights: • U-doped system with cubic structure is more stable than the monoclinic structure. • The elastic modulus of cubic structure is higher than the monoclinic structure. • U-doped weakens the resistance to shear deformation of ZrO 2 . • U-doped enhances the resistance to shape deformation for monoclinic structure. -- Abstract: The formation energies, elastic properties, Debye temperature and electronic structure of U-doped ZrO 2 within cubic and monoclinic structures are investigated by first-principles approach. The calculated formation energies show that the U-doped with cubic structure is more stable than that of monoclinic structure. The U-doped weakens the resistance to shear deformation whether cubic structure or monoclinic structure. However, the U-doped decreases the shape deformation of cubic structure in contrast to enhances the shape deformation for monoclinic structure. The Debye temperature of U-doped system is lower than the corresponding ZrO 2 . We found that the calculated electronic structure of these systems are consistent with the variation of formation energies

  8. Alternative route for the synthesis of high surface-area η-Al{sub 2}O{sub 3}/Nb{sub 2}O{sub 5} catalyst from aluminum waste

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, Francisco G.E. [Departamento de Engenharia Química, Universidade Federal de São Carlos, CEP 13565-905, São Carlos, SP (Brazil); Asencios, Yvan J.O. [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Av. Alm. Saldanha da Gama, 89, 11030-400, Santos, SP (Brazil); Rodella, Cristiane B. [Laboratório Nacional de Luz Sincrotron, Rua Giuseppe Máximo Scolfaro, 10.000 Polo II de Alta Tecnologia, 13083-970, Campinas, SP (Brazil); Porto, André L.M. [Departamento de Engenharia Química, Universidade Federal de São Carlos, CEP 13565-905, São Carlos, SP (Brazil); Assaf, Elisabete M., E-mail: eassaf@iqsc.usp.br [Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, 13560-970, São Carlos, SP (Brazil)

    2016-12-01

    This paper describes an alternative route for the production of a high-surface-area η-Al{sub 2}O{sub 3}/Nb{sub 2}O{sub 5} catalyst synthesized from aluminum waste and niobium ammonium oxalate (NH{sub 4}H{sub 2}[NbO−(C{sub 2}O{sub 4}){sub 3}]·3H{sub 2}O). The effects of thermal treatment on the morphology and crystal structure were examined by X-ray powder diffraction (XPD), surface area measurements (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence, dynamic scanning calorimetry (DSC) and thermogravimetry (TG) measurement. The catalysts were evaluated in the glycerol dehydration reaction. Catalytic tests were carried out with reactants in gas-phase with a fixed-bed reactor at 300° and 400 °C. - Highlights: • Alternative route for the production of a high-surface-area Al{sub 2}O{sub 3}/Nb{sub 2}O{sub 5} catalyst. • The catalyst was synthesized from aluminum waste and ammonium oxalato-niobate. • NbAl catalyst obtained showed high specific surface area (330 m{sup 2}/g). • The catalyst produced by this method showed promise in the dehydration of glycerol.

  9. Fluorescence and afterglow of Ca2Sn2Al2O9:Mn2+

    Science.gov (United States)

    Takemoto, Minoru; Iseki, Takahiro

    2018-03-01

    By using a polymerized complex method, we synthesized manganese (Mn)-doped Ca2Sn2Al2O9, which exhibits yellow fluorescence and afterglow at room temperature when excited by UV radiation. The material emits a broad, featureless fluorescence band centered at 564 nm, which we attribute to the presence of Mn2+ ions. The afterglow decay is well fit by a power-law function, rather than an exponential function. In addition, thermoluminescence analyses demonstrate that two different types of electron traps form in this material. Based on experimental results, we conclude that the fluorescence and afterglow both result from thermally assisted tunneling, in which trapped electrons are thermally excited to higher-level traps and subsequently tunnel to recombination centers.

  10. Effect of concentration variation on 2.0 µm emission of Ho3+-doped SiO2-Al2O3-Na2CO3-SrF2-CaF2 oxyfluorosilicate glasses

    Science.gov (United States)

    Gelija, Devarajulu; Borelli, Deva Prasad Raju

    2018-02-01

    The concentration variation of Ho3+ ion-doped SiO2-Al2O3-Na2CO3-SrF2-CaF2 glasses has been prepared by conventional melt quenching method. The thermal stability of 1 mol % of Ho3+-doped oxyfluorosilicate glass has been calculated using the differential thermal analysis (DTA) spectra. The phenomenological Judd-Ofelt intensity parameters Ωλ ( λ = 2, 4 and 6) were calculated for all concentrations of Ho3+ ions. The luminescence spectra in visible region of Ho3+ ion-doped glasses were recorded under the excitation wavelength of 452 nm. The spectra consists of several intense emission bands (5F4, 5S2) → 5I8 (547 nm), 5F3 → 5I8 (647 nm), 5F5 → 5I7 (660 nm) and (5F4, 5S2) → 5I7 (750 nm) in the range 500-780 nm. The fluorescence emission at ˜2.0 µm (5I7 → 5I8) was observed under the excitation of 488 nm Ar-ion laser. The stimulated emission cross section for 5I7 → 5I8 transition (˜2.0 µm) varies from 8.46 to 9.52 × 10-21 cm2, as calculated by the Fuchtbauer-Ladenburg (FL) theory. However, Mc-Cumber theory was used to calculate emission cross section values about 4.24-5.75 × 10-21 cm2 for the 5I7 → 5I8 transition in all concentrations of Ho3+-doped oxyfluorosilicate glasses. Therefore, these results reveal that the 0.5 mol % of Ho3+-doped oxyfluorosilicate glasses, exhibiting higher emission cross section, has potentially been used for laser applications at ˜ 2.0 µm.

  11. Preparation and characterization of Ce-doped HfO2 nanoparticles

    International Nuclear Information System (INIS)

    Gálvez-Barboza, S.; González, L.A.; Puente-Urbina, B.A.; Saucedo-Salazar, E.M.; García-Cerda, L.A.

    2015-01-01

    Highlights: • Ce-doped HfO 2 nanoparticles were prepared by a modified solgel method. • Ce-doped HfO 2 nanoparticles have a semispherical shape with sizes between 6 and 11.5 nm. • The samples doped with 10% in weight of Ce directly crystallized in a cubic structure. • A quick, straightforward and effective route for the preparation of Ce-doped nanoparticles. - Abstract: A modified solgel method to synthesize Ce-doped HfO 2 nanoparticles was carried out using a precursor material prepared with cerium nitrate, hafnium chloride, citric acid and ethylene glycol. The obtained precursor material was calcined at 500 and 700 °C for 2 h in air. The influence of the concentration of Ce and the calcination temperature was studied to observe the structural and morphological changes of the obtained materials. For the characterization, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman scattering (RS) were employed. The XRD patterns shown that the Ce-doped HfO 2 undergoes a structural transformation from monoclinic to cubic phase, which is significantly dependent on the Ce content and calcination temperature. TEM images have also confirmed the existence of semispherical nanoparticles with sizes between 6 and 11.5 nm

  12. Corrosion of thin, magnetron sputtered Nb_2O_5 films

    International Nuclear Information System (INIS)

    Pillis, Marina Fuser; Geribola, Guilherme Altomari; Scheidt, Guilherme; Gonçalves de Araújo, Edval; Lopes de Oliveira, Mara Cristina; Antunes, Renato Altobelli

    2016-01-01

    Highlights: • Niobium oxide based films were obtained by DC magnetron sputtering. • Different deposition times were tested. • The best corrosion resistance was obtained for the Nb_2O_5 film produced at 15′. • Film porosity determines the corrosion resistance. - Abstract: Niobium oxide based thin films were deposited on AISI 316 stainless steel substrates using reactive DC magnetron sputtering. Structure, composition and corrosion resistance of the niobium oxide films were studied. The corrosion behavior of the specimens was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The concentration of niobium and oxygen in the films was obtained by Rutherford backscattering spectroscopy (RBS). The film structure was analyzed by X-ray diffractometry. The corrosion resistance of the substrate was improved by the Nb_2O_5 layers. The best protective performance was achieved for the deposition time of 15 min.

  13. Ni doping effect on the electronic and sensing properties of 2D SnO2

    Science.gov (United States)

    Patel, Anjali; Roondhe, Basant; Jha, Prafulla K.

    2018-05-01

    In the present work using state of art first principles calculations under the frame work of density functional theory the effect of Nickel (Ni) doping on electronic as well as sensing properties of most stable two dimensional (2D) T-SnO2 phase towards ethanol (C2H5OH) has been observed. It has been found that Ni atom when dope on T-SnO2 causes prominent decrement in the band gap from 2.26 eV to 1.48 eV and improves the sensing phenomena of pristine T-SnO2 towards C2H5OH by increasing the binding energy from -0.18eV to -0.93eV. The comparative analysis of binding energy shows that Ni improves the binding of C2H5OH by 5.16 times the values for pristine T-SnO2. The doping of Ni into 2D T-SnO2 reduces the band gap through lowering of the conduction band minimum, thereby increasing the electron affinity which increases the sensing performance of T-SnO2. The variation in the electronic properties after and before the exposure of ethanol reinforced to use Ni:SnO2 nano structure for sensing applications. The results indicate that the Ni doped T-SnO2 can be utilized in improved optoelectronic as well as sensor devices in the future.

  14. Effects of Sm3+/Yb3+ co-doping and temperature on the Raman, IR spectra and structure of [TeO2-GeO2-K2O-Sm2O3/Yb2O3] glasses

    International Nuclear Information System (INIS)

    Shaltout, I.; Badr, Y.

    2006-01-01

    Effects of Sm 3+ /Yb 3+ co-doping on Raman scattering, IR absorption, temperature dependence of the Raman spectra up to 210 o C and the structure of two glass systems of the composition (80TeO 2 -10GeO 2 -8K 2 O-2Sm 2 O 3 /Yb 2 O 3 ) is discussed. It was found that the addition of Yb 3+ to the glass very strongly enhances the intensities of the antistokes' Raman bands at 155, 375, 557 and 828 cm -1 and quenches both the intensities of the stokes' vibration modes of the TeO 4 units in the range of 120-770 cm -1 and the intensities of the OH - stretching vibration modes in the range of 2600-3300 cm -1 . Sm 2 O 3 /Yb 2 O 3 rare earth co-doping has a great influence on removing and/or changing the nature of the OH - groups. The appearance and splitting of the stretching vibration modes of the OH - groups at lower frequencies (2770, 2970 cm -1 ) for the Sm +3 singly doped glass sample, compared to the band at ∼3200 cm -1 for the Sm 3+ /Yb 3+ co-doped glass sample, suggested that the OH - groups are more strongly bonded and incorporated with the glass matrix for the singly doped glass. Heating the sample up continuously weakens the hydrogen bonding of the OH - groups to the glass matrix leading to creation of NBO and breakdown of the connectivity of the OH - groups to the TeO 4 , TeO 3+1 and TeO 3 structural units. Raman bands at 286, 477, 666 and 769 cm -1 were assigned to its respective vibrations of Te 2 O 7 , TeO 4 -4 species, the (Te-O-Te) bending vibrations of the TeO 4 triagonal bipyramids (tbps), the axial symmetric stretching vibration modes (Te ax -O) s with bridging oxygen BO atoms and to the (Te-O) nbo non-bridging stretching vibration modes of the TeO 3+1 and/or TeO 3 pyramids

  15. Structural, electrical, and optical properties of polycrystalline NbO_2 thin films grown on glass substrates by solid phase crystallization

    International Nuclear Information System (INIS)

    Nakao, Shoichiro; Kamisaka, Hideyuki; Hirose, Yasushi; Hasegawa, Tetsuya

    2017-01-01

    We investigated the structural, electrical, and optical properties of polycrystalline NbO_2 thin films on glass substrates. The NbO_2 films were crystallized from amorphous precursor films grown by pulsed laser deposition at various oxygen partial pressures (P_O_2). The electrical and optical properties of the precursor films systematically changed with P_O_2, demonstrating that the oxygen content of the precursor films can be finely controlled with P_O_2. The precursors were crystallized into polycrystalline NbO_2 films by annealing under vacuum at 600 C. The NbO_2 films possessed extremely flat surfaces with branching patterns. Even optimized films showed a low resistivity (ρ) of 2 x 10"2 Ω cm, which is much lower than the bulk value of 1 x 10"4 Ω cm, probably because of the inferior crystallinity of the films compared with that of a bulk NbO_2 crystal. Both oxygen-rich and -poor NbO_2 films showed lower ρ than that of the stoichiometric film. The NbO_2 film with the highest ρ showed an indirect bandgap of 0.7 eV. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Tailoring luminescence properties of TiO2 nanoparticles by Mn doping

    International Nuclear Information System (INIS)

    Choudhury, B.; Choudhury, A.

    2013-01-01

    TiO 2 nanoparticles are doped with three different concentrations of Mn, 2%, 4% and 6% respectively. Absorption edge of TiO 2 is shifted from UV to visible region on amplification of Mn content. Room temperature photoluminescence spectra, excited at 320 nm, exhibit band edge and visible emission peaks associated with self trapped excitons, oxygen defects, etc. Doping of Mn increases the width and decreases the intensity of the UV emission peak. Potential fluctuations of impurities increase the width and auger type non-radiative recombination decreases the intensity of the UV emission peak. The intensity ratio of the UV to defect emission band decreases on doping, indicating degradation of structural quality. Excitation of pure and doped nanoparticles at 390 nm results in Mn 2+ emission peaks at 525 nm and 585 nm respectively. Photoluminescence excitation spectra also indicate the presence of Mn 2+ in the crystalline environment of TiO 2 . The oxygen defects and Mn related impurities act as efficient trap centers and increases the lifetime of the charge carriers. -- Highlights: ► Doping of Mn increases the d-spacing of TiO 2 nanoparticles. ► Characteristic d–d electronic transition of Mn 2+ is observed in the absorption spectra. ► Doping of Mn quenches the UV and visible emission peaks of TiO 2 . ► Photoexcitation at 390 nm generates emission peaks of Mn 2+

  17. Fabrication and electrical properties of textured strontium(0.53)barium(0.47)niobium(2)oxygen(6) ceramics prepared by templated grain growth

    Science.gov (United States)

    Duran, Cihangir

    Sr0.53Ba0.47Nb2O6 (SBN53) ceramics were textured by the templated grain growth (TGG), in a matrix of SrNb2O6 and BaNb2O6 powders. Acicular KSr2Nb5O15 (KSN) template particles, synthesized by a molten salt process, were used to texture the samples in the c direction (i.e., [001]). Template growth was assisted by adding V2O5 as a liquid phase former for some compositions. The texture fraction also increased with higher sintering temperatures or times and with initial template concentration due to the preferential growth of the template particles. When V2O5 was present, SBN53 phase formation initiated on the KSN templates and texture development started at temperatures as low as 950°C. Phase formation in the V2O5-free samples, however, initiated in the matrix (i.e., independent of the KSN templates). The liquid phase adversely affected the template growth by favoring anisotropic grain growth in the matrix, which caused lower texture fraction and broader texture distribution in [001] at low template concentrations. Increased template-template interaction (e.g., tangling) during tape casting also resulted in broader texture distribution. Therefore, an optimum template content was found to be ˜10--15 wt%. However, a texture fraction of 0.93 to 0.98 was obtained using only 5 wt% templates when anisotropic matrix grain growth was prevented. Phase evolution was studied in the randomly oriented samples as a function of quenching temperature, heating rate, and liquid phase, using KSN powder (rather than acicular particles) as a seed material. The formation temperature for SBN53 was lowered substantially by adding more seeds, decreasing the heating rate, and introducing a liquid. The temperature decreased from 1260°C for the samples with no seeds to 1130°C for the samples with 15.4 wt% seeds + 0.8 mol% V2O5 at a heating rate of 4°C/min. For the V2O5-free samples, the activation energy was considerably lowered from 554 +/- 15 kJ/mol for the samples with no seeds to 241

  18. Porous TiNb2O7 Nanospheres as ultra Long-life and High-power Anodes for Lithium-ion Batteries

    International Nuclear Information System (INIS)

    Cheng, Qiushi; Liang, Jianwen; Lin, Ning; Guo, Cong; Zhu, Yongchun; Qian, Yitai

    2015-01-01

    Graphical abstract: Due to the combinative merits of porosity and nanostructure, porous TiNb 2 O 7 nanospheres exhibit ultra long cyclic life and excellent rate performance for lithium ion batteries. - Highlights: • Porous TiNb 2 O 7 nanospheres have been fabricated with the assistance of block copolymer P123. • The as-prepared TiNb 2 O 7 anodes present a reversible capacity of 160 mA h/g after 10000 cycles at 5 C with a capacity loss of only 0.0033% per cycle. • The TiNb 2 O 7 anodes show good rate performance of 167 mA h/g at 50C. • The TiNb 2 O 7 materials maintain the morphology of nanospheres and the porous structure even after 10000 cycles. - Abstract: Porous TiNb 2 O 7 nanospheres comprised of nanoparticles have been synthesized with the assistance of block copolymer P123 (EO 20 PO 70 EO 20 ). Such porous TiNb 2 O 7 nanospheres, with diameter of 500 nm, exhibit a BET surface area of 23.4 m 2 /g and pore volume of 0.155 cm 3 /g. As the anodes for lithium-ion batteries, the TiNb 2 O 7 nanospheres present a reversible capacity of 160 mA h/g after 10000 cycles at 5 C with a capacity loss of only 0.0033% per cycle, and good rate performance of 167 mA h/g at 50 C. Furthermore, the TiNb 2 O 7 materials still maintain the morphology of nanospheres and the porous structure even after 10000 cycles

  19. Dielectric and magnetic properties of (Zn, Co) co-doped SnO2 nanoparticles

    International Nuclear Information System (INIS)

    Rajwali, Khan; Fang Ming-Hu

    2015-01-01

    Polycrystalline samples of (Zn, Co) co-doped SnO 2 nanoparticles were prepared using a co-precipitation method. The influence of (Zn, Co) co-doping on electrical, dielectric, and magnetic properties was studied. All of the (Zn, Co) co-doped SnO 2 powder samples have the same tetragonal structure of SnO 2 . A decrease in the dielectric constant was observed with the increase of Co doping concentration. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with doping concentration and frequency. Magnetization measurements revealed that the Co doping SnO 2 samples exhibits room temperature ferromagnetism. Our results illustrate that (Zn, Co) co-doped SnO 2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those reported previously, indicating that these (Zn, Co) co-doped SnO 2 materials can be used in the field of the ultrahigh dielectric material, high frequency device, and spintronics. (paper)

  20. Defect phase diagram for doping of Ga2O3

    Directory of Open Access Journals (Sweden)

    Stephan Lany

    2018-04-01

    Full Text Available For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn, a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T, O partial pressures (pO2, and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2 conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

  1. Raman spectra of the solid-solution between Rb sub 2 La sub 2 Ti sub 3 O sub 1 sub 0 and RbCa sub 2 Nb sub 3 O sub 1 sub 0

    CERN Document Server

    Kim, H J; Yun, H S

    2001-01-01

    A site preference of niobium atom in Rb sub 2 sub - sub x La sub 2 Ti sub 3 sub - sub x Nb sub x O sub 1 sub 0 (0.0<=x<=1.0) and RbLa sub 2 sub - sub x Ca sub x Ti sub 2 sub - sub x Nb sub 1 sub + sub x O sub 1 sub 0 (0.0<=x<= 2.0), which are the solid-solutions between Rb sub 2 La sub 2 Ti sub 3 O sub 1 sub 0 are RbCa sub 2 Nb sub 3 O sub 1 sub 0 , has been investigated by Raman spectroscopy. The Raman spectra of Rb sub 2 sub - sub x La sub 2 Ti sub 3 sub - sub x Nb sub x O sub 1 sub 0 (0.0<=x<=1.0) gave an evidence that niobium atoms substituted for titanium atoms preferably occupy the highly distorted outer octahedral sites rather than the central ones in triple-octahedral perovskite layers. In contrast, the Raman spectra of RbLa sub 2 sub - sub x Ca sub x Ti sub 2 sub - sub x Nb sub 1 sub + sub x O sub 1 sub 0 (0.0<=x<= 2.0) showed no clear information for the cationic arrangement in perovskite slabs. This difference indicated that a site preference of niobium atoms is observed onl...

  2. Eu3+-doped Y2O3 hexagonal prisms: Shape-controlled synthesis and tailored luminescence properties

    International Nuclear Information System (INIS)

    Yang, Errui; Li, Guangshe; Fu, Chaochao; Zheng, Jing; Huang, Xinsong; Xu, Wen; Li, Liping

    2015-01-01

    In this work, Eu 3+ doped Y 2 O 3 hexagonal prisms were synthesized by a novel two-phase approach, which involves water at the bottom as aqueous phase and oleylamine in the above as oil phase. With this unique reaction system, precursors of hexagonal prisms Y 4 O(OH) 9 (NO 3 ) were first obtained by simply varying the volume ratio of water to oleylamine. Time-dependent experiments were systematically performed to reveal the growth mechanism of the precursor. After subsequent heat treatment, these precursors transformed to Y 2 O 3 hexagonal prisms with controlled diameters and aspect ratios varying from 4 to 19. Such a transformation is preceded via a topotactic process, as indicated by TG-DTA and mass spectra. Eventually, all Eu 3+ doped Y 2 O 3 hexagonal prisms were found to exhibit an intensive red emission at 611 nm, which corresponds to 5 D 0 → 7 F 2 transition of Eu 3+ . With varying the aspect ratio of hexagonal prisms and increasing Eu 3+ concentration in Y 2 O 3 , an optimum external quantum efficiency was achieved. - Graphical abstract: In this work, Eu 3+ doped Y 2 O 3 hexagonal prisms with controlled aspect ratio from 4.4 to 19.3 were synthesized by transformation of the precursor Y 4 O(OH) 9 (NO 3 ) hexagonal prisms from a novel two-phase reaction system. The growth mechanism of the precursor has been systematically investigated, and a topotactic phase transformation from precursors to cubic Y 2 O 3 is for the first time put forward. By the size controlling and aspect ratio adjusting, the luminescence emission intensity as well as external quantum efficiency of Eu 3+ doped Y 2 O 3 hexagonal prisms is further tailored to show an optimum. - Highlights: • Eu 3+ doped Y 2 O 3 hexagonal prisms were synthesized by a novel two-phase approach. • Inheriting mechanism of prisms morphology from Y 4 O(OH) 9 (NO 3 ) to Y 2 O 3 was discussed. • Aspect ratio of prisms was tailored by the volume ratio of water to oleylamine. • Luminescence properties were

  3. Radiation resistance of GeO2-doped silica core optical fibers

    International Nuclear Information System (INIS)

    Shibata, Shuichi; Nakahara, Motohiro; Omori, Yasuharu

    1985-01-01

    Effects of hlogen addition to silica glass on the loss in optical fibers are examined by using halogen-free, chlorine-containing and fluorine-containing GeO 2 -doped silica core optical fibers. Measurements are made for dependence of induced loss in these optical fibers on various factors such as wavelength and total dose of gamma radiation as well as GeO 2 content. Ultraviolet absorption spectra are also observed. In addition, effects of halogens added to pure silica fibers are considered on the basis of Raman spectra of three different optical fibers (pure, F-doped, and F- and GeO 2 -codoped silica core). Thus, it is concluded that (1) addition of halogens (F and Cl) serves to decrease GeO defects and Ge(3) defects in GeO 2 -doped silica optical fibers ; (2) addition of halogens suppresses the increase in loss in GeO 2 -doped silica optical fibers induced by gamma radiation ; and (3) there are close relations between the increase in loss induced by gamma radiation and defects originally existing in the fibers. Effects of halogens added to GeO 2 -doped and pure silica optical fibers can be explained on the basis of the latter relations. (Nogami, K.)

  4. Synthesis and Photocatalytic Activity of Mo-Doped TiO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ji-guo Huang

    2015-01-01

    Full Text Available The undoped and Mo-doped TiO2 nanoparticles were synthesized by sol-gel method. The as-prepared samples were characterized by X-ray diffraction (XRD, diffuse reflectance UV-visible absorption spectra (UV-vis DRS, X-ray photoelectron spectra (XPS, and transmission electron microscopy (TEM. The photocatalytic activity was evaluated by photocatalytic degradation of methylene blue under irradiation of a 500 W xenon lamp and natural solar light outdoor. Effects of calcination temperatures and Mo doping amounts on crystal phase, crystallite size, lattice distortion, and optical properties were investigated. The results showed that most of Mo6+ took the place of Ti4+ in the crystal lattice of TiO2, which inhibited the growth of crystallite size, suppressed the transformation from anatase to rutile, and led to lattice distortion of TiO2. Mo doping narrowed the band gap (from 3.05 eV of TiO2 to 2.73 eV of TiMo0.02O and efficiently increased the optical absorption in visible region. Mo doping was shown to be an efficient method for degradation of methylene blue under visible light, especially under solar light. When the calcination temperature was 550°C and the Mo doping amount was 2.0%, the Mo-doped TiO2 sample exhibited the highest photocatalytic activity.

  5. Bubble template synthesis of Sn2Nb2O7 hollow spheres for enhanced visible-light-driven photocatalytic hydrogen production.

    Science.gov (United States)

    Zhou, Chao; Zhao, Yufei; Bian, Tong; Shang, Lu; Yu, Huijun; Wu, Li-Zhu; Tung, Chen-Ho; Zhang, Tierui

    2013-10-28

    Hierarchical Sn2Nb2O7 hollow spheres were prepared for the first time via a facile hydrothermal route using bubbles generated in situ from the decomposition of urea as soft templates. The as-obtained hollow spheres with a large specific surface area of 58.3 m(2) g(-1) show improved visible-light-driven photocatalytic H2 production activity in lactic acid aqueous solutions, about 4 times higher than that of the bulk Sn2Nb2O7 sample prepared by a conventional high temperature solid state reaction method.

  6. Effects of compositions and Nb-doping on microstructure and piezoelectric properties of PMS-PZ-PT system

    Energy Technology Data Exchange (ETDEWEB)

    Jiwen, Long; Haiyan, Chen; Zhongyan, Meng

    2003-05-25

    Sr-substituted (2 mol%) xPMS-(1-x)(PZ-PT) compositions were investigated systematically as a function of PMS concentrations as well as Niobium (Nb) contents. X-ray diffraction (XRD) patterns show that phases shift from tetragonal phase to rhombohedral phase with the increase of PMS concentrations and with the increase of Nb-doping contents in PMS2. The compositions with x=0.05 (PMS2) was found to have superior piezoelectric properties. The properties of the PMS2 compositions were optimized by the Nb-doping contents of 0.1 mol% (d{sub 33}=450 pC N{sup -1}, K{sub p}=0.65, Q{sub m}=1210). The compositions of PMS2 and 0.1 mol% Nb-doped compositions of PMS2 are practically suitable for ultrasonic motor (USM) applications.

  7. Collinear order in frustrated quantum antiferromagnet on square lattice (CuBr)LaNb2O7

    International Nuclear Information System (INIS)

    Oba, Noriaki; Kageyama, Hiroshi; Kitano, Taro

    2006-01-01

    Magnetic susceptibility, heat capacity, high-field magnetization and neutron diffraction measurements have been performed on a two-dimensional s=1/2 square-lattice system (CuBr)LaNb 2 O 7 , prepared by a topotactic ion-exchange reaction of a nonmagnetic double-layered perovskite RbLaNb 2 O 7 . (CuBr)LaNb 2 O 7 exhibits a second-order magnetic transition at 32K, in marked contrast to a spin-singlet nature for its Cl-based counterpart (CuCl)LaNb 2 O 7 , despite nearly identical structural parameters. The magnetic structure is a novel collinear antiferromagnetic (CAF) ordering characterized by a modulation vector q=(π, 0, π) with a reduced moment of 0.6μ B . Mixed ferromagnetic nearest-neighbor (J 1 ) and antiferromagnetic second-nearest-neighbor (J 2 ) interactions are of comparable strength (J 1 /k B =-35.6K and J 2 /k B =41.3K), placing the system in a more frustrated region of the CAF phase than ever reported. (author)

  8. Microstructural evolution of nanosized Ce0.8Gd0.2O1.9/Ni infiltrate in a Zr0.84Y0.16O1.92-Sr0.94Ti0.9Nb0.1O3-δ based SOFC anode under electrochemical evaluation

    DEFF Research Database (Denmark)

    Zhang, Wei; Kuhn, Luise Theil; Ramos, Tania

    are of paramount importance for performance and performance stability. Therefore an accurate understanding of the microstructure evolution during electrochemical operation will facilitate evaluating performances of SOFC anodes, and in turn optimize its design. Here we report a wealth of microstructural...... investigations of Ce0.8Gd0.2O1.9/Ni (hereafter CGO/Ni)-infiltrated Zr0.84Y0.16O1.92 composited Sr0.94Ti0.9Nb0.1O3-δ (STN94/8YSZ) anode in a symmetric cell design under a short electrochemical evaluation test (fingerprint test), applying electrochemical impedance spectroscopy (EIS) at mild 3% H2O/H2 and harsh 50...

  9. Titanium Dioxide-Based 64∘ YX LiNbO3 Surface Acoustic Wave Hydrogen Gas Sensors

    Directory of Open Access Journals (Sweden)

    A. Z. Sadek

    2008-01-01

    Full Text Available Amorphous titanium dioxide (TiO2 and gold (Au doped TiO2-based surface acoustic wave (SAW sensors have been investigated as hydrogen gas detectors. The nanocrystal-doped TiO2 films were synthesized through a sol-gel route, mixing a Ti-butoxide-based solution with diluted colloidal gold nanoparticles. The films were deposited via spin coating onto 64∘ YX LiNbO3 SAW transducers in a helium atmosphere. The SAW gas sensors were operated at various temperatures between 150 and 310∘C. It was found that gold doping on TiO2 increased the device sensitivity and reduced the optimum operating temperature.

  10. Relative Humidity Sensing Properties Of Cu2O Doped ZnO Nanocomposite

    International Nuclear Information System (INIS)

    Pandey, N. K.; Tiwari, K.; Tripathi, A.; Roy, A.; Rai, A.; Awasthi, P.

    2009-01-01

    In this paper we report application of Cu 2 O doped ZnO composite prepared by solid state reaction route as humidity sensor. Pellet samples of ZnO-Cu 2 O nanocrystalline powders with 2, 5 and 10 weight% of Cu 2 O in ZnO have been prepared. Pellets have been annealed at temperatures of 200-500 deg. C and exposed to humidity. It is observed that as relative humidity increases, resistance of the pellet decreases for the humidity from 10% to 90%. Sample with 5% of Cu 2 O doped in ZnO and annealed at 500 deg. C shows best results with sensitivity of 1.50 MΩ/%RH. In this case the hysteresis is low and the reproducibility high, making it the suitable candidate for humidity sensing.

  11. Spectroscopic studies of lutetium pyro-silicates Lu2Si2O7 doped with bismuth and europium

    International Nuclear Information System (INIS)

    Bretheau-Raynal, Francoise

    1981-01-01

    Single crystals of thortveitite structure pyro-silicates were grown by a floating zone technique associated with an arc image furnace. The samples were systematically characterized by X-Ray diffraction and microprobe analysis. Thanks to oriented single crystals of Lu 2 Si 2 O 7 , Yb 2 Si 2 O 7 and Sc 2 Si 2 O 7 , the recorded infrared and Raman spectra allow complete attribution of internal and external vibration modes, in good agreement with group theory predictions for C 2h factor group. Spectroscopic studies of Eu 3+ doping ion in Lu 2 Si 2 O 7 confirm C 2 point symmetry for the cationic site. Oscillator strengths and Judd-Ofelt parameters for Eu 3+ were calculated. A three level scheme ( 1 S 0 , 3 P 0 , 3 P 1 ) of Bi 3+ ion is used to explain radiative and non radiative mechanisms in Lu 2 Si 2 O 7 doped with bismuth. Finally, the mechanisms of low temperature (T =9 K) energy transfer between Bi 3+ and Eu 3+ in lutetium pyro-silicate was studied. The transfer occurs by non radiative process, without any diffusion of the excitation energy within the donor system and is due to dipole-dipole interactions between Bi 3+ and Eu 3+ ions. (author) [fr

  12. Study and characterization of the BBT (BaBi{sub 4}Ti{sub 4}O{sub 15}) ceramic added with 1 wt. % Nb{sub 2}O{sub 5}; Estudo e caracterizacao da ceramica BBT (BaBi{sub 4}Ti{sub 4}O{sub 15}) dopada com 1% de Nb{sub 2}O{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Silva, P.M.O.; Sales, A.J.M.; Freitas, D.B.; Oliveira, R.G.M.; Sombra, A.S.B., E-mail: paulo2003@gmail.com [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil); Sales, J.C. [Universidade Estadual Vale do Acarau (UVA), Fortaleza, CE (Brazil)

    2012-07-01

    This study aims to synthesize and characterize the ceramic BBT (BaBi{sub 4}TI{sub 4}O{sub 15}) doped with 1% by mass of the densification Nb2O5 to improve the products. The phase of the BBT has been found by solid state reaction. The mixed oxides starting processed by high-energy milling in planetary mill reactor polymer and spheres of zirconia and calcined at 850°C/3h. Later, 'bulks' prepared with the calcined powder were sintered at 950°C/3h. The calcined powder was characterized by X-ray diffraction data and refined by the beta 3.2 DBWSTools program using the Rietveld method. The grain morphology and distribution of pores on the surface of the 'bulks' were analyzed by Scanning Electron Microscopy. The result confirmed the refined to obtain the single phase with tetragonal structure BaBi{sub 4}TI{sub 4}O{sub 15} density of 5.088 g/cm3 calculated in the unit cell. SEM analysis by SEM showed improved densification of the doped. (author)

  13. Nb2O5 hollow nanospheres as anode material for enhanced performance in lithium ion batteries

    International Nuclear Information System (INIS)

    Sasidharan, Manickam; Gunawardhana, Nanda; Yoshio, Masaki; Nakashima, Kenichi

    2012-01-01

    Graphical abstract: Nb 2 O 5 hollow nanosphere constructed electrode delivers high capacity of 172 mAh g −1 after 250 cycles and maintains structural integrity and excellent cycling stability. Highlights: ► Nb 2 O 5 hollow nanospheres synthesis was synthesized by soft-template. ► Nb 2 O 5 hollow nanospheres were investigated as anode material in Li-ion battery. ► Nanostructured electrode delivers high capacity of 172 mAh g −1 after 250 cycles. ► The electrode maintains the structural integrity and excellent cycling stability. ► Nanosized shell domain facilitates fast lithium intercalation/deintercalation. -- Abstract: Nb 2 O 5 hollow nanospheres of average diameter ca. ∼29 nm and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb 2 O 5 hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g −1 after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g −1 . The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb 2 O 5 shell domain that facilitates fast lithium intercalation/deintercalation kinetics.

  14. Spectral and laser properties of Er3+/Yb3+/Ce3+ tri-doped Ca3NbGa3Si2O14 crystal at 1.55 µm

    Science.gov (United States)

    Gong, Guoliang; Chen, Yujin; Lin, Yanfu; Huang, Jianhua; Gong, Xinghong; Luo, Zundu; Huang, Yidong

    2018-04-01

    An Er3+/Yb3+/Ce3+ tri-doped Ca3NbGa3Si2O14 (CNGS) crystal was grown by the Czochralski method. Spectral properties of the crystal, including the polarized absorption and fluorescence spectra, the fluorescence decay, as well as the energy transfer efficiency from Yb3+ to Er3+ were investigated in detail. End-pumped by a 976 nm diode laser, a 1556 nm continuous-wave laser with a maximum output power of 202 mW and a slope efficiency of 11.4% was achieved in the Er,Yb,Ce:CNGS crystal. The results indicate the Er,Yb,Ce:CNGS crystal is a promising 1.55 µm laser gain medium.

  15. Structural, morphological, optical and photocatalytic investigation of Ag-doped TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Virender Singh; Tanwar, Amit [Department of Electronic Science, Kurukshetra University, Kurukshetra-136119 (India); Singh, Davender, E-mail: Davender-kadian@rediffmail.com; Maan, A. S. [Departments of Physics, Maharshi Dayanand University, Rohtak-124001 (India)

    2016-05-06

    The pure and Ag-doped TiO{sub 2} nanoparticles were prepared by using Titanium isoproxide (TTIP), silver nitrate sodium hydroxide and sodium hydroxide. The calcined nanoparticles at 400°C were characterized by means of X-ray diffraction (XRD). XRD analyses reveal that the nanoparticles of various doping concentration were having anatase phase. The particle size was calculated by Scherrer formula and was found 11.08 nm for pure TiO{sub 2} and 8.86 nm for 6 mol % Ag doped TiO{sub 2}. The morphology and nature of nanoparticles was analyzed by using scanning electron microscope (SEM), the optical absorption spectra of pure TiO{sub 2} and Ag-doped TiO{sub 2} nanoparticles showed that absorption edge increases towards longer wavelength from 390 nm (pure) to 450 nm (doped), also band gap energy calculated from Tauc’s plot decrease from 3.20eV to 2.92eV with increase in doing. The measurement of photocatalytic properties of pure TiO{sub 2} and Ag-doped TiO{sub 2} nanoparticles showed that Ag-doped TiO{sub 2} degrades MB dye more efficiently than pure TiO{sub 2}.

  16. α-Fe{sub 2}O{sub 3}/Ti–Nb–Zr–O composite photoanode for enhanced photoelectrochemical water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qiang [Institute of Microelectronic Materials and Technology, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Ding, Dongyan, E-mail: dyding@sjtu.edu.cn [Institute of Microelectronic Materials and Technology, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Ning, Congqin [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Wang, Xuewu [School of Information Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2015-06-15

    Highlights: • The Ti–Nb–Zr–O nanotube photoanodes were fabricated by electrochemical anodization. • The length of the Ti–Nb–Zr–O nanotube arrays increased with the increase of Zr content at the same anodization potential. • Nb- and Zr-doping could enhance the photocatalytic properties of the titanium oxide. • The modification of the α-Fe{sub 2}O{sub 3} improved photocatalytic activity of the Ti–Nb–Zr–O photoanode. - Abstract: Surface modification and doping of titanium dioxide (TiO{sub 2}) nanotubes are efficient ways to obtain improved photosensitive characteristics. Here we report photocatalytic activity of α-Fe{sub 2}O{sub 3} decorated Ti–Nb–Zr–O nanotube arrays. The Ti–Nb–Zr–O nanotube arrays were fabricated through anodization of Ti–Nb–Zr alloy in electrolytes of 1 M NaH{sub 2}PO{sub 4} containing 0.5 wt% HF. X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the heterojunction nanofilms. Nb- and Zr-doping could enhance the photocatalytic properties of the titanium oxide. However, more Zr-doping could lead to many defects that acted as recombination centers, which reduced the photocatalytic activity of the titanium oxide. The photocurrent density of the Ti–Nb–Zr–O nanotube photoanodes decorated with a small quantity of α-Fe{sub 2}O{sub 3} could exhibit three times as high as that of the undoped TiO{sub 2} nanotube photoanodes.

  17. Optical properties of ZrO2, SiO2 and TiO2-SiO2 xerogels and coatings doped with Eu3+ and Eu2+

    Directory of Open Access Journals (Sweden)

    Gonçalves Rogéria R.

    1999-01-01

    Full Text Available Eu3+ doped bulk monoliths and thin films were obtained by sol-gel methods in the ZrO2, SiO2 and SiO2-TiO2 systems. Eu3+ 5D0 ® 7FJ emission and decay time characteristics were measured during the entire experimental preparation route from the initial sol to the final xerogels. The crystalline phases identified were tetragonal ZrO2 and mixtures of rutile and anatase TiO2 at high temperature treatments in bulk samples. Good quality thin films were obtained for all systems by dip-coating optical glasses (Schott BK270. The same spectroscopic features were observed either for the bulk monoliths or the films. By appropriate heat treatments under H2 atmosphere Eu2+ containing samples could be obtained in the SiO2-TiO2 system.

  18. Perturbed angular correlation study of α - Nb2O5

    International Nuclear Information System (INIS)

    Shitu, Jorge; Massolo, C.P.; Bibiloni, A.G.; Renteria, Mario; Desimoni, Judith

    1989-01-01

    The TANDAR accelerator of the National Atomic Energy Commission has been used to obtain the non-conventional radioactive probe 100 Rh embedded in α - Nb 2 O 5 allowing the PAC study of the range of high electric field gradients in this semiconductor. A sintered oxide tablet, obtained from metallic Nb powder calcination in air at 1050deg C, was irradiated with a 100 MeV 12 C6+ beam for 15 hours to produce the 100 Rh probe through the reaction 93 Nb ( 12 C,5n) 100 Ag → 100 Pd → 100 Rh. The PAC measurements show a non-homogenous distribution of the probes substituting the Nb in lattice sites of high electric field gradient. The range of low electric field gradients was studied using the probe 111 In incorporated to the samples by diffusion. (Author) [es

  19. Optical excitations in CuO2-sheets doped and undoped with electrons

    International Nuclear Information System (INIS)

    Tokura, Y.; Arima, T.; Koshihara, S.; Takagi, H.; Ido, T.; Ishibashi, S.; Uchida, S.

    1989-01-01

    This paper reports optical reflectance spectra measured on single crystals of parent families of high T c copper oxide compounds with single-layered CuO 2 -sheets, which clearly show the strong transitons across the charge-transfer (CT) gaps at 1.5-2.0 eV in various types of CuO 2 -sheets. The carrier-doping effects on the CT excitations have been investigated on the Sr-doped La 2 CuO 4 and Ce-doped Nd 2 O 4 crystals

  20. Effect of concentration variation on 2.0 μm emission of Ho3+-doped SiO2-Al2O3-Na2CO3-SrF2-CaF2 oxyfluorosilicate glasses

    International Nuclear Information System (INIS)

    Gelija, Devarajulu; Borelli, Deva Prasad Raju

    2018-01-01

    The concentration variation of Ho 3+ ion-doped SiO 2 -Al 2 O 3 -Na 2 CO 3 -SrF 2 -CaF 2 glasses has been prepared by conventional melt quenching method. The thermal stability of 1 mol % of Ho 3+ -doped oxyfluorosilicate glass has been calculated using the differential thermal analysis (DTA) spectra. The phenomenological Judd-Ofelt intensity parameters Ω λ (λ = 2, 4 and 6) were calculated for all concentrations of Ho 3+ ions. The luminescence spectra in visible region of Ho 3+ ion-doped glasses were recorded under the excitation wavelength of 452 nm. The spectra consists of several intense emission bands ( 5 F 4 , 5 S 2 ) → 5 I 8 (547 nm), 5 F 3 → 5 I 8 (647 nm), 5 F 5 → 5 I 7 (660 nm) and ( 5 F 4 , 5 S 2 ) → 5 I 7 (750 nm) in the range 500-780 nm. The fluorescence emission at ∝ 2.0 μm ( 5 I 7 → 5 I 8 ) was observed under the excitation of 488 nm Ar-ion laser. The stimulated emission cross section for 5 I 7 → 5 I 8 transition (∝ 2.0 μm) varies from 8.46 to 9.52 x 10 -21 cm 2 , as calculated by the Fuchtbauer-Ladenburg (FL) theory. However, Mc-Cumber theory was used to calculate emission cross section values about 4.24-5.75 x 10 -21 cm 2 for the 5 I 7 → 5 I 8 transition in all concentrations of Ho 3+ -doped oxyfluorosilicate glasses. Therefore, these results reveal that the 0.5 mol % of Ho 3+ -doped oxyfluorosilicate glasses, exhibiting higher emission cross section, has potentially been used for laser applications at ∝ 2.0 μm. (orig.)

  1. Room-temperature ferromagnetism in pure and Co doped CeO2 powders

    International Nuclear Information System (INIS)

    Wen Qiye; Zhang Huaiwu; Song Yuanqiang; Yang Qinghui; Zhu Hao; Xiao, John Q

    2007-01-01

    We report the room-temperature (RT) ferromagnetism (FM) observed in pure and Co doped CeO 2 powder. An insulating nonmagnetic CeO 2 single crystal, after grinding into fine powder, shows an RT-FM with a small magnetization of 0.0045 emu g -1 . However, the CeO 2 powder became paramagnetic after oxygen annealing, which strongly suggests an oxygen vacancy meditated FM ordering. Furthermore, by doping Co into CeO 2 powder the FM can significantly enhance through a F-centre exchange (FCE) coupling mechanism, in which both oxygen vacancies and magnetic ions are involved. As the Co content increases, the FM of Co doped CeO 2 initially increases to a maximum 0.47 emu g -1 , and then degrades very quickly. The complex correlation between the Co content and saturation magnetization was well interpreted by supposing the coexistence of three subsets of Co ions in CeO 2 . Our results reveal that the large RT-FM observed in Co doped CeO 2 powder originates from a combination effect of oxygen vacancies and transition metal doping

  2. Carbon nanotube-TiO(2) hybrid films for detecting traces of O(2).

    Science.gov (United States)

    Llobet, E; Espinosa, E H; Sotter, E; Ionescu, R; Vilanova, X; Torres, J; Felten, A; Pireaux, J J; Ke, X; Van Tendeloo, G; Renaux, F; Paint, Y; Hecq, M; Bittencourt, C

    2008-09-17

    Hybrid titania films have been prepared using an adapted sol-gel method for obtaining well-dispersed hydrogen plasma-treated multiwall carbon nanotubes in either pure titania or Nb-doped titania. The drop-coating method has been used to fabricate resistive oxygen sensors based on titania or on titania and carbon nanotube hybrids. Morphology and composition studies have revealed that the dispersion of low amounts of carbon nanotubes within the titania matrix does not significantly alter its crystallization behaviour. The gas sensitivity studies performed on the different samples have shown that the hybrid layers based on titania and carbon nanotubes possess an unprecedented responsiveness towards oxygen (i.e. more than four times higher than that shown by optimized Nb-doped TiO(2) films). Furthermore, hybrid sensors containing carbon nanotubes respond at significantly lower operating temperatures than their non-hybrid counterparts. These new hybrid sensors show a strong potential for monitoring traces of oxygen (i.e. ≤10 ppm) in a flow of CO(2), which is of interest for the beverage industry.

  3. Carbon nanotube-TiO2 hybrid films for detecting traces of O2

    International Nuclear Information System (INIS)

    Llobet, E; Espinosa, E H; Sotter, E; Ionescu, R; Vilanova, X; Torres, J; Felten, A; Pireaux, J J; Ke, X; Tendeloo, G Van; Renaux, F; Paint, Y; Hecq, M; Bittencourt, C

    2008-01-01

    Hybrid titania films have been prepared using an adapted sol-gel method for obtaining well-dispersed hydrogen plasma-treated multiwall carbon nanotubes in either pure titania or Nb-doped titania. The drop-coating method has been used to fabricate resistive oxygen sensors based on titania or on titania and carbon nanotube hybrids. Morphology and composition studies have revealed that the dispersion of low amounts of carbon nanotubes within the titania matrix does not significantly alter its crystallization behaviour. The gas sensitivity studies performed on the different samples have shown that the hybrid layers based on titania and carbon nanotubes possess an unprecedented responsiveness towards oxygen (i.e. more than four times higher than that shown by optimized Nb-doped TiO 2 films). Furthermore, hybrid sensors containing carbon nanotubes respond at significantly lower operating temperatures than their non-hybrid counterparts. These new hybrid sensors show a strong potential for monitoring traces of oxygen (i.e. ≤10 ppm) in a flow of CO 2 , which is of interest for the beverage industry

  4. Absence of confinement in (SrTiO3)/( SrTi0.8Nb0.2O3 ) superlattices

    Science.gov (United States)

    Bouzerar, G.; Thébaud, S.; Bouzerar, R.; Pailhès, S.; Adessi, Ch.

    2018-03-01

    The reduction of dimensionality is considered an efficient pathway to boost the performances of thermoelectric materials. Quantum confinement of the carriers is expected to induce large Seebeck coefficients (S ) and it also suppresses the thermal conductivity by increasing the phonon scattering processes. However, quantum confinement in superlattices is not always easy to achieve and needs to be carefully validated. In the past decade, large values of S have been measured in (SrTiO3)/(SrTi0.8Nb0.2O3 ) superlattices [H. Ohta et al., Nat. Mater. 6, 129 (2007), 10.1038/nmat1821; Y. Mune et al., Appl. Phys. Lett. 91, 192105 (2007), 10.1063/1.2809364]. In the δ -doped compound, the reported S was almost six times larger than that of the bulk material. This huge increase has been attributed to the two-dimensional carrier confinement in the doped regions. Here, we demonstrate that the experimental data are well explained quantitatively assuming delocalized electrons in both in-plane and growth directions. Moreover, we rule out the confined electron hypothesis whose signature would be the suppression of the Seebeck coefficient. This strongly suggests that the presupposed confinement picture in these superlattices is unlikely.

  5. CATALYTIC HYDROCRACKING OF WASTE LUBRICANT OIL INTO LIQUID FUEL FRACTION USING ZnO, Nb2O5, ACTIVATED NATURAL ZEOLITE AND THEIR MODIFICATION

    Directory of Open Access Journals (Sweden)

    Wega Trisunaryanti

    2010-06-01

    Full Text Available Catalytic hydrocracking of waste lubricant oil into liquid fuel fraction using ZnO, Nb2O5, activated natural zeolite (ZAAH and their modification has been investigated. The zeolite was produced in Wonosari, Yogyakarta. Activation of the zeolite was carried out by refluxing with HCl 3M for 30 min, produced the activated natural zeolite (ZAAH. The ZnO/ZAAH catalyst was prepared by impregnation of Zn onto the ZAAH by ion exchange method using salt precursor of Zn(NO32.4H2O. The Nb2O5/ZAAH catalyst was prepared by mixing the ZAAH sample with Nb2O5 and oxalic acid solution until the paste was formed. The impregnation of Zn onto Nb2O5/ZAAH was carried out using the same method to that of the ZnO/ZAAH catalyst resulted ZnO/Nb2O5-ZAAH catalyst. Characterization of catalyst includes determination of Zn metal by Atomic Absorption Spectroscopy (AAS, acidity by gravimetric method and catalyst porosity by Surface Area Analyzer (NOVA-1000. Catalytic hydrocracking was carried out in a semi-batch reactor system using ZnO, ZAAH, ZnO/ZAAH and ZnO/Nb2O5-ZAAH catalysts at 450 oC under the H2 flow rate of 15 mL/min. and the ratio of catalyst/feed = 1/5. The composition of liquid products was analyzed by Gas Chromatograpy (GC.The results showed that impregnation of ZnO and/or Nb2O5 on the ZAAH increased the acidity and specific surface area of catalyst. The products of the hydrocracking process were liquid, coke and gas. Conversion of liquid products was increased by the increase of catalyst acidity. The highest liquid product was produced by ZnO/Nb2O5-ZAAH catalyst, 52.97 wt-%, consist of gasoline, 38.87 wt-% and diesel, 14.10 wt-%.   Keywords: hydrocracking, waste lubricant oil, liquid fuel fraction

  6. Hexagonal perovskites with cationic vacancies. 21. Structure of Ba/sub 4/Nb/sub 2/WvacantO/sub 12/ and Ba/sub 3/LaNb/sub 3/vacantO/sub 12/

    Energy Technology Data Exchange (ETDEWEB)

    Rother, H J; Kemmler-Sack, S; Treiber, U; Cyris, W R [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

    1980-07-01

    Compounds of type Ba/sub 4/M/sub 2/sup(V)WvacantO/sub 12/ and Ba/sub 3/LaM/sub 3/sup(V)vacantO/sub 12/ with Msup(V) = Nb, Ta belong to the group of rhombohedral 12 L stacking polytypes (space group R-3m, sequence (hhcc)/sub 3/). The structure determinations on powder patterns for the Nb compounds gave a refined, intensity related R' value of 6.3% (Ba/sub 4/Nb/sub 2/WvacantO/sub 12/) and 6.6% (Ba/sub 3/LaNb/sub 3/vacantO/sub 12/). The octahedral net consists of blocks of three face connected octahedra with a central void (M/sub 2/vacantO/sub 12/ unit), which are linked to each other through single corner sharing octahedra. In both compounds the M atoms in the M/sub 2/vacantO/sub 12/ groups are displaced in the direction of the central void. The A atoms move in the same direction but the dislocation for A in the hexagonal packed sheets (neighbouring the vacancies) is stronger than in the cubic packed AO/sub 3/ sheets. The results of the vibrational spectroscopic investigations are reported for Ba/sub 4/Nb/sub 2/WvacantO/sub 12/, Ba/sub 4/Ta/sub 2/WvacantO/sub 12/, Ba/sub 3/LaNb/sub 3/vacantO/sub 12/ and Ba/sub 4/CeW/sub 2/vacantO/sub 12/; they are discussed in connection with the factor group analysis.

  7. Caracterização de filmes finos de Nb2O5 com propriedades eletrocrômicas Caracterization of OF Nb2O5 thin films with electrochromic properties

    Directory of Open Access Journals (Sweden)

    C. O. Avellaneda

    1998-06-01

    Full Text Available The sols for thin electrochromic coatings of Nb2O5 were obtained by synthesis of the niobium butoxide from BuONa and NbCl5. The ~300nm thick films were deposited by dip-coating technique from the alkoxide solution and calcined at 560ºC in O2 atmosphere during 3 hours. The particles size of niobium oxide (V powder (~20mm was obtained from x-ray diffraction using the Scherrer equation. The coatings were characterized by cyclic voltammetry and cronoamperommetry techniques. The spectral variation of the optical transmittance were determined in situ as a function of the cyclical potencial and memory effect. The insertion process of lithium is reversible and change the film color from transparent (T=80% to dark blue (T=20%.

  8. Electrochemical degradation of a real textile effluent using boron-doped diamond or β-PbO2 as anode

    International Nuclear Information System (INIS)

    Aquino, Jose M.; Pereira, Gabriel F.; Rocha-Filho, Romeu C.; Bocchi, Nerilso; Biaggio, Sonia R.

    2011-01-01

    Highlights: · Diamond anode enables total abatement of a real textile effluent COD with low energy consumption. · Use of diamond anode enables excellent decolorization rate of effluent in the presence of Cl - ions. · Diamond anode might be an excellent option for electrochemical treatment of real textile effluents. · PbO 2 anode, due to low cost and easiness of preparation, may be an option to decolorize the effluents. - Abstract: Constant current electrolyses are carried out in a filter-press reactor using a boron-doped diamond (Nb/BDD) or a Ti-Pt/β-PbO 2 anode, varying current density (j) and temperature. The degradation of the real textile effluent is followed by its decolorization and chemical oxygen demand (COD) abatement. The effect of adding NaCl (1.5 g L -1 ) on the degradation of the effluent is also investigated. The Nb/BDD anode yields much higher decolorization (attaining the DFZ limit) and COD-abatement rates than the Ti-Pt/β-PbO 2 anode, at any experimental condition. The best conditions are j = 5 mA cm -2 and 55 o C, for the system's optimized hydrodynamic conditions. The addition of chloride ions significantly increases the decolorization rate; thus a decrease of more than 90% of the effluent relative absorbance is attained using an applied electric charge per unit volume of the electrolyzed effluent (Q ap ) of only about 2 kA h m -3 . Practically total abatement of the effluent COD is attained with the Nb/BDD anode using a Q ap value of only 7 kA h m -3 , with an energy consumption of about 30 kW h m -3 . This result allows to conclude that the Nb/BDD electrode might be an excellent option for the remediation of textile effluents.

  9. The effects of Zn doping on magnetic properties of Cu3Bi(SeO3)2O2Cl

    Science.gov (United States)

    Yang, Pei-Ying; Tseng, Wu-Jyun; Wu, Hung-Cheng; Kakarla, D. Chandrasekhar; Yang, Hung-Duen; Department of Physics, Natl Sun Yat Sen Univ Team

    Recently, layered spin-frustrated Cu3Bi(SeO3)2 O2Cl has received considerable research attention due to its unusual magnetic properties. Two inequivalent Cu2 + ions form a pseudo-kagome lattice that invokes spin frustration and anisotropic magnetic properties. In this study, the influence of Zn doping on the complex magnetic properties has been explored. Polycrystalline (Cu1-xZnx) Bi(SeO3)2 O2Cl (0 x 0.5) samples were synthesized using solid-state reaction and characterized by X-ray diffraction and magnetic measurements. The Zn doping strongly modulates the magnetic ground state of the system. The antiferromagnetic transition temperature TN = 24 K and magnetic field-induced hysteresis observed for x = 0 at low field are systematically shifted to lower temperature and reduced with Zn doping. These results can illustrate the insight of the occurrence of field-induced spin-flip type multiferroics in Cu3Bi(SeO3)2 O2Cl.

  10. Conductivity in alkali doped CoO-B2O3 glasses

    International Nuclear Information System (INIS)

    Nagaraja, N; Sankarappa, T; Santoshkumar; Sadashivaiah, P J; Yenkayya

    2009-01-01

    Two series of cobalt-borate glasses doped with Li 2 O and K 2 O in single and mixed proportions have been synthesized by melt quenching method and investigated for ac conductivity in the frequency range of 50Hz to 5MHz and temperature range of 310K to 610K. From the measured total conductivity, the pure ac component and its frequency exponent, s were determined. In the single alkali doped glasses, for all the frequencies, the conductivity increased with increase of Li 2 O up to 0.4 mole fractions and decreased for further increase of Li 2 O. The temperature dependence of conductivity has been analyzed using Mott's small polaron hopping model and activation energy for ac conduction has been determined. Based on conductivity and activation behaviors, in single alkali glasses, a change over of conduction mechanism predominantly from ionic to electronic has been predicted. In mixed alkali doped glasses, the conductivity passed through minimum and activation energy passed through maximum for second alkali (K 2 O) content of 0.2 mole fractions. This result revealed the mixed alkali effect to be occurring at 0.2 mole fractions of K 2 O. The frequency exponent, s, was compared with theoretical models such as Quantum Mechanical Tunneling and Correlated Barrier Hopping models and found them to be inadequate to explain the experimental observations. Time-temperature superposition principle has been verified in both the sets of glasses.

  11. Temperature-dependent luminescence and temperature-stimulated NIR-to-VIS up-conversion in Nd3+-doped La2O3-Na2O-ZnO-TeO2 glasses

    Science.gov (United States)

    Sobczyk, Marcin

    2013-04-01

    Telluride glasses of the composition xNd2O3-(7-x)La2O3-3Na2O-25ZnO-65TeO2, where (0≤x≤7) were prepared by the melt quench technique. Some physical and optical properties of the glasses were evaluated. The thermal behavior i.e. glass transition and crystallization temperatures were studied by using TGA-DTA technique. Optical properties of Nd3+-doped telluride glasses were investigated between 298 and 700 K. Basing on the obtained values of J-O parameter values (×10-20 cm2: Ω2=4.49±0.84, Ω4=5.03±0.61, Ω6=4.31±0.73), the radiative transition probabilities (AT), radiative lifetimes (τR), fluorescence branching ratios (β) and emission cross-sections (σem) were calculated for the 4F3/2→4IJ/2 (where J=9, 11 and 13) transitions of Nd3+ ions. The τR value of the 4F3/2 level amount to 164 μs and is slightly higher than the measured decay time of 162 μs. With the increasing of Nd2O3 concentration from 0.5 to 7.0 mol% the experimental lifetime of the fluorescent level decreases from 162 to 5.6 μs. The estimated quantum efficiency amount to 100%, based on a comparison of τR and the experimental decay time of a slightly doped Nd3+ telluride glass. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The 4F3/2→4I9/2 and 4F5/2→4I9/2 transitions were analyzed with respect to the fluorescence intensity ratio (FIR) and were found to be temperature dependent. Infrared-to-visible up-conversion emissions with a maximum at 603.0 and 635.3 nm were observed at high temperatures using the 804 nm excitation and are due to the 4G5/2→4I9/2 and 4G5/2→4I11/2 transitions of Nd3+ ions, respectively. The near quadratic dependence of fluorescence on excitation laser power confirms that two photons contribute to up-conversion of the orange emissions. The temperature-stimulated up-conversion excitation processes have been analyzed in detail. The optical results indicate that the investigated glasses are potentially applicable as a 1063 nm

  12. Atomic defects and doping of monolayer NbSe2

    OpenAIRE

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J.P.; Lawlor, Sean; Sanchez, Ana M.; Sloan, Jeremy; Gorbachev, Roman; Grigorieva, Irina; Krasheninnikov, Arkady V.; Haigh, Sarah

    2017-01-01

    We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reve...

  13. Improvements of uniformity and stoichiometry for zone-leveling Czochralski growth of MgO-doped LiNbO3 crystals

    International Nuclear Information System (INIS)

    Tsai, C.B.; Hsu, W.T.; Shih, M.D.; Tai, C.Y.; Hsieh, C.K.; Hsu, W.C.; Hsu, R.T.; Lan, C.W.

    2006-01-01

    The zone-leveling Czochralski (ZLCz) technique is a continuous feeding process and can be used for the growth of near-stoichiometric lithium niobate (SLN) single crystals. However, the finite crucible length can cause the variation of the zone length and thus the composition and stoichiometry, especially in the growth of a large diameter crystal. To solve the problems, several approaches were proposed for the growth of 4 cm-diameter 1 mol% MgO-doped SLN. The modification of the hot zone to minimize the zone variation was found useful for the uniformity, but the stoichiometry was inadequate even with the zone composition up to 60 mol% Li 2 O. A Li-excess feed was further used and a good Li/Nb ratio was obtained. Adding K 2 O (16 mol%) into the solution zone was useful as well, but it was inferior to using the Li-excess feed. In addition, a much lower growth rate was needed for getting an inclusion-free crystal

  14. Structural characteristics of Mg-doped (1-x)(K0.5Na0.5)NbO3-xLiSbO3 lead-free ceramics as revealed by Raman spectroscopy

    International Nuclear Information System (INIS)

    Zhu, W L; Meng, Y; Pezzotti, G; Zhu, J L; Wang, M S; Zhu, B; Zhu, X H; Zhu, J G; Xiao, D Q

    2011-01-01

    This paper presents a Raman spectroscopic study of compositional-change-induced structure variation and of the related mechanism of Mg doping in LiSbO 3 (LS)-modified (K 0.5 Na 0.5 )NbO 3 (KNN) ceramics. With increasing LS content from 0 to 0.06, a discontinuous shift towards higher wavenumbers was found for the band position of the A 1g (v 1 ) stretching mode of KNN, accompanied by a clearly nonlinear broadening of this band and a decrease in its intensity. Such morphological changes in the Raman spectrum result from two factors: (i) changes in polarizability/binding strength of the O-Nb-O vibration upon incorporation of Li ions in the KNN perovskitic structure and (ii) a polymorphic phase transition (PPT) from orthorhombic to tetragonal (O → T) phase at x > 0.04. Upon increasing the amount, w, of Mg dopant incorporated into the (1-x)KNN-xLS ceramic structure, the intensity of the Raman bands are enhanced, while the peak position and the full width at half maximum of the A 1g (v 1 ) mode was found to experience a clear dependence on both w and x. Raman characterization revealed that the mechanism of Mg doping is strongly correlated with the concentration of Li in the perovskite structure: Mg 2+ ions will preferentially replace Li + ions for low Mg doping while replace K/Na ions for higher doping of Mg. The PPT O → T was also found to be altered by the introduction of Mg and the critical value of LS concentration, x O-T , for incipient O → T transition in the KNN-xLS-wMT system was strongly dependent on Mg content, with x O→T being roughly equal to 0.04 + 2w, for the case of dilute Mg alloying. (paper)

  15. Faraday rotation and photoluminescence in heavily Tb(3+)-doped GeO2-B2O3-Al2O3-Ga2O3 glasses for fiber-integrated magneto-optics.

    Science.gov (United States)

    Gao, Guojun; Winterstein-Beckmann, Anja; Surzhenko, Oleksii; Dubs, Carsten; Dellith, Jan; Schmidt, Markus A; Wondraczek, Lothar

    2015-03-10

    We report on the magneto-optical (MO) properties of heavily Tb(3+)-doped GeO2-B2O3-Al2O3-Ga2O3 glasses towards fiber-integrated paramagnetic MO devices. For a Tb(3+) ion concentration of up to 9.7 × 10(21) cm(-3), the reported glass exhibits an absolute negative Faraday rotation of ~120 rad/T/m at 632.8 nm. The optimum spectral ratio between Verdet constant and light transmittance over the spectral window of 400-1500 nm is found for a Tb(3+) concentration of ~6.5 × 10(21) cm(-3). For this glass, the crystallization stability, expressed as the difference between glass transition temperature and onset temperature of melt crystallization exceeds 100 K, which is a prerequisite for fiber drawing. In addition, a high activation energy of crystallization is achieved at this composition. Optical absorption occurs in the NUV and blue spectral region, accompanied by Tb(3+) photoluminescence. In the heavily doped materials, a UV/blue-to-green photo-conversion gain of ~43% is achieved. The lifetime of photoluminescence is ~2.2 ms at a stimulated emission cross-section σem of ~1.1 × 10(-21) cm(2) for ~ 5.0 × 10(21) cm(-3) Tb(3+). This results in an optical gain parameter σem*τ of ~2.5 × 10(-24) cm(2)s, what could be of interest for implementation of a Tb(3+) fiber laser.

  16. Faraday rotation and photoluminescence in heavily Tb3+-doped GeO2-B2O3-Al2O3-Ga2O3 glasses for fiber-integrated magneto-optics

    Science.gov (United States)

    Gao, Guojun; Winterstein-Beckmann, Anja; Surzhenko, Oleksii; Dubs, Carsten; Dellith, Jan; Schmidt, Markus A.; Wondraczek, Lothar

    2015-01-01

    We report on the magneto-optical (MO) properties of heavily Tb3+-doped GeO2-B2O3-Al2O3-Ga2O3 glasses towards fiber-integrated paramagnetic MO devices. For a Tb3+ ion concentration of up to 9.7 × 1021 cm−3, the reported glass exhibits an absolute negative Faraday rotation of ~120 rad/T/m at 632.8 nm. The optimum spectral ratio between Verdet constant and light transmittance over the spectral window of 400–1500 nm is found for a Tb3+ concentration of ~6.5 × 1021 cm−3. For this glass, the crystallization stability, expressed as the difference between glass transition temperature and onset temperature of melt crystallization exceeds 100 K, which is a prerequisite for fiber drawing. In addition, a high activation energy of crystallization is achieved at this composition. Optical absorption occurs in the NUV and blue spectral region, accompanied by Tb3+ photoluminescence. In the heavily doped materials, a UV/blue-to-green photo-conversion gain of ~43% is achieved. The lifetime of photoluminescence is ~2.2 ms at a stimulated emission cross-section σem of ~1.1 × 10−21 cm2 for ~ 5.0 × 1021 cm−3 Tb3+. This results in an optical gain parameter σem*τ of ~2.5 × 10−24 cm2s, what could be of interest for implementation of a Tb3+ fiber laser. PMID:25754819

  17. Textured and tungsten-bronze-niobate-doped (K,Na,Li)(Nb,Ta)O3 piezoceramic materials

    International Nuclear Information System (INIS)

    Soller, Thomas; Bathelt, Robert; Benkert, Katrin; Bodinger, Hermann; Schuh, Carsten; Schlenkrich, Falko

    2010-01-01

    In this study, the effects of an alkaline-earth niobate doping in tungsten-bronze (TB) stoichiometry on the piezoelectric properties and the phase transition temperatures of lead-free (K,Na,Li)(Nb,Ta)O 3 ceramics were investigated. In particular, the TB compounds barium niobate (BN), barium sodium niobate (BNN) and strontium calcium sodium niobate (SCNN) were investigated. The TB-modified ceramics show promising piezoelectric properties with large-signal piezo coefficients, d 33 * lose to 400 pm/V, planar coupling coefficients, k p , up to 0.45 and Curie temperatures of approximately 310 .deg. C. In addition, the effect of texturing on the undoped (K,Na,Li)(Nb,Ta)O 3 base composition via templated grain growth (TGG) with microcrystalline NaNbO 3 templates was examined. Lotgering factors up to 81% and strain enhancements by a factor 1.5 with large-signal values of d 33 * up to 550 pm/V could be achieved in the textured samples.

  18. Preparation of MnO2 electrodes coated by Sb-doped SnO2 and their effect on electrochemical performance for supercapacitor

    International Nuclear Information System (INIS)

    Zhang, Yuqing; Mo, Yan

    2014-01-01

    Highlights: • Sb-doped SnO 2 coated MnO 2 electrodes (SS-MnO 2 electrodes) are prepared. • The capacitive property and stability of SS-MnO 2 electrode is superior to uncoated MnO 2 electrode and SnO 2 coated MnO 2 electrode. • Sb-doped SnO 2 coating enhances electrochemical performance of MnO 2 effectively. • SS-MnO 2 electrodes are desirable to become a novel electrode material for supercapacitor. - Abstract: To enhance the specific capacity and cycling stability of manganese binoxide (MnO 2 ) for supercapacitor, antimony (Sb) doped tin dioxide (SnO 2 ) is coated on MnO 2 through a sol-gel method to prepare MnO 2 electrodes, enhancing the electrochemical performance of MnO 2 electrode in sodium sulfate electrolytes. The structure and composition of SS-MnO 2 electrode are characterized by using scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-Ray diffraction spectroscopy (XRD). The electrochemical performances are evaluated and researched by galvanostatic charge-discharge test, cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). The results show that SS-MnO 2 electrodes hold porous structure, displaying superior cycling stability at large current work condition in charge-discharge tests and good capacity performance at high scanning rate in CV tests. The results of EIS show that SS-MnO 2 electrodes have small internal resistance. Therefore, the electrochemical performances of MnO 2 electrodes are enhanced effectively by Sb-doped SnO 2 coating

  19. Electrical and optical properties of Si-doped Ga2O3

    Science.gov (United States)

    Li, Yin; Yang, Chuanghua; Wu, Liyuan; Zhang, Ru

    2017-05-01

    The charge densities, band structure, density of states, dielectric functions of Si-doped β-Ga2O3 have been investigated based on the density functional theory (DFT) within the hybrid functional HSE06. The heavy doping makes conduction band split out more bands and further influences the band structure. It decreases the band gap and changes from a direct gap to an indirect gap. After doping, the top of the valence bands is mainly composed by the O-2p states, Si-3p states and Ga-4p states and the bottom of the conduction bands is almost formed by the Si-3s, Si-3p and Ga-4s orbits. The anisotropic optical properties have been investigated by means of the complex dielectric function. After the heavy Si doping, the position of absorption band edges did not change much. The slope of the absorption curve descends and indicates that the absorption became more slow for Si-doped β-Ga2O3 than undoped one due to the indirect gap of Si-doped β-Ga2O3.

  20. Tuning electronic properties of In2O3 nanowires by doping control

    International Nuclear Information System (INIS)

    Lei, B.; Li, C.; Zhang, D.; Tang, D.; Zhou, C.

    2004-01-01

    We present two effective routes to tune the electronic properties of single-crystalline In 2 O 3 nanowires by controlling the doping. The first method involves using different O 2 concentrations during the synthesis. Lightly (heavily) doped nanowires were produced by using high (low) O 2 concentrations, respectively, as revealed by the conductances and threshold voltages of nanowire-based field-effect transistors. Our second method exploits post-synthesis baking, as baking heavily doped nanowires in ambient air led to suppressed conduction and a positive shift of the threshold voltage, whereas baking lightly doped nanowires in vacuum displayed the opposite behavior. Our approaches offer viable ways to tune the electronic properties of many nonstoichiometric metal oxide systems such as In 2 O 3 , SnO 2 , and ZnO nanowires for various applications

  1. Preparation of Mn doped CeO_2 nanoparticles with enhanced ferromagnetism

    International Nuclear Information System (INIS)

    Ravi, S.; Winfred Shashikanth, F.

    2017-01-01

    Spherical-like CeO_2 and Mn-doped CeO_2 using 6-aminohexanoic acid as surfactant exhibit enhanced ferromagnetism. The optical absorption spectra reveal a red shift with a band gap of 2.51 eV. The mechanics of ferromagnetism and the red shift were analyzed. These results provide a promising platform for developing a dilute magnetic semiconductor in spintronics. - Highlights: • Pure and Mn-doped CeO_2 is prepared with aminohexanoic acid as capping. • They exhibit wide optical absorption with red-shift in their band gap. • Mn-doped CeO_2 nanoparticle exhibit hysteresis at room temperature. • Results were promising to use in spintronics and opto-electronics field.

  2. Study of magnetic defects in Nb{sub 2}VSbO{sub 10}

    Energy Technology Data Exchange (ETDEWEB)

    Typek, J., E-mail: typjan@zut.edu.pl [Institute of Physics, West Pomeranian University of Technology, Szczecin, Al. Piastow 48, 70-311 Szczecin (Poland); Cyran, A.; Zolnierkiewicz, G.; Bobrowska, M. [Institute of Physics, West Pomeranian University of Technology, Szczecin, Al. Piastow 48, 70-311 Szczecin (Poland); Filipek, E.; Piz, M. [Department of Inorganic and Analytical Chemistry, West Pomeranian University of Technology, Szczecin, Al. Piastow 42, 71-065 Szczecin (Poland)

    2017-02-15

    Magnetic properties of Nb{sub 2}VSbO{sub 10}, the compound formed in V–Sb–Nb oxide system, were investigated by dc magnetisation measurements using an MPMS-7 SQUID magnetometer and EPR conventional X–band Bruker E 500 spectrometer. Although the nominal valences of the constituting metal ions indicated a diamagnetic material, Nb{sub 2}VSbO{sub 10} displayed rich and interesting magnetic behaviour due to the existence of numerous defects related to oxygen vacancies. Isothermal magnetisation has revealed the presence of three spin subsystems – two different paramagnetic systems and antiferromagnetic spin clusters. EPR spectra showed the presence of three components, involving isolated and interacting V{sup 4+} ions as well as antiferromagnetic spin clusters. All these magnetic defects are the result of valence changes of metal ions due to charge compensation in the neighborhood of oxygen vacancies, most probably located on grains boundaries.

  3. Photocatalytic degradation of malathion using Zn2+-doped TiO2 nanoparticles: statistical analysis and optimization of operating parameters

    Science.gov (United States)

    Nasseri, Simin; Omidvar Borna, Mohammad; Esrafili, Ali; Rezaei Kalantary, Roshanak; Kakavandi, Babak; Sillanpää, Mika; Asadi, Anvar

    2018-02-01

    A Zn2+-doped TiO2 is successfully synthesized by a facile photodeposition method and used in the catalytic photo-degradation of organophosphorus pesticide, malathion. The obtained photocatalysts are characterized in detail by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). XRD results confirm the formation of the anatase and rutile phases for the Zn2+-doped TiO2 nanoparticles, with crystallite sizes of 12.9 nm. Zn2+-doped TiO2 that was synthesized by 3.0%wt Zn doping at 200 °C exhibited the best photocatalytic activity. 60 sets of experiments were conducted using response surface methodology (RSM) by adjusting five operating parameters, i.e. initial malathion concentration, catalyst dose, pH, reaction time at five levels and presence or absence of UV light. The analysis revealed that all considered parameters are significant in the degradation process in their linear terms. The optimum values of the variables were found to be 177.59 mg/L, 0.99 g/L, 10.99 and 81.04 min for initial malathion concentration, catalyst dose, pH and reaction time, respectively, under UV irradiation (UV ON). Under the optimized conditions, the experimental values of degradation and mineralization were 98 and 74%, respectively. Moreover, the effects of competing anions and H2O2 on photocatalyst process were also investigated.

  4. Redox behavior of a low-doped Pr-CeO_2(111) surface. A DFT+U study

    International Nuclear Information System (INIS)

    Milberg, Brian; Juan, Alfredo; Irigoyen, Beatriz

    2017-01-01

    Highlights: • Pr doping facilitates oxygen donation due to the easy formation of Pr"3"+/Pr"4"+ and Ce"3"+/Ce"4"+ redox couples. • Pr doping also favors the formation of superoxide (O_2"−) radicals on surface O-holes. • CO can be oxidized by superoxide radical forming a CO_2 molecule floating on the surface. • CO can also interact on the (O_2"−)/Pr"3"+ interphase and forms weakly adsorbed carbonate-type intermediates. - Abstract: In this work, we investigated the redox behavior (donation and replenishing of oxygen) of a low praseodymium (Pr)-doped CeO_2(111) surface. We considered a 3.7 at.% Pr doping and performed density functional calculations using the GGA formalism with the ‘U’ correction on Ce(4f) and Pr(4f) orbitals. Our results indicate that Pr doping promotes oxygen donation by lowering the energy necessary to form surface anionic vacancies. When the Ce_0_._9_6_3Pr_0_._0_3_7O_2(111) surface donates one oxygen, the two excess electrons locate on Pr and Ce cations and reduce them to Pr"3"+ and Ce"3"+ ones. Praseodymium doping also favors the activation of O_2 molecule on surface O-holes, leading to formation of a superoxide (O_2"−) radical as well as to reoxidation of the Ce"3"+ cation to Ce"4"+ one. Additionally, we used the CO molecular adsorption for testing the reactivity of those superoxide species. The calculations expose the ability of these radicals to oxidize CO forming a CO_2 molecule floating on the surface. However, when the superoxide is in the immediate vicinity of Pr dopant a carbonate-type species is formed. Our theoretical results may help to gain insight into redox properties and improved catalytic performance of low-doped Pr-CeO_2 solids.

  5. Surface and catalytic properties of MoO3/Al2O3 system doped with Co3O4

    International Nuclear Information System (INIS)

    Zahran, A.A.; Shaheen, W.M.; El-Shobaky, G.A.

    2005-01-01

    Thermal solid-solid interactions in cobalt treated MoO 3 /Al 2 O 3 system were investigated using X-ray powder diffraction. The solids were prepared by wet impregnation method using Al(OH) 3 , ammonium molybdate and cobalt nitrate solutions, drying at 100 deg. C then calcination at 300, 500, 750 and 1000 deg. C. The amount of MoO 3 , was fixed at 16.67 mol% and those of cobalt oxide were varied between 2.04 and 14.29 mol% Co 3 O 4 . Surface and catalytic properties of various solid samples precalcined at 300 and 500 deg. C were studied using nitrogen adsorption at -196 deg. C, conversion of isopropanol at 200-500 deg. C and decomposition of H 2 O 2 at 30-50 deg. C. The results obtained revealed that pure mixed solids precalcined at 300 deg. C consisted of AlOOH and MoO 3 phases. Cobalt oxide-doped samples calcined at the same temperature consisted also of AlOOH, MoO 3 and CoMoO 4 compounds. The rise in calcination temperature to 500 deg. C resulted in complete conversion of AlOOH into very poorly crystalline γ-Al 2 O 3 . The further increase in precalcination temperature to 750 deg. C led to the formation of Al 2 (MoO 4 ) 3 , κ-Al 2 O 3 besides CoMoO 4 and un-reacted portion of Co 3 O 4 in the samples rich in cobalt oxide. Pure MoO 3 /Al 2 O 3 preheated at 1000 deg. C composed of MoO 3 -αAl 2 O 3 solid solution (acquired grey colour). The doped samples consisted of the same solid solution together with CoMoO 4 and CoAl 2 O 4 compounds. The increase in calcination temperature of pure and variously doped solids from 300 to 500 deg. C increased their specific surface areas and total pore volume which suffered a drastic decrease upon heating at 750 deg. C. Doping the investigated system with small amounts of cobalt oxide (2.04 and 4 mol%) followed by heating at 300 and 500 deg. C increased its catalytic activity in H 2 O 2 decomposition. This increase, measured at 300 deg. C, attained 25.4- and 12.9-fold for the solids precalcined at 300 and 500 deg. C, respectively

  6. Electrical and magnetic properties of Nb2O5-γ crystallographic shear structures

    DEFF Research Database (Denmark)

    Cava, R.J.; Batlogg, B.; Krajewski, J.J.

    1991-01-01

    The reduced niobium oxides Nb25O62, Nb47O116, Nb22O54, and Nb12O29 have been prepared in pure polycrystalline form by a niobium-metal gettering technique. They are related to the high niobia parent structure through the action of cystallographic shear to accommodate oxygen deficiency in Nb2O5-del...

  7. Record high-nuclearity polyoxoniobates. Discrete nanoclusters {Nb_1_1_4}, {Nb_8_1}, and {Nb_5_2}, and extended frameworks based on {Cu_3Nb_7_8} and {Cu_4Nb_7_8}

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Lu; Zhu, Zeng-Kui; Wu, Yan-Lan; Qi, Yan-Jie; Li, Xin-Xiong; Zheng, Shou-Tian [State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fujian (China)

    2017-12-18

    A series containing the highest nuclearity polyoxoniobate (PONb) nanoclusters, ranging from dimers to tetramers, has been obtained. They include one 114-nuclear {Li_8 is contained in Nb_1_1_4O_3_1_6}, one 81-nuclear {Li_3K is contained in Nb_8_1O_2_2_5}, and one 52-nuclear {H_4Nb_5_2O_1_5_0}. The Nb nuclearity of these PONbs is remarkably larger than those of all known high-nuclearity PONbs (≤32). Furthermore, the introduction of 3d Cu{sup 2+} ions can lead to the generation of extended inorganic-organic hybrid frameworks built from novel, high-nuclearity, nanoscale heterometallic PONb building blocks {H_3Cu_3Nb_7_8O_2_2_2} or {H_3Cu_4(en)Nb_7_8O_2_2_2}. These building blocks also contain the largest number of Nb centers of any heterometallic PONbs reported to date. The synthesis of new-type PONbs has long been a challenging subject in PONb chemistry. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Formulation and Characterization of Cr2O3 Doped ZnO Thick Films as H2S Gas Sensor

    Directory of Open Access Journals (Sweden)

    A. V. PATIL

    2009-09-01

    Full Text Available Cr2O3 doped ZnO thick films have been prepared by screen printing technique and firing process. These films were characterized by X-ray diffraction (XRD, Scanning electron microscopy (SEM, and EDX. H2S gas sensing properties of these films were investigated at different operating temperatures and different H2S concentrations. The 7 wt. % Cr2O3 doped ZnO thick films exhibits excellent H2S gas sensing properties with maximum sensitivity of 99.12 % at 300 oC in air atmosphere with fast response and recovery time.

  9. Structural, electrical, and optical properties of polycrystalline NbO{sub 2} thin films grown on glass substrates by solid phase crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), Kawasaki (Japan); Kamisaka, Hideyuki [Department of Chemistry, The University of Tokyo (Japan); Hirose, Yasushi; Hasegawa, Tetsuya [Kanagawa Academy of Science and Technology (KAST), Kawasaki (Japan); Department of Chemistry, The University of Tokyo (Japan)

    2017-03-15

    We investigated the structural, electrical, and optical properties of polycrystalline NbO{sub 2} thin films on glass substrates. The NbO{sub 2} films were crystallized from amorphous precursor films grown by pulsed laser deposition at various oxygen partial pressures (P{sub O2}). The electrical and optical properties of the precursor films systematically changed with P{sub O2}, demonstrating that the oxygen content of the precursor films can be finely controlled with P{sub O2}. The precursors were crystallized into polycrystalline NbO{sub 2} films by annealing under vacuum at 600 C. The NbO{sub 2} films possessed extremely flat surfaces with branching patterns. Even optimized films showed a low resistivity (ρ) of 2 x 10{sup 2} Ω cm, which is much lower than the bulk value of 1 x 10{sup 4} Ω cm, probably because of the inferior crystallinity of the films compared with that of a bulk NbO{sub 2} crystal. Both oxygen-rich and -poor NbO{sub 2} films showed lower ρ than that of the stoichiometric film. The NbO{sub 2} film with the highest ρ showed an indirect bandgap of 0.7 eV. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. High-rate capability of three-dimensionally ordered macroporous T-Nb2O5 through Li+ intercalation pseudocapacitance

    Science.gov (United States)

    Lou, Shuaifeng; Cheng, Xinqun; Wang, Long; Gao, Jinlong; Li, Qin; Ma, Yulin; Gao, Yunzhi; Zuo, Pengjian; Du, Chunyu; Yin, Geping

    2017-09-01

    Orthorhombic Niobium oxide (T-Nb2O5) has been regarded as a promising anode material for high-rate lithium ion batteries (LIBs) due to its potential to operate at high rates with improved safety and high theoretical capacity of 200 mA h g-1. Herein, three-dimensionally ordered macroporous (3DOM) T-Nb2O5, with mesoporous hierarchical structure, was firstly prepared by a simple approach employing self-assembly polystyrene (PS) microspheres as hard templates. The obtained T-Nb2O5 anode material presents obvious and highly-efficiency pseudocapacitive Li+ intercalation behaviour, which plays a dominant role in the kinetics of electrode process. As a result, rapid Li+ intercalation/de-intercalation are achieved, leading to excellent rate capability and long cycle life. The 3DOM T-Nb2O5 shows a remarkable high capacity of 106 and 77 mA h g-1 at the rate of 20C and 50C. The work presented herein holds great promise for future design of material structure, and demonstrates the great potential of T-Nb2O5 as a practical high-rate anode material for LIBs.

  11. Enhanced Visible Light Photocatalytic Activity of V2O5 Cluster Modified N-Doped TiO2 for Degradation of Toluene in Air

    Directory of Open Access Journals (Sweden)

    Fan Dong

    2012-01-01

    Full Text Available V2O5 cluster-modified N-doped TiO2 (N-TiO2/V2O5 nanocomposites photocatalyst was prepared by a facile impregnation-calcination method. The effects of V2O5 cluster loading content on visible light photocatalytic activity of the as-prepared samples were investigated for degradation of toluene in air. The results showed that the visible light activity of N-doped TiO2 was significantly enhanced by loading V2O5 clusters. The optimal V2O5 loading content was found to be 0.5 wt.%, reaching a removal ratio of 52.4% and a rate constant of 0.027 min−1, far exceeding that of unmodified N-doped TiO2. The enhanced activity is due to the deposition of V2O5 clusters on the surface of N-doped TiO2. The conduction band (CB potential of V2O5 (0.48 eV is lower than the CB level of N-doped TiO2 (−0.19 V, which favors the photogenerated electron transfer from CB of N-doped TiO2 to V2O5 clusters. This function of V2O5 clusters helps promote the transfer and separation of photogenerated electrons and holes. The present work not only displays a feasible route for the utilization of low cost V2O5 clusters as a substitute for noble metals in enhancing the photocatalysis but also demonstrates a facile method for preparation of highly active composite photocatalyst for large-scale applications.

  12. Ab initio study of thermoelectric properties of doped SnO{sub 2} superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Borges, P.D., E-mail: pdborges@gmail.com [Instituto de Ciências Exatas e Tecnológicas, Universidade Federal de Viçosa, 38810-000 Rio Paranaíba, MG (Brazil); Silva, D.E.S.; Castro, N.S.; Ferreira, C.R.; Pinto, F.G.; Tronto, J. [Instituto de Ciências Exatas e Tecnológicas, Universidade Federal de Viçosa, 38810-000 Rio Paranaíba, MG (Brazil); Scolfaro, L. [Department of Physics, Texas State University, 78666 San Marcos, TX (United States)

    2015-11-15

    Transparent conductive oxides, such as tin dioxide (SnO{sub 2}), have recently shown to be promising materials for thermoelectric applications. In this work we studied the thermoelectric properties of Fe-, Sb- and Zn-uniformly doping and co-doping SnO{sub 2}, as well as of Sb and Zn planar (or delta)-doped layers in SnO{sub 2} forming oxide superlattices (SLs). Based on the semiclassical Boltzmann transport equations (BTE) in conjunction with ab initio electronic structure calculations, the Seebeck coefficient (S) and figure of merit (ZT) are obtained for these systems, and are compared with available experimental data. The delta doping approach introduces a remarkable modification in the electronic structure of tin dioxide, when compared with the uniform doping, and colossal values for ZT are predicted for the delta-doped oxide SLs. This result is a consequence of the two-dimensional electronic confinement and the strong anisotropy introduced by the doped planes. In comparison with the uniformly doped systems, our predictions reveal a promising use of delta-doped SnO{sub 2} SLs for enhanced S and ZT, which emerge as potential candidates for thermoelectric applications. - Graphical abstract: Band structure and Figure of merit for SnO2:Sb superlattice along Z direction, P. D. Borges, D. E. S. Silva, N. S. Castro, C. R. Ferreira, F. G. Pinto, J. Tronto and L. Scolfaro, Ab initio study of thermoelectric properties of doped SnO2 superlattices. - Highlights: • Thermoelectric properties of SnO{sub 2}-based alloys and superlattices. • High figure of merit is predicted for planar-doped SnO{sub 2} superlattices. • Nanotechnology has an important role for the development of thermoelectric devices.

  13. Microstructural evolution and tensile behavior of Ti{sub 2}AlNb alloys based α{sub 2}-phase decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei, E-mail: gackmol@163.com [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Zeng, Weidong, E-mail: zengwd@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Dong; Zhu, Bin; Zheng, Youping [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Liang, Xiaobo [Beijing Iron & Steel Research Institute, Beijing 100081 (China)

    2016-04-26

    The formation mechanism of the fine plate-like O-phases within α{sub 2}-phases and tensile behavior of an isothermally forged Ti–22Al–25Nb (at%) orthorhombic alloy at 1040 °C during heat treatment were investigated. The investigation indicated that the alloys were heat-treated in O+B2 phase region after α{sub 2}+B2 phase region isothermally forging, the equiaxed α{sub 2}-phase was not stable and decomposed into O+α{sub 2} phases. The α{sub 2} phases formed during isothermal forging process have higher concentration of Nb and begun to decompose during O+B2 phase region heat treatment. And then the α{sub 2} phases separated into Niobium-lean and Niobium-rich regions through the Niobium diffusion: α{sub 2}→α{sub 2} (Nb-lean)+O (Nb-rich). Nb-rich regions with composition similar to Ti{sub 2}AlNb transformed to the O-phase, while the Nb-lean regions remained untransformed and retained the α{sub 2}-phase. The deformation behavior and fracture mechanism of Ti–22Al–25Nb alloy at room temperature were discussed. The deformation behavior and microstructural evolution of this alloy at different temperatures and stain rates were also investigated using uniaxial tensile test.

  14. Effect of Indium Doping on the Sensitivity of SnO2 Gas Sensor

    International Nuclear Information System (INIS)

    Suharni; Sayono

    2009-01-01

    The dependence of sensitivity f SnO 2 gas sensors on indium concentration has been studied. Undoped and indium-doped SnO 2 gas sensors have been prepared by DC sputtering technique with following parameters i.e : electrode voltage of 3 kV, current 20 mA, vacuum pressure 1.8 × 10 -1 torr, deposition time 60 minutes and temperature of 200℃. The effect of weight variations of indium in order of 0.0370; 0.0485 and 0.0702 grams into SnO 2 thin film gas sensor for optimum result were investigated. The measurement of resistance, sensitivity and response time for various temperature for detecting of carbon monoxide (CO), Ammonia (NH 3 ) and acetone (CH 3 COCH 3 ) gas for indium doped has been done. From the analysis result shows that for indium doped 0.0702 g on the SnO 2 the resistance can be decreased from 832.0 kΩ to 3.9 kΩ and the operating temperature from 200℃ to 90℃ and improving the sensitivity from 15.92% to 40.09% and a response time from 30 seconds to 10 seconds for CO. (author)

  15. Hydrothermal synthesis of Fe-doped TiO2 nanostructure photocatalyst

    International Nuclear Information System (INIS)

    Nguyen, Van Nghia; Nguyen, Ngoc Khoa Truong; Nguyen, Phi Hung

    2011-01-01

    Fe-doped TiO 2 catalyst was prepared by the hydrothermal method. The resulting nanopowders were characterized by x-ray diffraction, transmission electron microscopy and Raman and UV-visible spectroscopies. The photocatalytic activity of the Fe-doped TiO 2 was tested by decomposition of methylene orange with a concentration of 10 mg l −1 in aqueous solution. The obtained results showed that methylene orange was significantly degraded after irradiation for 90 min under a halogen lamp and sunlight. The doping effect on the photocatalytic activity of the iron-doped catalyst samples are discussed

  16. Structure, nonstoichiometry, sintering and oxygen permeability of perovskite SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jin Na [College of Chemistry and Materials Science, Liaoning University of Petroleum and Chemical Technology, Fushun 113001 (China); State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Lu, Hui, E-mail: huilu@dicp.ac.cn [Greenhouse Gas Research Center, Climate Change Technology Research Division, Korea Institute of Energy Research, Daejeon 305-343 (Korea, Republic of); State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Gui, Jian Zhou [College of Chemistry and Materials Science, Liaoning University of Petroleum and Chemical Technology, Fushun 113001 (China); Kim, Jong Pyo; Son, Sou Hwan [Greenhouse Gas Research Center, Climate Change Technology Research Division, Korea Institute of Energy Research, Daejeon 305-343 (Korea, Republic of); Park, Jung Hoon, E-mail: pjhoon@kier.re.kr [Greenhouse Gas Research Center, Climate Change Technology Research Division, Korea Institute of Energy Research, Daejeon 305-343 (Korea, Republic of)

    2013-04-20

    Highlights: ► The novel Fe/Nb co-substituted SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides were characterized by the XRD, DSC, TG and SEM–EDS. ► The high structural stability of the co-substituted SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides. ► The excellent oxygen permeation performance of the co-substituted SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.10) membrane. -- Abstract: The novel Fe/Nb co-substituted SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides have been synthesized and characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG), and scanning electron microscopy (SEM). The XRD and DSC results demonstrate that the structural stability of the Fe/Nb co-substituted samples x = 0.05, 0.10 is improved greatly compared to the sample x = 0.00. The Fe/Nb co-doping in the SrCoO{sub 3−δ} oxide results in the improved structural stability of the SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides. The nonstoichiometric and sintering properties were investigated by TG and SEM, and the oxygen permeation fluxes were measured at 800–950 °C for the sample x = 0.10. The improved oxygen permeability of the ceramic SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.10) membrane compared to the (Ba{sub 0.5}Sr{sub 0.5})(Co{sub 0.8}Fe{sub 0.2})O{sub 3−δ} and SrCo{sub 0.8}Fe{sub 0.2}O{sub 3–δ} membranes, was observed under an air/He oxygen partial pressure gradient at 800–950 °C.

  17. Effect of oxygen vacancy and dopant concentration on the magnetic properties of high spin Co2+ doped TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Choudhury, B.; Choudhury, A.; Maidul Islam, A.K.M.; Alagarsamy, P.; Mukherjee, M.

    2011-01-01

    Co doped TiO 2 nanoparticles have been synthesized by a simple sol-gel route taking 7.5, 9.5 and 10.5 mol% of cobalt concentration. Formation of nanoparticles is confirmed by XRD and TEM. Increase in d-spacing occurs for (0 0 4) and (2 0 0) peak with increase in impurity content. Valence states of Co and its presence in the doped material is confirmed by XPS and EDX. The entire vacuum annealed samples show weak ferromagnetism. Increased magnetization is found for 9.5 mol% but this value again decreases for 10.5 mol% due to antiferromagnetic interactions. A blocking temperature of 37.9 K is obtained, which shows shifting to high temperature as the dopant concentration is increased. The air annealed sample shows only paramagnetic behavior. Temperature dependent magnetic measurements for the air annealed sample shows antiferromagnetic behavior with a Curie-Weiss temperature of -16 K. Here we report that oxygen vacancy and cobalt aggregates are a key factor for inducing ferromagnetism-superparamagnetism in the vacuum annealed sample. Appearance of negative Curie-Weiss temperature reveals the presence of antiferromagnetic Co 3 O 4 , which is the oxidation result of metallic Co or cobalt clusters present on the host TiO 2 . - Research highlights: → Oxygen vacancy induces ferromagnetism in cobalt doped anatase TiO2 nanoparticles. → On air annealing the sample loses ferromagnetism giving rise to paramagnetism. → Saturation magnetization decreases at higher doping concentration. → Blocking of magnetic moment occurs due to the presence of cobalt clusters.

  18. Design of high quality doped CeO2 solid electrolytes with nanohetero structure

    International Nuclear Information System (INIS)

    Mori, T.; Ou, D.R.; Ye, F.; Drennan, J.

    2006-01-01

    Doped cerium (CeO 2 ) compounds are fluorite related oxides which show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, a considerable interest has been shown in application of these materials for low (400-650 o C) temperature operation of solid oxide fuel cells (SOFCs). In this paper, our experimental data about the influence of microstructure at the atomic level on electrochemical properties were reviewed in order to develop high quality doped CeO 2 electrolytes in fuel cell applications. Using this data in the present paper, our original idea for a design of nanodomain structure in doped CeO 2 electrolytes was suggested. The nanosized powders and dense sintered bodies of M doped CeO 2 (M:Sm,Gd,La,Y,Yb, and Dy) compounds were fabricated. Also nanostructural features in these specimens were introduced for conclusion of relationship between electrolytic properties and domain structure in doped CeO 2 . It is essential that the electrolytic properties in doped CeO 2 solid electrolytes reflect in changes of microstructure even down to the atomic scale. Accordingly, a combined approach of nanostructure fabrication, electrical measurement and structure characterization was required to develop superior quality doped CeO 2 electrolytes in the fuel cells. (author)

  19. Synthesis, structural and paramagnetic properties of SnO{sub 2} doped NiO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Islam, I., E-mail: ishtihadahislam@gmail.com; Dwivedi, Sonam; Dar, Hilal A.; Dar, M. A.; Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India)

    2016-05-06

    In this work, Sn doped NiO nanoparticles were synthesized by co-precipitation route to explore the impact of doping on lattice structure, dielectric constant and magnetization. X-ray diffraction analysis confirmed cubic (Fd-3m) structure of Sn doped NiO. Average crystallite size decreases from 78.2 nm (Ni{sub 0.95}Sn{sub 0.05}O) to 64.23 nm (Ni{sub 0.8}Sn{sub 0.2}O). Scanning electron microscopy images confirm that nanocrystals have agglomerated spherical morphology. The Raman spectrum exhibits a strong, broad peak at 410 cm{sup -1} and is attributed to the Ni-O stretching mode and doped samples show a blue shift. The dielectric constants at about 1 Hz are measured to be about 1.795, 1.030, 0.442, and 0.302 × 10{sup 3} Ni{sub 1-x}Sn{sub x}O (x = 0.05, 0.1, 0.15, 0.2), respectively. The dielectric constant in nanoparticles of doped Ni{sub 1-x}Sn{sub x}O is three orders of magnitude higher as compared to pure NiO ceramics. The nature of magnetization - applied field (M-H) infers paramagnetic behaviour for Sn doped NiO nanoparticles.

  20. Bioactivity and structural properties of nanostructured bulk composites containing Nb2O5 and natural hydroxyapatite

    Science.gov (United States)

    Bonadio, T. G. M.; Sato, F.; Medina, A. N.; Weinand, W. R.; Baesso, M. L.; Lima, W. M.

    2013-06-01

    In this work, we investigate the bioactivity and structural properties of nanostructured bulk composites that are composed of Nb2O5 and natural hydroxyapatite (HAp) and are produced by mechanical alloying and powder metallurgy. X-ray diffraction and Raman spectroscopy data showed that the milling process followed by a heat treatment at 1000 °C induced chemical reactions along with the formation of the CaNb2O6, PNb9O25 and Ca3(PO4)2 phases. Rietveld refinement indicated significant changes in each phase weight fraction as a function of HAp concentration. These changes influenced the in vitro bioactivity of the material. XRD and FTIR analyses indicated that the composites exhibited bioactivity characteristics by forming a carbonated apatite layer when the composites were immersed in a simulated body fluid. The formed layers had a maximum thickness of 13 μm, as measured by confocal Raman spectroscopy and as confirmed by scanning electron microscopy. The results of this work suggest that the tested bulk composites are promising biomaterials for use in implants.