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Sample records for la-doped stannate basno3

  1. High-temperature thermoelectric properties of La-doped BaSnO3 ceramics

    International Nuclear Information System (INIS)

    Yasukawa, Masahiro; Kono, Toshio; Ueda, Kazushige; Yanagi, Hiroshi; Hosono, Hideo

    2010-01-01

    To elucidate the thermoelectric properties at high temperatures, perovskite-type La-doped BaSnO 3 ceramics were fabricated by a polymerized complex (PC) method and subsequent spark plasma sintering (SPS) technique. Fine powders of Ba 1-x La x SnO 3 (x = 0.00-0.07) were prepared by the PC method using citrate complexes, and SPS treatment converted the powders into dense ceramics with relative densities of 93-97%. The La content dependence of the lattice parameter suggested that the solubility of La for Ba sites was approximately x = 0.03. The temperature dependence of the electrical conductivity σ and Seebeck coefficient S showed that each La-doped ceramic was an n-type degenerate semiconductor in the measured temperature range of 373-1073 K. The La content dependence of the S values indicated that the electron carrier concentration increased successively up to x = 0.03, which was the solubility limit of the La atoms. The thermoelectric power factors S 2 σ increased drastically with La doping, and reached a maximum for x = 0.01 with values of 0.8 x 10 -4 W m -1 K -2 at 373 K to 2.8 x 10 -4 W m -1 K -2 at 1073 K.

  2. Adsorption-controlled growth of La-doped BaSnO3 by molecular-beam epitaxy

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    Hanjong Paik

    2017-11-01

    Full Text Available Epitaxial La-doped BaSnO3 films were grown in an adsorption-controlled regime by molecular-beam epitaxy, where the excess volatile SnOx desorbs from the film surface. A film grown on a (001 DyScO3 substrate exhibited a mobility of 183 cm2 V−1 s−1 at room temperature and 400 cm2 V−1 s−1 at 10 K despite the high concentration (1.2 × 1011 cm−2 of threading dislocations present. In comparison to other reports, we observe a much lower concentration of (BaO2 Ruddlesden-Popper crystallographic shear faults. This suggests that in addition to threading dislocations, other defects—possibly (BaO2 crystallographic shear defects or point defects—significantly reduce the electron mobility.

  3. THz characterization and demonstration of visible-transparent/terahertz-functional electromagnetic structures in ultra-conductive La-doped BaSnO3 Films.

    Science.gov (United States)

    Arezoomandan, Sara; Prakash, Abhinav; Chanana, Ashish; Yue, Jin; Mao, Jieying; Blair, Steve; Nahata, Ajay; Jalan, Bharat; Sensale-Rodriguez, Berardi

    2018-02-23

    We report on terahertz characterization of La-doped BaSnO 3 (BSO) thin-films. BSO is a transparent complex oxide material, which has attracted substantial interest due to its large electrical conductivity and wide bandgap. The complex refractive index of these films is extracted in the 0.3 to 1.5 THz frequency range, which shows a metal-like response across this broad frequency window. The large optical conductivity found in these films at terahertz wavelengths makes this material an interesting platform for developing electromagnetic structures having a strong response at terahertz wavelengths, i.e. terahertz-functional, while being transparent at visible and near-IR wavelengths. As an example of such application, we demonstrate a visible-transparent terahertz polarizer.

  4. High temperature impedance spectroscopy of barium stannate ...

    Indian Academy of Sciences (India)

    (M = Ba, Sr, Ca and Pb). ... Barium stannate (BaSnO3) is a cubic pervoskite oxide com- .... were gold-sputtered and scanned in different regions using .... de ions. Water insertion into the oxide structure can be re- presented as the process of ...

  5. Dopant-site-dependent scattering by dislocations in epitaxial films of perovskite semiconductor BaSnO3

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    Useong Kim

    2014-05-01

    Full Text Available We studied the conduction mechanism in Sb-doped BaSnO3 epitaxial films, and compared its behavior with that of the mechanism of its counterpart, La-doped BaSnO3. We found that the electron mobility in BaSnO3 films was reduced by almost 7 times when the dopant was changed from La to Sb, despite little change in the effective mass of the carriers. This indicates that the scattering rate of conduction electrons in the BaSnO3 system is strongly affected by the site at which the dopants are located. More importantly, we found that electron scattering by threading dislocations also depends critically on the dopant site. We propose that the large enhancement of scattering by the threading dislocations in Sb-doped BaSnO3 films is caused by the combination effect of the change in the distribution of Sb impurities in the films, the formation of the Sb impurity clusters near the threading dislocations, and the conduction electron clustering near the Sb impurities.

  6. Hybrid functional calculation of electronic and phonon structure of BaSnO3

    International Nuclear Information System (INIS)

    Kim, Bog G.; Jo, J.Y.; Cheong, S.W.

    2013-01-01

    Barium stannate, BaSnO 3 (BSO), with a cubic perovskite structure, has been highlighted as a promising host material for the next generation transparent oxide electrodes. This study examined theoretically the electronic structure and phonon structure of BSO using hybrid density functional theory based on the HSE06 functional. The electronic structure results of BSO were corrected by extending the phonon calculations based on the hybrid density functional. The fundamental thermal properties were also predicted based on a hybrid functional calculation. Overall, a detailed understanding of the electronic structure, phonon modes and phonon dispersion of BSO will provide a theoretical starting-point for engineering applications of this material. - Graphical Abstract: (a) Crystal structure of BaSnO 3 . The center ball is Ba and small (red) ball on edge is oxygen and SnO 6 octahedrons are plotted as polyhedron. (b) Electronic band structure along the high symmetry point in the Brillouin zone using the HSE06 hybrid functional. (c) The phonon dispersion curve calculated using the HSE06 hybrid functional (d) Zone center lowest energy F 1u phonon mode. Highlights: ► We report the full hybrid functional calculation of not only the electronic structure but also the phonon structure for BaSnO 3 . ► The band gap calculation of HSE06 revealed an indirect gap with 2.48 eV. ► The effective mass at the conduction band minimum and valence band maximum was calculated. ► In addition, the phonon structure of BSO was calculated using the HSE06 functional. ► Finally, the heat capacity was calculated and compared with the recent experimental result.

  7. Atomic mapping of Ruddlesden-Popper faults in transparent conducting BaSnO3-based thin films.

    Science.gov (United States)

    Wang, W Y; Tang, Y L; Zhu, Y L; Suriyaprakash, J; Xu, Y B; Liu, Y; Gao, B; Cheong, S-W; Ma, X L

    2015-11-03

    Doped BaSnO3 has arisen many interests recently as one of the promising transparent conducting oxides for future applications. Understanding the microstructural characteristics are crucial for the exploration of relevant devices. In this paper, we investigated the microstructural features of 0.001% La doped BaSnO3 thin film using both conventional and aberration corrected transmission electron microscopes. Contrast analysis shows high densities of Ruddlesden-Popper faults in the film, which are on {100} planes with translational displacements of 1/2a  . Atomic EELS element mappings reveal that the Ruddlesden-Popper faults are Ba-O layer terminated, and two kinds of kink structures at the Ruddlesden-Popper faults with different element distributions are also demonstrated. Quantitative analysis on lattice distortions of the Ruddlesden-Popper faults illustrates that the local lattice spacing poses a huge increment of 36%, indicating that large strains exist around the Ruddlesden-Popper faults in the film.

  8. All-perovskite transparent high mobility field effect using epitaxial BaSnO3 and LaInO3

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    Useong Kim

    2015-03-01

    Full Text Available We demonstrate an all-perovskite transparent heterojunction field effect transistor made of two lattice-matched perovskite oxides: BaSnO3 and LaInO3. We have developed epitaxial LaInO3 as the gate oxide on top of BaSnO3, which were recently reported to possess high thermal stability and electron mobility when doped with La. We measured the dielectric properties of the epitaxial LaInO3 films, such as the band gap, dielectric constant, and the dielectric breakdown field. Using the LaInO3 as a gate dielectric and the La-doped BaSnO3 as a channel layer, we fabricated field effect device structure. The field effect mobility of such device was higher than 90 cm2 V−1 s−1, the on/off ratio was larger than 107, and the subthreshold swing was 0.65 V dec−1. We discuss the possible origins for such device performance and the future directions for further improvement.

  9. pn junctions based on a single transparent perovskite semiconductor BaSnO3

    Science.gov (United States)

    Kim, Hoon Min; Kim, Useong; Park, Chulkwon; Kwon, Hyukwoo; Lee, Woongjae; Kim, Tai Hoon; Kim, Kee Hoon; Char, Kookrin; Mdpl, Department Of Physics; Astronomy Team; Censcmr, Department Of Physics; Astronomy Team

    2014-03-01

    Successful p doping of transparent oxide semiconductor will further increase its potential, especially in the area of optoelectronic applications. We will report our efforts to dope the BaSnO3 (BSO) with K by pulsed laser deposition. Although the K doped BSO exhibits rather high resistivity at room temperature, its conductivity increases dramatically at higher temperatures. Furthermore, the conductivity decreases when a small amount of oxygen was removed from the film, consistent with the behavior of p type doped oxides. We have fabricated pn junctions by using K doped BSO as a p type and La doped BSO as an n type material. I_V characteristics of these devices show the typical rectifying behavior of pn junctions. We will present the analysis of the junction properties from the temperature dependent measurement of their electrical properties, which shows that the I_V characteristics are consistent with the material parameters such as the carrier concentration, the mobility, and the bandgap. Our demonstration of pn junctions based on a single transparent perovskite semiconductor further enhances the potential of BSO system with high mobility and stability.

  10. Origins of n -type doping difficulties in perovskite stannates

    Science.gov (United States)

    Weston, L.; Bjaalie, L.; Krishnaswamy, K.; Van de Walle, C. G.

    2018-02-01

    The perovskite stannates (A SnO3 ; A = Ba, Sr, Ca) are promising for oxide electronics, but control of n -type doping has proved challenging. Using first-principles hybrid density functional calculations, we investigate La dopants and explore the formation of compensating acceptor defects. We find that La on the A site always behaves as a shallow donor, but incorporation of La on the Sn site can lead to self-compensation. At low La concentrations and in O-poor conditions, oxygen vacancies form in BaSnO3. A -site cation vacancies are found to be dominant among the native compensating centers. Compared to BaSnO3, charge compensation is a larger problem for the wider-band-gap stannates, SrSnO3 and CaSnO3, a trend we can explain based on conduction-band alignments. The formation of compensating acceptor defects can be inhibited by choosing oxygen-poor (cation-rich) growth or annealing conditions, thus providing a pathway for improved n -type doping.

  11. Structural properties, electric response and electronic feature of BaSnO3 perovskite

    International Nuclear Information System (INIS)

    Cuervo Farfan, J.; Arbey Rodriguez, J.; Fajardo, F.; Vera Lopez, E.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2009-01-01

    It has been observed that the semiconducting compound SnO 2 presents very good results as gas sensor. One important development has been performed to study perovskite oxides for this relevant application. One oxide material which constitutes an excellent candidate for this technological application is BaSnO 3 . Polycrystalline samples with single phase of BaSnO 3 were synthesized by using the solid state reaction method. Samples were characterized structurally by means of X-ray diffraction (XRD) technique. Rietveld refinement, by using the GSAS code, reveals that this material synthesizes in a cubic perovskite, space group Pm3m (no. 221), with lattice parameter 4.1190(3)A. Electric response was examined through the impedance spectroscopy technique. Results of Bode diagram, from an equivalent circuit, evidence the semiconductor character of material. We carried out a theoretical study by means of the calculation of the bands diagram and the density of states of the BaSnO 3 . Calculation was performed by employing the density functional theory (DFT), with the generalized gradient approach (GGA). DFT theory permitted to establish that BaSnO 3 material has an indirect semiconducting behavior. The calculated gap for this perovskite-like stagnate is at least 0.4 eV. Bulk modulus for material was also determined to be 132 GPa.

  12. Properties of second phase (BaSnO3, Sn) added-YBCO thick films

    International Nuclear Information System (INIS)

    Ban, E.; Matsuoka, Y.

    1997-01-01

    The improvement of the critical current density J c of YBCO thick films has been attempted by adding BaSnO 3 powder and ultrafine Sn particles, whose diameter is about 2 μm and 7 x 10 -2 μm, respectively. It was found that the addition of a small amount of these particles was effective for the enhancement of J c of thick films prepared by a liquid-phase processing method. The 1 wt.% BaSnO 3 films fired at T s =1040-1060 C and the 3 wt.% Sn films (T s =1030-1060 C) showed J c values (77 K, 0 T) of about 2.1-2.4 x 10 3 Acm -2 and 3.1-3.5 x 10 3 Acm -2 , respectively, as compared to 2.0 x 10 3 Acm -2 for the undoped films. (orig.)

  13. Influence of adding BaSnO3 nanoparticles on magnetic transport properties for CuTl-1223 phase

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    M.ME. Barakat

    Full Text Available Co-precipitation method and solid-state reaction technique were used to synthesize BaSnO3 nanoparticles and (BaSnO3x/Cu0.5Tl0.5Ba2Ca2Cu3O10−δ samples, 0.00 ≤ x ≤ 1.50 wt%, respectively. All samples were characterized using X-ray powder diffraction (XRD and electrical resistivity measurements at different applied DC magnetic fields ranged from 0.29 to 4.40 kG. The relative volume fraction, superconducting transition temperature, Tc, and hole carriers concentration, P, were enhanced by increasing x up to 0.25 wt%, beyond which they were decreased for further increase in the addition of BaSnO3 nanoparticles. Both thermally activated flux creep (TAFC model and Ambegaokar and Halperin (AH theory were used to analyze the magnetoresistance data for (BaSnO3x/CuTl-1223 samples. An enhancement in the derived magnetic superconducting parameters, including the flux pinning energy, U, critical current density, Jc(0, and upper critical magnetic field, Bc2(0, as well as a decrement in the coherence length at 0 K, ξ(0, was achieved by adding BaSnO3 nanoparticles up to 0.25 wt%. A reverse trend was recorded for further addition of BaSnO3 nanoparticles. The electronic thermal conductivity, κe, was decreased by increasing applied magnetic fields below Tc. Keywords: CuTl-1223 phase, BaSnO3 nanoparticles, Flux pinning energy, Critical current density

  14. Structural and dielectric studies of Ce doped BaSnO3 perovskite nanostructures

    Science.gov (United States)

    Angel, S. Lilly; Deepa, K.; Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

    2018-04-01

    Undoped and Cerium (Ce) doped BaSnO3(BSO) nanostructures were synthesized by co-precipitation method. The cubic structure and perovskite phase were confirmed by X-ray diffraction (XRD). The crystallite size of BSO is 41nm and when Ce ion concentration is increased, the crystallite sizesdecreased. The nanocube, nanocuboids and nanorods are observed from SEM analysis. The purity of the undoped and doped samples are confirmed by EDS spectrum. For larger defects, wide band gap was obtained from UV-Vis and PL spectrum. The dielectric constants are increased at low frequencies when Ce impurities are introduced in the BSO matrix at Sn site.

  15. Structural Properties of Barium Stannate.

    Energy Technology Data Exchange (ETDEWEB)

    Phelan, D.; Han, F.; Lopez-Bezanilla, A.; Krogstad, M. J.; Gim, Y.; Rong, Y.; Zhang, J.; Parshall, D.; Zheng, H.; Cooper, S. L.; Feygenson, M.; Yang, Wenge; Chen, Yu-Sheng

    2018-06-01

    BaSnO3 has attracted attention as a transparent conducting oxide with high room temperature carrier mobility. We report a series of measurements that were carried out to assess the structure of BaSnO3 over a variety of length scales. Measurements included single crystal neutron and x-ray diffraction, Rietveld and pair distribution analysis of neutron powder diffraction, Raman scattering, and high-pressure x-ray diffraction. Results from the various diffraction probes indicate that both the long-range and local structures are consistent with the cubic symmetry. The diffraction data under pressure was consistent with a robustly cubic phase up to 48.9 GPa, which is supported by density functional calculations. Additionally, transverse phonon velocities were determined from measured dispersion of the transverse acoustic phonon branches, the results of which are in good agreement with previous theoretical estimates and ultrasound measurements.

  16. Mobility-electron density relation probed via controlled oxygen vacancy doping in epitaxial BaSnO3

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    Koustav Ganguly

    2017-05-01

    Full Text Available The recently discovered high room temperature mobility in wide band gap semiconducting BaSnO3 is of exceptional interest for perovskite oxide heterostructures. Critical open issues with epitaxial films include determination of the optimal dopant and understanding the mobility-electron density (μ-n relation. These are addressed here through a transport study of BaSnO3(001 films with oxygen vacancy doping controlled via variable temperature vacuum annealing. Room temperature n can be tuned from 5 × 1019 cm−3 to as low as 2 × 1017 cm−3, which is shown to drive a weak- to strong-localization transition, a 104-fold increase in resistivity, and a factor of 28 change in μ. The data reveal μ ∝ n0.65 scaling over the entire n range probed, important information for understanding mobility-limiting scattering mechanisms.

  17. On the possibility of room temperature ferromagnetism on chunk-shape BaSnO3/ZnO core/shell nanostructures

    Science.gov (United States)

    Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

    2018-04-01

    Core/shell BaSnO3/ZnO (BS-ZO) nanostructures were prepared by oxalate precipitation method and wet-chemical method. BaSnO3 (BSO) cubic perovskite structure and ZnO hexagonal wurtzite structure were confirmed by X-ray diffraction (XRD). The crystallite sizes is 23 nm, 29 nm and 27 nm for BSO, ZnO and BS-ZO, respectively. Chunk-shape and cuboids morphology observed from scanning electron microscopy (SEM) analysis. The magnetic properties were studied by VSM for bare and core-shell nano systems and the room temperature ferromagnetism observed for core-shell nanostructures. The BSO/ZnO shows enhanced coercivity and saturated magnetization as compared with BSO and ZnO nanostructures.

  18. Interface energy band alignment at the all-transparent p-n heterojunction based on NiO and BaSnO3

    Science.gov (United States)

    Zhang, Jiaye; Han, Shaobo; Luo, Weihuang; Xiang, Shuhuai; Zou, Jianli; Oropeza, Freddy E.; Gu, Meng; Zhang, Kelvin H. L.

    2018-04-01

    Transparent oxide semiconductors hold great promise for many optoelectronic devices such as transparent electronics, UV-emitting devices, and photodetectors. A p-n heterojunction is the most ubiquitous building block to realize these devices. In this work, we report the fabrication and characterization of the interface properties of a transparent heterojunction consisting of p-type NiO and n-type perovskite BaSnO3. We show that high-quality NiO thin films can be epitaxially grown on BaSnO3 with sharp interfaces because of a small lattice mismatch (˜1.3%). The diode fabricated from this heterojunction exhibits rectifying behavior with a ratio of 500. X-ray photoelectron spectroscopy reveals a type II or "staggered" band alignment with valence and conduction band offsets of 1.44 eV and 1.86 eV, respectively. Moreover, a large upward band bending potential of 0.90 eV for BaSnO3 and a downward band bending potential of 0.15 eV for NiO were observed in the interface region. Such electronic properties have important implication for optoelectronic applications as the large built-in potential provides favorable energetics for photo-generated electron-hole separation/migration.

  19. Zinc stannate nanostructures: hydrothermal synthesis

    International Nuclear Information System (INIS)

    Baruah, Sunandan; Dutta, Joydeep

    2011-01-01

    Nanostructured binary semiconducting metal oxides have received much attention in the last decade owing to their unique properties rendering them suitable for a wide range of applications. In the quest to further improve the physical and chemical properties, an interest in ternary complex oxides has become noticeable in recent times. Zinc stannate or zinc tin oxide (ZTO) is a class of ternary oxides that are known for their stable properties under extreme conditions, higher electron mobility compared to its binary counterparts and other interesting optical properties. The material is thus ideal for applications from solar cells and sensors to photocatalysts. Among the different methods of synthesizing ZTO nanostructures, the hydrothermal method is an attractive green process that is carried out at low temperatures. In this review, we summarize the conditions leading to the growth of different ZTO nanostructures using the hydrothermal method and delve into a few of its applications reported in the literature. (topical review)

  20. Alkaline earth stannates: The next silicon?

    Energy Technology Data Exchange (ETDEWEB)

    Ismail-Beigi, Sohrab, E-mail: sohrab.ismail-beigi@yale.edu; Ahn, Charles H. [Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States); Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structure and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Walker, Frederick J. [Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structure and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Cheong, Sang-Wook [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Rutgers Center for Emergent Materials, Rutgers University, Piscataway, New Jersey 08854 (United States); Rabe, Karin M. [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States)

    2015-06-01

    Semiconductor materials are being used in an increasingly diverse array of applications, with new device concepts being proposed each year for solar cells, flat-panel displays, sensors, memory, and spin transport. This rapid progress of invention outpaces the development of new semiconductor materials with the required properties and performance. In many applications, high carrier mobility at room temperature is required in addition to specific functional properties critical to the device concept. We review recent developments on high mobility stannate perovskite oxide materials and devices.

  1. Alkaline earth stannates: The next silicon?

    Directory of Open Access Journals (Sweden)

    Sohrab Ismail-Beigi

    2015-06-01

    Full Text Available Semiconductor materials are being used in an increasingly diverse array of applications, with new device concepts being proposed each year for solar cells, flat-panel displays, sensors, memory, and spin transport. This rapid progress of invention outpaces the development of new semiconductor materials with the required properties and performance. In many applications, high carrier mobility at room temperature is required in addition to specific functional properties critical to the device concept. We review recent developments on high mobility stannate perovskite oxide materials and devices.

  2. Synthesis and Characterization of Pure and Al Modified BaSnO3 Thick Film Resistor and Studies of its Gas Sensing Performance

    Directory of Open Access Journals (Sweden)

    N. U. PATIL

    2013-02-01

    Full Text Available In this work we report the synthesis, microstructure, electric properties and sensing performance of BaSnO3 (BS powder, it was prepared by solid state mechano-chemical method. As prepared powder is calcinated at temperatures 1000 °C and 1200 °C and tested for crystallization. Thick films were prepared using simple yet effective screen-printing technology. Structural and electrical analyses were performed and the results have been correlated. The pure BS film shows good response (S=9.8 to NH3 at elevated temperature up to 500 °C along with response other gases with lower sensitivity such as CO2, CO, H2S for various gas concentrations, when the pure film is surface modified with Al2O3, film improves the selectivity and sensitivity. Maximum response (S=21.2 was found to H2S gas at temperature of 300 °C for gas concentration as low as up to 100 ppm. The characterization of the films was done by XRD, SEM and TGA. Crystallite size, surface area, electric properties and gas sensitivity of the films were measured and presented.

  3. Stannate conversion coatings on Mg-8Li alloy

    International Nuclear Information System (INIS)

    Yang Lihui; Zhang Milin; Li Junqing; Yu Xiang; Niu Zhongyi

    2009-01-01

    The stannate conversion coatings (SnCC) on Mg-8Li alloy were investigated by simple immersion method. The surface morphology and composition were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction spectroscopy (XRD) techniques. The corrosion resistance was assessed by means of potentiodynamic polarization measurements and electrochemical impedance spectra (EIS). The effects of time of a stannate bath on the quality of stannate conversion coatings were investigated by SEM and EIS. It was found that the coating particles were mainly composed of hemispherical particles MgSnO 3 .3H 2 O. A comparison of results revealed the coating treated for 60 min exhibited the most uniform, dense and corrosion-resistant

  4. Blue photoluminescence in Ti-doped alkaline-earth stannates

    International Nuclear Information System (INIS)

    Yamashita, Takahiro; Ueda, Kazushige

    2007-01-01

    Blue photoluminescence properties of Ti-doped alkaline-earth stannates, A 2 (Sn 1- x Ti x )O 4 (A=Ca, Sr, Ba) (x=0.005-0.15), were examined at room temperature. These stannates showed intense broad emission bands peaking at 445 nm for Ca 2 SnO 4 , at 410 nm for Sr 2 SnO 4 , and at 425 nm for Ba 2 SnO 4 under UV excitation. Emission intensities were relatively insensitive to Ti concentration and no sharp concentration quenching was observed. Mixing alkaline-earth ions in the crystal structures did not increase the emission intensities in the A 2 (Sn 1- x Ti x )O 4 system. The excitation spectra of these stannates exhibited broad bands just below the fundamental absorption edges, implying that luminescence centers do not consist of the component elements in the host materials. It was suggested that the isolated TiO 6 complexes are possible luminescence centers in these materials, as previously proposed in other Ti-doped stannates such as Mg 2 SnO 4 and Y 2 Sn 2 O 7 . - Graphical abstract: Blue photoluminescence properties of Ti-doped alkaline-earth stannates, A 2 (Sn 1- x Ti x )O 4 (A=Ca, Sr, Ba) (x=0.005-0.15), were examined at room temperature. These stannates showed intense broad emission bands peaking at 445 nm for Ca 2 SnO 4 , at 410 nm for Sr 2 SnO 4 , and at 425 nm for Ba 2 SnO 4 under UV excitation

  5. Lanthanide stannate pyrochlores (Ln2Sn2O7; Ln = Nd, Gd, Er) at high pressure.

    Science.gov (United States)

    Turner, Katlyn M; Tracy, Cameron L; Mao, Wendy L; Ewing, Rodney C

    2017-11-09

    Lanthanide stannate pyrochlores (Ln2Sn2O7; Ln=Nd, Gd, and Er) were investigated in situ to 50 GPa in order to determine their structural response to compression and compare it to that of lanthanide titanate, zirconate, and hafnate pyrochlores. The cation radius ratio of A3+/B4+ in pyrochlore oxides (A2B2O7) is thought to be the dominant property that influences their compression response. The ionic radius of Sn4+ is intermediate to that of Ti4+, Zr4+, and Hf4+, but the bond in stannate pyrochlore is more covalent than the bonds in titanates, zirconate, and hafnates. In stannates, the pyrochlore cation and anion sublattices begin to disorder at 0.3 GPa. The extent of sublattice disorder vs. pressure is greater in stannates with a smaller Ln3+ cation. Stannate pyrochlores (Fd-3m) begin a sluggish transformation to a cotunnite-like structure (Pnma) at ~28 GPa; similar transitions have been observed in titanate, zirconate, and hafnate pyrochlore at varying pressures with cation radius ratio. The extent of the phase transition vs. pressure varies directly with the size of the Ln3+ cation. Post-decompression from ~50 GPa, Er2Sn2O7 and Gd2Sn2O7 adopt a pyrochlore structure, rather than the multiscale defect-fluorite + weberite structure adopted by Nd2Sn2O7 that is characteristic of titanate, zirconate, and hafnate pyrochlore treated to similar conditions. Like pyrochlore titanates, zirconates, and hafnates, the bulk modulus, B0, of stannates varies linearly and inversely with cation radius ratio. The trends of bulk moduli in stannates in this study are in excellent agreement with previous experimental studies on stannates, and suggest that the size of the Ln3+ cation is a primary determining factor of B0. Additionally, when normalized to rA/rB, the bulk moduli of stannates are comparable to those of zirconates and hafnates, which vary from titanates. Our results suggest that the cation radius ratio strongly influences the bulk moduli of stannates as well as

  6. Introduction of BaSnO3 and BaZrO3 artificial pinning centres into 2G HTS wires based on PLD-GdBCO films. Phase I of the industrial R&D programme at SuperOx

    Science.gov (United States)

    Chepikov, V.; Mineev, N.; Degtyarenko, P.; Lee, S.; Petrykin, V.; Ovcharov, A.; Vasiliev, A.; Kaul, A.; Amelichev, V.; Kamenev, A.; Molodyk, A.; Samoilenkov, S.

    2017-12-01

    An industrial R&D programme is ongoing at SuperOx, aimed at improving 2G HTS wire performance in magnetic field. We introduce perovskite artificial pinning centres (APC) into the HTS layer matrix. In contrast to most studies described in the literature, we use the high rate production processing parameters and PLD equipment at SuperOx. This paper reports the results of Phase I of this programme. We fabricated 2G HTS wires by pulsed laser deposition of GdBCO films doped with 6%, 12% and 18% (molar) of BaSnO3 and 6% (molar) of BaZrO3, and compared their performance with an undoped reference sample. The depositions were carried out at production growth rates of 375, 560 and 750 nm min-1 by varying laser pulse frequency. BaZrO3 and BaSnO3 formed columnar semi-coherent nanoinclusions in the GdBCO film matrix. The average transverse size of the nanocolumns was about 5 nm, and their volume density correlated with the dopant concentration. All doped samples exhibited much lower angular anisotropy of in-field critical current and higher lift-factors than the undoped sample. Samples containing 6% BaSnO3 and deposited at the lower growth rates, had higher I c than the undoped sample in the entire temperature range, in a wide range of magnetic field (B//c). The sample containing 6% BaZrO3 had higher I c than the undoped sample at 20 and 4.2 K. These results are an encouraging start of our programme, as they show a positive impact of APC introduced into 2G HTS wires fabricated at production throughput. Phase II work will be focussed on maximising the improvements in specific temperature and field conditions, as well as on the verification of reproducibility of the improvements in production wires.

  7. Study of the magnetic disaccommodation in La doped YIG

    International Nuclear Information System (INIS)

    Torres, C.; Hernandez-Gomez, P.; Francisco, C. de; Munoz, J.M.; Alejos, O.; Gonzalez Arias, A.; Perdigao, J.M.; Ferreira, A.R.

    2005-01-01

    The relaxation of the initial magnetic permeability of La doped yttrium iron garnet (YIG) samples with nominal composition Y 3-x La x Fe 5 O 12 (0 2 atmosphere when the La content is at least of 0.3. These results have been interpreted in terms of the formation of a secondary perovskite phase when the La solubility limit is reached. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Synthesis of Bismuth Stannate Nanoparticles with High Photocatalytic Activity under the Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    G. Gnanamoorthy

    2017-06-01

    Full Text Available Malachite Green is one of the most important organic dye, it contains triphenylmethane groups and it has been widely used for many industries. The hazardous dyes were rapidly act on immune and reproductive systems with carcinogenic effect of human health. Different methods were used for the hazardous removal in various industries, such as photocatalysis, biological treatment and adsorption process. The bismuth stannate nanoparticles have special properties of the hydrogen storage, biomolecule detection, gas sensors and catalysis. The bismuth stannate nanoparticles can be used for the degradation of organic pollutants and bismuth stannate is an important ternary oxide semiconductor with a wide band gap material. The composites were synthesized by a hydrothermal method, the obtained product was characterized by XRD, Raman, the morphology structure was confirmed by scanning electron microscopy and optical properties were carried out by DRS-UV-Vis spectroscopy. The excellent photocatalytic performance of the catalyst was evaluated by malachite green under the visible light.

  9. Lanthanide stannate pyrochlores (Ln2Sn2O7; Ln  =  Nd, Gd, Er) at high pressure

    Science.gov (United States)

    Turner, Katlyn M.; Tracy, Cameron L.; Mao, Wendy L.; Ewing, Rodney C.

    2017-12-01

    Lanthanide stannate pyrochlores (Ln2Sn2O7; Ln  =  Nd, Gd, and Er) were investigated in situ to 50 GPa in order to determine their structural response to compression and compare their response to that of lanthanide titanate, zirconate, and hafnate pyrochlores. The cation radius ratio of A3+/B4+ in pyrochlore oxides (A2B2O7) is thought to be the dominant feature that influences their response on compression. The ionic radius of Sn4+ is intermediate to that of Ti4+, Zr4+, and Hf4+, but the 〈Sn-O〉 bond in stannate pyrochlore is more covalent than the 〈B-O〉 bonds in titanates, zirconate, and hafnates. In stannates, based on in situ Raman spectroscopy, pyrochlore cation and anion sublattices begin to disorder with the onset of compression, first measured at 0.3 GPa. The extent of sublattice disorder versus pressure is greater in stannates with a smaller Ln3+ cation. Stannate pyrochlores (Fd-3m) begin a sluggish transformation to an orthorhombic, cotunnite-like structure at ~28 GPa similar transitions have been observed in titanate, zirconate, and hafnate pyrochlores at varying pressures (18-40 GPa) with cation radius ratio. The extent of the phase transition versus pressure varies directly with the size of the Ln3+ cation. Post-decompression from ~50 GPa, Er2Sn2O7 and Gd2Sn2O7 adopt a pyrochlore structure, rather than the multi-scale defect-fluorite  +  weberite-type structure adopted by Nd2Sn2O7 that is characteristic of titanate, zirconate, and hafnate pyrochlores under similar conditions. Like pyrochlore titanates, zirconates, and hafnates, the bulk modulus, B 0, of stannates varies linearly and inversely with cation radius ratio from 1 1 1 GPa (Nd2Sn2O7) to 251 GPa (Er2Sn2O7). The trends of bulk moduli in stannates in this study are in excellent agreement with previous experimental studies on stannates and suggest that the size of the Ln3+ cation is the primary determining factor of B 0. Additionally, when normalized to r A

  10. The pressure-induced structural response of rare earth hafnate and stannate pyrochlore from 0.1-50 GPa

    Science.gov (United States)

    Turner, K. M.; Rittman, D.; Heymach, R.; Turner, M.; Tracy, C.; Mao, W. L.; Ewing, R. C.

    2017-12-01

    Complex oxides with the pyrochlore (A2B2O7) and defect-fluorite ((A,B)4O7) structure-types undergo structural transformations under high-pressure. These compounds are under consideration for applications including as a proposed waste-form for actinides generated in the nuclear fuel cycle. High-pressure transformations in rare earth hafnates (A2Hf2O7, A=Sm, Eu, Gd, Dy, Y, Yb) and stannates (A2Sn2O7, A=Nd, Gd, Er) were investigated to 50 GPa by in situ Raman spectroscopy and synchrotron x-ray diffraction (XRD). Rare-earth hafnates form the pyrochlore structure for A=La-Tb and the defect-fluorite structure for A=Dy-Lu. Lanthanide stannates form the pyrochlore structure. Raman spectra revealed that at ambient pressure all compositions have pyrochlore-type short-range order. Stannate compositions show a larger degree of pyrochlore-type short-range ordering relative to hafnates. In situ high-pressure synchrotron XRD showed that rare earth hafnates and stannates underwent a pressure-induced phase transition to a cotunnite-like (Pnma) structure that begins between 18-25 GPa in hafnates and between 30-33 GPa in stannates. The phase transition is not complete at 50 GPa, and upon decompression, XRD indicates that all compositions transform to defect-fluorite with an amorphous component. In situ Raman spectroscopy showed that disordering in stannates and hafnates occurs gradually upon compression. Pyrochlore-structured hafnates retain short-range order to a higher pressure (30 GPa vs. <10 GPa) than defect-fluorite-structured hafnates. Hafnates and stannates decompressed from 50 GPa show Raman spectra consistent with weberite-type structures, also reported in irradiated stannates. The second-order Birch-Murnaghan equation of state fit gives a bulk modulus of 250 GPa for hafnate compositions with the pyrochlore structure, and 400 GPa for hafnate compositions with the defect-fluorite structure. Stannates have a lower bulk modulus relative to hafnates (between 80-150 GPa

  11. Radiation Induced Color Centers in a La Doped PWO Crystal

    CERN Document Server

    Deng, Qun

    1998-01-01

    This report presents result of a study on radiation induced color center densities in a La doped lead tungstate ( PWO) crystal. The creation and annihilation constants of radiation induced color centers were determined by using transmittance data measured for a PWO sample before and during Co-60 gamma ray irradiation at a dose rate of 15 rad/hr. Following a model of color center kinetics, these constants were used to calculate color center densities under irradiations at 100 rad/hr. The result was found to be in a good agreement with experimental data, indicating that this model of color center kinetics can be used to predict behavior of PWO crystals under irradiation.

  12. Investigation of the tunnel magnetoresistance in junctions with a strontium stannate barrier

    Science.gov (United States)

    Althammer, Matthias; Mishra, Rohan; Borisevich, Albina J.; Singh, Amit Vikam; Keshavarz, Sahar; Yurtisigi, Mehmet Kenan; Leclair, Patrick; Gupta, Arunava

    We experimentally investigate the structural, magnetic and electrical transport properties of La0.67Sr0.33MnO3 based magnetic tunnel junctions with a SrSnO3 barrier. Our results show that despite the high density of defects in the strontium stannate barrier the observed tunnel magnetoresistance is comparable to tunnel junctions with a better lattice matched SrTiO3 barrier, reaching values of up to 350 % at T = 5 K . Further analysis of the current-voltage characteristics of the junction and the bias voltage dependence of the observed tunnel magnetoresistance show a decrease of the TMR with increasing bias voltage. Our results suggest that by reducing the structural defects in the strontium stannate barrier, even larger TMR ratios might be possible in the future. We gratefully acknowledge financial support via NSF-ECCS Grant No. 1509875.

  13. Nootropic effects of bis(citratogermanates (stannates with different metals (Mg, Co in their structure

    Directory of Open Access Journals (Sweden)

    V. V. Godovan

    2014-10-01

    Full Text Available Aim. Nootropic effects of bis(citratogermanates (stannates with different metals (Mg, Co have been investigated in this article. With this aim the peculiarities of conditioned reflex formation as well as short- and long-term memory manifestations under the influence of the investigated coordinative compounds have been studied for 256 rats with the help of pathophysiological and pharmacological methods. Methods and results. It has been shown that stannates influence on the development of active avoidance conditioned reflex as well as on the manifestations of mnestic functions. It has been found that germacit and gercocit induce positive nootropic effects that occur in case of low dose drugs administration and are characterized by relief of conditioned reflex formation and by short- and long-term memory improvement at the same time. Conclusion. Stanmacit and stancocit also have nootropic effects that dependent on dose and are characterized by nootropic effect during administration in low doses and by amnestic effect at doses starting from 1/40 LD50. This indicates that stannates show nootropic activity

  14. La doping effect on TZM alloy oxidation behavior

    International Nuclear Information System (INIS)

    Yang, Fan; Wang, Kuai-She; Hu, Ping; He, Huan-Cheng; Kang, Xuan-Qi; Wang, Hua; Liu, Ren-Zhi; Volinsky, Alex A.

    2014-01-01

    Highlights: • The oxidation can be resisted by doping La into TZM alloy. • La doped TZM alloy has more compact organization. • It can rise the starting temperature of severe oxidation reaction by more than 50 °C. • Effectively slow down the oxidation rate. • Provide guidance for experiments of improving high-temperature oxidation resistance. - Abstract: Powder metallurgy methods were utilized to prepare lanthanum-doped (La-TZM) and traditional TZM alloy plates. High temperature oxidation experiments along with the differential thermal analysis were employed to study the oxidation behavior of the two kinds of TZM alloys. An extremely volatile oxide layer was generated on the surface of traditional TZM alloy plates when the oxidation started. Molybdenum oxide volatilization exposed the alloy matrix, which was gradually corroded by oxygen, losing its quality with serious surface degradation. The La-TZM alloy has a more compact structure due to the lanthanum doping. The minute lanthanum oxide particles are pinned at the grain boundaries and refine the grains. Oxide layer generated on the matrix surface can form a compact coating, which effectively blocks the surface from being corroded by oxidation. The oxidation resistance of La-TZM alloys has been enhanced, expanding its application range

  15. Effect of La doping on crystalline orientation, microstructure and dielectric properties of PZT thin films

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wencai; Li, Qi; Wang, Xing [Dalian Univ. of Technology, Dalian (China). School of Mechanical Engineering; Yin, Zhifu [Jilin Univ., Changchun (China). Faculty of the School of Mechanical Science and Engineering; Zou, Helin [Dalian Univ. of Technology, Dalian (China). Key Lab. for Micro/Nano Systems and Technology

    2017-11-01

    Lanthanum (La)-modified lead zirconate titanate (PLZT) thin films with doping concentration from 0 to 5 at.-% have been fabricated by sol-gel methods to investigate the effects of La doping on crystalline orientation, microstructure and dielectric properties of the modified films. The characterization of PLZT thin films were performed by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and precision impedance analysis. XRD analysis showed that PLZT films with La doping concentration below 4 at.-% exhibited (100) preferred orientation. SEM results indicated that PLZT films presented dense and columnar microstructures when La doping concentration was less than 3 at.-%, while the others showed columnar microstructures only at the bottom of the cross section. The maximum dielectric constant (1502.59 at 100 Hz) was obtained in a 2 at.-% La-doped film, which increased by 53.9 % compared with undoped film. Without introducing a seed layer, (100) oriented PLZT thin films were prepared by using conventional heat treatment process and adjusting La doping concentration.

  16. Influence of La Doping on Magnetic and Optical Properties of Bismuth Ferrite Nanofibers

    Directory of Open Access Journals (Sweden)

    Ziang Zhang

    2012-01-01

    Full Text Available The influence of La doping on the crystal structure, ferromagnetic, and optical properties of BFO nanofibers was investigated. Bi1−xLaxFeO3 ultrafine nanofibers were synthesized by the electrospinning method. The surface morphology and crystal structure of the as-spun and sintered fibers were not affected by the doping. The impurity phases of the BFO crystals were weakened with the increment of La concentration. The magnetization field curves showed that the magnetization weakened under low La doping proportion, but strengthened with the increase of the doped proportion. The magnetization curves also showed continuous strong enhancement of ferromagnetic behavior. The results of UV-vis and photoabsorption testing revealed little influence of La doping on the optical property.

  17. Synthesis of humidity sensitive zinc stannate nanomaterials and modelling of Freundlich adsorption isotherm model

    Science.gov (United States)

    Sharma, Alfa; Kumar, Yogendra; Shirage, Parasharam M.

    2018-04-01

    The chemi-resistive humidity sensing behaviour of as prepared and annealed ZnSnO3 nanoparticles synthesized using a wet chemical synthesis method was investigated. The effect of stirring temperature over the evolution of varied nanomorphology of zinc stannate is in accordance to Ostwald's ripening law. At room temperature, an excellent humidity sensitivity of ˜800% and response/recovery time of 70s./102s. is observed for ZnSnO3 sample within 08-97% relative humidity range. The experimental data observed over the entire range of RH values well fitted with the Freundlich adsorption isotherm model, and revealing two distinct water adsorption regimes. The excellent humidity sensitivity observed in the nanostructures is attributed to Grotthuss mechanism considering the availability and distribution of available adsorption sites. This present result proposes utilization of low cost synthesis technique of ZnSnO3 holds the promising capabilities as potential candidate for the fabrication of next generation humidity sensors.

  18. Experimental and first-principles study of ferromagnetism in Mn-doped zinc stannate nanowires

    KAUST Repository

    Deng, Rui; Zhou, Hang; Li, Yong-Feng; Wu, Tao; Yao, Bin; Qin, Jie-Ming; Wan, Yu-Chun; Jiang, Da-Yong; Liang, Qing-Cheng; Liu, Lei

    2013-01-01

    Room temperature ferromagnetism was observed in Mn-doped zinc stannate (ZTO:Mn) nanowires, which were prepared by chemical vapor transport. Structural and magnetic properties and Mn chemical states of ZTO:Mn nanowires were investigated by X-ray diffraction, superconducting quantum interference device (SQUID) magnetometry and X-ray photoelectron spectroscopy. Manganese predominantly existed as Mn2+ and substituted for Zn (Mn Zn) in ZTO:Mn. This conclusion was supported by first-principles calculations. MnZn in ZTO:Mn had a lower formation energy than that of Mn substituted for Sn (MnSn). The nearest neighbor MnZn in ZTO stabilized ferromagnetic coupling. This observation supported the experimental results. © 2013 AIP Publishing LLC.

  19. Experimental and first-principles study of ferromagnetism in Mn-doped zinc stannate nanowires

    KAUST Repository

    Deng, Rui

    2013-07-17

    Room temperature ferromagnetism was observed in Mn-doped zinc stannate (ZTO:Mn) nanowires, which were prepared by chemical vapor transport. Structural and magnetic properties and Mn chemical states of ZTO:Mn nanowires were investigated by X-ray diffraction, superconducting quantum interference device (SQUID) magnetometry and X-ray photoelectron spectroscopy. Manganese predominantly existed as Mn2+ and substituted for Zn (Mn Zn) in ZTO:Mn. This conclusion was supported by first-principles calculations. MnZn in ZTO:Mn had a lower formation energy than that of Mn substituted for Sn (MnSn). The nearest neighbor MnZn in ZTO stabilized ferromagnetic coupling. This observation supported the experimental results. © 2013 AIP Publishing LLC.

  20. Application of Eh-pH diagram for room temperature precipitation of zinc stannate microcubes in an aqueous media

    International Nuclear Information System (INIS)

    Al-Hinai, Ashraf T.; Al-Hinai, Muna H.; Dutta, Joydeep

    2014-01-01

    Graphical abstract: - Highlights: • One pot aqueous synthesis of zinc stannate (ZnSnO 3 ) particles at low temperature. • Synthesis designed with the assistance of potential-pH diagram. • ZnSnO 3 estimated to be stable between pH 8 and 12 was used for synthesis of the particles. • ZnSnO 3 ·3H 2 O were formed during the precipitation of zinc stannate. - Abstract: Potential-pH diagram assisted-design for controlled precipitation is an attractive method to obtain engineered binary and ternary oxide particles. Aqueous synthesis conditions of zinc stannate (ZnSnO 3 ) particles at low temperature were formulated with the assistance of potential-pH diagram. The pH of a solution containing stoichiometric amounts of Zn 2+ and Sn 4+ was controlled for the precipitation in a one pot synthesis step at room temperature (25 °C). The effect of the concentration of the reactants on the particle size was studied by varying the concentration of the precursor (Zn 2+ + Sn 4+ ) solution. Scanning electron micrographs show that the particles are monodispersed micron sized cubes formed by the self-organization of nano-sized crystallites. The obtained microcubes characterized by X-ray Diffraction and thermo gravimetric analysis (TGA) show that the particles are in ZnSnO 3 ·3H 2 O form

  1. Effect of compositional variations in the lead lanthanum zirconate stannate titanate system on electrical properties

    International Nuclear Information System (INIS)

    Markowski, K.; Park, S.E.; Yoshikawa, Shoko; Cross, L.E.

    1996-01-01

    The purpose of this work was to evaluate the effect of compositional modifications on the electrical properties of lead lanthanum zirconate stannate titanate (PLZST) ceramics, as well as to examine their electrically induced phase-change behavior. Variations in the Ti:Sn ratio were evaluated. Increased Ti 4+ content produced the following: decreased switching field, related to an increased antiferroelectric-ferroelectric (AFE-FE) transition temperature; constant hysteresis (ΔE) correlated with a constant temperature of the maximum dielectric constant (T max ); a sharper dielectric-constant maximum peak; and increased room-temperature dielectric constant (K). Variations in the Zr:Sn ratio also were evaluated. Increased Zr 4+ content produced the following: increased hysteresis with increased T max , decreased maximum dielectric constant, and decreased switching field with increased AFE-FE transition temperature (T AFE-FE ). From these results, with respect to compositional modifications, the AFE-FE switching field (E AFE-FE ) and ΔE were observed to be dependent strongly on T AFE-FE and T max , respectively. Negligible change existed in the strain achievable at the switching field, which remained constant for all compositions at ∼0.16%. The significance of this research was the ability demonstrated to tailor the properties of phase-change materials through compositional modifications

  2. Thermoluminescence kinetic parameters of different amount La-doped ZnB2O4

    International Nuclear Information System (INIS)

    Kucuk, Nil; Gozel, Aziz Halit; Yüksel, Mehmet; Dogan, Tamer; Topaksu, Mustafa

    2015-01-01

    The kinetic parameters of 1%, 2%, 3% and 4% La-doped ZnB 2 O 4 phosphors (i.e. ZnB 2 O 4 :0.01La, ZnB 2 O 4 :0.02La, ZnB 2 O 4 :0.03La and ZnB 2 O 4 :0.04La) synthesized by nitric acid method have been calculated. Thermoluminescence (TL) glow curves of ZnB 2 O 4 :La phosphors after beta-irradiation showed a very well defined main peak having the maximum temperature at around 200 °C and a shoulder peak at around 315 °C with a constant heating rate of 5 °C/s. The kinetic parameters of ZnB 2 O 4 :La phosphors TL glow peaks (i.e. order of kinetics (b), activation energies (E a ) and frequency factors (s)) have been determined and evaluated by Computerized Glow Curve Deconvolution (CGCD), and Peak Shape (PS) methods using the glow curve data. From the results, it can conclude that the values of E a obtained with these methods for ZnB 2 O 4 :La phosphors are consistent with each other, but the s values differ considerably. - Highlights: • Calculation of TL kinetic parameters for La-doped ZnB 2 O 4 . • La-doped ZnB 2 O 4 was synthesized by nitric acid method. • Well defined main peak at about 200 °C

  3. Surface modification of sol–gel synthesized TiO{sub 2} nanoparticles induced by La-doping

    Energy Technology Data Exchange (ETDEWEB)

    Grujić-Brojčin, M., E-mail: myramyra@ipb.ac.rs [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Armaković, S. [Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences, University of Novi Sad, Trg D. Obradovića 3, 21000 Novi Sad (Serbia); Tomić, N. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Abramović, B. [Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences, University of Novi Sad, Trg D. Obradovića 3, 21000 Novi Sad (Serbia); Golubović, A.; Stojadinović, B. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Kremenović, A. [Faculty of Mining and Geology, Laboratory for Crystallography, University of Belgrade, Đušina 7, 11000 Belgrade (Serbia); Babić, B. [Institute of Nuclear Sciences “Vinča”, University of Belgrade, 11001 Belgrade (Serbia); Dohčević-Mitrović, Z.; Šćepanović, M. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia)

    2014-02-15

    The influence of La-doping in the range of 0.5–6.0 mol% on structural and morphological properties of TiO{sub 2} nanopowders synthesized by sol–gel routine has been investigated by XRPD, AFM, EDS and BET measurements, as well as Raman spectroscopy. The XRPD and Raman measurements have revealed the anatase phase as dominant in all nanopowders, with crystallite size decreasing from ∼ 15 nm in pure TiO{sub 2} to ∼ 12 nm in La-doped samples. The BET data suggest that all samples are fully mesoporous, with mean pore diameters in the range of ∼ 6–8 nm. The specific surface area and the complexity of pore structure are greater in doped samples than in pure TiO{sub 2} sample. The spectroscopic ellipsometry has apparently shown that the band gap has been gradually increased with the increase of La content. The STM and STS techniques have been used successfully to evaluate the surface morphology and electronic properties of La-doped nanopowders. All investigated properties have been related to photocatalytic activity, tested in degradation of a metoprolol tartrate salt (0.05 mM), and induced by UV-radiation. All doped samples showed increased photocatalytic activity compared to pure TiO{sub 2}, among which the 0.65 mol% La-doped sample appeared to be the most efficient. - Highlights: • Effects of La-doping on structural, morphological and electronic properties of TiO{sub 2} nanopowders. • Surface morphology and electronic properties of La-doped nanopowders evaluated by STM/STS. • Spectroscopic ellipsometry shown gradual increase of bandgap with the increase of La content. • Photocatalytic activity of samples was tested in degradation of MET under UV light.

  4. Sensitization of Perovskite Strontium Stannate SrSnO3 towards Visible-Light Absorption by Doping

    Directory of Open Access Journals (Sweden)

    Hungru Chen

    2014-01-01

    Full Text Available Perovskite strontium stannate SrSnO3 is a promising photocatalyst. However, its band gap is too large for efficient solar energy conversion. In order to sensitize SrSnO3 toward visible-light activities, the effects of doping with various selected cations and anions are investigated by using hybrid density functional calculations. Results show that doping can result in dopant level to conduction band transitions which lie lower in energy compared to the original band gap transition. Therefore, it is expected that doping SrSnO3 can induce visible-light absorption.

  5. DFT+U study of self-trapping, trapping, and mobility of oxygen-type hole polarons in barium stannate

    Science.gov (United States)

    Geneste, Grégory; Amadon, Bernard; Torrent, Marc; Dezanneau, Guilhem

    2017-10-01

    The charge-transfer insulating perovskite oxides currently used as fuel cell electrolytes undergo, at high temperature, an oxidation reaction 1/2 O2(g ) +VO••→OOX+2 h• , that produces oxygen-type holes. Understanding the nature and mobility of these oxygen-type holes is an important step to improve the performance of devices, but presents a theoretical challenge since, in their localized form, they cannot be captured by standard density functional theory. Here, we employ the DFT+U formalism with a Hubbard correction on the p orbitals of oxygen to investigate several properties of these holes, in the particular case of BaSnO3. We describe the small oxygen-type hole polarons, the self-trapping at their origin, and their trapping by trivalent dopants (Ga, Sc, In, Lu, Y, Gd, La). Strong similarities with protonic defects are observed concerning the evolution of the trapping energy with ionic radius of the dopant. Moreover, we show that long-range diffusion of holes is a complex phenomenon, that proceeds by a succession of several mechanisms. However, the standard implementation of DFT+U within the projector augmented-wave (PAW) formalism leads to use very large, unphysical values of U for the O-p orbital. We propose here a slightly modified DFT+U scheme, that takes into account the fact that the O-p is truncated in usual DFT+U implementation in PAW. This scheme yields more physical values of U than the ones traditionally used in the literature, and describes well the properties of the hole polaron.

  6. Radiation-induced color centers in La-doped PbWO sub 4 crystals

    CERN Document Server

    Deng, Q; Zhu, R Y

    1999-01-01

    This report presents the result of a study on radiation-induced color center densities in La-doped lead tungstate (PbWO sub 4) crystals. The creation and annihilation constants of radiation-induced color centers were determined by using transmittance data measured for a PbWO sub 4 sample before and during sup 6 sup 0 Co gamma-ray irradiation at a dose rate of 15 rad/h. Following a model of color center kinetics, these constants were used to calculate color center densities under irradiations at 100 rad/h. The result was found to be in good agreement with experimental data, indicating that the behaviour of PbWO sub 4 crystals under irradiation can be predicted according to this model.

  7. Conduction band edge effective mass of La-doped BaSnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    James Allen, S., E-mail: allen@itst.ucsb.edu; Law, Ka-Ming [Physics Department, University of California, Santa Barbara, California 93106-5100 (United States); Raghavan, Santosh; Schumann, Timo; Stemmer, Susanne [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

    2016-06-20

    BaSnO{sub 3} has attracted attention as a promising material for applications requiring wide band gap, high electron mobility semiconductors, and moreover possesses the same perovskite crystal structure as many functional oxides. A key parameter for these applications and for the interpretation of its properties is the conduction band effective mass. We measure the plasma frequency of La-doped BaSnO{sub 3} thin films by glancing incidence, parallel-polarized resonant reflectivity. Using the known optical dielectric constant and measured electron density, the resonant frequency determines the band edge electron mass to be 0.19 ± 0.01. The results allow for testing band structure calculations and transport models.

  8. The effect of temperature and addition of reducing agent on sodium stannate preparation from cassiterite by the alkaline roasting process

    Science.gov (United States)

    Lalasari, Latifa Hanum; Andriyah, Lia; Arini, Tri; Firdiyono, F.

    2018-04-01

    Sodium stannate is an intermediate compound with the formula Na2SnO3. This compound is easily dissolved in water and has many applications in the electroplating industry, tin alloy production, and catalysts for organic synthesis. In this occasion was investigated the effect of temperature and the addition of reducing agent on making of sodium stannate phase from cassiterite by an alkaline roasting process using sodium carbonate (Na2CO3). Firstly, cassiterite was roasted at 700 °C for 3 hours and continued leaching process using 10% HCl solution at 110 °C for 2 hours. The cassiterite residue than was dried at 110 °C and mixed homogenously with a Na2CO3 decomposer at a mass ratio Na2CO3/cassiterite as 5:3 for the decomposition process. It was done by variation temperatures (300 °C, 700 °C, 800 °C, 870 °C, 900 °C) for 3 hours, variation times (3, 4, 5 hours) at a roasting temperature of 700 °C and addition of reducing agent such as sub-bituminous coal. The result of the experiment shows that cassiterite prepared by roasting and acid leaching process has the chemical composition as follows: 59.98% Sn, 22.58% O, 3.20% Ce, 3.15% La, 2.57% Nd, 1.67% Ti, 1.56% Fe, 1.24% P, 0.62% Ca and others. The Na2SnO3 phase begins to form at a roasting temperature of 870 °C for 3 hours. Although the roasting times was extended from 3 hours to 5 hours at 700 °C, the Na2SnO3 phase also has not yet formed. In other conditions, the addition of coal reducing agent to the roasting process would cause formations of Sn metal besides Na2SnO3 phase at 870 °C. At temperatures lower than 870 °C, the addition of coal only forms Sn metal, whereas the sodium stannate phase is not formed.

  9. Effect of annealing on the electrical, optical and structural properties of cadmium stannate thin films prepared by spray pyrolysis technique

    International Nuclear Information System (INIS)

    Kumaravel, R.; Krishnakumar, V.; Gokulakrishnan, V.; Ramamurthi, K.; Jeganathan, K.

    2010-01-01

    Polycrystalline thin films of cadmium stannate (Cd 2 SnO 4 ) were deposited by spray pyrolysis method on the Corning substrates at substrate temperature of 525 o C. Further, the films were annealed at 600 o C in vacuum for 30 min. These films were characterized for their structural, electrical and optical properties. The experimental results showed that the post-deposition annealing in vacuum has a significant influence on the properties of the films. The average grain size of the film was increased from 27.3 to 35.0 nm on heat treatment. The average optical transmittance in the visible region (500-850 nm) is decreased from 81.4% to 73.4% after annealing in vacuum. The minimum resistivity achieved in the present study for the vacuum annealed films is the lowest among the reported values for the Cd 2 SnO 4 thin films prepared by spray pyrolysis method.

  10. Tris(cyclohexylammonium cis-dichloridobis(oxalato-κ2O1,O2stannate(IV chloride monohydrate

    Directory of Open Access Journals (Sweden)

    Modou Sarr

    2013-11-01

    Full Text Available The crystal structure of the title compound, (C6H14N3[Sn(C2O42Cl2]Cl·H2O, contains three cyclohexylammonium cations, one stannate(IV dianion, one isolated chloride anion and one lattice water molecule. The cyclohexylammonium cations adopt chair conformations. In the complex anion, two bidentate oxalate ligands and two chloride anions in cis positions coordinate octahedrally to the central SnIV atom. The cohesion of the molecular entities is ensured by the formation of N—H...O, O—H...O, O—H...Cl and N—H...Cl interactions involving cations, anions and the lattice water molecule, giving rise to a layer-like arrangement parallel to (010.

  11. Observation of long phase-coherence length in epitaxial La-doped CdO thin films

    Science.gov (United States)

    Yun, Yu; Ma, Yang; Tao, Songsheng; Xing, Wenyu; Chen, Yangyang; Su, Tang; Yuan, Wei; Wei, Jian; Lin, Xi; Niu, Qian; Xie, X. C.; Han, Wei

    2017-12-01

    The search for long electron phase-coherence length, which is the length that an electron can keep its quantum wavelike properties, has attracted considerable interest in the last several decades. Here, we report the long phase-coherence length of ˜3.7 μm in La-doped CdO thin films at 2 K. Systematical investigations of the La doping and the temperature dependences of the electron mobility and the electron phase-coherence length reveal contrasting scattering mechanisms for these two physical properties. Furthermore, these results show that the oxygen vacancies could be the dominant scatters in CdO thin films that break the electron phase coherence, which would shed light on further investigation of phase-coherence properties in oxide materials.

  12. Synthesis and pressure effects on the La doped CaFe{sub 2}As{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Soo Hyun; Park, Tuson [Dept. of physics, Sungkyunkwan University, Suwon (Korea, Republic of); Shang, T.; Yuan, H. Q. [Dept. of physics, Zhejiang University, Hangzhou (China)

    2014-09-15

    We have synthesized La doped CaFe2As{sub 2} single crystals with Sn flux in an evacuated quartz ampule. Doping and pressure effects on the magnetic and superconducting properties of the under-doped Ca{sub 1-x}La{sub x}Fe{sub 2}As{sub 2} (x=0.08, 0.1) were studied by measuring electrical resistivity under quasi-hydrostatic pressure up to 21 kbar. Magnetic transition temperatures for all studied concentrations were sharply suppressed with slight amplitude of pressure, less than 3 kbar, while superconducting transition temperatures were robust against pressure. In this communication, we report temperature-pressure phase diagram for the La-doped CaFe{sub 2}As{sub 2} single crystals.

  13. Effects of pH and temperature on the deposition properties of stannate chemical conversion coatings formed by the potentiostatic technique on AZ91 D magnesium alloy

    International Nuclear Information System (INIS)

    Elsentriecy, Hassan H.; Azumi, Kazuhisa; Konno, Hidetaka

    2008-01-01

    The effects of pH and temperature of a stannate bath on the quality of stannate chemical conversion coatings formed on AZ91 D magnesium alloy by using the potentiostatic polarization technique at E = -1.1 V were investigated in order to improve uniformity and corrosion protection performance of the coating films. It was found that the uniformity and corrosion resistance of coating films deposited by potentiostatic polarization were closely associated with pH and temperature of the coating bath. The pH and temperature to obtain the best coating film were investigated as a function of corrosion protection performance evaluated by curves of potentiodynamic anodic polarization conducted in borate buffer solution. Scanning electron microscope observation and electrochemical corrosion tests of the stannate-coated samples confirmed significant improvement in uniformity and corrosion resistivity of coating films deposited by the potentiostatic technique by modifying the pH and temperature of the coating bath. It was also found that uniformity and corrosion resistivity of the coating films deposited by the potentiostatic technique were considerably improved compared to those of coatings deposited by the simple immersion method at the best conditions of pH and temperature of the coating bath

  14. Application of E{sub h}-pH diagram for room temperature precipitation of zinc stannate microcubes in an aqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hinai, Ashraf T., E-mail: ashraf@squ.edu.om [Department of Chemistry, College of Science, Sultan Qaboos University, 123, Alkhoud (Oman); Al-Hinai, Muna H. [Department of Chemistry, College of Science, Sultan Qaboos University, 123, Alkhoud (Oman); Water Research Center, Sultan Qaboos University, 123, Alkhoud (Oman); Dutta, Joydeep, E-mail: dutta@squ.ed.om [Water Research Center, Sultan Qaboos University, 123, Alkhoud (Oman)

    2014-01-01

    Graphical abstract: - Highlights: • One pot aqueous synthesis of zinc stannate (ZnSnO{sub 3}) particles at low temperature. • Synthesis designed with the assistance of potential-pH diagram. • ZnSnO{sub 3} estimated to be stable between pH 8 and 12 was used for synthesis of the particles. • ZnSnO{sub 3}·3H{sub 2}O were formed during the precipitation of zinc stannate. - Abstract: Potential-pH diagram assisted-design for controlled precipitation is an attractive method to obtain engineered binary and ternary oxide particles. Aqueous synthesis conditions of zinc stannate (ZnSnO{sub 3}) particles at low temperature were formulated with the assistance of potential-pH diagram. The pH of a solution containing stoichiometric amounts of Zn{sup 2+} and Sn{sup 4+} was controlled for the precipitation in a one pot synthesis step at room temperature (25 °C). The effect of the concentration of the reactants on the particle size was studied by varying the concentration of the precursor (Zn{sup 2+} + Sn{sup 4+}) solution. Scanning electron micrographs show that the particles are monodispersed micron sized cubes formed by the self-organization of nano-sized crystallites. The obtained microcubes characterized by X-ray Diffraction and thermo gravimetric analysis (TGA) show that the particles are in ZnSnO{sub 3}·3H{sub 2}O form.

  15. THE STUDY OF HIGH DIELECTRIC CONSTANT MECHANISM OF La-DOPED Ba0.67Sr0.33TiO3 CERAMICS

    Science.gov (United States)

    Xu, Jing; He, Bo; Liu, Han Xing

    It is a common and effective method to enhance the dielectric properties of BST ceramics by adding rare-earth elements. In this paper, it is important to analyze the cause of the high dielectric constant behavior of La-doped BST ceramics. The results show that proper rare earth La dopant (0.2≤x≤0.7) may greatly increase the dielectric constant of BST ceramics, and also improve the temperature stability, evidently. According to the current-voltage (J-V) characteristics, the proper La-doped BST ceramics may reach the better semiconductivity, with the decrease and increase in La doping, the ceramics are insulators. By using the Schottky barrier model and electric microstructure model to find the surface or grain boundary potential barrier height, the width of the depletion layer and grain size do play an important role in impacting the dielectric constant.

  16. Transparent front contact optimization in dye sensitized solar cells: use of cadmium stannate and titanium oxide by sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Braga, A., E-mail: antonio.braga@iit.it [CNR-IDASC SENSOR Lab and Department of Chemistry and Physics, Brescia University, Via Valotti 9, 25131 Brescia (Italy); Baratto, C. [CNR-IDASC SENSOR Lab and Department of Chemistry and Physics, Brescia University, Via Valotti 9, 25131 Brescia (Italy); Bontempi, E. [INSTM and Chemistry for Technologies Laboratory, University of Brescia, Via Branze 28, 25133 Brescia (Italy); Colombi, P. [Centro Coating C.S.M.T. Gestione S.c.a.r.l., Via Branze, 45 25123 Brescia (Italy); Sberveglieri, G. [CNR-IDASC SENSOR Lab and Department of Chemistry and Physics, Brescia University, Via Valotti 9, 25131 Brescia (Italy)

    2014-03-31

    A reliable transparent front contact of cadmium stannate (CTO) and titanium oxide (TiO{sub 2}) entirely deposited by magnetron sputtering has been studied and applied to build standard dye-sensitized solar cell. CTO gives very high average optical transmittance (T{sub avg} ≥ 90%) along with competitive sheet resistance (R{sub sheet} ≤ 15 Ω/sq), while a very thin layer of TiO{sub 2} (thickness < 5 nm) acts as buffer layer to prevent charge recombination. The matched materials allow achievement of good performances of the cells, in terms of short circuit current and power conversion efficiency. UV-visible spectrophotometry, glancing incident X-rays diffraction and X-rays reflectivity techniques were used to characterize thin films before cell realization; sealed solar cells were tested under simulated solar irradiance at 1 Sun to determine functional properties. - Highlights: • Double layer cadmium stannate–TiO{sub 2} transparent front contact by sputtering. • Very thin TiO{sub 2} buffer layer for charge recombination prevention. • Application of novel transparent contact in standard dye sensitized solar cells.

  17. Transparent front contact optimization in dye sensitized solar cells: use of cadmium stannate and titanium oxide by sputtering

    International Nuclear Information System (INIS)

    Braga, A.; Baratto, C.; Bontempi, E.; Colombi, P.; Sberveglieri, G.

    2014-01-01

    A reliable transparent front contact of cadmium stannate (CTO) and titanium oxide (TiO 2 ) entirely deposited by magnetron sputtering has been studied and applied to build standard dye-sensitized solar cell. CTO gives very high average optical transmittance (T avg ≥ 90%) along with competitive sheet resistance (R sheet ≤ 15 Ω/sq), while a very thin layer of TiO 2 (thickness < 5 nm) acts as buffer layer to prevent charge recombination. The matched materials allow achievement of good performances of the cells, in terms of short circuit current and power conversion efficiency. UV-visible spectrophotometry, glancing incident X-rays diffraction and X-rays reflectivity techniques were used to characterize thin films before cell realization; sealed solar cells were tested under simulated solar irradiance at 1 Sun to determine functional properties. - Highlights: • Double layer cadmium stannate–TiO 2 transparent front contact by sputtering. • Very thin TiO 2 buffer layer for charge recombination prevention. • Application of novel transparent contact in standard dye sensitized solar cells

  18. Preparation of bismuth stannate/silver@silver chloride film samples with enhanced photocatalytic performance and self-cleaning ability.

    Science.gov (United States)

    Zhao, Xiaojuan; Lv, Xiang; Cui, Hongda; Wang, Tianhe

    2017-12-01

    We report a novel technique to fabricate bismuth stannate/silver@silver chloride (Bi 2 Sn 2 O 7 /Ag@AgCl) films on conventional glass substrates. The film exhibited a remarkable self-cleaning capability against organic dyes under visible light. Porous Bi 2 Sn 2 O 7 (BSO) film was first sintered on a glass substrate, followed by implantation of AgCl in it and photo-induction to produce Ag@AgCl. The degradation of organic dyes and photoelectrochemical studies indicate that, compared with BSO film, Bi 2 Sn 2 O 7 /Ag@AgCl film had a much improved photocatalytic ability, probably due to the enhanced electron transfer efficiency and synergistic effect of visible light absorption of the two semiconductors. The possible mechanism of this marked improvement was investigated and interpreted in terms of electrons and holes separation efficiency and charge circulation routes at the interfaces within the Bi 2 Sn 2 O 7 /Ag@AgCl composite film. The film provided in this study may well have practical applications due to its simplicity of preparation, excellent photocatalytic ability and reasonable stability. Copyright © 2017. Published by Elsevier Inc.

  19. Influence of Al grain boundaries segregations and La-doping on embrittlement of intermetallic NiAl

    Energy Technology Data Exchange (ETDEWEB)

    Kovalev, Anatoly I., E-mail: a_kovalev@sprg.ru; Wainstein, Dmitry L.; Rashkovskiy, Alexander Yu.

    2015-11-01

    Highlights: • We investigated Al grain boundaries segregations in ordered pure and La-doped NiAl. • Structural segregation of Al decreases critical strain for brittle cracks nucleation. • La alloying sharply improves plasticity of NiAl intermetallic. • Metallicity of interatomic bonds on grain boundaries increases at La alloying. • We have experimentally measured by EELFS that La atoms are located in Al sublattice. - Abstract: The microscopic nature of intergranular fracture of NiAl was experimentally investigated by the set of electron spectroscopy techniques. The paper demonstrates that embrittlement of NiAl intermetallic compound is caused by ordering of atomic structure that leads to formation of structural aluminum segregations at grain boundaries (GB). Such segregations contain high number of brittle covalent interatomic bonds. The alloying by La increases the ductility of material avoiding Al GB enrichment and disordering GB atomic structure. The influence of La alloying on NiAl mechanical properties was investigated. GB chemical composition, atomic and electronic structure transformations after La doping were investigated by AES, XPS and EELFS techniques. To qualify the interatomic bonds metallicity the Fermi level (E{sub F}) position and electrons density (n{sub eff}) in conduction band were determined in both undoped and doped NiAl. Basing on experimental results the physical model of GB brittleness formation was proposed.

  20. Photocatalytic degradation of commercial phoxim over La-doped TiO2 nanoparticles in aqueous suspension.

    Science.gov (United States)

    Dai, Ke; Peng, Tianyou; Chen, Hao; Liu, Juan; Zan, Lin

    2009-03-01

    Photocatalytic degradation of commercial phoxim emulsion in aqueous suspension was investigated by using La-doped mesoporous TiO2 nanoparticles (m-TiO2) as the photocatalyst under UV irradiation. Effects of La-doping level, calcination temperature, and additional amount of the photocatalyst on the photocatalytic degradation efficiency were investigated in detail. Experimental results indicate that 20 mg L(-1) phoxim in 0.5 g L(-1) La/m-TiO2 suspension (the initial pH 4.43) can be decomposed as prolonging the irradiation time. Almost 100% phoxim was decomposed after 4 h irradiation according to the spectrophotometric analyses, whereas the mineralization rate of phoxim just reached ca. 80% as checked by ion chromatography (IC) analyses. The elimination of the organic solvent in the phoxim emulsion as well as the formation and decomposition of some degradation intermediates were observed by high-performance liquid chromatography-mass spectroscopy (HPLC-MS). On the basis of the analysis results on the photocatalytic degradation intermediates, two possible photocatalytic degradation pathways are proposed under the present experimental conditions, which reveal that both the hydrolysis and adsorption of phoxim under UV light irradiation play important roles during the photocatalytic degradation of phoxim.

  1. Structural characteristics and UV-light enhanced gas sensitivity of La-doped ZnO nanoparticles

    International Nuclear Information System (INIS)

    Ge Chunqiao; Xie Changsheng; Hu Mulin; Gui Yanghai; Bai Zikui; Zeng Dawen

    2007-01-01

    La-doped ZnO nanoparticles were synthesized by sol-gel method starting from zinc acetate dihydrate, lanthanum sesquioxide, alcohol and nitric acid. The crystal structure and morphology of the nanoparticles were characterized by XRD, FESEM, respectively. The thermal decomposition behavior of the the ZnO-based xerogel was detected by TG-DSC. The results show that as-prepared nanoparticles with the hexagonal wurtzite contain the adsorbed water and some organic compounds below 300 o C, which is the key to the calcinations of the ZnO-based xerogel. Pure ZnO and La-doped ZnO thick film sensors were prepared and tested for specific sensitivity to alcohol and benzene with (and without) UV-light excitation. Among all, 10 at.%La-ZnO-based sensors are significantly sensitive to 100 ppm alcohol and 100 ppm benzene. There is an obvious enhancement of the gas-sensing performances with UV-light excitation. That is, the sensitivity to 100 ppm benzene rises twice. The observed sensitivity to alcohol and benzene could be explained with the surface adsorption theory and the conduction-band theory

  2. Crystal structure, dielectric, ferroelectric and energy storage properties of La-doped BaTiO3 semiconducting ceramics

    Directory of Open Access Journals (Sweden)

    Venkata Sreenivas Puli

    2015-09-01

    Full Text Available Polycrystalline La-doped BaTiO3 (Ba(1-xLax\tTiO3 [x=0,0.0005,0.001,0.003] ceramics (denoted as BTO,BLT1,BLT2,BLT3 were synthesized by conventional solid-state reaction method and characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, and Raman spectroscopy. XRD and Raman spectra revealed single-phase tetragonal perovskite crystalline structure. Well-saturated polarization–electric field (P–E hysteresis loops were observed with the measurement frequency of 50 Hz at room temperature and confirmed ferroelectric nature of these ceramics and a high recoverable electrical energy storage density of 0.350 J/cm3 with energy efficiency (n∼9%, which is useful in energy storage capacitor applications. Dielectric studies revealed anomalies around 415–420 K and near the Curie temperature. The latter is attributed to the ferroelectric to paraelectric phase transition. Better dielectric performances were obtained for La-doped samples sintered at 1350°C for 4 h. Grain growth is inhibited with lanthanum (La incorporation into the BTO lattice. Room temperature semiconducting behavior with positive temperature coefficient of resistivity (PTCR behavior at TC is attributed to electron compensation mechanism.

  3. La Doping of CdS for Enhanced CdS/CdSe Quantum Dot Cosensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Xiaolei Qi

    2015-01-01

    Full Text Available CdS/CdSe system of quantum dot cosensitized solar cells (QDCSCs is one of the most attractive structures for high-efficiency due to its effect of level adjusting. However, the stepwise structure formed between levels of CdS and CdSe has a limitation for enhancing the efficiencies. Metal ions doping in quantum dots have emerged as a common way for changing the Fermi level, band gap, and conductance. Here we report an innovative concept for the rare earth materials La-doped of the CdS layer in the CdS/CdSe QDCSCs by means of the successive ionic layer adsorption and reaction (SILAR. Then we tested that La doped quantum dots can help more electrons accumulate in CdS film, which makes the Fermi level shift up and form a stepped structure. This method leads to enhanced absorption intensity, obviously increasing current density in CdS/CdSe QDCSCs. Our research is a new exploration for improving efficiencies of quantum dot sensitized solar cells.

  4. Reply to the 'Comment on "Proton transport in barium stannate: classical, semi-classical and quantum regime"'.

    Science.gov (United States)

    Geneste, Grégory; Hermet, Jessica; Dezanneau, Guilhem

    2017-08-09

    We respond to the erroneous criticisms about our modeling of proton transport in barium stannate [G. Geneste et al., Phys. Chem. Chem. Phys., 2015, 17, 19104]. In this previous work, we described, on the basis of density-functional calculations, proton transport in the classical and semi-classical regimes, and provided arguments in favor of an adiabatic picture for proton transfer at low temperature. We re-explain here our article (with more detail and precision), the content of which has been distorted in the Comment, and reiterate our arguments in this reply. We refute all criticisms. They are completely wrong in the context of our article. Even though a few of them are based on considerations probably true in some metals, they make no sense here since they do not correspond to the content of our work. It has not been understood in the Comment that two competitive configurations, associated with radically different transfer mechanisms, have been studied in our work. It has also not been understood in the Comment that the adiabatic regime described for transfer occurs in the protonic ground state, in a very-low barrier configuration with the protonic ground state energy larger than the barrier. Serious confusion has been made in the Comment with the case of H in metals like Nb or Ta, leading to the introduction of the notion of (protonic) "excited-state proton transfer", relevant for H in some metals, but (i) that does not correspond to the (ground state) adiabatic transfers here described, and (ii) that does not correspond to what is commonly described as the "adiabatic limit for proton transfer" in the scientific literature. We emphasize, accordingly, the large differences between proton transfer in the present oxide and hydrogen jumps in metals like Nb or Ta, and the similarities between proton transfer in the present oxide and in acid-base solutions. We finally describe a scenario for proton transfer in the present oxide regardless of the temperature regime.

  5. La-doped Al2O3 supported Au nanoparticles: highly active and selective catalysts for PROX under PEMFC operation conditions.

    Science.gov (United States)

    Lin, Qingquan; Qiao, Botao; Huang, Yanqiang; Li, Lin; Lin, Jian; Liu, Xiao Yan; Wang, Aiqin; Li, Wen-Cui; Zhang, Tao

    2014-03-14

    La-doped γ-Al2O3 supported Au catalysts show high activity and selectivity for the PROX reaction under PEMFC operation conditions. The superior performance is attributed to the formation of LaAlO3, which suppresses H2 oxidation and strengthens CO adsorption on Au sites, thereby improving competitive oxidation of CO at elevated temperature.

  6. Influence of Al grain boundaries segregations and La-doping on embrittlement of intermetallic NiAl

    Science.gov (United States)

    Kovalev, Anatoly I.; Wainstein, Dmitry L.; Rashkovskiy, Alexander Yu.

    2015-11-01

    The microscopic nature of intergranular fracture of NiAl was experimentally investigated by the set of electron spectroscopy techniques. The paper demonstrates that embrittlement of NiAl intermetallic compound is caused by ordering of atomic structure that leads to formation of structural aluminum segregations at grain boundaries (GB). Such segregations contain high number of brittle covalent interatomic bonds. The alloying by La increases the ductility of material avoiding Al GB enrichment and disordering GB atomic structure. The influence of La alloying on NiAl mechanical properties was investigated. GB chemical composition, atomic and electronic structure transformations after La doping were investigated by AES, XPS and EELFS techniques. To qualify the interatomic bonds metallicity the Fermi level (EF) position and electrons density (neff) in conduction band were determined in both undoped and doped NiAl. Basing on experimental results the physical model of GB brittleness formation was proposed.

  7. Application of La-Doped SrTiO3 in Advanced Metal-Supported Solid Oxide Fuel Cells

    Directory of Open Access Journals (Sweden)

    Sabrina Presto

    2018-03-01

    Full Text Available Composite materials frequently allow the drawbacks of single components to be overcome thanks to a synergistic combination of material- and structure-specific features, leading to enhanced and also new properties. This is the case of a metallic-ceramic composite, a nickel-chromium-aluminum (NiCrAl foam impregnated with La-doped Strontium Titanate (LST. This particular cermet has very interesting properties that can be used in different fields of application, namely: mechanical robustness provided by the metal foam; and chemical stability in harsh conditions of temperature and atmosphere by promotion of a thin protective layer of alumina (Al2O3; high electronic conductivity given by a percolating ceramic conducting phase, i.e., La-doped Strontium Titanate. In this paper, its application as a current collector in a metal-supported Solid Oxide Fuel Cells (SOFC was studied. Firstly, the electronic properties of different compositions, stoichiometric and under stoichiometric, of LST were analyzed to choose the best one in terms of conductivity and phase purity. Then, LST chemical stability was studied in the presence of Al2O3 at different temperatures, gas compositions and aging times. Finally, stability and conductivity of LST-impregnated NiCrAl foam composite materials were measured, and LST was found to be fully compatible with the NiCrAl foam, as no reactions were detected in oxidizing and reducing atmosphere after up to 300 h operation at 750 °C and 900 °C between the Al2O3 layer and LST. Results showed that the composite is suitable as a current collector in innovative designs of metal-supported SOFC, like the Evolve cell, in which the metallic part is supposed not only to provide the structural stability to the cell, but also to play the role of current collector due to the impregnation of ceramic material.

  8. Crystal structure of 2-methyl-1H-imidazol-3-ium aquatrichlorido(oxalato-κ2O,O′stannate(IV

    Directory of Open Access Journals (Sweden)

    Mouhamadou Birame Diop

    2015-05-01

    Full Text Available The tin(IV atom in the complex anion of the title salt, (C4H7N2[Sn(C2O4Cl3(H2O], is in a distorted octahedral coordination environment defined by three chlorido ligands, an oxygen atom from a water molecule and two oxygen atoms from a chelating oxalate anion. The organic cation is linked through a bifurcated N—H...O hydrogen bond to the free oxygen atoms of the oxalate ligand of the complex [Sn(H2OCl3(C2O4]− anion. Neighbouring stannate(IV anions are linked through O—H...O hydrogen bonds involving the water molecule and the two non-coordinating oxalate oxygen atoms. In combination with additional N—H...Cl hydrogen bonds between cations and anions, a three-dimensional network is spanned.

  9. Preparation of Pd-loaded La-doped TiO{sub 2} nanotubes and investigation of their photocatalytic activity under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Zong, Lanlan; Li, Qiuye, E-mail: qiuyeli@henu.edu.cn; Zhang, Jiwei; Wang, Xiaodong; Yang, Jianjun [Henan University, Key Laboratory for Special Functional Materials (China)

    2013-11-15

    Orthorhombic titanic acid nanotubes (TAN) have large BET surface area and small-diameter one-dimensional nanotubular morphology, so they can work as a good supporter and a precursor of TiO{sub 2}. However, in our former research, we found that calcination of TAN to anatase TiO{sub 2} would destroy the nanotubular structure and decrease the BET surface area sharply. In this work, we utilized the pillar effect of the foreign nanoparticles (La{sub 2}O{sub 3}) to keep the nanotubular morphology of TiO{sub 2}, and obtained the anatase TiO{sub 2} nanotubes with large BET surface area. For improving the photocatalytic activity, Pd nanoparticles were loaded as the electron traps on the surface of La-doped TiO{sub 2} by photo-deposition method. The photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, diffuse reflectance spectra, and N{sub 2} adsorption–desorption isotherms measurement. Their photocatalytic activities were evaluated by the removal of propylene under visible light irradiation (λ ≥ 420 nm). The results showed that the photocatalytic activity of Pd-loaded La-doped TiO{sub 2} nanotubes improved effectively compared with that of La-doped TiO{sub 2} and pure TiO{sub 2}.

  10. 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)

  11. Evaluation of La-Doped Mesoporous Bioactive Glass as Adsorbent and Photocatalyst for Removal of Methylene Blue from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Liying Li

    2015-01-01

    Full Text Available A series of La-doped mesoporous bioactive glass (BG-La materials with excellent biosafety and hypotoxicity have been prepared and tested as adsorbent. The study was aimed to evaluate the possibility of utilizing BG-La for the adsorptive removal of methylene blue (MB from aqueous solution and test the adsorption and desorption behavior of this new material. The process parameters affecting adsorption behaviors such as pH, contact time, and initial concentration and the photocatalytic degradation of MB were systematically investigated. The result showed that BG-La had excellent removal rate (R of MB, and BG-La showed better photocatalytic effect than undoped mesoporous bioactive glass (BG. Furthermore, the MB loaded BG-La was easily desorbed with acid solution due to its electronegativity and mesoporous structure. The result indicated that these materials can be employed as candidates for removal of dye pollutant owing to their high removal rate, excellent photocatalytic effect, desorption performance, and their reusability.

  12. 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).

  13. Effect of La doping on the ferroic order in Pb-based perovskite-type relaxor ferroelectrics

    Science.gov (United States)

    Maier, B. J.; Welsch, A.-M.; Mihailova, B.; Angel, R. J.; Zhao, J.; Paulmann, C.; Engel, J. M.; Marshall, W. G.; Gospodinov, M.; Petrova, D.; Bismayer, U.

    2011-04-01

    The structural alteration induced by the substitution of three-valent cations with an isotropic electronic outermost shell for Pb2+ in perovskite-type relaxors was investigated in the solid solutions Pb1-xLaxSc(1+x)/2Ta(1-x)/2O3, x =0.08 (PST-La) and Pb1-xLaxSc(1+x)/2Nb(1-x)/2O3, x =0.23 (PSN-La). In order to distinguish the “charge” effects from “strain” effects associated with the incorporation of La3+ in the structure, Sr-containing PbSc0.5Nb0.5O3 was characterized as well. The structure of the compounds was analyzed by in situ Raman spectroscopy, single-crystal x-ray diffraction, and powder neutron diffraction at different temperatures or pressures. It is shown that the embedding of La3+ strongly affects the ferroic structural species due to strain effects through a disturbance of the system of lone-pair electrons associated with Pb2+ and a decrease in the tolerance factor. La doping suppresses the dynamical coupling between off-centered Pb and B-site cations and enhances antiphase BO6 octahedral tilting which, depending on the level of doping, may lead to long-range order of antiphase BO6 tilts at ambient conditions and frustrated antiferroelectric order of Pb ions at low temperatures.

  14. Crystalline and Electronic Structures and Magnetic and Electrical Properties of La-Doped Ca2Fe2O5 Compounds

    Science.gov (United States)

    Phan, T. L.; Tho, P. T.; Tran, N.; Kim, D. H.; Lee, B. W.; Yang, D. S.; Thiet, D. V.; Cho, S. L.

    2018-01-01

    Brownmillerite Ca2Fe2O5 has been observed to exhibit many outstanding properties that are applicable to ecotechnology. However, very little work on doped Ca2Fe2O5 compounds has been carried out to widen their application scope. We present herein a detailed study of the crystalline/geometric and electronic structures and magnetic and electrical properties of Ca2- x La x Fe2O5 ( x = 0 to 1) prepared by conventional solid-state reaction. X-ray diffraction patterns indicated that the compounds with x = 0 to 0.05 exhibited brownmillerite-type single phase. La doping with higher content ( x ≥ 0.1) stimulated additive formation of Grenier- (LaCa2Fe3O8) and perovskite-type (LaFeO3) phases. Extended x-ray absorption fine structure spectroscopy at the Fe K-edge and electron spin resonance spectroscopy revealed presence of Fe3+ in the parent Ca2Fe2O5 ( x = 0) and both Fe3+ and Fe4+ in the doped compounds ( x ≥ 0.05). The Fe4+ content tended to increase with increasing x. This stimulates ferromagnetic exchange interactions between Fe3+ and Fe4+ ions and directly influences the magnetic properties of Ca2- x La x Fe2O5. Electrical resistivity ( ρ) measurements in the temperature range of T = 20 K to 400 K revealed that all the compounds exhibit insulator behavior; the ρ( T) data for x ≥ 0.1 could be described based on the adiabatic small polaron hopping model.

  15. Competing exchange bias and field-induced ferromagnetism in La-doped BaFe O3

    Science.gov (United States)

    Fita, I.; Wisniewski, A.; Puzniak, R.; Iwanowski, P.; Markovich, V.; Kolesnik, S.; Dabrowski, B.

    2017-04-01

    An exchange bias (EB) effect was observed in mixed valent L axB a1 -xFe O3 (x =0.125 , 0.25, 0.33) perovskites exhibiting the antiferromagnetic (AFM) helical order among F e4 + ions coexisting with the ferromagnetic (FM) cluster phase in the ground state. The L a3 + ions for B a2 + site substitution, associated with increase in number of the AFM coupled F e3 + - F e4 + pairs as well as some F e3 + - F e3 + pairs, leads to strengthening of the AFM phase and consequently to the alteration of the EB characteristics, which depend on level of the La doping x . At low doping x ≤0.25 , an abnormal dependence of the EB field, HEB, on the cooling field, Hcool, was found. The HEB increases rapidly with increasing cooling field at low Hcool, but it falls suddenly at cooling fields higher than 20 kOe, reducing by an order of magnitude at 90 kOe. The suppression of EB is caused by the field-induced increased volume of the FM phase, due to the transformation of the AFM helical spin structure into the FM one. Thus, low-doped L axB a1 -xFe O3 demonstrates a competition of two alternate cooling-field-induced effects, one of which leads to the EB anisotropy and another one to the enhanced ferromagnetism. In contrast, the x =0.33 sample, having a strong AFM constituent, shows no field-induced FM and no drop in the EB field. Accordingly, the HEB vs Hcool dependence was found to be well explained in the framework of a model describing phase-separated AFM-FM systems, namely, the model assuming isolated FM clusters of size ˜4 nm embedded in the AFM matrix.

  16. 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

  17. Study on mechanism of photocatalytic performance of La-doped TiO2/Ti photoelectrodes by theoretical and experimental methods

    International Nuclear Information System (INIS)

    Xin Yanjun; Liu Huiling

    2011-01-01

    TiO 2 photoelectrodes with various nanostructures have been successfully prepared by the anodization method. The morphology, microstructure and optical properties of as-prepared photoelectrodes were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet/visible light diffuse reflectance spectra (UV/vis/DRS), surface photovoltage spectroscopy (SPS) and photocurrent. The electronic structure and optical properties of La doped/undoped TiO 2 photoelectrodes with different crystal structures were calculated by the density function theory. The photocatalytic and photoelectrocatalytic activities of as-prepared photoelectrodes were evaluated. The results showed that the anodization potentials played a crucial role in the surface morphology and microstructure. Both results of theoretical calculations and experimental tests demonstrated that La-doped photoelectrodes were more sensitive to light than undoped one. The difference of photoelectrodes performance was ascribed to the crystal configuration, impurity energy levels and long-range orientation moving of photogenerated carriers. - Graphical abstract: Photophysical chemistry processes in as-prepared TiO 2 photoelectrodes. Overall scheme of TiO 2 photoelectrodes: (A) movement of photoelectrons and holes without bias potentials; (B) movement of photoelectrons and holes at applied bias potentials; (a) and (b) were the transmission of photogenerated electrons and holes of local enlargement of (A) (black open circle): (a) photoelectrons movement in P-TiO 2 photoelectrodes and La-TiO 2 photoelectrodes, the red dot line denotes the top of valence band (VB) and the bottom of conduction band (CB) of pure photoelectrodes; (b) photoelectrons movement in P-160 and La-160 TiO 2 photoelectrodes (mixed crystal phase). The number refers to as follows: (1) transmission process of photoelectrons and holes; (2) recombination process of photoelectrons and holes. Arrows represent the moving direction of

  18. 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.

  19. Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca(3-x)Sn₃Nb₂O₁₄:xEu³⁺.

    Science.gov (United States)

    Sreena, T S; Prabhakar Rao, P; Francis, T Linda; Raj, Athira K V; Babu, Parvathi S

    2015-05-14

    New stannate based displaced pyrochlore-type red phosphors, Ca(3-x)Sn3Nb2O14:xEu(3+), were prepared via a conventional solid state method. The influence of partial occupancy of Sn in both A and B sites of the pyrochlore-type oxides on the photoluminescence properties was studied using powder X-ray diffraction, FT-Raman, transmission electron microscopy, scanning electron microscopy with energy dispersive spectrometry, UV-visible absorption spectroscopy, and photoluminescence excitation and emission spectra with lifetime measurements. The structural analysis establishes that these oxides belong to a cubic displaced pyrochlore type structure with a space group Fd3̄m. These phosphors exhibit strong absorptions at near UV and blue wavelength regions and emit intense multiband emissions due to Eu(3+ 5)D0-(7)F(0, 1, 2) transitions. The absence of characteristic MD transition splitting points out that local cation disorder exists in this type of displaced pyrochlores, reducing the D(3d) inversion symmetry, which is not evidenced by such disorder in the X-ray diffraction analysis. The unusual forbidden intense sharp (5)D0-(7)F0 transition indicates single site occupancy of Eu(3+) with a narrower range of bonding environment, preventing the cluster formation. This is supported by the stable (5)D0 lifetime with Eu(3+) concentration. The Judd-Ofelt intensity parameter assessment corroborates these results. The CIE color coordinates of these phosphors were found to be (0.60, 0.40), which are close to the NTSC standard values (0.67, 0.33) for a potential red phosphor.

  20. The normal state resistivity of CaTh- and La-doped Y(Nd-123 superconductors in the bipolaron model

    Directory of Open Access Journals (Sweden)

    S. Ghorbani

    2007-12-01

    Full Text Available Polycrystalline samples of Y1-2xCaxThxBa2Cu3O7-δ (with 0.00 ≤x ≤ 0.075 and NdBa2-xLaxCu3O7-δ (with 0.0≤x≤ 0.30 were prepared by the standard solid state method. The transport and superconducting properties have been studied by the resistivity measurements as a function of temperature and doping concentration. Data of resistivity as a function of temperature was analyzed in terms of the bipolaran model. The model well described resistivity data up to near the critical temperature. Obtained results suggested that the hole localization is the main reason for superconducting suppression in the charge neutral doped cuprates and the La doped Nd-123 in addition charge filling.

  1. Structural/surface characterization and catalytic evaluation of rare-earth (Y, Sm and La) doped ceria composite oxides for CH{sub 3}SH catalytic decomposition

    Energy Technology Data Exchange (ETDEWEB)

    He, Dedong; Chen, Dingkai; Hao, Husheng; Yu, Jie; Liu, Jiangping; Lu, Jichang; Liu, Feng [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China); Wan, Gengping [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China); Research Center for Analysis and Measurement, Hainan University, Haikou, 570228 (China); He, Sufang [Research Center for Analysis and Measurement, Kunming University of Science and Technology, Kunming, 650093 (China); Luo, Yongming, E-mail: environcatalysis222@yahoo.com [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China)

    2016-12-30

    Highlights: • Ce{sub 0.75}RE{sub 0.25}O{sub 2-δ} (RE = Y, Sm and La) were synthesized by citrate complexation method. • Ce{sub 0.75}Y{sub 0.25}O{sub 2-δ} exhibited the best stability for the decomposition of CH{sub 3}SH. • Cation radius played a key role in determining structure and surface characteristics. • Catalytic behavior depended on synergistic role of oxygen vacancies and basic sites. • Ce{sub 2}S{sub 3} accumulation on the surface was responsible for the deactivation of catalyst. - Abstract: A series of rare earth (Y, Sm and La) doped ceria composite oxides and pure CeO{sub 2} were synthesized and evaluated by conducting CH{sub 3}SH catalytic decomposition test. Several characterization studies, including XRD, BET, Raman, H{sub 2}-TPR, XPS, FT-IR, CO{sub 2}-TPD and CH{sub 3}SH-TPD, were undertaken to correlate structural and surface properties of the obtained ceria-based catalysts with their catalytic performance for CH{sub 3}SH decomposition. More oxygen vacancies and increased basic sites exhibited in the rare earth doped ceria catalysts. Y doped ceria sample (Ce{sub 0.75}Y{sub 0.25}O{sub 2-δ}), with a moderate increase in basic sites, contained more oxygen vacancies. More structural defects and active sites could be provided, and a relatively small amount of sulfur would accumulate, which resulted in better catalytic performance. The developed catalyst presented good catalytic behavior with stability very similar to that of typical zeolite-based catalysts reported previously. However, La doped ceria catalyst (Ce{sub 0.75}La{sub 0.25}O{sub 2-δ}) with the highest alkalinity was not the most active one. More sulfur species would be adsorbed and a large amount of cerium sulfide species (Ce{sub 2}S{sub 3}) would accumulate, which caused deactivation of the catalysts. The combined effect of increased oxygen vacancies and alkalinity led to the catalytic stability of Ce{sub 0.75}Sm{sub 0.25}O{sub 2-δ} sample was comparable to that of pure Ce

  2. Influence of La doping and synthesis method on the properties of CoFe{sub 2}O{sub 4} nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Mansour, S.F. [Physics Department, Faculty of Science, Zagazig University, Zagazig (Egypt); Hemeda, O.M. [Physics Department, Faculty of Science, Tanta University, Tanta (Egypt); El-Dek, S.I., E-mail: didi5550000@gmail.com [Materials Science and Nanotechnology Department, Faculty of Post Graduate Studies for Advanced Sciences (PSAS), Beni-Suef University, Beni-Suef (Egypt); Salem, B.I. [Physics Department, Faculty of Science, Tanta University, Tanta (Egypt)

    2016-12-15

    Nanocrystals of La doped CoFe{sub 2}O{sub 4} were synthesized using three different techniques: flash autocombustion, citrate–nitrate and the standard ceramic technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the obtained nanocrystals. All samples were crystallized in a spinel structure with cubic symmetry. The decrease in the lattice constant was endorsed to the large difference in ionic radii of both La{sup +3} (1.216 Å) and Fe (0.65 Å) in 6-f coordination. The citrate method displayed superior M{sub s} values amongst all techniques. The coercivity was found to exhibit largest values for the citrate method and then the flash while smallest values are associated with ceramic technique. - Highlights: • CoLa{sub x}Fe{sub 2−x}O{sub 4} nanocrystals crystallized in spinel cubic structure using 3 techniques. • The decrease in the lattice constant is due to the difference in ionic radius of La{sup +3} and Fe{sup 3+}. • The citrate method exhibit largest values of M{sub s} amongst all techniques. • Coercivity exhibits largest values for citrate and then flash, smallest for ceramic technique.

  3. Effect of oxygen vacancy distribution on the thermoelectric properties of La-doped SrTiO3 epitaxial thin films

    KAUST Repository

    Sarath Kumar, S. R.; Abutaha, Anas I.; Hedhili, Mohamed N.; Alshareef, Husam N.

    2012-01-01

    A detailed study of the role of oxygen vacancies in determining the effective mass and high temperature (300–1000 K) thermoelectricproperties of La-doped epitaxial SrTiO3 thin films is presented. It is observed that at intermediate temperatures, a transition from degenerate to non-degenerate behavior is observed in the Seebeck coefficient, but not electrical conductivity, which is attributed to heterogeneous oxygen non-stoichiometry. Heikes formula is found to be invalid for the films with oxygen vacancies. By fitting the spectroscopic ellipsometry (SE) data, obtained in the range 300–2100 nm, using a Drude-Lorentz dispersion relation with two Lorentz oscillators, the electrical and optical properties of the films are extracted. Using the excellent agreement between the transport properties extracted from SE modeling and direct electrical measurements, we demonstrate that an increase in concentration of oxygen vacancies results in a simultaneous increase of both carrier concentration and electron effective mass, resulting in a higher power factor.

  4. Effect of oxygen vacancy distribution on the thermoelectric properties of La-doped SrTiO3 epitaxial thin films

    KAUST Repository

    Sarath Kumar, S. R.

    2012-12-03

    A detailed study of the role of oxygen vacancies in determining the effective mass and high temperature (300–1000 K) thermoelectricproperties of La-doped epitaxial SrTiO3 thin films is presented. It is observed that at intermediate temperatures, a transition from degenerate to non-degenerate behavior is observed in the Seebeck coefficient, but not electrical conductivity, which is attributed to heterogeneous oxygen non-stoichiometry. Heikes formula is found to be invalid for the films with oxygen vacancies. By fitting the spectroscopic ellipsometry (SE) data, obtained in the range 300–2100 nm, using a Drude-Lorentz dispersion relation with two Lorentz oscillators, the electrical and optical properties of the films are extracted. Using the excellent agreement between the transport properties extracted from SE modeling and direct electrical measurements, we demonstrate that an increase in concentration of oxygen vacancies results in a simultaneous increase of both carrier concentration and electron effective mass, resulting in a higher power factor.

  5. Electrochemical Performance of a Carbon Nanotube/La-Doped TiO2 Nanocomposite and its Use for Preparation of an Electrochemical Nicotinic Acid Sensor

    Directory of Open Access Journals (Sweden)

    Hanxing Liu

    2008-11-01

    Full Text Available A carbon nanotube/La-doped TiO2 (La-TiO2 nanocomposite (CLTN was prepared by a procedure similar to a complex/adsorption process. Scanning electron microscopy (SEM images show that the La-TiO2 distributes on the carbon nanotube walls. The CLTN was mixed with paraffin to form a CLTN paste for the CLTN paste electrode (CLTNPE. The electrochemical characteristics of CLTNPE were compared with that of conventional carbon electrodes such as the carbon paste electrode (CPE and glass carbon electrode (GC. The CLTNPE exhibits electrochemical activity and was used to investigate the electrochemistry of nicotinic acid (NA. The modified electrode has a strong electrocatalytic effect on the redox of NA. The cyclic voltammetry (CV redox potential of NA at the CLTNPE is 320 mV. The oxidation process of NA on the CLTNPE is pH dependent. A sensitive chronoamperometric response for NA was obtained covering a linear range from 1.0×10-6 mol·L-1 to 1.2×10-4 mol·L-1, with a detection limit of 2.7×10-7 mol·L-1. The NA sensor displays a remarkable sensitivity and stability. The mean recovery of NA in the human urine is 101.8%, with a mean variation coefficient (RSD of 2.6%.

  6. Effect of thickness and composition on the structure and ordering in La-doped intergranular films between Si{sub 3}N{sub 4} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Yun [Interfacial Molecular Science Laboratory, Department of Materials Science and Engineering, Rutgers University, 607 Taylor Rd., Piscataway, NJ 08855 (United States); Garofalini, Stephen H., E-mail: shg@rutgers.edu [Interfacial Molecular Science Laboratory, Department of Materials Science and Engineering, Rutgers University, 607 Taylor Rd., Piscataway, NJ 08855 (United States)

    2011-08-15

    Molecular dynamics simulations were used to determine the effect of the composition and thickness on the atomistic structure of La-Si-O-N intergranular films (IGFs) between prism and misaligned high-index silicon nitride crystals. Results showed that ordered La adsorption onto the prism-terminated surface is not affected by the orientation of the opposing crystal, although the extent of the ordering away from the interface is affected by IGF thickness. La adsorption at ordered sites 1 and 2 on the prism surface occurred for almost all of the compositions in both 1.8 and 0.6 nm thick IGFs and at sites farther from the prism interface in the thicker IGF, similar to adsorption in triple points. La adsorption on the prism surface occurred at sites precisely the same as seen in high-angle annular dark field scanning transmission electron microscopy studies. Saturation of available sites is affected by the thickness of the IGF, which governs the number of La ions (and N ions) in the IGF, with lower site filling in the thinner IGF. There are clear energy differences for La in the interior of the IGF vs. the interface based on composition and IGF thickness, with the thicker IGF showing greater variation in driving forces for segregation or La incorporation into the IGF. Fracture is affected by both composition and thickness and occurs in the glassy IGF and not in the ordered interfacial regions, consistent with experimentally observed intergranular fracture for La-doped silicon nitride. Segregation of La to the interface affects N distribution within the interior of the IGF, which affects strength.

  7. Al-, Y-, and La-doping effects favoring intrinsic and field induced ferroelectricity in HfO2: A first principles study

    Science.gov (United States)

    Materlik, Robin; Künneth, Christopher; Falkowski, Max; Mikolajick, Thomas; Kersch, Alfred

    2018-04-01

    III-valent dopants have shown to be most effective in stabilizing the ferroelectric, crystalline phase in atomic layer deposited, polycrystalline HfO2 thin films. On the other hand, such dopants are commonly used for tetragonal and cubic phase stabilization in ceramic HfO2. This difference in the impact has not been elucidated so far. The prospect is a suitable doping to produce ferroelectric HfO2 ceramics with a technological impact. In this paper, we investigate the impact of Al, Y, and La doping, which have experimentally proven to stabilize the ferroelectric Pca21 phase in HfO2, in a comprehensive first-principles study. Density functional theory calculations reveal the structure, formation energy, and total energy of various defects in HfO2. Most relevant are substitutional electronically compensated defects without oxygen vacancy, substitutional mixed compensated defects paired with a vacancy, and ionically compensated defect complexes containing two substitutional dopants paired with a vacancy. The ferroelectric phase is strongly favored with La and Y in the substitutional defect. The mixed compensated defect favors the ferroelectric phase as well, but the strongly favored cubic phase limits the concentration range for ferroelectricity. We conclude that a reduction of oxygen vacancies should significantly enhance this range in Y doped HfO2 thin films. With Al, the substitutional defect hardly favors the ferroelectric phase before the tetragonal phase becomes strongly favored with the increasing concentration. This could explain the observed field induced ferroelectricity in Al-doped HfO2. Further Al defects are investigated, but do not favor the f-phase such that the current explanation remains incomplete for Al doping. According to the simulation, doping alone shows clear trends, but is insufficient to replace the monoclinic phase as the ground state. To explain this fact, some other mechanism is needed.

  8. Electrochemical performance of BaSnO3 anode material for lithium-ion battery prepared by molten salt method

    CSIR Research Space (South Africa)

    Nithyadharseni, P

    2016-01-01

    Full Text Available Perovskite-like structure BaSnO(sub3) ceramic oxide has been prepared by low temperature molten salt method using KOH as a flux and Ba(OH)(sub2) and BaCl(sub2) as precursors. The as-prepared compounds were characterized by various techniques...

  9. Influence of difference quantity La-doped TiO{sub 2} photoanodes on the performance of dye-sensitized solar cells: A strategy for choosing an appropriate doping quantity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zige; Li, Guoxiang; Cui, Zijian; Zhang, Kaiyue; Feng, Yaqing [School of Chemical Engineering and Technology, Tianjin University, Weijin Roard 92#, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Weijin Roard 92#, Tianjin 300072 (China); Meng, Shuxian, E-mail: msxmail@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Weijin Roard 92#, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Weijin Roard 92#, Tianjin 300072 (China)

    2016-05-15

    Facilitated by TiO{sub 2} particles adsorbing lanthanide ions in hydrosol, La-doped TiO{sub 2} was produced by a hydrothermal method. The structure, optical and photoluminescence properties of down-converting photoelectrode with the La{sup 3+} were characterized by X-ray (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray detector (EDX) and N{sub 2} adsorption-desorption isotherms measurement. The photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs) fabricated with 0.05 g-La/TiO{sub 2} reached 7.02%, which gave an efficiency improved by 10.36% compared with that of cells fabricated from pure TiO{sub 2}. The improvement in efficiency was ascribed to more dyes adsorbed on the surface of TiO{sub 2}. - Graphical abstract: (a) J–V curves of La-doped photoelectrodes with different La(NO{sub 3}){sub 3}·6H{sub 2}O amounts; (b) the curves of efficiency changing with the amount of La(NO{sub 3}){sub 3}·6H{sub 2}O. The photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs) fabricated with 0.05 g-La/TiO{sub 2} reached 7.02%, which gave an efficiency improved by 10.36% compared with that of cells fabricated from pure TiO{sub 2}.

  10. Piezoelectric properties and diffusion phase transition around PPT of La-doped (Na{sub 0.52}K{sub 0.44}Li{sub 0.04}) Nb{sub 0.8}Ta{sub 0.2}O{sub 3} lead-free piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Wenlong, E-mail: yangwenlong1983@163.com; Wang, Li; Li, Haidong; Han, Junsheng; Xiu, Hanjiang; Zhou, Zhongxiang

    2016-10-01

    Lead-free ceramics (Na{sub 0.52}K{sub 0.44}Li{sub 0.04}){sub 1−3x}La{sub x}Nb{sub 0.8}Ta{sub 0.2}O{sub 3} (KNLNT-Lax, x=0.00, 0.25, 0.5, 0.75, 1.00, 1.25 mol%) as non-polluting materials were prepared by solid state reaction method. The structure, piezoelectric proprieties and temperature stability of KNLNT ceramic with different La doping concentrations were investigated. The results show a transition from orthorhombic-tetragonal mix phase to tetragonal single phase with the variation of La{sup 3+} concentrations. The SEM micrographs of surface and fractured surface show a dense microstructure with few micropores. The La-doped KNLTN ceramic will be an alternative candidate contributes to excellent piezoelectric properties, which are found in the 0.75 mol% La-doped KNLNT ceramics, with d{sub 33}=215pC/N, k{sub p}=42.8%and Q{sub m}=89. It has been remarkably improved that the temperature stability of KNLTN-Lax piezoelectric properties at room temperature, and the dielectric relaxation can be observed obviously. The mechanism of La doping was analyzed in terms of valence compensation and polymorphic phase transition (PPT) diffusion. The orthorhombic-tetragonal phase transition around room temperature and the relaxation transition were considered contributing to the excellent piezoelectric performance and improved temperature stability of La{sup 3+}-doped KNLTN.

  11. Preparation of Ce- and La-Doped Li4Ti5O12 Nanosheets and Their Electrochemical Performance in Li Half Cell and Li4Ti5O12/LiFePO4 Full Cell Batteries

    Directory of Open Access Journals (Sweden)

    Meng Qin

    2017-06-01

    Full Text Available This work reports on the synthesis of rare earth-doped Li4Ti5O12 nanosheets with high electrochemical performance as anode material both in Li half and Li4Ti5O12/LiFePO4 full cell batteries. Through the combination of decreasing the particle size and doping by rare earth atoms (Ce and La, Ce and La doped Li4Ti5O12 nanosheets show the excellent electrochemical performance in terms of high specific capacity, good cycling stability and excellent rate performance in half cells. Notably, the Ce-doped Li4Ti5O12 shows good electrochemical performance as anode in a full cell which LiFePO4 was used as cathode. The superior electrochemical performance can be attributed to doping as well as the nanosized particle, which facilitates transportation of the lithium ion and electron transportation. This research shows that the rare earth doped Li4Ti5O12 nanosheets can be suitable as a high rate performance anode material in lithium-ion batteries.

  12. Preparation of Ce- and La-Doped Li4Ti5O12 Nanosheets and Their Electrochemical Performance in Li Half Cell and Li4Ti5O12/LiFePO4 Full Cell Batteries

    Science.gov (United States)

    Qin, Meng; Li, Yueming; Lv, Xiao-Jun

    2017-01-01

    This work reports on the synthesis of rare earth-doped Li4Ti5O12 nanosheets with high electrochemical performance as anode material both in Li half and Li4Ti5O12/LiFePO4 full cell batteries. Through the combination of decreasing the particle size and doping by rare earth atoms (Ce and La), Ce and La doped Li4Ti5O12 nanosheets show the excellent electrochemical performance in terms of high specific capacity, good cycling stability and excellent rate performance in half cells. Notably, the Ce-doped Li4Ti5O12 shows good electrochemical performance as anode in a full cell which LiFePO4 was used as cathode. The superior electrochemical performance can be attributed to doping as well as the nanosized particle, which facilitates transportation of the lithium ion and electron transportation. This research shows that the rare earth doped Li4Ti5O12 nanosheets can be suitable as a high rate performance anode material in lithium-ion batteries. PMID:28632167

  13. High temperature impedance spectroscopy of barium stannate

    Indian Academy of Sciences (India)

    ... differential thermal analysis, thermogravimetric analysis and Fourier transform infrared techniques. Electrical properties were studied using a.c. impedance spectroscopy technique in the temperature range of 50–650 °C and frequency range of 10 Hz–13 MHz. The complex impedance plots at temperature ≥ 300 °C show ...

  14. Interface energy band alignment at the all-transparent p-n heterojunction based on NiO and BaSnO3

    NARCIS (Netherlands)

    Zhang, Jiaye; Han, Shaobo; Luo, Weihuang; Xiang, Shuhuai; Zou, Jianli; Oropeza, Freddy E.; Gu, Meng; Zhang, Kelvin H.L.

    2018-01-01

    Transparent oxide semiconductors hold great promise for many optoelectronic devices such as transparent electronics, UV-emitting devices, and photodetectors. A p-n heterojunction is the most ubiquitous building block to realize these devices. In this work, we report the fabrication and

  15. Mobility Optimization in LaxBa1-xSnO3 Thin Films Deposited via High Pressure Oxygen Sputtering

    Science.gov (United States)

    Postiglione, William Michael

    BaSnO3 (BSO) is one of the most promising semiconducting oxides currently being explored for use in future electronic applications. BSO possesses a unique combination of high room temperature mobility (even at very high carrier concentrations, > 1019 cm-3), wide band gap, and high temperature stability, making it a potentially useful material for myriad applications. Significant challenges remain however in optimizing the properties and processing of epitaxial BSO, a critical step towards industrial applications. In this study we investigate the viability of using high pressure oxygen sputtering to produce high mobility La-doped BSO thin films. In the first part of our investigation we synthesized, using solid state reaction, phase-pure stoichiometric polycrystalline 2% La-doped BaSnO 3 for use as a target material in our sputtering system. We verified the experimental bulk lattice constant, 4.117 A, to be in good agreement with literature values. Next, we set out to optimize the growth conditions for DC sputtering of La doped BaSnO3. We found that mobility for all our films increased monotonically with deposition temperature, suggesting the optimum temperature for deposition is > 900 °C and implicating a likely improvement in transport properties with post-growth thermal anneal. We then preformed systematic studies aimed at probing the effects of varying thickness and deposition rate to optimize the structural and electronic transport properties in unbuffered BSO films. In this report we demonstrate the ability to grow 2% La BSO thin films with an effective dopant activation of essentially 100%. Our films showed fully relaxed (bulk), out-of-plane lattice parameter values when deposited on LaAlO3, MgO, and (LaAlO3)0.3(Sr2 TaAlO6)0.7 substrates, and slightly expanded out-of-plane lattice parameters for films deposited on SrTiO3, GdScO3, and PrScO3 substrates. The surface roughness's of our films were measured via AFM, and determined to be on the nm scale or better

  16. Solid phase epitaxial growth of high mobility La:BaSnO_3 thin films co-doped with interstitial hydrogen

    International Nuclear Information System (INIS)

    Niedermeier, Christian A.; Rhode, Sneha; Fearn, Sarah; Moram, Michelle A.; Ide, Keisuke; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-01-01

    This work presents the solid phase epitaxial growth of high mobility La:BaSnO_3 thin films on SrTiO_3 single crystal substrates by crystallization through thermal annealing of nanocrystalline thin films prepared by pulsed laser deposition at room temperature. The La:BaSnO_3 thin films show high epitaxial quality and Hall mobilities up to 26 ± 1 cm"2/Vs. Secondary ion mass spectroscopy is used to determine the La concentration profile in the La:BaSnO_3 thin films, and a 9%–16% La doping activation efficiency is obtained. An investigation of H doping to BaSnO_3 thin films is presented employing H plasma treatment at room temperature. Carrier concentrations in previously insulating BaSnO_3 thin films were increased to 3 × 10"1"9" cm"−"3 and in La:BaSnO_3 thin films from 6 × 10"1"9" cm"−"3 to 1.5 × 10"2"0" cm"−"3, supporting a theoretical prediction that interstitial H serves as an excellent n-type dopant. An analysis of the free electron absorption by infrared spectroscopy yields a small (H,La):BaSnO_3 electron effective mass of 0.27 ± 0.05 m_0 and an optical mobility of 26 ± 7 cm"2/Vs. As compared to La:BaSnO_3 single crystals, the smaller electron mobility in epitaxial thin films grown on SrTiO_3 substrates is ascribed to threading dislocations as observed in high resolution transmission electron micrographs.

  17. Equilibrium and kinetic studies of the stannate(IV)-polyol reaction ...

    African Journals Online (AJOL)

    Bulletin of the Chemical Society of Ethiopia. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 24, No 3 (2010) >. Log in or Register to get access to full text downloads.

  18. La-doped BaTiO3 heterostructures: Compensating the polarization discontinuity

    Directory of Open Access Journals (Sweden)

    D. P. Kumah

    2013-12-01

    Full Text Available We demonstrate a route to manipulate the polarization and internal electric field of a complex oxide heterostructure using a layering sequence based on the LaAlO3-SrTiO3 interface. By combining sensitive atomic-level mapping of the structure using direct x-ray phase-retrieval methods with theoretical modeling of the electrostatic charge and polarization, we have devised a novel single-domain polar heterostructure. We find that ionic rearrangement results in strain and free energy minimization, and eliminates the polarization discontinuity leading to a two-fold increase of the spontaneous polarization towards the surface of an ultra-thin single-domain BaTiO3 film.

  19. Crystal chemistry and thermal behavior of La doped (U, Th)O2

    Science.gov (United States)

    Keskar, Meera; Shelke, Geeta P.; Shafeeq, Muhammed; Krishnan, K.; Sali, S. K.; Kannan, S.

    2017-12-01

    X-ray diffraction, chemical and thermal studies of [(U0.2Th0.8)1-yLay]O2+x (LUTL) and [(U0.3Th0.7)1-yLay]O2+x (UTL); compounds (where y ≤ 0.4) were carried out. These compounds were synthesized by gel combustion method followed by heating in reduced atmospheres at 1673 K. To co-relate lattice parameters with metal and oxygen concentrations, reduced oxides were heated in Ar, CO2 and air atmospheres. Retention of FCC phase was confirmed in all mixed oxides with y ≤ 0.4. The cubic lattice parameters could be expressed in a linear equation of x and y as: a (Ǻ) = 5.5709 - 0.187 x + 0.032 y; [x Oxidation studies and simple ionic model calculations suggested that uranium is predominantly present as a mixture of +5 and + 6 states when La/U ratio ∼2. Oxidation kinetics of mixed oxides was studied by non-isothermal method using thermogravimetry and was found to be a diffusion controlled reaction. High temperature X-ray diffraction studies of LUTL and UTL mixed oxides showed positive thermal expansion in the temperature range of 298-1273 K and % expansion increases with La concentration.

  20. Temperature stability and electrical properties in La-doped KNN-based ceramics

    KAUST Repository

    Lv, Xiang; Wu, Jiagang; Zhu, Jianguo; Xiao, Dingquan; Zhang, Xixiang

    2018-01-01

    To improve the temperature stability and electrical properties of KNN‐based ceramics, we simultaneously consider the phase boundary and the addition of rare earth element (La), 0.96K0.5Na0.5Nb0.96Sb0.04O3‐0.04(Bi1‐xLax)0.5Na0.5ZrO3 (0 ≤ x ≤ 1.0) ceramics. More specifically, we investigate how the phase boundary and the addition of La3+ affect the phase structure, electrical properties, and temperature stability of the ceramic. We show that increasing the La3+ content leads to a change in phase structure, from a rhombohedral‐tetragonal (R‐T) phase coexistence to a cubic phase. More importantly, we show that the appropriate addition of La3+ (x = 0.2) can simultaneously improve the unipolar strain (from 0.127% to 0.147%) and the temperature stability (i.e., the unipolar strain of 0.147% remains unchanged when T is increased from 25 to 80°C). In addition, we find that the ceramics with x = 0.2 exhibit a large piezoelectric constant (d33) of ~430 pC/N, a high Curie temperature (TC) of ~240°C and a fatigue‐free behavior (after 106 electric cycles). The enhanced electrical properties mostly originate from the easy domain switching, whereas the improved temperature stability can be attributed to the R‐T phase boundary and the appropriate addition of La3+.

  1. A quantum mechanical study of La-doped Pb(Zr,Ti)O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Stashans, Arvids [Grupo de Fisica de Cristales, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)]. E-mail: arvids@utpl.edu.ec; Maldonado, Frank [Grupo de Fisica de Cristales, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)

    2007-04-15

    Lanthanum-modified Pb(Zr,Ti)O{sub 3} (PZT) crystals have been investigated applying a quantum-mechanical approach based on the Hartree-Fock theory. A morphotropic phase boundary (MPB), PbZr{sub 0.53}Ti{sub 0.47}O{sub 3}, of the crystal was considered throughout the study. The obtained results show the outward atomic displacements with respect to the La impurity within the defective region and also the increase of covalent nature in the chemical bonding of the material. These outcomes are discussed and analyzed in light of the available experimental data. The occurrence of Jahn-Teller self-trapped electron polarons is predicted in the present report.

  2. A quantum mechanical study of La-doped Pb(Zr,Ti)O3

    International Nuclear Information System (INIS)

    Stashans, Arvids; Maldonado, Frank

    2007-01-01

    Lanthanum-modified Pb(Zr,Ti)O 3 (PZT) crystals have been investigated applying a quantum-mechanical approach based on the Hartree-Fock theory. A morphotropic phase boundary (MPB), PbZr 0.53 Ti 0.47 O 3 , of the crystal was considered throughout the study. The obtained results show the outward atomic displacements with respect to the La impurity within the defective region and also the increase of covalent nature in the chemical bonding of the material. These outcomes are discussed and analyzed in light of the available experimental data. The occurrence of Jahn-Teller self-trapped electron polarons is predicted in the present report

  3. Nonvolatile resistive switching in metal/La-doped BiFeO3/Pt sandwiches.

    Science.gov (United States)

    Li, Mi; Zhuge, Fei; Zhu, Xiaojian; Yin, Kuibo; Wang, Jinzhi; Liu, Yiwei; He, Congli; Chen, Bin; Li, Run-Wei

    2010-10-22

    The resistive switching (RS) characteristics of a Bi(0.95)La(0.05)FeO(3) (La-BFO) film sandwiched between a Pt bottom electrode and top electrodes (TEs) made of Al, Ag, Cu, and Au have been studied. Devices with TEs made of Ag and Cu showed stable bipolar RS behaviors, whereas those with TEs made of Al and Au exhibited unstable bipolar RS. The Ag/La-BFO/Pt structure showed an on/off ratio of 10(2), a retention time > 10(5) s, and programming voltages TEs under a bias voltage. The maximum current before the reset process (on-to-off switching) was found to increase linearly with the current compliance applied during the set process (off-to-on switching).

  4. Temperature stability and electrical properties in La-doped KNN-based ceramics

    KAUST Repository

    Lv, Xiang

    2018-04-16

    To improve the temperature stability and electrical properties of KNN‐based ceramics, we simultaneously consider the phase boundary and the addition of rare earth element (La), 0.96K0.5Na0.5Nb0.96Sb0.04O3‐0.04(Bi1‐xLax)0.5Na0.5ZrO3 (0 ≤ x ≤ 1.0) ceramics. More specifically, we investigate how the phase boundary and the addition of La3+ affect the phase structure, electrical properties, and temperature stability of the ceramic. We show that increasing the La3+ content leads to a change in phase structure, from a rhombohedral‐tetragonal (R‐T) phase coexistence to a cubic phase. More importantly, we show that the appropriate addition of La3+ (x = 0.2) can simultaneously improve the unipolar strain (from 0.127% to 0.147%) and the temperature stability (i.e., the unipolar strain of 0.147% remains unchanged when T is increased from 25 to 80°C). In addition, we find that the ceramics with x = 0.2 exhibit a large piezoelectric constant (d33) of ~430 pC/N, a high Curie temperature (TC) of ~240°C and a fatigue‐free behavior (after 106 electric cycles). The enhanced electrical properties mostly originate from the easy domain switching, whereas the improved temperature stability can be attributed to the R‐T phase boundary and the appropriate addition of La3+.

  5. Barium Staminate as Semiconductor Working Electrodes for Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Fu-an Guo

    2010-01-01

    Full Text Available Dye-sensitized solar cells (DSSCs are fabricated with perovskite-type BaSnO3 as the photoelectrode materials. Different preparation methods including coprecipitation, hydrothermal, and solid state reaction are employed to synthesize BaSnO3 particles to optimize the photoelectric activities of electrode materials. The photoelectric properties of BaSnO3 particles and the performances of DSSCs are investigated by surface photovoltage spectroscopy and current-voltage measurements. The light-to-electricity conversion of 1.1% is preliminarily reached on the DSSC made of the coprecipitation-derived BaSnO3 particles. Large current density of hole injection into the HOMO level of N719 dye from the valence band of BaSnO3 and reduced photogenerated charge recombination in BaSnO3 could be responsible for the observed solar cell performance of the DSSC fabricated from the coprecipitation-derived BaSnO3 particles.

  6. Electric properties and phase transition behavior in lead lanthanum zirconate stannate titanate ceramics with low zirconate content

    Science.gov (United States)

    Zeng, Tao; Lou, Qi-Wei; Chen, Xue-Feng; Zhang, Hong-Ling; Dong, Xian-Lin; Wang, Gen-Shui

    2015-11-01

    The phase transitions, dielectric properties, and polarization versus electric field (P-E) hysteresis loops of Pb0.97La0.02(Zr0.42Sn0.58-xTix)O3 (0.13≤ x ≤0.18) (PLZST) bulk ceramics were systematically investigated. This study exhibited a sequence of phase transitions by analyzing the change of the P-E hysteresis loops with increasing temperature. The antiferroelectric (AFE) to ferroelectric (FE) phase boundary of PLZST with the Zr content of 0.42 was found to locate at the Ti content between 0.14 and 0.15. This work is aimed to improve the ternary phase diagram of lanthanum-doped PZST with the Zr content of 0.42 and will be a good reference for seeking high energy storage density in the PLZST system with low-Zr content. Project supported by the National Natural Science Foundation of China (Grant Nos. 51202273, 11204304, and 11304334) and the Science and Technology Commission of Shanghai Municipality, China (Grant No. 14DZ2261000).

  7. Study of magnetic and electrical properties of La doped Mn-Zn nanoferrites synthesized by co-precipitation technique

    International Nuclear Information System (INIS)

    Panwar, Neena; Thakur, Atul; Thakur, Preeti

    2013-01-01

    Lanthanum manganese zinc ferrite powder of the composition Mn 0.4 Zn 0.6 La 0.4 Fe 1.6 O 4 were synthesized via co-precipitation technique. Metallic chlorides of manganese, zinc and iron in which Lanthanum is doped were taken. Sodium hydroxide (NaOH) base was used as precipitant agent. The calcinations (presintering) were performed at 700℃ for 3h and sintering at different temperatures 900℃, 850℃, 800℃ also for 3h. The structural investigation of the prepared sample was performed with X-ray diffraction (XRD) and scanning electron microscope (SEM). For studying magnetic properties vibrating sample magnetometer (VSM) are used. Electrical properties were studied by DC resistivity set up. (author)

  8. Magnetic and electrical properties of the La doped Mn-Zn ferrite nanoparticles synthesized by the co-precipitation method

    International Nuclear Information System (INIS)

    Chandel, Vipin; Vijeta; Thakur, Atul; Thakur, Preeti

    2013-01-01

    In the present study, nano crystalline Mn-Zn-La ferrite with chemical formula Mn 0.4 Zn 0.6 La 0.3 Fe 1.7 O 4 was successfully synthesized by a co-precipitation method. The prepared powders were presintered at 700℃. The pallets formed were finally sintered at 700℃, 800℃ and 900℃ for 3h reach. The structural and morphological behavior was investigated by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD confirms the formation of the expected spinel structure. Scanning Electron Microscopy (SEM) was used to characterize the microstructure of the ferrite samples i.e. grain morphology, grain size, grain size distribution and shape. Fourier transform infrared spectroscopy (FTIR) confirms the peaks of different molecules in the given sample. Electrical and magnetic properties were studied by using dc resistivity set up and vibrating sample magnetometer (VSM). (author)

  9. Kinetic Monte Carlo model of defect transport and irradiation effects in La-doped CeO2

    International Nuclear Information System (INIS)

    Oaks, Aaron; Yun Di; Ye Bei; Chen Weiying; Stubbins, James F.

    2011-01-01

    A generalized Kinetic Monte Carlo code was developed to study oxygen mobility in UO 2 type nuclear fuels, using lanthanum doped CeO 2 as a surrogate material. Molecular Statics simulations were performed using interatomic potentials for CeO 2 developed by Gotte, Minervini, and Sayle to calculate local configuration-dependent oxygen vacancy migration energies. Kinetic Monte Carlo simulations of oxygen vacancy diffusion were performed at varying lanthanum dopant concentrations using the developed generalized Kinetic Monte Carlo code and the calculated configuration-dependent migration energies. All three interatomic potentials were found to confirm the lanthanum trapping effect. The results of these simulations were compared with experimental data and the Gotte potential was concluded to yield the most realistic diffusivity curve.

  10. Electrochemical performance of La-doped Sr{sub 2}MgMoO{sub 6-{delta}} in natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yuan [Texas Materials Institute, ETC 9.102, The University of Texas at Austin, Austin, TX 78712 (United States); College of Physics, Jilin University, 2519 Jiefang Road, Changchun 130023, Jilin Province (China); Huang, Yun-Hui; Goodenough, John B. [Texas Materials Institute, ETC 9.102, The University of Texas at Austin, Austin, TX 78712 (United States); Ying, Jie-Rong [Texas Materials Institute, ETC 9.102, The University of Texas at Austin, Austin, TX 78712 (United States); Institute of Nuclear and New Energy Technology, Tsinghua University, P.O. Box 1021, Beijing 102201 (China)

    2007-08-15

    Modification of the double perovskite Sr{sub 2}MgMoO{sub 6-{delta}} by La substitution has shown that Sr{sub 2-x}La{sub x}MgMoO{sub 6-{delta}} with 0.6 {<=} x {<=} 0.8 has better performance as the anode of a solid oxide fuel cell. With a Sr{sub 1.2}La{sub 0.8}MgMoO{sub 6-{delta}} anode, LSGM electrolyte, SrCo{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} cathode, and a La{sub 0.5}Ce{sub 0.4}O{sub 1.7-{delta}} buffer layer between the anode and the electrolyte, a maximum power density of 550 mW/cm{sup 2} has been obtained for a SOFC operating on wet methane (3%H{sub 2}O) at 800 C. The performance of the SOFC using C{sub 2}H{sub 6} fuel, like that of CH{sub 4}, changes little on switching from dry C{sub 2}H{sub 6} to 3% H{sub 2}O/C{sub 2}H{sub 6}, but improvement with wet C{sub 3}H{sub 8} shows that some steam will need to be added to a moderately desulfurized natural-gas fuel. (author)

  11. Fabrication of La-doped TiO2 Film Electrode and investigation of its electrocatalytic activity for furfural reduction

    International Nuclear Information System (INIS)

    Wang, Fengwu; Xu, Mai; Wei, Lin; Wei, Yijun; Hu, Yunhu; Fang, Wenyan; Zhu, Chuan Gao

    2015-01-01

    Lanthanum trivalent ions (La 3+ ) doped nano-TiO 2 film electrode was prepared by the sol–gel method. The prepared electrode was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The electrocatalytic properties of the roughened TiO 2 film electrode towards the electrocatalytic reduction of furfural to furfural alcohol were evaluated by CV and preparative electrolysis experiments. The results of the optimum molar ratio of La: Ti was 0.005:1. Experimental evidence was presented that the La nano-TiO 2 electrode exhibited higher electrocatalytic activity for the reduction of furfural than the undoped nano-TiO 2 electrode in N,N-dimethylformamide medium. Bulk electrolysis studies were also carried out for the reduction of furfural and the product was confirmed by NMR

  12. Structural, thermal, electrical and magnetic properties of pure and 50% La doped BiFeO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jangid, S.; Barbar, S.K.; Bala, Indu [Department of Physics, M.L. Sukhadia University, Durga Nursery Road, Udaipur, Rajasthan 313001 (India); Roy, M., E-mail: mroy1959@yahoo.co.in [Department of Physics, M.L. Sukhadia University, Durga Nursery Road, Udaipur, Rajasthan 313001 (India)

    2012-09-15

    Polycrystalline ceramic samples of pure and 50% La substituted BiFeO{sub 3} have been prepared by standard solid state reaction method using high purity oxides and carbonates. The formation of the single phase compound as well as its chemical analysis has been checked by X-ray diffraction and energy dispersive X-ray microanalysis (EDAX) techniques. A better agreement between observed and calculated X-ray powder diffraction patterns was obtained by performing the Rietveld refinement with a structural model using the non-centrosymmetric space group R3c. The lattice parameters in both the cases have been refined but the over-all structure remains the same. The microstructural studies have been carried out using scanning electron microscopy (SEM). Modulated differential scanning calorimetry (MDSC) has been used to detect the Neel/transition temperature in the compounds. The activation energies calculated from log {sigma} vs 1/T curve are 0.81 eV and 1.13 eV respectively. Vibrating sample magnetometer (VSM) has been used to study the magnetic behaviour of the compounds. It has been observed that by 50% La substitution the insulating behaviour of the material has been improved and showing the antiferromagnetic to weak ferromagnetic behaviour.

  13. Enhanced activity and stability of La-doped CeO2 monolithic catalysts for lean-oxygen methane combustion.

    Science.gov (United States)

    Zhu, Wenjun; Jin, Jianhui; Chen, Xiao; Li, Chuang; Wang, Tonghua; Tsang, Chi-Wing; Liang, Changhai

    2018-02-01

    Effective utilization of coal bed methane is very significant for energy utilization and environment protection. Catalytic combustion of methane is a promising way to eliminate trace amounts of oxygen in the coal bed methane and the key to this technology is the development of high-efficiency catalysts. Herein, we report a series of Ce 1-x La x O 2-δ (x = 0-0.8) monolithic catalysts for the catalytic combustion of methane, which are prepared by citric acid method. The structural characterization shows that the substitution of La enhance the oxygen vacancy concentration and reducibility of the supports and promote the migration of the surface oxygen, as a result improve the catalytic activity of CeO 2 . M-Ce 0.8 La 0.2 O 2-δ (monolithic catalyst, Ce 0.8 La 0.2 O 2-δ coated on cordierite honeycomb) exhibits outstanding activity for methane combustion, and the temperature for 10 and 90% methane conversion are 495 and 580 °C, respectively. Additionally, Ce 0.8 La 0.2 O 2-δ monolithic catalyst presents excellent stability at high temperature. These Ce 1-x La x O 2-δ monolithic materials with a small amount of La incorporation therefore show promises as highly efficient solid solution catalysts for lean-oxygen methane combustion. Graphical abstract ᅟ.

  14. Effect of La doping on interface barrier between Si-passivated Ge and insulating HfO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kolomiiets, Nadiia M.; Afanas' ev, Valery V.; Madia, Oreste; Stesmans, Andre [Department of Physics and Astronomy, University of Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium); Cott, Daire J.; Collaert, Nadine [Imec, Kapeldreef 75, 3001 Leuven (Belgium); Thean, Aaron [Imec, Kapeldreef 75, 3001 Leuven (Belgium); National University of Singapore (Singapore)

    2016-12-15

    By analyzing internal photoemission of electrons from Si/SiO{sub x}-passivated Ge into insulating HfO{sub 2} we found that insertion of additional La interlayer between SiO{sub x} and HfO{sub 2} leads to dramatic increase (more than by factor of 20) of the barrier transparency. However, no measurable variation of the interface barrier height is observed suggesting that La induces intermixing of near-interface oxide stack resulting in development of additional density of states corresponding to conduction band of LaO{sub x} and HfO{sub x} sub-networks. At the same time, photoemission results indicate the presence of discrete positive charges in the near-interface oxide layer which may explain the observed ∝1 V shift of capacitance-voltage curves. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Gas sensing properties of zinc stannate (Zn{sub 2}SnO{sub 4}) nanowires prepared by carbon assisted thermal evaporation process

    Energy Technology Data Exchange (ETDEWEB)

    Tharsika, T., E-mail: tharsika@siswa.um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Haseeb, A.S.M.A., E-mail: haseeb@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Akbar, S.A., E-mail: akbar.1@osu.edu [Center for Industrial Sensors and Measurements (CISM), Department of Materials Science and Engineering, Ohio State University, 2041 College Road, Columbus, OH 43210 (United States); Sabri, M.F.M., E-mail: faizul@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Wong, Y.H., E-mail: yhwong@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-01-05

    Highlights: • Zn{sub 2}SnO{sub 4} nanowires are grown on Au/alumina substrate by a carbon assisted thermal evaporation process. • Optimum growth conditions for Zn{sub 2}SnO{sub 4} nanowires are determined. • Ethanol gas is selectively sensed with high sensitivity. - Abstract: Zn{sub 2}SnO{sub 4} nanowires are successfully synthesized by a carbon assisted thermal evaporation process with the help of a gold catalyst under ambient pressure. The as-synthesized nanowires are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) equipped with an energy dispersive X-ray spectroscopy (EDS). The XRD patterns and elemental mapping via TEM–EDS clearly indicate that the nanowires are Zn{sub 2}SnO{sub 4} with face centered spinel structure. HRTEM image confirms that Zn{sub 2}SnO{sub 4} nanowires are single crystalline with an interplanar spacing of 0.26 nm, which is ascribed to the d-spacing of (3 1 1) planes of Zn{sub 2}SnO{sub 4}. The optimum processing condition and a possible formation mechanism of these Zn{sub 2}SnO{sub 4} nanowires are discussed. Additionally, sensor performance of Zn{sub 2}SnO{sub 4} nanowires based sensor is studied for various test gases such as ethanol, methane and hydrogen. The results reveal that Zn{sub 2}SnO{sub 4} nanowires exhibit excellent sensitivity and selectivity toward ethanol with quick response and recovery times. The response of the Zn{sub 2}SnO{sub 4} nanowires based sensors to 50 ppm ethanol at an optimum operating temperature of 500 °C is about 21.6 with response and recovery times of about 116 s and 182 s, respectively.

  16. Monoanionic Tin Oligomers Featuring Sn–Sn or Sn–Pb Bonds: Synthesis and Characterization of a Tris(TriheteroarylstannylStannate and -Plumbate

    Directory of Open Access Journals (Sweden)

    Kornelia Zeckert

    2016-06-01

    Full Text Available The reaction of the lithium tris(2-pyridylstannate [LiSn(2-py6OtBu3] (py6OtBu = C5H3N-6-OtBu, 1, with the element(II amides E{N(SiMe32}2 (E = Sn, Pb afforded complexes [LiE{Sn(2-py6OtBu3}3] for E = Sn (2 and E = Pb (3, which reveal three Sn–E bonds each. Compounds 2 and 3 have been characterized by solution NMR spectroscopy and X-ray crystallographic studies. Large 1J(119Sn–119/117Sn as well as 1J(207Pb–119/117Sn coupling constants confirm their structural integrity in solution. However, contrary to 2, complex 3 slowly disintegrates in solution to give elemental lead and the hexaheteroarylditin [Sn(2-py6OtBu3]2 (4.

  17. Surface spin effects in La-doped CoFe.sub.2./sub.O.sub.4./sub. nanoparticles prepared by microemulsion route

    Czech Academy of Sciences Publication Activity Database

    Burianová, Simona; Poltierová Vejpravová, Jana; Holec, Petr; Plocek, J.; Nižňanský, D.

    2011-01-01

    Roč. 110, č. 7 (2011), "073902-1"-"073902-7" ISSN 0021-8979 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40320502 Keywords : CoFe 2 O 4 nanoparticles * lanthanum doping * microemulsion route * high coercivity * surface spin effects Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.168, year: 2011

  18. Characterization of deep level defects and thermally stimulated depolarization phenomena in La-doped TlInS{sub 2} layered semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Seyidov, MirHasan Yu., E-mail: smirhasan@gyte.edu.tr; Suleymanov, Rauf A.; Mikailzade, Faik A. [Department of Physics, Gebze Technical University, Gebze, Kocaeli 41400 (Turkey); Institute of Physics of NAS of Azerbaijan, H. Javid ave. 33, Baku AZ-1143 (Azerbaijan); Kargın, Elif Orhan [Department of Physics, Gebze Technical University, Gebze, Kocaeli 41400 (Turkey); Odrinsky, Andrei P. [Institute of Technical Acoustics, National Academy of Sciences of Belarus, Lyudnikov ave. 13, Vitebsk 210717 (Belarus)

    2015-06-14

    Lanthanum-doped high quality TlInS{sub 2} (TlInS{sub 2}:La) ferroelectric-semiconductor was characterized by photo-induced current transient spectroscopy (PICTS). Different impurity centers are resolved and identified. Analyses of the experimental data were performed in order to determine the characteristic parameters of the extrinsic and intrinsic defects. The energies and capturing cross section of deep traps were obtained by using the heating rate method. The observed changes in the Thermally Stimulated Depolarization Currents (TSDC) near the phase transition points in TlInS{sub 2}:La ferroelectric-semiconductor are interpreted as a result of self-polarization of the crystal due to the internal electric field caused by charged defects. The TSDC spectra show the depolarization peaks, which are attributed to defects of dipolar origin. These peaks provide important information on the defect structure and localized energy states in TlInS{sub 2}:La. Thermal treatments of TlInS{sub 2}:La under an external electric field, which was applied at different temperatures, allowed us to identify a peak in TSDC which was originated from La-dopant. It was established that deep energy level trap BTE43, which are active at low temperature (T ≤ 156 K) and have activation energy 0.29 eV and the capture cross section 2.2 × 10{sup −14} cm{sup 2}, corresponds to the La dopant. According to the PICTS results, the deep level trap center B5 is activated in the temperature region of incommensurate (IC) phases of TlInS{sub 2}:La, having the giant static dielectric constant due to the structural disorders. From the PICTS simulation results for B5, native deep level trap having an activation energy of 0.3 eV and the capture cross section of 1.8 × 10{sup −16} cm{sup 2} were established. A substantial amount of residual space charges is trapped by the deep level localized energy states of B5 in IC-phase. While the external electric field is applied, permanent dipoles, which are originated from the charged B5 deep level defects, are aligned in the direction of the applied electric field and the equilibrium polarization can be reached in a relatively short time. When the polarization field is maintained, while cooling the temperature of sample to a sufficiently low degrees, the relaxation times of the aligned dipoles drastically increases. Practically, frozen internal electric field or electrets states remain inside the TlInS{sub 2}:La when the applied bias field is switched off. The influence of deep level defects on TSDC spectra of TlInS{sub 2}:La has been revealed for the first time.

  19. Characterization of deep level defects and thermally stimulated depolarization phenomena in La-doped TlInS2 layered semiconductor

    International Nuclear Information System (INIS)

    Seyidov, MirHasan Yu.; Suleymanov, Rauf A.; Mikailzade, Faik A.; Kargın, Elif Orhan; Odrinsky, Andrei P.

    2015-01-01

    Lanthanum-doped high quality TlInS 2 (TlInS 2 :La) ferroelectric-semiconductor was characterized by photo-induced current transient spectroscopy (PICTS). Different impurity centers are resolved and identified. Analyses of the experimental data were performed in order to determine the characteristic parameters of the extrinsic and intrinsic defects. The energies and capturing cross section of deep traps were obtained by using the heating rate method. The observed changes in the Thermally Stimulated Depolarization Currents (TSDC) near the phase transition points in TlInS 2 :La ferroelectric-semiconductor are interpreted as a result of self-polarization of the crystal due to the internal electric field caused by charged defects. The TSDC spectra show the depolarization peaks, which are attributed to defects of dipolar origin. These peaks provide important information on the defect structure and localized energy states in TlInS 2 :La. Thermal treatments of TlInS 2 :La under an external electric field, which was applied at different temperatures, allowed us to identify a peak in TSDC which was originated from La-dopant. It was established that deep energy level trap BTE43, which are active at low temperature (T ≤ 156 K) and have activation energy 0.29 eV and the capture cross section 2.2 × 10 −14 cm 2 , corresponds to the La dopant. According to the PICTS results, the deep level trap center B5 is activated in the temperature region of incommensurate (IC) phases of TlInS 2 :La, having the giant static dielectric constant due to the structural disorders. From the PICTS simulation results for B5, native deep level trap having an activation energy of 0.3 eV and the capture cross section of 1.8 × 10 −16 cm 2 were established. A substantial amount of residual space charges is trapped by the deep level localized energy states of B5 in IC-phase. While the external electric field is applied, permanent dipoles, which are originated from the charged B5 deep level defects, are aligned in the direction of the applied electric field and the equilibrium polarization can be reached in a relatively short time. When the polarization field is maintained, while cooling the temperature of sample to a sufficiently low degrees, the relaxation times of the aligned dipoles drastically increases. Practically, frozen internal electric field or electrets states remain inside the TlInS 2 :La when the applied bias field is switched off. The influence of deep level defects on TSDC spectra of TlInS 2 :La has been revealed for the first time

  20. Mo, Mn and La doped TiO{sub 2}: Synthesis, characterization and photocatalytic activity for the decolourization of three different chromophoric dyes

    Energy Technology Data Exchange (ETDEWEB)

    Umar, K.; Haque, M.M. [Department of Chemistry, Aligarh Muslim University, Aligarh 202 002 (India); Muneer, M., E-mail: readermuneer@gmail.com [Department of Chemistry, Aligarh Muslim University, Aligarh 202 002 (India); Harada, T.; Matsumura, M. [Research Center for Solar Energy Chemistry, Osaka University, 1-3 Machikaneyama, Toyonaka 560-8531 (Japan)

    2013-11-25

    Highlights: •Detail study on synthesis, characterization and photocatalytic activity of doped-TiO{sub 2}. •SEM images indicates partial crystalline nature with rough surfaces. •The XRD analysis shows the partial crystalline nature and anatase phase. •The UV–Vis absorption spectra showed λ{sub max} shift towards longer wavelength. •TiO{sub 2} with dopant 0.75% (Mo), 1.0% (Mn, La) showed best photocatalytic efficiency. -- Abstract: Nanocrystalline TiO{sub 2} particles doped with different concentrations of Molybdenum (Mo), Manganese (Mn) and Lanthanum (La) (0.25–1.0%) were synthesized using sol–gel method and characterized by standard analytical techniques such as X-ray diffraction (XRD), UV–Vis spectroscopy and Scanning Electron Microscopy (SEM). The XRD analysis shows the partial crystalline nature and anatase phase. The SEM images of undoped and doped TiO{sub 2} at different magnifications also show the partial crystalline nature with rough surfaces. The photocatalytic activity of the synthesized particles (TiO{sub 2} doped with Mo, Mn and La) was tested by studying the decolourization of three different chromophoric dyes such as Acid Red 88 (azo dye), Gentian Violet (triphenylmethane dye) and Remazol Brilliant Blue R (anthraquinone dye) as a function of time on irradiation in aqueous suspension in an immersion well photochemical reactor with a 500 W halogen linear lamp in the presence of atmospheric oxygen. The results indicate that TiO{sub 2} with dopant concentration of 0.75% (Mo) and 1.0% (Mn, La) showed the highest photocatalytic activity as compared to the other dopant concentrations for the decolourization of all the dyes.

  1. Effects of ordered mesoporous structure and La-doping on the microwave absorbing properties of CoFe2O4

    Science.gov (United States)

    Shang, Tao; Lu, Qingshan; Chao, Luomeng; Qin, Yanli; Yun, Yuehou; Yun, Guohong

    2018-03-01

    Low-density ordered mesoporous CoFe2O4 (Osbnd CFO) and CoLa0.12Fe1.88O4 (Osbnd CLFO) are prepared by nanocasting method using mesoporous silica SBA-15 as a hard-template. The crystal structure, surface chemical state, magnetic properties and electromagnetic parameters are characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption measurement, X-ray photoelectron spectroscopy, physical property measurement system and vector network analyzer. The results show that all the samples formed a single phase with cubic spinel structure. Meanwhile Osbnd CFO and Osbnd CLFO possess a highly ordered mesostructure. Comparing with particle CoFe2O4 (P-CFO), Osbnd CFO with high specific surface area exhibits lower magnetic saturation (Ms), higher imaginary part of complex permittivity (ε‧‧) and imaginary part of the complex permeability (μ‧‧). The minimum reflection loss (RL) of Osbnd CFO reaches -27.36 dB with a matching thickness of 3.0 mm. The enhancement of the microwave absorbing performances of Osbnd CFO can be mainly attributed to the good impedance matching, high electromagnetic wave attenuation and multiple reflections of electromagnetic wave originated from the ordered mesoporous structure. The Ms of Osbnd CLFO decreases after La3+ doping, while the specific surface area, coercivity value, ε‧‧ and μ‧‧ of Osbnd CLFO increase. The minimum RL of Osbnd CLFO reaches -46.47 dB with a thickness of 3.0 mm, and the effective absorption frequency bandwidth reaches 4.9 GHz.

  2. A study on the development of high-Tc superconducting wire

    International Nuclear Information System (INIS)

    Won, Dong Yeon; Lee, Hee Gyoun; Kim, Chan Joong

    1991-09-01

    High magnetization YBaCuO superconductor was prepared with additions of BaSnO 3 , SnO 2 and SiC by partial melt processing. Addition of BaSnO 3 increased the magnetic property of YBaCuO by flux pinning action of finely dispersed BaSnO 3 particles, while addition of SnO 2 decreased the magnetic property, because the size of particle was larger than that of BaSnO 3 . BiPbSrCaCuO superconducting tape of single filament was prepared by powder-in-tube method using silver as a shearth material. The fabrication techniques involves powder packing, swaging, drawing and cold rolling/pressing method. The final dimension of wire after drawing is 1.2mm diameter. The wire was pressed into a tape form with a thickness of 70micron and a width of 3mm. The obtained critical current density of the prepared tape was 2000A/cm 2 at 77K. (Author)

  3. Band-gap engineering of functional perovskites through quantum confinement and tunneling

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Pandey, Mohnish; Thygesen, Kristian Sommer

    2015-01-01

    An optimal band gap that allows for a high solar-to-fuel energy conversion efficiency is one of the key factors to achieve sustainability. We investigate computationally the band gaps and optical spectra of functional perovskites composed of layers of the two cubic perovskite semiconductors BaSnO3...... and BaTaO2N. Starting from an indirect gap of around 3.3 eV for BaSnO3 and a direct gap of 1.8 eV for BaTaO2N, different layerings can be used to design a direct gap of the functional perovskite between 2.3 and 1.2 eV. The variations of the band gap can be understood in terms of quantum confinement...

  4. Chemically stable perovskites as cathode materials for solid oxide fuel cells: La-doped Ba0.5Sr0.5Co0.8Fe0.2O(3-δ).

    Science.gov (United States)

    Kim, Junyoung; Choi, Sihyuk; Jun, Areum; Jeong, Hu Young; Shin, Jeeyoung; Kim, Guntae

    2014-06-01

    Ba0.5Sr0.5Co0.8Fe0.2O(3-δ) (BSCF) has won tremendous attention as a cathode material for intermediate-temperature solid-oxide fuel cells (IT-SOFC) on the basis of its fast oxygen-ion transport properties. Nevertheless, wide application of BSCF is impeded by its phase instabilities at intermediate temperature. Here we report on a chemically stable SOFC cathode material, La0.5Ba0.25Sr0.25Co0.8Fe0.2O(3-δ) (LBSCF), prepared by strategic approaches using the Goldschmidt tolerance factor. The tolerance factors of LBSCF and BSCF indicate that the structure of the former has a smaller deformation of cubic symmetry than that of the latter. The electrical property and electrochemical performance of LBSCF are improved compared with those of BSCF. LBSCF also shows excellent chemical stability under air, a CO2-containg atmosphere, and low oxygen partial pressure while BSCF decomposed under the same conditions. Together with this excellent stability, LBSCF shows a power density of 0.81 W cm(-2) after 100 h, whereas 25 % degradation for BSCF is observed after 100 h. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A novel design of anode-supported solid oxide fuel cells with Y 2O 3-doped Bi 2O 3, LaGaO 3 and La-doped CeO 2 trilayer electrolyte

    Science.gov (United States)

    Guo, Weimin; Liu, Jiang

    Anode-supported solid oxide fuel cells (SOFCs) with a trilayered yttria-doped bismuth oxide (YDB), strontium- and magnesium-doped lanthanum gallate (LSGM) and lanthanum-doped ceria (LDC) composite electrolyte film are developed. The cell with a YDB (18 μm)/LSGM (19 μm)/LDC (13 μm) composite electrolyte film (designated as cell-A) shows the open-circuit voltages (OCVs) slightly higher than that of a cell with an LSGM (31 μm)/LDC (17 μm) electrolyte film (designated as cell-B) in the operating temperature range of 500-700 °C. The cell-A using Ag-YDB composition as cathode exhibits lower polarization resistance and ohmic resistance than those of a cell-B at 700 °C. The results show that the introduction of YDB to an anode-supported SOFC with a LSGM/LDC composite electrolyte film can effectively block electronic transport through the cell and thus increased the OCVs, and can help the cell to achieve higher power output.

  6. Intelligent Combustion. A gas boiler with a new control and safety device using the signals of a semiconductor-sensor

    International Nuclear Information System (INIS)

    Rusche, S.; Kostrzewa, G.

    1999-01-01

    The present controls of small gas boilers use an actual differential pressure of the flowing air to regulate the gas valve. It is also possible to combine the change of the gas flow rate and the air volume mechanically. In both of these methods, it is neglected that the air volume required for complete combustion is strongly affected by changing gas quality. The article discusses the use of a BaSnO3 semiconductor control sensor, which is heated by the flame and changes electrical resistance with temperature, O2 and CO content in the burning chamber. It also describes a new burner concept using the sensor

  7. Ultrafast microwave hydrothermal synthesis and characterization of Bi1-xLaxFeO3 micronized particles

    DEFF Research Database (Denmark)

    Ponzoni, C.; Cannio, M.; Boccaccini, Dino

    2015-01-01

    to 815 degrees C as function of the La-doping for all the doped powders. At higher levels of La doping, i.e. x = 0.30 and 0.45, significant weight losses occur above 860 degrees C suggesting a change in the physical and chemical properties. Finally, magnetic measurements are carried out at room...

  8. Structural, magnetic and dielectric properties of Bi{sub 1−x} La{sub x}FeO{sub 3} (x=0, 0.1, 0.15 and 0.2)

    Energy Technology Data Exchange (ETDEWEB)

    Jian, Zhu [School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China); Pavan Kumar, N. [Departmant of Physics, Osmania University, Hyderabad 500007 (India); Zhong, Min; Yemin, Hu [School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China); Venugopal Reddy, P., E-mail: paduruvenugopalreddy@gmail.com [Departmant of Physics, Osmania University, Hyderabad 500007 (India); Vidya Jyothi Institute of Technology, Aziz Nagar Gate, C.B. Post, Hyderabad, 500 075 (India)

    2015-07-15

    With a view to understand the influence of doping Bismuth ferrite with Lanthanum on structural, magnetic and dielectric behavior, a series of samples were prepared by the solid state reaction technique. After characterizing the samples with XRD and SEM studies, magnetic and dielectric measurements were carried out. Although Bismuth ferrite is having impurity phase, La doped ones are having single phase. One of the interesting results of La doped samples is the exhibition of negative magnetization at low temperatures. All the three La doped samples are found to exhibit magnetization peaks at 246 K. Similarly, the dielectric constant is also found to exhibit two transitions at 500 K and 645 K. Efforts were made to explain the observed behaviour. - Highlights: • The doping of La helped in reducing the impurity phase of BiFeO{sub 3}. • All the La doped samples are found to exhibit negative magnetization. • La doped BFO might be considered for future device applications.

  9. Ecofriendly Fire Retardant and Rot Resistance Finishing of Jute Fabric Using Tin and Boron Based Compound

    Science.gov (United States)

    Samanta, Ashis Kumar; Bagchi, Arindam

    2017-06-01

    Treatment with sodium stannate followed by treatment with boric acid imparts jute fabric wash fast fire resistance property as indicated by its Limiting Oxygen Index (LOI) value and 45° inclined flammability test results. The treatment was carried out by impregnation of sodium stannate followed by impregnation with an aqueous solution of boric acid and drying. Application of sodium stannate (20%) and boric acid (20%) treatment on jute fabric showed balanced flame retardancy property (LOI value 34) with some loss in fabric tenacity (loss of tenacity is 14.5%). Treated fabric retained good fire retardant property after three consecutive washing. Treated fabric also possessed good rot resistance property as indicated by soil burial test and strength retention after 21 days soil burial was found to be 65%. It is found that of sodium stannate and boric acid combination by double bath process form a synergistic durable fire-retardant as well as rot resistant when impregnated on jute material, which is considerably greater than the use of either sodium stannate or boric acid alone. TGA, FTIR and SEM analysis are also reported to support the results and reaction mechanism.

  10. A novel design of anode-supported solid oxide fuel cells with Y{sub 2}O{sub 3}-doped Bi{sub 2}O{sub 3}, LaGaO{sub 3} and La-doped CeO{sub 2} trilayer electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Weimin [School of Chemistry and Engineering, South China University of Technology, The Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, Guangzhou 510640 (China); Department of Biological and Chemical Engineering, Guangxi University of Technology, Liuzhou 545006 (China); Liu, Jiang [School of Chemistry and Engineering, South China University of Technology, The Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, Guangzhou 510640 (China)

    2010-12-15

    Anode-supported solid oxide fuel cells (SOFCs) with a trilayered yttria-doped bismuth oxide (YDB), strontium- and magnesium-doped lanthanum gallate (LSGM) and lanthanum-doped ceria (LDC) composite electrolyte film are developed. The cell with a YDB (18 {mu}m)/LSGM (19 {mu}m)/LDC (13 {mu}m) composite electrolyte film (designated as cell-A) shows the open-circuit voltages (OCVs) slightly higher than that of a cell with an LSGM (31 {mu}m)/LDC (17 {mu}m) electrolyte film (designated as cell-B) in the operating temperature range of 500-700 C. The cell-A using Ag-YDB composition as cathode exhibits lower polarization resistance and ohmic resistance than those of a cell-B at 700 C. The results show that the introduction of YDB to an anode-supported SOFC with a LSGM/LDC composite electrolyte film can effectively block electronic transport through the cell and thus increased the OCVs, and can help the cell to achieve higher power output. (author)

  11. Bulletin of Materials Science | News

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 26; Issue 5. Issue front cover thumbnail. Volume 26, Issue 5. August 2003, pages 461-568. pp 461-464 Sensor Materials. Preparation, characterization and dielectric behaviour of some yttrium doped strontium stannates · P K Bajpai Kuldeep Ratre Mukul Pastor T P ...

  12. Corrosion mitigation of rare-earth metals containing magnesium EV31A-T6 alloy via chrome-free conversion coating treatment

    International Nuclear Information System (INIS)

    Hamdy, Abdel Salam; Butt, Darryl P.

    2013-01-01

    Highlights: • Protective stannate coatings have been proposed for rare-earth-EV31A-T6 magnesium alloy. • A simple coating method based on direct treatment of EV31A-T6 in a diluted stannate was found promising. • Surface modification prior to stannate coating offer no substantial advantage over directly coating. • Stannate conversion coatings decrease corrosion rates by a factor of 1/7. • The coating does not display any self-healing characteristics as shown in AZ91D. -- Abstract: Magnesium alloys posses unique mechanical and physical characteristics making them attractive light-weight materials for several strategic industries such as electronics, computer, automotive and aerospace. Due to their high chemical reactivity and poor corrosion resistance, the protection of magnesium alloys from corrosion is one of the hottest topics in materials science and engineering. Addition of rare-earth metals (RE) as alloying elements to magnesium alloys is one of the common approaches to improve their mechanical properties and, sometimes, the corrosion resistance. However, the potential difference between the RE metals phase formed in the Mg matrix enhances the galvanic corrosion at the interfaces where RE metals inert phase acts as cathode and the active Mg matrix acts as anode. This paper introduces a simple one-step clean conversion coating treatment for improving the protection of RE containing magnesium EV31A-T6 alloy in Cl − media

  13. Tailoring the vortex pinning strength of YBCO thin films by systematic incorporation of hybrid artificial pinning centers

    International Nuclear Information System (INIS)

    Jha, Alok K; Matsumoto, Kaname; Horide, Tomoya; Saini, Shrikant; Mele, Paolo; Ichinose, Ataru; Yoshida, Yutaka; Awaji, Satoshi

    2015-01-01

    The effect of hybrid (columnar and spherical together) artificial pinning centers (APCs) on the vortex pinning properties of YBa 2 Cu 3 O 7−δ (YBCO) thin films is investigated in detail on the basis of variation of critical current density (J C ) with applied magnetic field and also with the orientation of the applied magnetic field at 65 K and 77 K. Premixed YBCO + BaSnO 3 composite targets are used for the deposition of the YBCO films which consist of self-assembled BaSnO 3 nanocolumns (1D APCs); on the other hand, for the deposition of the YBCO films with hybrid APCs (BaSnO 3 nanocolumns together with Y 2 O 3 nanoparticles), the surface of the premixed YBCO + BaSnO 3 composite targets are modified by putting a thin Y 2 O 3 sectored piece on the premixed YBCO + BaSnO 3 composite targets by means of silver paste. F pmax value increases systematically with incorporation of 1D and 1D and 3D APCs and it also shifts towards higher applied magnetic fields. Films with 1D APCs exhibit a strong J C peak at Θ = 0° (H//c-axis) whereas films consisting of hybrid APCs exhibit enhanced J C at all the investigated angular regimes. A possible mechanism of vortex pinning in samples with hybrid APCs is also discussed suggesting the role of 1D and 3D APCs. (paper)

  14. Structural, electrical, and magnetic properties of Pb2−xLaxCrO5 (0≤x≤0.15)

    International Nuclear Information System (INIS)

    Indovski, Biljana; Singh, M.P.; Razavi, F.S.

    2013-01-01

    We report structural, electrical, and magnetic properties of a parent and La-doped polycrystalline Pb 2−x La x CrO 5 . The X-ray study suggests that La-doping alters the lattice parameters of Pb 2 CrO 5 and the solubility limit of La is 7.5%. Temperature dependent resistivity data exhibit that both doped and parent materials are semiconducting in nature. Furthermore, La-doping induces electrical conduction and significantly reduces the electrical bandgap of Pb 2 CrO 5 . A lowest bandgap of 1.16 eV is observed in the samples containing 7.5% of La. Magnetic measurements reveal that Pb 2 CrO 5 is characterized by a weak Curie–Weiss type paramagnetic behavior with the effective magnetic moment of 0.17 μ B . Also, La-doping has induced a ferromagnetic behavior with a Curie temperature of 293 K. Observed physical properties are explained based on the possible oxygen vacancy and multiple oxidation states of Cr induced by La-doping

  15. Thermal expansion and conductivity of RE2Sn2O7 (RE = La, Nd, Sm, Gd, Er and Yb) pyrochlores

    International Nuclear Information System (INIS)

    Feng, J.; Xiao, B.; Zhou, R.; Pan, W.

    2013-01-01

    Graphical abstract: Calculated cohesive energies and formation enthalpies of RE 2 Sn 2 O 7 compounds. The formation enthalpies at 298 K are more close to the experimental values. -- The calculated cohesive energies and formation enthalpies of Rare earth stannate (RE 2 Sn 2 O 7 ) compounds are in good agreement with the corresponding experimental values. The thermal expansion coefficients (TECs) of rare earth stannates are 7–9 × 10 −6 K −1 at high temperature. The results show that local spin density approximation predicts smaller TECs than the real values. The computed thermal conductivity of RE 2 Sn 2 O 7 is 1.8–2.5 W (m · K) −1 at 1273 K using the Slack–Clarke model, indicating that RE 2 Sn 2 O 7 compounds exhibit good thermal insulating properties at high temperature

  16. Structural and dielectric studies on Ag doped nano ZnSnO3

    Science.gov (United States)

    Deepa, K.; Angel, S. Lilly; Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

    2018-04-01

    Undoped and Ag-doped nano Zinc Stannate (ZSO) ternary oxide were prepared by co-precipitation method. The crystallographic, morphological and optical properties of the synthesized nanoparticles were studied using X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis) and Scanning electron microscopy (SEM). The electrical properties of the synthesized samples were studied by dielectric measurements. Higher concentration Ag doped ZSO nanoparticles exhibit higher dielectric constant at low frequency.

  17. Dipyridinium tribromidochloridobis(4-chlorophenylstannate(IV

    Directory of Open Access Journals (Sweden)

    Kong Mun Lo

    2009-06-01

    Full Text Available The tin atom in the substituted ammonium stannate(IV, (C5H6N2[SnBr3(C6H4Cl2Cl], lies on a center of symmetry in a distorted octahedral coordination geometry. Each independent halogen site is occupied by bromine and chlorine anions in an approximate 3:1 ratio. The pyridinium cation forms a hydrogen bond to only one of the halogen atoms.

  18. Dielectric relaxation study of Pb sub 1 sub - sub x La sub x MoO sub 4 sub + subdelta (x = 0-0.3) oxide-ion conductors

    CERN Document Server

    Zhang, G G; Wang, X P; Yi, Z G

    2003-01-01

    DC conductivity and dielectric relaxation measurements are exploited to study the influence of La substitution on the dielectric properties and oxygen-ion transportation in PbMoO sub 4 samples. The DC conductivity of La-doped samples is about 10 sup - sup 3 S cm sup - sup 1 around 1073 K. A dielectric loss peak with activation energy of 0.6-0.8 eV is observed in the temperature spectrum as well as in the frequency spectrum for all La-doped PbMoO sub 4 samples. With increasing La doping content, this peak becomes higher and shifts to higher temperature or lower frequency, and the activation energy becomes larger. It is suggested that this dielectric loss peak is associated with the short-distance diffusion of oxygen ions (or oxygen vacancies) between the 16f and 8e sites of the scheelite structure type with I4 sub 1 /a symmetry.

  19. Study of disorder effects in La substituted Ca2FeMoO6 ferrimagnet using magnetic and transport measurements

    International Nuclear Information System (INIS)

    Muthuselvam, I. Panneer; Poddar, Asok; Bhowmik, R.N.

    2009-01-01

    We have substituted non-magnetic La in ferrimagnetic Ca 2-x La x FeMoO 6 double perovskite. The cell volume showed expansion with the increase of La substitution in monoclinic crystal structure and space group P2 I /n. Analysis of XRD spectrum indicated the increase of disorder in lattice structure. Surface structure of the material is modified from adhesive type for x = 0 sample to brittle type in La doped samples, suggesting the increase of grain boundary contributions. DC magnetization and ac susceptibility measurements showed reduction of magnetic moment, enhancement of T C , and cluster spin-glass phase in the ferromagnetic matrix. These experimental results confirmed the enhancement of magnetic disorder in La doped samples. The reduction of metallic nature in the compound provided additional support of enhanced disorder upon La doping in double perovskite structure.

  20. Electronic Materials and Applications 2014 (Abstracts)

    Science.gov (United States)

    2015-04-02

    electric fatigue at TU Darmstadt (SFB595) . In Germany he served the Deutsche Forschungsgemeinschaft (DFG) a four-year term as speaker of the review...epitaxial La-doped PZT films at low concentrations of La-doping M. Hordagoda*, D. Mukherjee, University of South Florida, USA; D. Ghosh, J. Jones...S1-P001-2014) Effect of viscosity and thickness in PZT - PZNN tape casting process for energy harvesting system D. Song*, M. Woo, D. Cho, T. Sung

  1. Substitutional Doping for Aluminosilicate Mineral and Superior Water Splitting Performance

    Science.gov (United States)

    Zhang, Yi; Fu, Liangjie; Shu, Zhan; Yang, Huaming; Tang, Aidong; Jiang, Tao

    2017-07-01

    Substitutional doping is a strategy in which atomic impurities are optionally added to a host material to promote its properties, while the geometric and electronic structure evolution of natural nanoclay mineral upon substitutional metal doping is still ambiguous. This paper first designed an efficient lanthanum (La) doping strategy for nanotubular clay (halloysite nanotube, HNT) through the dynamic equilibrium of a substitutional atom in the presence of saturated AlCl3 solution, and systematic characterization of the samples was performed. Further density functional theory (DFT) calculations were carried out to reveal the geometric and electronic structure evolution upon metal doping, as well as to verify the atom-level effect of the La doping. The CdS loading and its corresponding water splitting performance could demonstrate the effect of La doping. CdS nanoparticles (11 wt.%) were uniformly deposited on the surface of La-doped halloysite nanotube (La-HNT) with the average size of 5 nm, and the notable photocatalytic hydrogen evolution rate of CdS/La-HNT reached up to 47.5 μmol/h. The results could provide a new strategy for metal ion doping and constructive insight into the substitutional doping mechanism.

  2. Influence of processing parameters on PZT thick films

    International Nuclear Information System (INIS)

    Huang, Oliver; Bandyopadhyay, Amit; Bose, Susmita

    2005-01-01

    We have studied influence of processing parameters on the microstructure and ferroelectric properties of lead zirconate titanate (PZT)-based thick films in the range of 5-25 μm. PZT and 2% La-doped PZT thick films were processed using a modified sol-gel process. In this process, PZT- and La-doped PZT powders were first prepared via sol-gel. These powders were calcined and then used with respective sols to form a slurry. Slurry composition was optimized to spin-coat thick films on platinized Si substrate (Si/SiO 2 /Ti/Pt). Spinning rate, acceleration and slurry deposition techniques were optimized to form thick films with uniform thickness and without any cracking. Increasing solids loading was found to enhance the surface smoothness of the film and decrease porosity. Films were tested for their electrical properties and ferroelectric fatigue response. The maximum polarization obtained was 40 μC/cm 2 at 250 kV/cm for PZT thick film and 30 μC/cm 2 at 450 kV/cm for La-doped PZT thick film. After 10 9 cycles of fatiguing at 35 kHz, La-doped PZT showed better resistance for ferroelectric fatigue compared with un-doped PZT films

  3. Laser energy tuning of carrier effective mass and thermopower in epitaxial oxide thin films

    KAUST Repository

    Abutaha, Anas I.; Sarath Kumar, S. R.; Alshareef, Husam N.

    2012-01-01

    The effect of the laser fluence on high temperature thermoelectric properties of the La doped SrTiO3 (SLTO) thin films epitaxially grown on LaAlO3 〈100〉 substrates by pulsed laser deposition is clarified. It is shown that oxygen vacancies

  4. An epitaxial transparent conducting perovskite oxide: double-doped SrTiO3

    NARCIS (Netherlands)

    Ravichandran, Jayakanth; Siemons, W.; Heijmerikx, Herman; Huijben, Mark; Majumdar, Arun; Ramesh, Ramamoorthy

    2010-01-01

    Epitaxial thin films of strontium titanate doped with different concentrations of lanthanum and oxygen vacancies were grown on LSAT substrates by pulsed laser deposition technique. Films grown with 5−15% La doping and a critical growth pressure of 1−10 mTorr showed high transparency (>70−95%) in the

  5. Improvement of the optoelectronic properties of tin oxide transparent conductive thin films through lanthanum doping

    Energy Technology Data Exchange (ETDEWEB)

    Mrabet, C., E-mail: chokri.mrabet@hotmail.com; Boukhachem, A.; Amlouk, M.; Manoubi, T.

    2016-05-05

    This work highlights some physical investigations on tin oxide thin films doped with different lanthanum content (ratio La–to-Sn = 0–3%). Such doped thin films have been successfully grown by spray pyrolysis onto glass substrates at 450 °C. X-ray diffraction (XRD) patterns showed that SnO{sub 2}:La thin films were polycrystalline with tetragonal crystal structure. The preferred orientation of crystallites for undoped SnO{sub 2} thin film was along (110) plane, whereas La-doped ones have rather preferential orientations along (200) direction. Although the grain size values exhibited a decreasing tendency with increasing doping content confirming the role of La as a grain growth inhibitor, dislocation density and microstrain values showed an increasing tendency. Also, Raman spectroscopy shows the bands corresponding to the tetragonal structure for the entire range of La doping. The same technique confirms the presence of La{sub 2}O{sub 3} as secondary phase. Moreover, SEM images showed a porous architecture with presence of big clusters with different sizes and shapes resulting from the agglomeration of small grains round shaped. Photoluminescence spectra of SnO{sub 2}:La thin films exhibit a decrease in the emission intensity with La concentration due to the decrease in grain size. Optical transmittance spectra of the films showed high transparency (∼80%) in the visible region. The dispersion of the refractive index is discussed using both Cauchy model and Wemple–Di-Domenico method. The optical band gap values vary slightly with La doping and were found to be around 3.8 eV. It has been found that La doping causes a pronounced decrease in the sheet resistance by up to two orders of magnitude and allows improving the Haacke's figure of merit (Φ) of the sprayed thin films. Moreover, we have introduced for a first time a new figure of merit for qualifying photo-thermal conversion applications. The obtained high conducting and transparent SnO{sub 2}:La

  6. Thermoelectric transport properties of BaBiTe{sub 3}-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yiming; Zhao, Li-Dong, E-mail: zhaolidong@buaa.edu.cn

    2017-05-15

    BaBiTe{sub 3}, a material with low thermal conductivity, is an inferior thermoelectric material due to the poor electrical properties originated from its narrow band gap. We choose two types of dopants, K and La, trying to optimize its electrical transport properties. The minority carriers, which harm the Seebeck coefficient in this system, are suppressed by La doping. With the increase of both electrical conductivity and Seebeck coefficient, the power factor of 3% La doped BaBiTe{sub 3} reaches 3.7 μW cm{sup −1} K{sup −2} which increased by 40% from undoped BaBiTe{sub 3}. Besides high power factor, the thermal conductivity is also reduced in it. Eventually, a high ZT value, 0.25 at 473 K, for n-type BaBiTe{sub 3} is achieved in 3% La doped BaBiTe{sub 3}. - Graphical abstract: BaBiTe{sub 3} possesses a low thermal conductivity. However, it is an inferior thermoelectric material due to the poor electrical properties originated from its narrow band gap. A high ZT value of 0.25 at 473 K for n-type BaBiTe{sub 3} can be achieved through optimizing electrical transport properties via La doping. - Highlights: • BaBiTe{sub 3} is an analogue of these promising thermoelectric materials: such as CsBi{sub 4}Te{sub 6} and K{sub 2}Bi{sub 8}Se{sub 13}, etc. • BaBiTe{sub 3} possesses a low thermal conductivity. • La is an effective dopant to enhance electrical transport properties. • A high ZT value of 0.25 at 473 K can be achieved in n-type La-doped BaBiTe{sub 3}.

  7. Ultrafast microwave hydrothermal synthesis and characterization of Bi1−xLaxFeO3 micronized particles

    International Nuclear Information System (INIS)

    Ponzoni, C.; Cannio, M.; Boccaccini, D.N.; Bahl, C.R.H.; Agersted, K.; Leonelli, C.

    2015-01-01

    In this work a microwave assisted hydrothermal method is applied to successfully synthesize lanthanum doped bismuth ferrites (BLFO, Bi 1−x La x FeO 3 where x = 0, 0.15, 0.30 and 0.45). The growth mechanism of the Bi 1−x La x FeO 3 crystallites is discussed in detail. The existence of the single-phase perovskite structure for all the doped samples is confirmed by the X-ray powder diffraction patterns. A peak shift, observed at lower angle with increasing La doping concentration, indicates that the BiFeO 3 lattice is doped. The results of TG/DTA show a shift in the transition temperature from 805 °C to 815 °C as function of the La-doping for all the doped powders. At higher levels of La doping, i.e. x = 0.30 and 0.45, significant weight losses occur above 860 °C suggesting a change in the physical and chemical properties. Finally, magnetic measurements are carried out at room temperature for pure BiFeO 3 and Bi 0.85 La 0.15 FeO 3 . The results indicate that the materials are both weakly ferromagnetic, with no significant hysteresis in the curves. - Graphical abstract: Display Omitted - Highlights: • MW hydrothermal method applied to synthesize Bi 1−x La x FeO 3 , x = 0, 0.15, 0.30, 0.45. • A single-phase perovskite structure for all the samples was confirmed by XRD. • A T c shift in La doped BiFeO 3 DTA was observed as function of the La-doping. • Magnetic measurements indicate that the materials are weakly ferromagnetic

  8. Ultrafast microwave hydrothermal synthesis and characterization of Bi{sub 1−x}La{sub x}FeO{sub 3} micronized particles

    Energy Technology Data Exchange (ETDEWEB)

    Ponzoni, C. [Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Modena 42025 (Italy); Cannio, M., E-mail: maria.cannio@unimore.it [Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Modena 42025 (Italy); Boccaccini, D.N.; Bahl, C.R.H.; Agersted, K. [Department of Energy Conversion and Storage, Technical University of Denmark Frederiksborgvej, 4000 Roskilde (Denmark); Leonelli, C. [Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Modena 42025 (Italy)

    2015-07-15

    In this work a microwave assisted hydrothermal method is applied to successfully synthesize lanthanum doped bismuth ferrites (BLFO, Bi{sub 1−x}La{sub x}FeO{sub 3} where x = 0, 0.15, 0.30 and 0.45). The growth mechanism of the Bi{sub 1−x}La{sub x}FeO{sub 3} crystallites is discussed in detail. The existence of the single-phase perovskite structure for all the doped samples is confirmed by the X-ray powder diffraction patterns. A peak shift, observed at lower angle with increasing La doping concentration, indicates that the BiFeO{sub 3} lattice is doped. The results of TG/DTA show a shift in the transition temperature from 805 °C to 815 °C as function of the La-doping for all the doped powders. At higher levels of La doping, i.e. x = 0.30 and 0.45, significant weight losses occur above 860 °C suggesting a change in the physical and chemical properties. Finally, magnetic measurements are carried out at room temperature for pure BiFeO{sub 3} and Bi{sub 0.85}La{sub 0.15}FeO{sub 3}. The results indicate that the materials are both weakly ferromagnetic, with no significant hysteresis in the curves. - Graphical abstract: Display Omitted - Highlights: • MW hydrothermal method applied to synthesize Bi{sub 1−x}La{sub x}FeO{sub 3}, x = 0, 0.15, 0.30, 0.45. • A single-phase perovskite structure for all the samples was confirmed by XRD. • A T{sub c} shift in La doped BiFeO{sub 3} DTA was observed as function of the La-doping. • Magnetic measurements indicate that the materials are weakly ferromagnetic.

  9. Effects of rapid thermal annealing on structural, chemical, and electrical characteristics of atomic-layer deposited lanthanum doped zirconium dioxide thin film on 4H-SiC substrate

    International Nuclear Information System (INIS)

    Lim, Way Foong; Quah, Hock Jin; Lu, Qifeng; Mu, Yifei; Ismail, Wan Azli Wan; Rahim, Bazura Abdul; Esa, Siti Rahmah; Kee, Yeh Yee; Zhao, Ce Zhou

    2016-01-01

    Graphical abstract: - Highlights: • Studies of RTA temperatures on La doped ZrO2 atomic layer deposited on 4HSiC. • Oxygen vacancies improved insulating and catalytic properties of La doped ZrO2. • 700 °C annealed sample showed the highest EB, k value, and sensitivity on O2. • La doped ZrO2 was proposed as a potential metal reactive oxide on 4H-SiC. - Abstract: Effects of rapid thermal annealing at different temperatures (700–900 °C) on structural, chemical, and electrical characteristics of lanthanum (La) doped zirconium oxide (ZrO_2) atomic layer deposited on 4H-SiC substrates have been investigated. Chemical composition depth profiling analysis using X-ray photoelectron spectroscopy (XPS) and cross-sectional studies using high resolution transmission electron microscopy equipped with energy dispersive X-ray spectroscopy line scan analysis were insufficient to justify the presence of La in the investigated samples. The minute amount of La present in the bulk oxide was confirmed by chemical depth profiles of time-of-flight secondary ion mass spectrometry. The presence of La in the ZrO_2 lattice led to the formation of oxygen vacancies, which was revealed through binding energy shift for XPS O 1s core level spectra of Zr−O. The highest amount of oxygen vacancies in the sample annealed at 700 °C has yielded the acquisition of the highest electric breakdown field (∼ 6.3 MV/cm) and dielectric constant value (k = 23) as well as the highest current–time (I–t) sensor response towards oxygen gas. The attainment of both the insulating and catalytic properties in the La doped ZrO_2 signified the potential of the doped ZrO_2 as a metal reactive oxide on 4H-SiC substrate.

  10. Fabrication of lanthanum-doped thorium dioxide by high-energy ball milling and spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Scott, Spencer M.; Yao, Tiankai [Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States); Lu, Fengyuan [Department of Mechanical & Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803 (United States); Xin, Guoqing; Zhu, Weiguang [Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States); Lian, Jie, E-mail: lianj@rpi.edu [Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States)

    2017-03-15

    Abstract: High-energy ball milling was used to synthesize Th{sub 1-x}La{sub x}O{sub 2-0.5x} (x = 0.09, 0.23) solid solutions, as well as improve the sinterability of ThO{sub 2} powders. Dense La-doped ThO{sub 2} pellets with theoretical density above 94% were consolidated by spark plasma sintering at temperatures above 1400 °C for 20 min, and the densification behavior and the non-equilibrium effects on phase and structure were investigated. A lattice contraction of the SPS-densified pellets occurred with increasing ball milling duration, and a secondary phase with increased La-content was observed in La-doped pellets. A dependence on the La-content and sintering duration for the onset of localized phase segregation has been proposed. The effects of high-energy ball milling, La-content, and phase formation on the thermal diffusivity were also studied for La-doped ThO{sub 2} pellets by laser flash measurement. Increasing La-content and high energy ball milling time decreases thermal diffusivity; while the sintering peak temperature and holding time beyond 1600 °C dramatically altered the temperature dependence of the thermal diffusivity beyond 600 °C. - Highlights: • Lanthanum incorporation into ThO{sub 2} by high energy ball milling and rapid consolidation by spark plasma sintering. • Elucidation of phase behavior of the La-doped ThO{sub 2} and the contributions of La incorporation and SPS sintering conditions. • Investigation of the effects of La incorporation and high energy ball milling on the thermal behavior of La-doped ThO{sub 2}.

  11. Critical current density and microwave surface resistance of 5-cm-diameter YBCO films on LaAlO3 substrates prepared by MOD using an infrared image furnace

    International Nuclear Information System (INIS)

    Manabe, T.; Kondo, W.; Yamaguchi, I.; Sohma, M.; Tsuchiya, T.; Tsukada, K.; Mizuta, S.; Kumagai, T.

    2005-01-01

    Inductive critical current density (J c ) and microwave surface resistance (R s ) were investigated for 0.7-μm-thick epitaxial YBa 2 Cu 3 O 7-y (YBCO) films on 5-cm-diameter LaAlO 3 substrates prepared by a chemical solution-based metal organic deposition (MOD) process using an infrared image furnace. By varying the heating rate at ramp during the final heat treatment, we obtained various orientations of YBCO; the c- and a-axis orientation at a slower rate, i.e., 20-100 deg C/min while the pure c-axis orientation at a faster rate, 200 deg C/min. The c-axis-oriented YBCO films showed excellent superconducting properties; for example, a high inductive-J c (77 K) of 2.6 MA/cm 2 and low R s (12 GHz)'s of 0.24 and 0.52 mΩ at 50 and 77 K, respectively, by a sapphire rod resonator method. The c- and a-axis-oriented films exhibited a lower J c and a higher R s . It was found that the J c and R s values of MOD-derived YBCO films showed a strong correlation; approximately, R s is inversely proportional to J c . This correlation is in good agreement with a previous report by Ohshima et al. for sputtered-YBCO films on BaSnO 3 -buffered MgO substrates

  12. Quick screening for new flux pinning materials in YBCO films with the combinatorial-PLD method

    International Nuclear Information System (INIS)

    Yoshimura, T.; Ichino, Y.; Yoshida, Y.; Takai, Y.; Kita, R.; Suzuki, K.; Takeuchi, T.

    2011-01-01

    An effective way to improve the superconducting properties in REBa 2 Cu 3 O y (REBCO) films under a magnetic field is to dope artificial pinning centers (APC). The pinning performance depends on the content of the APC materials. Usually, the optimal APC content is explored by preparing films one at a time from the REBCO target using different APC material content, which is an extremely time-consuming process. The combinatorial-PLD (C-PLD) method allowed us to prepare films that continuously changed in composition across a single substrate. In this study, we used the C-PLD method to prepare BaSnO 3 (BSO)-doped YBCO films. The films were deposited on SrTiO 3 substrate using a fourth-harmonic Nd:YAG laser. From the results of the J c -B curves at 77 K and B//c, the film that contained 3.2 vol.% of BSO exhibited the best pinning performance in this study. We showed that the C-PLD method was efficient for quick screening of the optimal APC content with only one deposition. We also used the C-PLD method to explore new APC materials, and proved that it can quickly evaluate the new APC materials Ba 3 Cu 3 In 4 O 12 and BaTbO 3 .

  13. First-principles calculations of mobility

    Science.gov (United States)

    Krishnaswamy, Karthik

    First-principles calculations can be a powerful predictive tool for studying, modeling and understanding the fundamental scattering mechanisms impacting carrier transport in materials. In the past, calculations have provided important qualitative insights, but numerical accuracy has been limited due to computational challenges. In this talk, we will discuss some of the challenges involved in calculating electron-phonon scattering and carrier mobility, and outline approaches to overcome them. Topics will include the limitations of models for electron-phonon interaction, the importance of grid sampling, and the use of Gaussian smearing to replace energy-conserving delta functions. Using prototypical examples of oxides that are of technological importance-SrTiO3, BaSnO3, Ga2O3, and WO3-we will demonstrate computational approaches to overcome these challenges and improve the accuracy. One approach that leads to a distinct improvement in the accuracy is the use of analytic functions for the band dispersion, which allows for an exact solution of the energy-conserving delta function. For select cases, we also discuss direct quantitative comparisons with experimental results. The computational approaches and methodologies discussed in the talk are general and applicable to other materials, and greatly improve the numerical accuracy of the calculated transport properties, such as carrier mobility, conductivity and Seebeck coefficient. This work was performed in collaboration with B. Himmetoglu, Y. Kang, W. Wang, A. Janotti and C. G. Van de Walle, and supported by the LEAST Center, the ONR EXEDE MURI, and NSF.

  14. Photocatalytic degradation of the Paracetamol drug using Lanthanum doped ZnO nanoparticles and their in-vitro cytotoxicity assay

    International Nuclear Information System (INIS)

    Shakir, Mohammad; Faraz, Mohd; Sherwani, Mohd Asif; Al-Resayes, Saud I.

    2016-01-01

    The doping of semiconductor by rare earth metals nanoparticles is an effective way for increasing photocatalytic activity. Zinc oxide and Lanthanum doped Zinc oxide nanoparticles were synthesized by modifying the gel-combustion method. It was found that La can greatly enhance the cytotoxicity and photocatalytic activity of ZnO nanoparticles towards various cell lines and Paracetamol drug. These nanoparticles were characterized by various spectroscopic and other techniques which clearly revealed the presence of lanthanum ions. The absorption edge shifts towards the visible region after doping with La ions. This shift shows that the doping of La ions is favorable for absorbing the visible light. The comparative photocatalytic and cytotoxicity activity revealed that La doped ZnO nanoparticles remarkably enhanced activities as compared to the ZnO nanoparticles. The outcome of these studies offers valuable for planning La doped ZnO nanoparticles having cytotoxicity and photocatalytic activities helpful for the formulation of anticancer product and waste water remediation.

  15. 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.)

  16. 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.

  17. In-situ synchrotron x-ray study of the crystallization behavior of Ce0.9La0.1O2−x thin films deposited on NiW alloy substrates by chemical solution method

    DEFF Research Database (Denmark)

    Yue, Zhao; Grivel, Jean-Claude; Abrahamsen, Asger Bech

    2011-01-01

    The phase and texture formation of La doped CeO2 (CLO) films deposited by the chemical solution method are studied by in situ synchrotron x-ray diffraction. It is found that the CLO crystallites forms excellent in-plane texture as soon as the phase appears at 860°C, indicating that interfacial nu...... by diffusion. The success of this work demonstrates the possibility of studying crystallization behaviors of solution derived films using a non-destructive method, which has the potential of being applicable to most types of thin film samples.......The phase and texture formation of La doped CeO2 (CLO) films deposited by the chemical solution method are studied by in situ synchrotron x-ray diffraction. It is found that the CLO crystallites forms excellent in-plane texture as soon as the phase appears at 860°C, indicating that interfacial...

  18. Enhanced ferroelectric and piezoelectric properties in La-modified PZT ceramics

    Science.gov (United States)

    Kour, P.; Pradhan, S. K.; Kumar, Pawan; Sinha, S. K.; Kar, Manoranjan

    2016-06-01

    The effect of lanthanum (La) doping on ferroelectric and piezoelectric properties of lead zirconate titanate (PZT) sample has been investigated. Pb1- x La x Zr0.52Ti0.48O3 ceramics with x = 0.00, 0.02, 0.04, 0.06 and 0.10 were prepared by the sol-gel technique. Raman and Fourier transforms infrared spectroscopy have been employed to understand the structural modification due to ionic size mismatch. Raman spectra show the existence of both rhombohedral and tetragonal crystal symmetries. It also shows the dielectric relaxation with increase in La concentration in the sample. The increase in lattice strain due to La doping increases the remnant polarization and coercive field. The linear piezoelectric coefficient increases with the increase in La concentration. It reveals that La-substituted PZT is a better candidate for piezoelectric sensor applications as compared to that of PZT.

  19. Photocatalytic degradation of the Paracetamol drug using Lanthanum doped ZnO nanoparticles and their in-vitro cytotoxicity assay

    Energy Technology Data Exchange (ETDEWEB)

    Shakir, Mohammad, E-mail: shakir078@yahoo.com [Department of Chemistry, Aligarh Muslim University, Aligarh 202002 (India); Faraz, Mohd [Department of Chemistry, Aligarh Muslim University, Aligarh 202002 (India); Sherwani, Mohd Asif [Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002 (India); Al-Resayes, Saud I. [Department of Chemistry, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia)

    2016-08-15

    The doping of semiconductor by rare earth metals nanoparticles is an effective way for increasing photocatalytic activity. Zinc oxide and Lanthanum doped Zinc oxide nanoparticles were synthesized by modifying the gel-combustion method. It was found that La can greatly enhance the cytotoxicity and photocatalytic activity of ZnO nanoparticles towards various cell lines and Paracetamol drug. These nanoparticles were characterized by various spectroscopic and other techniques which clearly revealed the presence of lanthanum ions. The absorption edge shifts towards the visible region after doping with La ions. This shift shows that the doping of La ions is favorable for absorbing the visible light. The comparative photocatalytic and cytotoxicity activity revealed that La doped ZnO nanoparticles remarkably enhanced activities as compared to the ZnO nanoparticles. The outcome of these studies offers valuable for planning La doped ZnO nanoparticles having cytotoxicity and photocatalytic activities helpful for the formulation of anticancer product and waste water remediation.

  20. Dibutylammonium bis(hydrogen methylphosphonato-κOtriphenylstannate(IV

    Directory of Open Access Journals (Sweden)

    Tidiane Diop

    2012-10-01

    Full Text Available The asymmetric unit of the title organotin salt, (C8H20N[Sn(C6H53(CH4O3P2], contains two dibutylammonium cations and two stannate(IV anions consisting each of two monodentately bonding methyl hydrogenphosphate groups attached to an Sn(C6H5 unit. The overall coordination environment of the two SnIV atoms is trigonal–bipyramidal defined by three phenyl C atoms in equatorial positions and two methyl hydrogenphosphate O atoms at the apical sites. In the crystal, the stannate(IV anions are linked to each other via pairs of short O—H...O hydrogen bonds, leading to an infinite chain extending parallel to the b-axis direction. Neighbouring chains are linked by N—H...O hydrogen bonds involving the butylammonium cations, giving a two-dimensional structure parallel to the ab plane. The crystal under investigation was found to be twinned by reticular merohedry with twin fractions of 0.5342 (7:0.4658 (7.

  1. Corrosion of AZ91D magnesium alloy with a chemical conversion coating and electroless nickel layer

    International Nuclear Information System (INIS)

    Huo Hongwei; Li Ying; Wang Fuhui

    2004-01-01

    A chemical conversion treatment and an electroless nickel plating were applied to AZ91D alloy to improve its corrosion resistance. By conversion treatment in alkaline stannate solution, the corrosion resistance of the alloy was improved to some extent as verified by immersion test and potentiodynamic polarization test in 3.5 wt.% NaCl solution at pH 7.0. X-ray diffraction patterns of the stannate treated AZ91D alloy showed the presence of MgSnO 3 · H 2 O, and SEM images indicated a porous structure, which provided advantage for the adsorption during sensitisation treatment prior to electroless nickel plating. A nickel coating with high phosphorus content was successfully deposited on the chemical conversion coating pre-applied to AZ91D alloy. The presence of the conversion coating between the nickel coating and the substrate reduced the potential difference between them and enhanced the corrosion resistance of the alloy. An obvious passivation occurred for the nickel coating during anodic polarization in 3.5 wt.% NaCl solution

  2. Study on CexLa1-xO2 Buffer Layer used in Coated Conductors by Chemical Solution Method

    DEFF Research Database (Denmark)

    Zhao, Yue; Suo, Hongli; Grivel, Jean-Claude

    2009-01-01

    Developing multi-functional single buffer layer is one of the most important challenges for simplification of coated conductors configuration. Ladoped CeO2 films were prepared by chemical solution method. And surface morphology and texture quality of the La-doped CeO2 films were investigated...... method. It suggects that Ce0.9La0.1O2 film prepared by chemical solution route have a promising prospect for the simplification of coated conductors configuration....

  3. Property change of advanced tungsten alloys due to neutron irradiation

    International Nuclear Information System (INIS)

    Fukuda, Makoto; Hasegawa, Akira; Tanno, Takashi; Nogami, Shuhei; Kurishita, Hiroaki

    2013-01-01

    This study investigates the effect of neutron irradiation on the functional properties of pure tungsten (W) and advanced tungsten alloys (e.g., lanthanum (La)-doped W, potassium (K)-doped W, and ultra-fine-grained (UFG) W–TiC alloys) tested in the Japan Materials Testing Reactor (JMTR) or experimental fast reactor Joyo. The irradiation temperature and damage were in the range 804–1073 K and 0.15–0.47 dpa, respectively. TEM images of all samples after 0.42 dpa irradiation at 1023 K showed voids, black dots, and dislocation loops, indicating that similar damage structures were formed in pure W, La-doped W, K-doped W, and UFG W–0.5 wt% TiC. The electrical resistivity of all specimens increased following neutron irradiation. Nearly identical electrical resistivity and irradiation hardening were observed in pure W, La-doped W, and K-doped W. The electrical resistivity of UFG W–TiC was higher than that of other specimens before and after irradiation, which may be attributed to its ultra-fine-grain structure, as well as the presence of impurities introduced during the alloying process. Compared to the other specimens, the UFG W–TiC was more resistant to irradiation hardening

  4. Electrical characterization and impedance response of lanthanum doped barium titanate ceramics

    Directory of Open Access Journals (Sweden)

    Mančić D.

    2008-01-01

    Full Text Available The dielectric permittivity and dissipation factor of La-doped and undoped BaTiO3 were investigated as a function of frequency and temperature. The impedance response was used to study the electrical properties of La-doped BaTiO3 over the temperature range from room temperature (RT to 350°C. La-doped and undoped BaTiO3, obtained by a modified Pechini method, were sintered in air at 1300°C for 2 and 16 hours. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE. The most suitable electrical circuit for the interpretation of experimental results is found to be the equivalent circuit consisting of resistors and CPE elements which replace the capacitor elements. The contribution of grain boundary resistance to the total resistance of a system is remarkable at low temperature. Dielectric permittivity of doped BaTiO3 was in the range of 8000 to 12000 at 1 kHz and the dissipation factor was less than 1%.

  5. Fabrication of 93.7 m long PLD-EuBCO + BaHfO_3 coated conductors with 103 A/cm W at 77 K under 3 T

    International Nuclear Information System (INIS)

    Yoshida, T.; Ibi, A.; Takahashi, T.; Yoshizumi, M.; Izumi, T.; Shiohara, Y.

    2015-01-01

    Highlights: • A 93.7 m long EuBCO + BHO CC with 103 A/cm W at 77 K under 3 T was obtained. • The 93.7 m long CC showed high I_c values and high n-values with high uniformity. • The average I_c value at 77 K under 3 T was estimated by that at 77 K under 0.3 T. - Abstract: Introduction of artificial pinning centers such as BaHfO_3 (BHO), BaZrO_3 (BZO) and BaSnO_3 (BSO) into REBa_2Cu_3O_7_−_δ (REBCO) coated conductor (CC) layers could improve the in-field critical currents (I_c) in wide ranges of temperatures and magnetic fields. In particular, a combination of EuBCO + BHO has been found to be effective for attaining high in-field I_c performance by means of IBAD/PLD process in short length samples. In this work, we have successfully fabricated a 93.7 m long EuBCO + BHO CC with 103 A/cm W at 77 K under a magnet field (B) of 3 T applied perpendicular to the CC (B//c). The 93.7 m long EuBCO + BHO CC had high uniformity of I_c values and n-values without any trend of fluctuations, independent of the external field up to 0.3 T. I_c–B–applied angle (θ) profiles of the 93.7 m long EuBCO + BHO CC sample showed the high in-field I_c values in all directions of applied magnetic fields especially B//c (at θ ∼ 180°, I_c = 157 A/cm W) at 77 K under 3 T. The profiles were about the same as those in a short length sample.

  6. Phase transition and water incorporation into Eu2Sn2O7 pyrochlore at high pressure

    Science.gov (United States)

    Zhang, F. X.; Lang, M.; Ewing, R. C.

    2016-04-01

    Structural changes of europium stannate pyrochlore, Eu2Sn2O7, have been investigated at high pressures with in situ Raman spectroscopy, photoluminescence (PL), and synchrotron X-ray diffraction (XRD) techniques. The XRD measurements suggest that a pressure-induced phase transition starts at 34.4 GPa. The PL spectrum from Eu3+ cations also suggests a phase transition above 36 GPa. XRD analysis shows that the unit cell of the cubic phase deviates from the equation of state at pressures above 23.8 GPa. This is due to the incorporation of water from the pressure medium in the structure at high pressures, which is confirmed by optical spectroscopy measurements.

  7. Structural and electrochemical behavior of sol-gel ZrO2 ceramic film on chemically pre-treated AZ91D magnesium alloy

    International Nuclear Information System (INIS)

    Li Qing; Chen Bo; Xu Shuqiang; Gao Hui; Zhang Liang; Liu Chao

    2009-01-01

    In the present investigation sol-gel-based ZrO 2 ceramic film was obtained using zirconium acetate as the precursor material. The film was deposited on AZ91D magnesium alloy by a dip-coating technique. An uniform stannate conversion coating as chemical pretreatment was employed as an intermediate layer prior to deposition of the ZrO 2 film in order to provide advantage for the formation of sol-gel-based ZrO 2 layer. The corrosion properties, structure, composition and morphology of these coatings on AZ91D magnesium alloy were studied by potentiodynamic polarization tests, EIS, XRD, SEM, respectively. According to the electrochemical tests, the corrosion resistance of AZ91D magnesium alloy was found to be greatly improved by means of this new environment-friendly surface treatment.

  8. Preparation of antimony-doped nanoparticles by hydrothermal method

    Institute of Scientific and Technical Information of China (English)

    JIANG Ming-xi; YANG Tian-zu; GU Ying-ying; DU Zuo-juan; LIU Jian-ling

    2005-01-01

    Antimony-doped tin oxide(ATO) nanoparticles were prepared by the mild hydrothermal method at 200 ℃ using sodium stannate, antimony oxide, sodium hydroxide and sulfuric acid as the starting materials. The doped powders were examined by differential thermal analysis(DTA), X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The doping levels of antimony were determined by volumetric method and iodimetry.The results show that antimony is incorporated into the crystal lattice of tin oxide and the doping levels of antimony in the resulting powders are 2.4%, 4.3 % and 5.1 % (molar fraction). The mean particle size of ATO nanoparticles is in the range of 25 - 30 nm. The effects of antimony doping level on the crystalline size and crystallinity were also discussed.

  9. Rare earths: harvesting basic research for technology

    International Nuclear Information System (INIS)

    Jagatap, B.N.

    2014-01-01

    In recent years, rare earths are increasingly becoming a versatile platform for basic research that presents enormous technological potentials. A variety of nano-sized inorganic matrices varying from oxides, phosphates, gallates and aluminates, tungstates, stannates, vanadates to fluorides doped with different lanthanide ions have been synthesized and their optical properties have been investigated in the Chemistry Group, BARC. Another interesting application is laser cooling of solids using rare earth doped glasses with potential applications in remote cooling of electronic devices. Combining the luminescence properties of rare earths with photonic crystals is yet another potent area with wide ranging applications. In this presentation we provide an overview of these developments with examples from the R and D programs of the Chemistry Group, BARC

  10. Characterization of CaSn(OH6 and CaSnO3 Nanostructures Synthesized by a New Precursor

    Directory of Open Access Journals (Sweden)

    S. Moshtaghi

    2015-04-01

    Full Text Available In this paper, calcium stannate nanoparticles were synthesized by a fast and simple co-precipitation procedure. For CaSnO3 preparation ammonia was used as precipitation agent. The effect of various surfactants such as cationic, anionic and neutral on the morphology of the products was investigated. By changing in Ca(Sal2 as a new precursor different morphologies were obtained. Ligand as a capping agent with steric hindrance leads to preparation of product with lower particle size. These semiconductor nanostructures have photo-catalyst activities and can degrade organic dyes as water pollution. The synthesized materials were characterized by X-ray diffraction (XRD technique, scanning electron microscopy (SEM Fourier transform infrared (FT-IR and UV-visible spectroscopy.

  11. High-mobility BaSnO{sub 3} grown by oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Raghavan, Santosh; Schumann, Timo; Kim, Honggyu; Zhang, Jack Y.; Cain, Tyler A.; Stemmer, Susanne, E-mail: stemmer@mrl.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

    2016-01-01

    High-mobility perovskite BaSnO{sub 3} films are of significant interest as new wide bandgap semiconductors for power electronics, transparent conductors, and as high mobility channels for epitaxial integration with functional perovskites. Despite promising results for single crystals, high-mobility BaSnO{sub 3} films have been challenging to grow. Here, we demonstrate a modified oxide molecular beam epitaxy (MBE) approach, which supplies pre-oxidized SnO{sub x}. This technique addresses issues in the MBE of ternary stannates related to volatile SnO formation and enables growth of epitaxial, stoichiometric BaSnO{sub 3}. We demonstrate room temperature electron mobilities of 150 cm{sup 2} V{sup −1} s{sup −1} in films grown on PrScO{sub 3}. The results open up a wide range of opportunities for future electronic devices.

  12. Electrical transport properties of spray deposited transparent conducting ortho-Zn2SnO4 thin films

    Science.gov (United States)

    Ramarajan, R.; Thangaraju, K.; Babu, R. Ramesh; Joseph, D. Paul

    2018-04-01

    Ortho Zinc Stannate (Zn2SnO4) exhibits excellent electrical and optical properties to serve as alternate transparent electrode in optoelectronic devices. Here we have optimized ortho-Zn2SnO4 thin film by spray pyrolysis method. Deposition was done onto a pre-heated glass substrate at a temperature of 400 °C. The XRD pattern indicated films to be polycrystalline with cubic structure. The surface of films had globular and twisted metal sheet like morphologies. Films were transparent in the visible region with band gap around 3.6 eV. Transport properties were studied by Hall measurements at 300 K. Activation energies were calculated from Arrhenius's plot from temperature dependent electrical measurements and the conduction mechanism is discussed.

  13. Development of high-performance transparent conducting oxides and their impact on the performance of CdS/CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Coutts, T.J.; Wu, X.; Sheldon, P.; Rose, D.H. [National Renewable Energy Lab., Golden, CO (United States)

    1998-09-01

    This paper begins with a review of the modeled performance of transparent conducting oxides (TCOs) as a function of their free-carrier concentration, mobility, and film thickness. It is shown that it is vital to make a film with high mobility to minimize the width and height of the free-carrier absorption band, and to optimize the optical properties. The free-carrier concentration must be kept sufficiently small that the absorption band does not extend into that part of the spectrum to which the solar cell responds. Despite this consideration, a high electrical conductivity is essential to minimize series resistance losses. Hence, a high mobility is vital for these materials. The fabrication of thin-films of cadmium stannate is then discussed, and their performance is compared with that of tin oxide, both optically and as these materials influence the performance of CdTe solar cells.

  14. Oxidation Characteristics and Electrical Properties of Doped Mn-Co Spinel Reaction Layer for Solid Oxide Fuel Cell Metal Interconnects

    Directory of Open Access Journals (Sweden)

    Pingyi Guo

    2018-01-01

    Full Text Available To prevent Cr poisoning of the cathode and to retain high conductivity during solid oxide fuel cell (SOFC operation, Cu or La doped Co-Mn coatings on a metallic interconnect is deposited and followed by oxidation at 750 °C. Microstructure and composition of coatings after preparation and oxidation is analyzed by X-ray diffraction (XRD and scanning electron microscopy (SEM. High energy micro arc alloying process, a low cost technique, is used to prepare Cu or La doped Co-Mn coatings with the metallurgical bond. When coatings oxidized at 750 °C in air for 20 h and 100 h, Co3O4 is the main oxide on the surface of Co-38Mn-2La and Co-40Mn coatings, and (Co,Mn3O4 spinel continues to grow with extended oxidation time. The outmost scales of Co-33Mn-17Cu are mainly composed of cubic MnCo2O4 spinel with Mn2O3 after oxidation for 20 h and 100 h. The average thickness of oxide coatings is about 60–70 μm after oxidation for 100 h, except that Co-40Mn oxide coatings are a little thicker. Area-specific resistance of Cu/La doped Co-Mn coatings are lower than that of Co-40Mn coating. (Mn,Co3O4/MnCo2O4 spinel layer is efficient at blocking the outward diffusion of chromium and iron.

  15. Impact of doping on the ionic conductivity of ceria: A comprehensive model

    KAUST Repository

    Wang, Hao

    2013-06-13

    Doped ceria is considered as an electrolyte for solid oxide fuel cell applications. The introduction of dopants in the ceria lattice will affect its electronic structure and, in turn, its ionic conductivity. Simulation of these issues using density functional theory becomes complicated by the random distribution of the constituent atoms. Here we use the generalized gradient approximation with on-site Coulomb interaction in conjunction with the special quasirandom structures method to investigate 18.75% and 25% Y, Gd, Sm, Pr, and La doped ceria. The calculated lattice constants and O migration energies allow us to explain the behavior of the conductivity as obtained in experiments.

  16. Effect of La3+ substitution on the phase transitions, microstructure and electrical properties of Bi1−xLaxFeO3 ceramics

    International Nuclear Information System (INIS)

    Zhang, Qiang; Zhu, Xiaohong; Xu, Yunhui; Gao, Haobin; Xiao, Yunjun; Liang, Dayun; Zhu, Jiliang; Zhu, Jianguo; Xiao, Dingquan

    2013-01-01

    Highlights: ► Structural properties of Bi 1−x La x FeO 3 ceramics are improved by La 3+ substitution. ► Significant magnetoelectric responses are observed in Bi 1−x La x FeO 3 ceramics. ► T C is lowered while T N is enhanced in the La-doped BiFeO 3 ceramics. ► Much higher dielectric constant is obtained in the La-doped BiFeO 3 ceramics. ► The ferroelectric properties are enhanced in the La-doped BiFeO 3 ceramics. - Abstract: Multiferroic Bi 1−x La x FeO 3 (x = 0.00, 0.05, 0.10, 0.15, 0.20) (represented as B 1−x L x FO) ceramics were prepared using the conventional solid state reaction route. The effects of La 3+ doping on the density, phase structure, morphology, dielectric and ferroelectric properties were investigated. Judging from X-ray diffraction patterns, all the B 1−x L x FO ceramic samples were well crystallized in a pure perovskite phase while the crystal structure changed from rhombohedral to orthorhombic with increasing the La 3+ substitution. SEM observations clearly revealed that the grain size was remarkably decreased by La 3+ doping. As a result, the ferroelectric Curie temperature was lowered in the La-doped ceramics. However, the abnormal dielectric responses near the antiferromagnetic Néel temperature (T N ) demonstrated the existence of remarkable magnetoelectric coupling in the Bi 1−x La x FeO 3 ceramics, and the T N was shown to increase substantially with the increase in La 3+ doping content. It was found that the dielectric permittivity of the ceramics was significantly increased and the dielectric loss was slightly increased with the increase in La 3+ content. The dielectric constant ε r of the Bi 0.85 La 0.15 FeO 3 ceramic at 10 kHz reached as high as 1008, 20 times larger than that for pure BiFeO 3 . In addition, the ferroelectric properties of the B 1−x L x FO ceramics were improved and the remanent polarization was increased by La 3+ doping. This is probably because the A-site doping with more stable La 3+ could

  17. Composition and local bonding in RE-Si-M-O-N (M=Mg, Al ; RE=La, Lu) glasses

    Energy Technology Data Exchange (ETDEWEB)

    Fouquet-Parry, V. [Service de Physique et de Chimie des Surfaces et des Interfaces, DSM/DRECAM/SPCSI, CEA Saclay, 91191 Gif sur Yvette Cedex (France); Paumier, F. [Laboratoire de Metallurgie Physique - UMR 6630 CNRS, Department of Materials Sciences, University of Poitiers (France); Guittet, M.J. [Service de Physique et de Chimie des Surfaces et des Interfaces, DSM/DRECAM/SPCSI, CEA Saclay, 91191 Gif sur Yvette Cedex (France); Gautier-Soyer, M. [Service de Physique et de Chimie des Surfaces et des Interfaces, DSM/DRECAM/SPCSI, CEA Saclay, 91191 Gif sur Yvette Cedex (France)], E-mail: mgautiersoyer@cea.fr; Satet, R.; Hoffmann, M.J. [Institut fuer Keramik im Maschinenbau, Universitaet Karlsruhe (Thailand), Haid-und-Neu-Strasse 7, D 76131 Karlsruhe (Germany); Becher, P.F.; Painter, G.S. [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)

    2008-05-30

    Two series of oxynitride glasses, RE-Si-Mg-O-N (M=Mg, Al ; RE=La, Lu), have been studied by X-Ray photoelectron spectroscopy (XPS). The oxygen 1s photoelectron lineshape reveals a striking difference depending on the rare earth, both in the Mg series and in the Al series. Specifically, the oxygen 1s photoelectron lines of the La doped glasses are broader than the ones of the Lu doped glasses. This result is an experimental evidence that Lu has a larger affinity for oxygen versus nitrogen than La, as theoretically predicted by the first-principles calculations by Painter et al.

  18. Electric controlling of surface metal-insulator transition in the doped BaTiO3 film

    Directory of Open Access Journals (Sweden)

    Wei Xun

    2017-07-01

    Full Text Available Based on first-principles calculations, the BaTiO3(BTO film with local La-doping is studied. For a selected concentration and position of doping, the surface metal-insulator transition occurs under the applied electric field, and the domain appears near the surface for both bipolar states. Furthermore, for the insulated surface state, i.e., the downward polarization state in the doped film, the gradient bandgap structure is achieved, which favors the absorption of solar energy. Our investigation can provide an alternative avenue in modification of surface property and surface screening effect in polar materials.

  19. Investigations on Structural, Mechanical, and Dielectric Properties of PVDF/Ceramic Composites

    Directory of Open Access Journals (Sweden)

    Anshuman Srivastava

    2015-01-01

    Full Text Available Polymer ceramic composites are widely used for embedded capacitor application. In the present work PVDF has been used as a matrix and CCTO and LaCCTO have been used as reinforcement. Extrusion process has been used for the synthesis of composites. X-ray diffraction (XRD patterns confirm the formation of single phase CCTO, and LaCCTO in its pure as well as composite state. It is found that La doping in CCTO considerably increases the dielectric constant and reduces the dielectric loss. A similar trend is observed in the composites with the increasing content of CCTO and LaCCTO.

  20. Laser energy tuning of carrier effective mass and thermopower in epitaxial oxide thin films

    KAUST Repository

    Abutaha, Anas I.

    2012-04-18

    The effect of the laser fluence on high temperature thermoelectric properties of the La doped SrTiO3 (SLTO) thin films epitaxially grown on LaAlO3 〈100〉 substrates by pulsed laser deposition is clarified. It is shown that oxygen vacancies that influence the effective mass of carriers in SLTO films can be tuned by varying the laser energy. The highest power factor of 0.433 W K−1 m−1 has been achieved at 636 K for a filmdeposited using the highest laser fluence of 7 J cm−2 pulse−1.

  1. Thermopower studies of doped CeAl sub 2 and UAl sub 2

    CERN Document Server

    Park, J G

    1997-01-01

    We have studied the thermopower of U doped CeAl sub 2 and Ce and La doped UAl sub 2. Despite different ground state properties of CeAl sub 2 and UAl sub 2 , the former being an antiferromagnetic heavy-fermion compound and the latter non-magnetic, we have found that not only thermopower data for pure CeAl sub 2 and UAl sub 2 are similar but also the thermopower results of doped samples behave similarly. Although the similarity seen in pure systems is yet to be understood, we interpret the doping effects as the results of changes in energy dependent relaxation time with doping. (author)

  2. Excitonic Wigner crystal and high T sub c ferromagnetism in RB sub 6

    CERN Document Server

    Kasuya, T

    2000-01-01

    The mechanisms for the high T sub c ferromagnetism in La-doped divalent hexaborides DB sub 6 are studied in detail comparing with similar family materials, in particular with YbB sub 6 , EuB sub 6 and Ce monopnictides. It is shown that in DB sub 6 the light-electron-heavy-hole paired excitonic states form the Wigner crystal, or Wigner glass in actual materials, in which the conventional intersite electron exchange interactions similar to that in Ni dominate the pair singlet formation due to the intra pair mixing causing a ferromagnetic spin glass-like ordering of electron spins. In the La-doped system La sub x D sub 1 sub - sub x B sub 6 , the population of molecular La impurity states with giant moments increases as x approaches the optimal value x sub 0 approx 0.005 for high T sub c providing vacant states for the roton-like fluctuations, which cause the high T sub c at the boundary of the delocalization of electron carriers. Therefore, the critical La concentration for delocalization coincides with the opt...

  3. Photoluminescence properties of cerium oxide nanoparticles as a function of lanthanum content

    International Nuclear Information System (INIS)

    Deus, R.C.; Cortés, J.A.; Ramirez, M.A.; Ponce, M.A.; Andres, J.; Rocha, L.S.R.

    2015-01-01

    Highlights: • CeO 2 nanoparticles were obtained by microwave-hydrothermal method. • Rietveld refinement reveals a cubic structure. • KOH mineralizer agent exhibit weak agglomeration at low temperature and shorter time. - Abstract: The structural and photoluminescent properties at room temperature of CeO 2 and La-doped CeO 2 particles were undertaken. The obtained particles were synthesized by a microwave-assisted hydrothermal method (MAH) under different lanthanum contents. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), Ultra-violet spectroscopy (UV–vis) and photoluminescence (PL) measurements were carried out. XRD revealed that the powders are free of secondary phases and crystallize in the cubic structure. Raman data show that increasing La doping content increase oxygen vacancies due to lattice expansion. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. Lanthanum addition creates oxygen vacancies and shifts the photoluminescence in the low energy range leading to intense PL emission

  4. Photoluminescence properties of cerium oxide nanoparticles as a function of lanthanum content

    Energy Technology Data Exchange (ETDEWEB)

    Deus, R.C. [Universidade Estadual Paulista, Unesp —Faculdade de Engenharia de Guaratinguetá, Av. Dr Ariberto Pereira da Cunha 333, Bairro Pedregulho, P.O. Box 355, 12.516-410 Guaratinguetá, São Paulo, Brazil, (Brazil); Cortés, J.A., E-mail: leandrosrr89@gmail.com [Universidade Estadual Paulista, Unesp —Faculdade de Engenharia de Guaratinguetá, Av. Dr Ariberto Pereira da Cunha 333, Bairro Pedregulho, P.O. Box 355, 12.516-410 Guaratinguetá, São Paulo, Brazil, (Brazil); Ramirez, M.A. [Universidade Estadual Paulista, Unesp —Faculdade de Engenharia de Guaratinguetá, Av. Dr Ariberto Pereira da Cunha 333, Bairro Pedregulho, P.O. Box 355, 12.516-410 Guaratinguetá, São Paulo, Brazil, (Brazil); Ponce, M.A. [Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA) (CONICET-Universidad Nacional de Mar del Plata), Juan B. Justo 4302, 7600 Mar del Plata (Argentina); Andres, J. [Laboratório Interdisciplinar em Cerâmica, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, 14801-907 Araraquara, São Paulo (Brazil); Rocha, L.S.R. [Universidade Estadual Paulista, Unesp —Faculdade de Engenharia de Guaratinguetá, Av. Dr Ariberto Pereira da Cunha 333, Bairro Pedregulho, P.O. Box 355, 12.516-410 Guaratinguetá, São Paulo, Brazil, (Brazil); and others

    2015-10-15

    Highlights: • CeO{sub 2} nanoparticles were obtained by microwave-hydrothermal method. • Rietveld refinement reveals a cubic structure. • KOH mineralizer agent exhibit weak agglomeration at low temperature and shorter time. - Abstract: The structural and photoluminescent properties at room temperature of CeO{sub 2} and La-doped CeO{sub 2} particles were undertaken. The obtained particles were synthesized by a microwave-assisted hydrothermal method (MAH) under different lanthanum contents. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), Ultra-violet spectroscopy (UV–vis) and photoluminescence (PL) measurements were carried out. XRD revealed that the powders are free of secondary phases and crystallize in the cubic structure. Raman data show that increasing La doping content increase oxygen vacancies due to lattice expansion. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. Lanthanum addition creates oxygen vacancies and shifts the photoluminescence in the low energy range leading to intense PL emission.

  5. Fabrication of Schottky Junction Between Au and SrTiO3

    Science.gov (United States)

    Inoue, Akira; Izumisawa, Kei; Uwe, Hiromoto

    2001-05-01

    A Schottky junction with a high rectification ratio between Au and La-doped SrTiO3 has been fabricated using a simple surface treatment. Highly La-doped (5%) SrTiO3 single crystals are annealed in O2 atmosphere at about 1000°C for 1 h and etched in HNO3 for more than five min. The HNO3 etching is performed in a globe box containing N2 to prevent pollution from the air. After the treatment, Au is deposited on the SrTiO3 surface in a vacuum (˜ 10-7 Torr) with an e-gun evaporator. The current voltage characteristics of the junction have shown excellent rectification properties, although junctions using neither annealed nor etched SrTiO3 exhibit high leak current in reverse voltage. The rectification ratio of the junction at 1 V is more than six orders of magnitude and there is no hysteresis in the current voltage spectra. The logarithm of the current is linear with the forward bias voltage. The ideal factor of the junction is estimated to be about 1.68. These results suggest that, if prevented from being pollution by the air, a good Schottky junction can be obtained by easy processes such as annealing in oxygen atmosphere and surface etching with acid.

  6. Photocatalytic degradation of Reactive Black 5 and Malachite Green with ZnO and lanthanum doped nanoparticles

    International Nuclear Information System (INIS)

    Kaneva, N; Bojinova, A; Papazova, K

    2016-01-01

    Here we report the preparation of ZnO particles with different concentrations of La 3 + doping (0, 0.5 and 1 wt%) via sol-gel method. The nanoparticles are synthesized directly from Zn(CH 3 COO) 2 .2H 2 O in the presence of 1-propanol and triethylamine at 80°C. The conditions are optimized to obtain particles of uniform size, easy to isolate and purify. The nanoparticles are characterized by SEM, XRD and UV-Vis analysis. The photocatalytic properties of pure and La-doped ZnO are studied in the photobleaching of Malachite Green (MG) and Reactive Black 5 (RB5) dyes in aqueous solutions upon UV illumination. It is observed that the rate constant increases with the La loading up to 1 wt%. The doping helps to achieve complete mineralization of MG within a short irradiation time. 1 wt% La-doped ZnO nanoparticles show highest photocatalytic activity. The La 3+ doped ZnO particles degrade faster RB5 than MG. The reason is weaker N=N bond in comparison with the C-C bond between the central carbon atom and N,N-dimethylaminobenzyl in MG. The as-prepared ZnO particles can find practical application in photocatalytic purification of textile wastewaters. (paper)

  7. Radiation damage in barium fluoride detector materials

    International Nuclear Information System (INIS)

    Levey, P.W.; Kierstead, J.A.; Woody, C.L.

    1988-01-01

    To develop radiation hard detectors, particularly for high energy physics studies, radiation damage is being studied in BaF 2 , both undoped and doped with La, Ce, Nd, Eu, Gd and Tm. Some dopants reduce radiation damage. In La doped BaF 2 they reduce the unwanted long lifetime luminescence which interferes with the short-lived fluorescence used to detect particles. Radiation induced coloring is being studied with facilities for making optical measurements before, during and after irradiation with 60 C0 gamma rays. Doses of 10 6 rad, or less, create only ionization induced charge transfer effects since lattice atom displacement damage is negligible at these doses. All crystals studied exhibit color center formation, between approximately 200 and 800 nm, during irradiation and color center decay after irradiation. Thus only measurements made during irradiation show the total absorption present in a radiation field. Both undoped and La doped BaF 2 develop damage at minimum detectable levels in the UV---which is important for particle detectors. For particle detector applications these studies must be extended to high dose irradiations with particles energetic enough to cause lattice atom displacement damage. In principle, the reduction in damage provided by dopants could apply to other applications requiring radiation damage resistant materials

  8. Lanthanum-doped mesostructured strontium titanates synthesized via sol–gel combustion route using citric acid as complexing agent

    Energy Technology Data Exchange (ETDEWEB)

    Sukpanish, Polthep [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Lertpanyapornchai, Boontawee [Program in Petrochemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Yokoi, Toshiyuki [Division of Catalytic Chemistry, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Ngamcharussrivichai, Chawalit, E-mail: Chawalit.Ng@chula.ac.th [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand)

    2016-09-15

    In the present work, a series of lanthanum-doped mesostructured strontium titanate (LMST) materials with different La/Sr ratios were synthesized via a sol–gel combustion method in the presence of citric acid as a complexing agent and Pluronic P123 as a templating agent. The effects of the amount of doped La and calcination temperature on the physicochemical properties of the LMSTs were examined using various techniques. Powder X-ray diffraction confirmed the substitution of La{sup 3+} into the SrTiO{sub 3} lattice, generating cubic perovskite La{sub x}Sr{sub 1−x}TiO{sub 3}, for the LMST materials calcined at 600 °C. The purity and crystallinity of the desired perovskite phase were enhanced by citric acid addition. The solubility limit of La{sup 3+} substitution at an La/Sr ratio of 0.43 was determined by structural and morphological studies. Increasing the La doping amount decreased the crystallinity and compositional homogeneity, because an La-rich amorphous phase segregated on the surface, but improved the mesoporosity. N{sub 2} physisorption measurements indicated that the LMSTs had a bimodal pore size distribution, of which the larger one was characterized by the crystallite size of mixed oxides, and the specific surface area of 24.9–37.3 m{sup 2} g{sup −1}. The formation of mesopores in the LMST materials synthesized via sol–gel combustion was explained based on a combination of soft- and hard-templating chemistries. - Highlights: • La-doped mesoporous SrTiO{sub 3} (LMST) was prepared first time via sol-gel combustion. • Pluronic P123 triblock copolymer was used as a cheap templating agent. • Citric acid as a complexing agent enhanced the purity and crystallinity of SrTiO{sub 3}. • The textural properties of LMST were improved by increasing the La doping amount. • Mesopore formation was explained by a combined soft- and hard-templating route.

  9. Magnetic, dielectric and microwave absorption properties of rare earth doped Ni–Co and Ni–Co–Zn spinel ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Stergiou, Charalampos, E-mail: stergiou@cperi.certh.gr

    2017-03-15

    In this article we analyze the electromagnetic properties of rare earth substituted Ni–Co and Ni–Co–Zn cubic ferrites in the microwave band, along with their performance as microwave absorbing materials. Ceramic samples with compositions Ni{sub 0.5}Co{sub 0.5}Fe{sub 2−x}R{sub x}O{sub 4} and Ni{sub 0.25}Co{sub 0.5}Zn{sub 0.25}Fe{sub 2−x}R{sub x}O{sub 4} (R=Y and La, x=0, 0.02), fabricated with the solid state reaction method, were characterized with regard to the complex permeability μ*(f) and permittivity ε*(f) up to 20 GHz. The rare earth substitutions basically affect the microwave μ*(f) spectra and the dynamic magnetization mechanisms of domain wall motion and magnetization rotation. Key parameters for this effect are the reduced magnetocrystalline anisotropy and the created crystal inhomogeneities. Moreover, permittivity is increased with the Y and La content, due to the enhancement of the dielectric orientation polarization. Regarding the electromagnetic wave attenuation, the prepared ferrites exhibit narrowband return losses (RL) by virtue of the cancellation of multiple reflections, when their thickness equals an odd multiple of quarter-wavelength. Interestingly, the zero-reflection conditions are satisfied in the vicinity of the ferromagnetic resonance. As the rare earth doping shifts this mechanism to lower frequencies, loss peaks with RL>46 dB occur at 4.1 GHz and 5 GHz for Y and La-doped Ni–Co–Zn spinels, whereas peaks with RL>40 dB appear at 18 GHz and 19 GHz for Y and La-doped Ni–Co spinels, respectively. The presented experimental findings underline the potential of cubic ferrites with high Co concentration in the suppression of electromagnetic reflections well above the 1 GHz region. - Highlights: • Due to cation distribution, magnetic anisotropy drops in Y and La doped samples. • Microwave permeability spectra shift to lower frequencies with rare earth doping. • Permittivity is increased due to crystal modifications

  10. Electromagnetic behavior of radar absorbing materials based on Ca hexaferrite modified with Co-Ti ions and doped with La

    Directory of Open Access Journals (Sweden)

    Valdirene Aparecida da Silva

    2009-06-01

    Full Text Available Radar Absorbing Materials (RAM are compounds that absorb incidental electromagnetic radiation in tuned frequencies and dissipate it as heat. Its preparation involves the adequate processing of polymeric matrices filled with compounds that act as radar absorbing centers in the microwave range. This work shows the electromagnetic evaluation of RAM based on CoTi and La doped Ca hexaferrite. Vibrating Sample Magnetization analyses show that ion substitution promoted low values for the parameters of saturation magnetization (123.65 Am2/kg and coercive field (0.07 T indicating ferrite softening. RAM samples obtained using different hexaferrite concentrations (40-80 per cent, w/w show variations in complex permeability and permittivity parameters and also in the performance of incidental radiation attenuation. Microwave attenuation values between 40 and 98 per cent were obtained.

  11. Nature of the valence band states in Bi2(Ca, Sr, La)3Cu2O8

    International Nuclear Information System (INIS)

    Wells, B.O.; Lindberg, P.A.P.; Shen, Z.; Dessau, D.S.; Spicer, W.E.; Lindau, I.; Mitzi, D.B.; Kapitulnik, A.

    1990-01-01

    We have used photoemission spectroscopy to examine the symmetry of the occupied states of the valence band for the La doped superconductor Bi 2 (Ca, Sr, La) 3 Cu 2 O 8 . While the oxygen states near the bottom of the 7 eV wide valence band exhibit predominantly O 2p z symmetry, the states at the top of the valence band extending to the Fermi level are found to have primarily O 2p x and O 2p y character. We have also examined anomalous intensity enhancements in the valence band feature for photon energies near 18 eV. These enhancements, which occur at photon energies ranging from 15.8 to 18.0 eV for the different valence band features, are not consistent with either simple final state effects or direct O2s transitions to unoccupied O2p states

  12. Energy dispersions of single-crystalline Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ superconductors determined using angle-resolved photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Lindberg, P.A.P.; Shen, Z.; Dessau, D.S.; Wells, B.O.; Mitzi, D.B.; Lindau, I.; Spicer, W.E.; Kapitulnik, A.

    1989-01-01

    Angle-resolved photoemission studies of single-crystalline La-doped Bi-Sr-Ca-Cu- 90-K superconductors (Bi 2.0 Sr 1.8 Ca 0.8 La 0.3 Cu 2.1 O 8+δ ) were performed utilizing synchrotron radiation covering the photon energy range 10--40 eV. The data conclusively reveal a dispersionless character of the valence-band states as a function of the wave-vector component parallel to the c axis, in agreement with the predictions of band calculations. Band effects are evident from both intensity modulations of the spectral features in the valence band and from energy dispersions as a function of the wave vector component lying in the basal a-b plane

  13. Structure and optical band gaps of (Ba,Sr)SnO{sub 3} films grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Schumann, Timo; Raghavan, Santosh; Ahadi, Kaveh; Kim, Honggyu; Stemmer, Susanne, E-mail: stemmer@mrl.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

    2016-09-15

    Epitaxial growth of (Ba{sub x}Sr{sub 1−x})SnO{sub 3} films with 0 ≤ x ≤ 1 using molecular beam epitaxy is reported. It is shown that SrSnO{sub 3} films can be grown coherently strained on closely lattice and symmetry matched PrScO{sub 3} substrates. The evolution of the optical band gap as a function of composition is determined by spectroscopic ellipsometry. The direct band gap monotonously decreases with x from to 4.46 eV (x = 0) to 3.36 eV (x = 1). A large Burnstein-Moss shift is observed with La-doping of BaSnO{sub 3} films. The shift corresponds approximately to the increase in Fermi level and is consistent with the low conduction band mass.

  14. Relativistic electronic structure calculations on endohedral Gd rate at C60, La rate at C60, Gd rate at C74, and La rate at C74

    International Nuclear Information System (INIS)

    Lu, J.; Zhang, X.; Zhao, X.

    2000-01-01

    Relativistic discrete-variational local density functional calculations on endohedral Gd rate at C 60 , La rate at C 60 ,Gd rate at C 74 , and La rate at C 74 are performed. All the C 60 - and C 74 -derived levels are lowered upon endohedral Gd and La doping. Both the Gd (4f 7 5d 1 6s 2 ) and La (5d 1 6s 2 ) atoms only donate their two 6s valence electrons to the cages, leaving behind their 5d electrons when they are placed at the cage centers. Compared with large-band-gap C 60 , small-band-gap C 74 and Gd (La)-metallofullerenes have strong both electron-donating and electron-accepting characters, and the calculated ionization potentials and electron affinities for them agree well with the available experimental data. (orig.)

  15. Influence of La and Sr addition on the structural parameter of PbTiO3

    International Nuclear Information System (INIS)

    Garcia, D.; Mascarenhas, Y.P.; Oliveira Paiva Santos, C. de; Eiras, J.A.

    1989-01-01

    Compositions of (Pb 1-x Ln x ) (Ti 1-y Mn y )O 3 (Ln = La, Sr; 0 0 C and sintered at 1200 0 C. The influence of the adition of La and Sr in the structural parameters of the tetragonal lattice of the lead titanate (PbTiO 3 ) was investigated with X-ray diffraction. The doping, with La or Sr, increase the lattice parameter a and decrease de parameter c of the PbTiO 3 . The variation of a and c increase with the dopant concentration and is greather in the La doped samples. The addition of 1% mol of Mn in these compositions increase the their sinterability. The apparent densites were compared with those calculated from the lattice parameters a and c. A decrease of the Curie temperature T c was observed when the concentration of La or Sr was increased. (author) [pt

  16. Neutron irradiation effects on grain-refined W and W-alloys

    International Nuclear Information System (INIS)

    Hasegawa, A.; Fukuda, M.; Tanno, T.; Nogami, S.; Yabuuchi, K.; Tanaka, T.; Muroga, T.

    2014-10-01

    Microstructural data of neutron irradiated Tungsten (W) such as size and number density of voids and precipitates obtained by W up to 1.5dpa irradiation in the temperature range of 400-800degC were compiled quantitatively. Nucleation and growth process of these defects were clarified and a qualitative prediction of the damage structure development and hardening of W in fusion reactor environments were made taking into account the solid transmutation effects for the first time. To improve recrystallization behavior and low temperature embrittlement, grain refined-W alloys were fabricated by K- or La-doping method. Rhenium addition to the grain refining process was also examined to improve mechanical properties. Characterizations of unirradiated materials were performed. (author)

  17. Dopant rearrangement and superconductivity in Bi2Sr2-xLaxCuO6 thin films under annealing

    International Nuclear Information System (INIS)

    Cancellieri, C; Lin, P H; Ariosa, D; Pavuna, D

    2007-01-01

    By combining x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and AC susceptibility measurements we investigate the evolution of structural and superconducting properties of La-doped Bi-2201 thin films grown by pulsed laser deposition (PLD) under different annealing conditions. We find that the main effect of oxygen annealing is to improve the crystal coherence by enabling La cation migration to the Sr sites. This activates the desired hole doping. Short-time Ar annealing removes the interstitial oxygen between the BiO layers, fine adjusting the effective hole doping. The superconducting critical temperature is consequently enhanced. However, longer annealings result in phase separation and segregation of the homologous compound Bi-1201. We attribute this effect to the loss of Bi during the annealing

  18. CaSnO 3 obtained by modified Pechini method applied in the photocatalytic degradation of an azo dye

    Directory of Open Access Journals (Sweden)

    G. L. Lucena

    Full Text Available Abstract Pure forms of alkaline-earth stannates with perovskite structure (ASnO3, A= Ca2+, Sr2+, Ba2+ have been used as photocatalysts. In this work, CaSnO3 perovskite sample was synthesized by a modified Pechini method at 800 ºC and characterized by X-ray diffraction (XRD, UV-visible spectroscopy, infrared spectroscopy and Raman spectroscopy. The photocatalytic degradation of remazol golden yellow (RNL dye under UV radiation was evaluated. The XRD pattern showed that the synthesis method favored the orthorhombic CaSnO3 crystallization. According to the Raman spectrum, a material with high short-range order was obtained despite of the relatively low synthesis temperature, compared to the solid-state reaction one. The highest photocatalytic activity was attained at pH 3, which presented 51% discoloration and improved activity of 35% compared to discoloration solely due to adsorption (absence of radiation. The point of zero charge (PZC and the photocatalytic results indicated that a direct mechanism prevailed at pH 3, whereas an indirect mechanism prevailed at pH 6.

  19. Hierarchical Assembly of Multifunctional Oxide-based Composite Nanostructures for Energy and Environmental Applications

    Directory of Open Access Journals (Sweden)

    Hui-Jan Lin

    2012-06-01

    Full Text Available Composite nanoarchitectures represent a class of nanostructured entities that integrates various dissimilar nanoscale building blocks including nanoparticles, nanowires, and nanofilms toward realizing multifunctional characteristics. A broad array of composite nanoarchitectures can be designed and fabricated, involving generic materials such as metal, ceramics, and polymers in nanoscale form. In this review, we will highlight the latest progress on composite nanostructures in our research group, particularly on various metal oxides including binary semiconductors, ABO3-type perovskites, A2BO4 spinels and quaternary dielectric hydroxyl metal oxides (AB(OH6 with diverse application potential. Through a generic template strategy in conjunction with various synthetic approaches—such as hydrothermal decomposition, colloidal deposition, physical sputtering, thermal decomposition and thermal oxidation, semiconductor oxide alloy nanowires, metal oxide/perovskite (spinel composite nanowires, stannate based nanocompostes, as well as semiconductor heterojunction—arrays and networks have been self-assembled in large scale and are being developed as promising classes of composite nanoarchitectures, which may open a new array of advanced nanotechnologies in solid state lighting, solar absorption, photocatalysis and battery, auto-emission control, and chemical sensing.

  20. Raman identification of cuneiform tablet pigments: emphasis and colour technology in ancient Mesopotamian mid-third millennium

    Directory of Open Access Journals (Sweden)

    Daniele Chiriu

    2017-03-01

    Full Text Available Cuneiform tablets tell the life and culture of Sumerian people in a sort of black and white tale because of the binary engraving technique. A leading question arises: did Mesopotamian people apply some kind of colour to decorate their tablets or to put emphasis on selected words? Some administrative and literary Sumerian cuneiform tablets of mid-third Millennium B.C. from the site of Kish (central Mesopotamia, modern Iraq were dug up in twentieth-century and stored at the Ashmolean Museum of the Oxford University. Non-destructive micro-Raman spectroscopy is a powerful technique to detect the presence of residual pigments eventually applied to the engraving signs. Yellow, orange, red and white pigments have been detected and a possible identification has been proposed in this work. In particular yellow pigments are identified as Crocoite (PbCrO4, Lead stannate (Pb2SnO4; red pigments − hematite (Fe2O3 and cuprite (Cu2O; White pigments − Lead carbonate (PbCO3, calcium phosphate (Ca3(PO42, titanium dioxide (TiO2, gypsum (CaSO4.2H2O; orange pigment a composition of red and yellow compounds. These results suggest that Sumerian people invented a new editorial style, to overcome the binary logic of engraving process and catch the reader’s eye by decorating cuneiform tablets. Finally, the coloured rendering of the tablet in their original view is proposed.

  1. Method to remove ammonia using a proton-conducting ceramic membrane

    Science.gov (United States)

    Balachandran, Uthamalinga; Bose, Arun C

    2003-10-07

    An apparatus and method for decomposing NH.sub.3. A fluid containing NH.sub.3 is passed in contact with a tubular membrane that is a homogeneous mixture of a ceramic and a first metal, with the ceramic being selected from one or more of a cerate having the formula of M'Ce.sub.1-x M".sub.3-.delta., zirconates having the formula M'Zr.sub.1-x M"O.sub.3-.delta., stannates having the formula M'Sn.sub.1-x M'O.sub.3-.delta., where M' is a group IIA metal, M" is a dopant metal of one or more of Ca, Y, Yb, In, Nd, Gd or mixtures thereof and .delta. is a variable depending on the concentration of dopant and is in the range of from 0.001 to 0.5, the first metal is a group VIII or group IB element selected from the group consisting of Pt, Ag, Pd, Fe, Co, Cr, Mn, V, Ni, Au, Cu, Rh, Ru and mixtures thereof. The tubular membrane has a catalytic metal on the side thereof in contact with the fluid containing NH.sub.3 which is effective to cause NH.sub.3 to decompose to N.sub.2 and H.sub.2. When the H.sub.2 contacts the membrane H.sup.+ ions are formed which pass through the membrane driving the NH.sub.3 decomposition toward completion.

  2. Cloning, characterization and anion inhibition study of a β-class carbonic anhydrase from the caries producing pathogen Streptococcus mutans.

    Science.gov (United States)

    Dedeoglu, Nurcan; De Luca, Viviana; Isik, Semra; Yildirim, Hatice; Kockar, Feray; Capasso, Clemente; Supuran, Claudiu T

    2015-07-01

    The oral pathogenic bacterium involved in human dental caries formation Streptococcus mutans, encodes for two carbonic anhydrase (CA, EC 4.2.1.1) one belonging to the α- and the other one to the β-class. This last enzyme (SmuCA) has been cloned, characterized and investigated for its inhibition profile with a major class of CA inhibitors, the inorganic anions. Here we show that SmuCA has a good catalytic activity for the CO2 hydration reaction, with kcat 4.2×10(5)s(-1) and kcat/Km of 5.8×10(7)M(-1)×s(-1), being inhibited by cyanate, carbonate, stannate, divannadate and diethyldithiocarbamate in the submillimolar range (KIs of 0.30-0.64mM) and more efficiently by sulfamide, sulfamate, phenylboronic acid and phenylarsonic acid (KIs of 15-46μM). The anion inhibition profile of the S. mutans enzyme is very different from other α- and β-CAs investigated earlier. Identification of effective inhibitors of this new enzyme may lead to pharmacological tools useful for understanding the role of S. mutans CAs in dental caries formation, and eventually the development of pharmacological agents with a new mechanism of antibacterial action. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Production of 122Sb for the study of environmental pollution

    International Nuclear Information System (INIS)

    Mahdi Sadeghi; Mohammadreza Aboudzadeh; Parvin Sarabadani; Milad Enferadi

    2011-01-01

    This article presents, 122 Sb (T 1/2 = 2.723 days, I β- 97.59%) was produced via the nat Sn(p,xn) nuclear process at the AMIRS (Cyclone-30, IBA, Belgium). The electrodeposition experiments were carried out by potassium stannate trihydrate (K 2 Sn(OH) 6 ) and potassium hydroxide. The optimum conditions of the electrodeposition of tin were as follows: 40 g/L nat Sn, 20 g/L KOH, 115 g/L K 2 Sn(OH) 6 , DC current density of 5 A/dm 2 with a bath temperature of 75 deg C. The electroplated Tin-target was irradiated with 26.5 MeV protons at current of 180 μA for 20 min. Solvent extraction of no-carrier-added 122 Sb from irradiated Tin-natural target hydrochloric solution was investigated using di-n-butyl ether (C 8 H 18 O). Yields of about 3.61 MBq/μAh were experimentally obtained. (author)

  4. Optical Waveguide Lightmode Spectroscopy (OWLS as a Sensor for Thin Film and Quantum Dot Corrosion

    Directory of Open Access Journals (Sweden)

    Jinke Tang

    2012-12-01

    Full Text Available Optical waveguide lightmode spectroscopy (OWLS is usually applied as a biosensor system to the sorption-desorption of proteins to waveguide surfaces. Here, we show that OWLS can be used to monitor the quality of oxide thin film materials and of coatings of pulsed laser deposition synthesized CdSe quantum dots (QDs intended for solar energy applications. In addition to changes in data treatment and experimental procedure, oxide- or QD-coated waveguide sensors must be synthesized. We synthesized zinc stannate (Zn2SnO4 coated (Si,TiO2 waveguide sensors, and used OWLS to monitor the relative mass of the film over time. Films lost mass over time, though at different rates due to variation in fluid flow and its physical effect on removal of film material. The Pulsed Laser Deposition (PLD technique was used to deposit CdSe QD coatings on waveguides. Sensors exposed to pH 2 solution lost mass over time in an expected, roughly exponential manner. Sensors at pH 10, in contrast, were stable over time. Results were confirmed with atomic force microscopy imaging. Limiting factors in the use of OWLS in this manner include limitations on the annealing temperature that maybe used to synthesize the oxide film, and limitations on the thickness of the film to be studied. Nevertheless, the technique overcomes a number of difficulties in monitoring the quality of thin films in-situ in liquid environments.

  5. Effect of swift heavy ion irradiation on structural, optical and electrical properties of Cd2SnO4 thin films

    International Nuclear Information System (INIS)

    Kumaravel, R.; Gokulakrishnan, V.; Ramamurthi, K.; Sulania, Indra; Kanjilal, D.; Asokan, K.; Avasthi, D.K.

    2010-01-01

    Transparent conducting cadmium stannate thin films were prepared by spray pyrolysis method on Corning substrate at a temperature of 525 o C. The prepared films are irradiated using 120 MeV swift Ag 9+ ions for the fluence in the range 1 x 10 12 to 1 x 10 13 ions cm -2 and the structural, optical and electrical properties were studied. The intensity of the film decreases with increasing ion fluence and amorphization takes place at higher fluence (1 x 10 13 ions cm -2 ). The transmittance of the films decreases with increasing ion fluence and also the band gap value decreases with increasing ion fluence. The resistivity of the film increased from 2.66 x 10 -3 Ω cm (pristine) to 5.57 x 10 -3 Ω cm for the film irradiated with 1 x 10 13 ions cm -2 . The mobility of the film decreased from 31 to 12 cm 2 /V s for the film irradiated with the fluence of 1 x 10 13 ions cm -2 .

  6. The Effect of Eu Doping on Microstructure, Morphology and Methanal-Sensing Performance of Highly Ordered SnO2 Nanorods Array

    Directory of Open Access Journals (Sweden)

    Yanping Zhao

    2017-11-01

    Full Text Available Layered Eu-doped SnO2 ordered nanoarrays constructed by nanorods with 10 nm diameters and several hundred nanometers length were synthesized by a substrate-free hydrothermal route using alcohol and water mixed solvent of sodium stannate and sodium hydroxide at 200 °C. The Eu dopant acted as a crystal growth inhibitor to prevent the SnO2 nanorods growth up, resulting in tenuous SnO2 nanorods ordered arrays. The X-ray diffraction (XRD revealed the tetragonal rutile-type structure with a systematic average size reduction and unit cell volume tumescence, while enhancing the residual strain as the Eu-doped content increases. The surface defects that were caused by the incorporation of Eu ions within the surface oxide matrix were observed by high-resolution transmission electron microscope (HRTEM. The results of the response properties of sensors based on the different levels of Eu-doped SnO2 layered nanoarrays demonstrated that the 0.5 at % Eu-doped SnO2 layered nanorods arrays exhibited an excellent sensing response to methanal at 278 °C. The reasons of the enhanced sensing performance were discussed from the complicated defect surface structure, the large specific surface area, and the excellent catalytic properties of Eu dopant.

  7. Magnetic properties and local structure of the binary elements codoped Bi1−xLaxFe0.95Mn0.05O3

    International Nuclear Information System (INIS)

    Li, Yongtao; Zhang, Hongguang; Liu, Hao; Dong, Xueguang; Li, Qi; Chen, Wei; Mao, Weiwei; Li, Xing’ao; Dong, Chenglin; Ren, Shanling

    2014-01-01

    Highlights: • For the samples Bi 1−x La x (Fe 0.95 Mn 0.05 )O 3 (x = 0, 0.10, 0.15, 0.20), the magnetization changes nonmonotonously with La doping. • Doping La ions affects the local structures of Mn atoms instead of those of Fe atoms by analyzing XAFS data. • The changes of magnetic property result from the changes of the Mn–O bond length. - Abstract: Polycrystalline Bi 1−x La x Fe 0.95 Mn 0.05 O 3 (x = 0, 0.10, 0.15, 0.20) samples were successfully synthesized via sol–gel method. The magnetic properties and local structures of all these samples are investigated. By increasing lanthanum content from 0 to 0.15, the magnetization increases, while it decreases by further La doping. The results of local structures of Fe atoms and Mn atoms which were measured using X-ray absorption fine structure (XAFS) spectra of Fe and Mn K-edge demonstrate that the former has no change, whereas the latter exhibits systematical change of the Mn–O bond length, resulting from doped La ions. We demonstrate that doped La ions affect the local structures of Mn atoms, whereas it has no influence on the local structures of Fe atoms. Finally, to explain the magnetization phenomenon, we analyze interrelation between magnetic property and the Mn–O bond length on the basis of the local structure distortion of the samples

  8. Design and exploration of semiconductors from first principles: A review of recent advances

    Science.gov (United States)

    Oba, Fumiyasu; Kumagai, Yu

    2018-06-01

    Recent first-principles approaches to semiconductors are reviewed, with an emphasis on theoretical insight into emerging materials and in silico exploration of as-yet-unreported materials. As relevant theory and methodologies have developed, along with computer performance, it is now feasible to predict a variety of material properties ab initio at the practical level of accuracy required for detailed understanding and elaborate design of semiconductors; these material properties include (i) fundamental bulk properties such as band gaps, effective masses, dielectric constants, and optical absorption coefficients; (ii) the properties of point defects, including native defects, residual impurities, and dopants, such as donor, acceptor, and deep-trap levels, and formation energies, which determine the carrier type and density; and (iii) absolute and relative band positions, including ionization potentials and electron affinities at semiconductor surfaces, band offsets at heterointerfaces between dissimilar semiconductors, and Schottky barrier heights at metal–semiconductor interfaces, which are often discussed systematically using band alignment or lineup diagrams. These predictions from first principles have made it possible to elucidate the characteristics of semiconductors used in industry, including group III–V compounds such as GaN, GaP, and GaAs and their alloys with related Al and In compounds; amorphous oxides, represented by In–Ga–Zn–O transparent conductive oxides (TCOs), represented by In2O3, SnO2, and ZnO; and photovoltaic absorber and buffer layer materials such as CdTe and CdS among group II–VI compounds and chalcopyrite CuInSe2, CuGaSe2, and CuIn1‑ x Ga x Se2 (CIGS) alloys, in addition to the prototypical elemental semiconductors Si and Ge. Semiconductors attracting renewed or emerging interest have also been investigated, for instance, divalent tin compounds, including SnO and SnS; wurtzite-derived ternary compounds such as ZnSnN2 and CuGaO2; perovskite oxides such as SrTiO3 and BaSnO3; and organic–inorganic hybrid perovskites, represented by CH3NH3PbI3. Moreover, the deployment of first-principles calculations allows us to predict the crystal structure, stability, and properties of as-yet-unreported materials. Promising materials have been explored via high-throughput screening within either publicly available computational databases or unexplored composition and structure space. Reported examples include the identification of nitride semiconductors, TCOs, solar cell photoabsorber materials, and photocatalysts, some of which have been experimentally verified. Machine learning in combination with first-principles calculations has emerged recently as a technique to accelerate and enhance in silico screening. A blend of computation and experimentation with data science toward the development of materials is often referred to as materials informatics and is currently attracting growing interest.

  9. Raman analysis of ancient pigments on a tile from the Citadel of Algiers

    Science.gov (United States)

    Kock, L. D.; De Waal, D.

    2008-12-01

    A micro-Raman spectroscopy study of a multi-coloured (yellow, blue, white, redish-brown and brown-black) tile shard from the Citadel of Algiers was undertaken. XRD and EDX were used as complementary techniques. The study shows that the heterogeneous three-shade yellow pigment on the tile is composed largely of the ancient ternary (Pb-Sn-Sb) pyrochlore oxide with a dominant Pb-O vibration at 127 cm -1 consistent with the Pb 2SnSbO 6.5 structure as verified by XRD. The literature assignment of this band at 132 cm -1 probably comes from a mixture of pigments. The redish-brown and the brown-black pigments are found to be Naples yellow (Pb 2Sb 2O 7) and lead(II) stannate (Pb 2SnO 4), respectively, while cobalt blue (CoAl 2O 4) gives the blue colour and cassiterite (SnO 2) is the origin of the white colour. The bulk of the tile body is composed mainly of hematite (α-Fe 2O 3), maghemite (γ-Fe 2O 3), magnetite (Fe 3O 4) and Quartz (α-SiO 2) with traces of calcite (CaCO 3) and amorphous carbon. Micro-Raman spectroscopy proved to be very useful in the characterization of pigments as well as the tile body. These results further establish Raman spectroscopy as a technique of choice for the analysis of pigments on archaeological artifacts. The results obtained here could be used in the restoration and preservation programme of the Citadel itself which stands today as a symbol of pre-colonial Algerian heritage.

  10. Mesoporous Zn2SnO4 as effective electron transport materials for high-performance perovskite solar cells

    International Nuclear Information System (INIS)

    Bao, Sha; Wu, Jihuai; He, Xin; Tu, Yongguang; Wang, Shibo; Huang, Miaoliang; Lan, Zhang

    2017-01-01

    Highlights: •Large grain and mesoporous Zn 2 SnO 4 are synthesized by a facile hydrothermal method. •Perovskite device with Zn 2 SnO 4 electron transport layer get efficiency of 17.21%. •While the device with TiO 2 electron transport layer obtain an efficiency of 14.83%. •Superior photovoltaic performance stems from the intrinsic characteristics of Zn 2 SnO 4 . -- Abstract: Electron transport layer with higher carrier mobility and suitable band gap structure plays a significant role in determining the photovoltaic performance of perovskite solar cells (PSCs). Here, we report a synthesis of high crystalline zinc stannate (Zn 2 SnO 4 ) by a facile hydrothermal method. The as-synthesized Zn 2 SnO 4 possesses particle size of 20 nm, large surface area, mesoporous hierarchical structure, and can be used as a promising electron-transport materials to replace the conventional mesoporous TiO 2 material. A perovskite solar cell with structure of FTO/blocking layer/Zn 2 SnO 4 /CH 3 NH 3 PbI 3 /Spiro-OMeOTAD/Au is fabricated, and the preparation condition is optimized. The champion device based on Zn 2 SnO 4 electron transport material achieves a power conversion efficiency of 17.21%, while the device based on TiO 2 electron transport material gets an efficiency of 14.83% under the same experimental conditions. The results render Zn 2 SnO 4 an effective candidate as electron transport material for high performance perovskite solar cells and other devices.

  11. Role of active species on photocatalytic degradation of remazol golden yellow textile dye employing SrSnO_3 or TiO_2 as catalyst

    International Nuclear Information System (INIS)

    Teixeira, Ana Rita Ferreira Alves

    2015-01-01

    Heterogeneous photocatalysis is an important alternative for environmental remediation, with the possibility of its use for degradation of textile dyes effluents, as remazol golden yellow (RNL). Many semiconductors can be employed as photocatalysts, highlighting commercial TiO_2 P25 Evonik, a mixture of anatase and rutile phases. Other materials have been studied for such application, including SrSnO_3. In this work, strontium stannate was synthesized by the modified Pechini method and its photocatalytic activity on the degradation of the RNL textile was evaluated, as well as the activity for the commercial P25. The aim of this study was determining the role of each active specie on the photodegradation of the RNL system. In order to achieve such objective, some experiments were carried out in the presence of hydroxyl radical, hole and electron scavengers (isopropanol, formic acid and silver, respectively). The photocatalysts were characterized by X-ray diffraction (XDR), infrared spectroscopy (IV), Raman spectroscopy, UV-visible spectroscopy, surface area by BET method, and zero charge potential. SrSnO_3 obtained showed strontium carbonate as secondary phase, and this may have caused a short-range disorder for the material. The photocatalytic performance was evaluated by UV-Vis spectroscopy analysis of the RNL solutions before and after UVC irradiation in the presence of catalysts. The use of scavengers showed that, for both catalysts, hydroxyl radical play a major role, holes have an important participation on the formation of these radicals while electrons have no considerable participation. The results confirm that recombination is a limiting factor for SrSnO_3 and P25. (author)

  12. Photoacoustic spectroscopy investigation of sintered zinc-tin-oxide ceramics

    Directory of Open Access Journals (Sweden)

    Ivetić Tamara B.

    2007-01-01

    Full Text Available In this paper the changes that occurred in differently activated ZnO-SnO2 and sintered samples were investigated using photoacoustic spectroscopy. ZnO and SnO2 powders, mixed in the molar ratio 2:1, were mechanically activated in a planetary ball mill for 10-160 min. The mixtures were pres­sed and isothermally sintered at 1300°C for two hours. X-ray diffraction analysis of the obtained sintered samples was performed in order to investigate changes of the phase composition and confirmed only the presence of a pure zinc stannate (Zn2SnO4 phase in all the sintered samples as a result of the solid state reaction and reaction sintering between the starting ZnO and SnO2 powders. The microstructure of the sintered sam­ples was examined by scanning electron microscopy and showed that mechanical activation leads to the formation of a structure with reduced particle size which accelerates spinel formation. Grain growth of the spinel phase slows down the densification process and together with the agglomerates formed during mechanical activation causes the appearance of a porous microstructure. The photoacoustic (PA phase and amplitude spectra of the sintered samples were recorded as a function of the chopped frequency of the laser beam used (red laser with a power of 25 mW, λ=632 nm in a thermal-transmission detection configuration. PA experimental data were analyzed using the Rosenzweig-Gersho thermal-piston model, which enabled determination of the thermal diffusivity, ZT (m2s-1, diffusion coefficient of the minority free carriers D (m2s-1 and the optical absorption coefficient (m-1. The detected differences of the measured thermal-electrical properties of the obtained Zn2SnO4 ceramics indicate changes in the material induced by the different preparation procedure of the starting powders before the sintering process.

  13. 2D SnO2 Nanosheets: Synthesis, Characterization, Structures, and Excellent Sensing Performance to Ethylene Glycol

    Directory of Open Access Journals (Sweden)

    Wenjin Wan

    2018-02-01

    Full Text Available Two dimensional (2DSnO2 nanosheets were synthesized by a substrate-free hydrothermal route using sodium stannate and sodium hydroxide in a mixed solvent of absolute ethanol and deionized water at a lower temperature of 130 °C. The characterization results of the morphology, microstructure, and surface properties of the as-prepared products demonstrated that SnO2 nanosheets with a tetragonal rutile structure, were composed of oriented SnO2 nanoparticles with a diameter of 6–12 nm. The X-ray diffraction (XRD and high-resolution transmission electron microscope (FETEM results demonstrated that the dominant exposed surface of the SnO2 nanoparticles was (101, but not (110. The growth and formation was supposed to follow the oriented attachment mechanism. The SnO2 nanosheets exhibited an excellent sensing response toward ethylene glycol at a lower optimal operating voltage of 3.4 V. The response to 400 ppm ethylene glycol reaches 395 at 3.4 V. Even under the low concentration of 5, 10, and 20 ppm, the sensor exhibited a high response of 6.9, 7.8, and 12.0 to ethylene glycol, respectively. The response of the SnO2 nanosheets exhibited a linear dependence on the ethylene glycol concentration from 5 to 1000 ppm. The excellent sensing performance was attributed to the present SnO2 nanoparticles with small size close to the Debye length, the larger specific surface, the high-energy exposed facets of the (101 surface, and the synergistic effects of the SnO2 nanoparticles of the nanosheets.

  14. Synthesis and photoluminescence of Ca-(Sn,Ti)-Si-O compounds

    International Nuclear Information System (INIS)

    Abe, Shunsuke; Yamane, Hisanori; Yoshida, Hisashi

    2010-01-01

    The phase relation of the compounds prepared in the CaO-SnO 2 -SiO 2 system at 1673 K and in the CaO-TiO 2 -SiO 2 system at 1573 K was investigated in order to explore new Ti 4+ -activated stannate phosphors. Solid solutions of Ca(Sn 1-x Ti x )SiO 5 and Ca 3 (Sn 1-y Ti y )Si 2 O 9 were synthesized at x = 0-1.0 and y = 0-0.10, respectively, and their crystal structures were analyzed by powder X-ray diffraction. Photoluminescence of these solid solutions was observed in a broad range of a visible light wavelength region under ultraviolet (UV) light excitation. The peaks of the emission band of Ca(Sn 0.97 Ti 0.03 )SiO 5 and Ca 3 (Sn 0.925 Ti 0.075 )Si 2 O 9 were at 510 nm under excitation of 252 nm and at 534 nm under excitation of 258 nm, respectively. The absorption edges estimated by the diffuse reflectance spectra were at 300 nm (4.1 eV) for CaSnSiO 5 and at 270 nm (4.6 eV) for Ca 3 SnSi 2 O 9 , suggesting that the excitation levels in Ca(Sn 1-x Ti x )SiO 5 were above the band gap of the host, although the levels in Ca 3 (Sn 1-y Ti y )Si 2 O 9 were within the band gap and near the conduction band edge.

  15. Effect of Pr6O11 doping in electrical and microstructural properties of SnO2-based varistors

    Directory of Open Access Journals (Sweden)

    Hervê Stangler Irion

    2014-04-01

    Full Text Available The influence of the dopant Pr6O11 was investigated with regard to the electrical and microstructural properties of the system (98.95-x%SnO2.1.0%CoO.0.05%Ta2O5.x%Pr6O11, where x = 0.05%, 0.10%, 0.30% and 0.50% in mol. Pr6O11 doping modifies the electrical behavior of the ceramics. The electrical parameters were: α = 8.0, EB = 319 V cm-1 and Vb = 0.66 V barrier-1 for the system without Pr6O11 and α = 17.0, EB = 853 V cm-1 and Vb = 1.15 V barrier-1 with the addition of 0.10% in mol Pr6O11. The system with 0.05% in mol Pr6O11 had the same non-linearity coefficient α as the system with 0.10% in mol. However, breakdown electrical field and voltage per barrier rates were lower (EB = 708 V cm-1 and Vb = 0.98 V barrier-1. The low rates in the breakdown electrical field enabled the varistor systems under study to be used in protection systems for low-voltage energy grids. In the case of Pr6O11 concentrations above 0.10% in mol, the presence of the dopant became deleterious to the varistor’s electrical characteristics. This effect was due to an increase in praseodymium stannate (Pr2Sn2O7 secondary phase. The crystalline phase coupled to the cassiterite (SnO2 phase was found with XRD and SEM/EDS and quantified by Rietveld’s refining method.

  16. Incorporation of trace elements in Portland cement clinker: Thresholds limits for Cu, Ni, Sn or Zn

    International Nuclear Information System (INIS)

    Gineys, N.; Aouad, G.; Sorrentino, F.; Damidot, D.

    2011-01-01

    This paper aims at defining precisely, the threshold limits for several trace elements (Cu, Ni, Sn or Zn) which correspond to the maximum amount that could be incorporated into a standard clinker whilst reaching the limit of solid solution of its four major phases (C 3 S, C 2 S, C 3 A and C 4 AF). These threshold limits were investigated through laboratory synthesised clinkers that were mainly studied by X-ray Diffraction and Scanning Electron Microscopy. The reference clinker was close to a typical Portland clinker (65% C 3 S, 18% C 2 S, 8% C 3 A and 8% C 4 AF). The threshold limits for Cu, Ni, Zn and Sn are quite high with respect to the current contents in clinker and were respectively equal to 0.35, 0.5, 0.7 and 1 wt.%. It appeared that beyond the defined threshold limits, trace elements had different behaviours. Ni was associated with Mg as a magnesium nickel oxide (MgNiO 2 ) and Sn reacted with lime to form a calcium stannate (Ca 2 SnO 4 ). Cu changed the crystallisation process and affected therefore the formation of C 3 S. Indeed a high content of Cu in clinker led to the decomposition of C 3 S into C 2 S and of free lime. Zn, in turn, affected the formation of C 3 A. Ca 6 Zn 3 Al 4 O 15 was formed whilst a tremendous reduction of C 3 A content was identified. The reactivity of cements made with the clinkers at the threshold limits was followed by calorimetry and compressive strength measurements on cement paste. The results revealed that the doped cements were at least as reactive as the reference cement.

  17. Structure and phase transformation behavior of electroless Ni-P alloys containing tin and tungsten

    International Nuclear Information System (INIS)

    Balaraju, J.N.; Jahan, S. Millath; Jain, Anjana; Rajam, K.S.

    2007-01-01

    Autocatalytic ternary Ni-Sn-P, Ni-W-P and quaternary Ni-W-Sn-P films were prepared using alkaline citrate-based baths and compared with binary Ni-P coatings. Energy dispersive analysis of X-ray (EDAX) showed that binary Ni-P deposit contained 11.3 wt.% of phosphorus. Codeposition of tungsten in Ni-P matrix resulted in ternary Ni-W-P with 5 wt.% P and 7.8 wt.% of tungsten. Incorporation of tin led to ternary Ni-Sn-P deposit containing 0.4 wt.% Sn and 10.3 wt.% P. Presence of both sodium tungstate and sodium stannate in the basic bath had resulted in quaternary coating with 6.9 wt.% W, traces of Sn and 6.4 wt.% P. X-ray diffraction patterns of all the deposits revealed a single, broad peak which showed the nanocrystalline nature of the deposits. For the first time in related literature, the presence of a metastable phase Ni 12 P 5 in ternary deposits is reported in the present study. Metallographic cross-sections of all the deposits revealed the banded/lamellar structure. Scanning electron microscopy (SEM) studies of the deposits showed smooth nodules for ternary deposits, but coarse and well-defined nodules for quaternary deposits. DSC studies of phase transformation behavior of the ternary Ni-Sn-P deposit revealed a single sharp exothermic peak at 365 o C. However, ternary Ni-W-P and quaternary Ni-W-Sn-P deposits exhibited a low temperature peak at 300 o C, a split type high temperature peak at 405 and 440 o C and a very high temperature peak at 550 o C. Higher activation energy values were obtained for W-based alloy deposits. Presence of W and Sn has helped to retain high microhardness values even at higher temperatures indicating an improved thermal stability

  18. Structural, electronic and magnetic properties of the series of double perovskites (Ca,Sr){sub 2−x}La{sub x}FeIrO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Bufaiçal, L., E-mail: lbufaical@ufg.br [Instituto de Física, Universidade Federal de Goiás, 74001-970 Goiânia, GO (Brazil); Adriano, C. [Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859 Campinas, SP (Brazil); Lora-Serrano, R. [Instituto de Física, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Duque, J.G.S. [Núcleo de Física, Universidade Federal de Sergipe, Campus Itabaiana, 49500-000 Itabaiana, SE (Brazil); Mendonça-Ferreira, L. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-170 Santo André, SP (Brazil); Rojas-Ayala, C.; Baggio-Saitovitch, E.; Bittar, E.M. [Centro Brasileiro de Pesquisas Físicas, 22290-180 Rio de Janeiro, RJ (Brazil); Pagliuso, P.G. [Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859 Campinas, SP (Brazil)

    2014-04-01

    Polycrystalline samples of the series of double perovskites Sr{sub 2−x}La{sub x}FeIrO{sub 6} were synthesized. Their structural, electronic and magnetic properties were investigated by X-ray powder diffraction, Mössbauer spectroscopy, magnetic susceptibility, heat capacity and electrical resistivity experiments. The compounds crystallize in a monoclinic structure and were fitted in space group P2{sub 1}/n, with a significant degree of Fe/Ir cationic disorder. As in Ca{sub 2−x}La{sub x}FeIrO{sub 6} the Sr-based system seems to evolve from an antiferromagnetic ground state for the end members (x=0.0 and x=2.0) to a ferrimagnetic order in the intermediate regions (x∼1). Since Mössbauer spectra indicate that Fe valence remains 3+ with doping, this tendency of change in the nature of the microscopic interaction could be attributed to Ir valence changes, induced by La{sup 3+} electrical doping. Upon comparing both Ca and Sr series, Sr{sub 2−x}La{sub x}FeIrO{sub 6} is more structurally homogenous and presents higher magnetization and transition temperatures. Magnetic susceptibility measurements at high temperatures on Sr{sub 1.2}La{sub 0.8}FeIrO{sub 6} indicate a very high ferrimagnetic Curie temperature T{sub C}∼700K. For the Sr{sub 2}FeIrO{sub 6} compound, electrical resistivity experiments under applied pressure suggest that this material might be a Mott insulator. - Graphical abstract: The Weiss constant as a function of La doping for the (Ca,Sr){sub 2−x}La{sub x}FeIrO{sub 6} series, indicating changes in Fe–Ir magnetic coupling on both families. - Highlights: • The double perovskite series (Ca,Sr){sub 2−x}La{sub x}FeIrO{sub 6} were synthesized. • Changes in the Fe-Ir magnetic coupling due to La doping on both series. • Evidence of high T{sub C} on Sr{sub 1.2}La{sub 0.8}FeIrO{sub 6}. • Indication of Mott insulator behavior on Sr{sub 2}FeIrO{sub 6}.

  19. Oxygen vacancy induced by La and Fe into ZnO nanoparticles to modify ferromagnetic ordering

    International Nuclear Information System (INIS)

    Verma, Kuldeep Chand; Kotnala, R.K.

    2016-01-01

    We reported long-range ferromagnetic interactions in La doped Zn 0.95 Fe 0.05 O nanoparticles that mediated through lattice defects or vacancies. Zn 0.92 Fe 0.05 La 0.03 O (ZFLaO53) nanoparticles were synthesized by a sol–gel process. X-ray fluorescence spectrum of ZFLaO53 detects the weight percentage of Zn, Fe, La and O. X-ray diffraction shows the hexagonal Wurtzite ZnO phase. The Rietveld refinement has been used to calculate the lattice parameters and the position of Zn, Fe, La and O atoms in the Wurtzite unit cell. The average size of ZFLaO53 nanoparticles is 99 nm. The agglomeration type product due to OH ions with La results into ZnO nanoparticles than nanorods that found in pure ZnO and Zn 0.95 Fe 0.05 O sample. The effect of doping concentration to induce Wurtzite ZnO structure and lattice defects has been analyzed by Raman active vibrational modes. Photoluminescence spectra show an abnormal emission in both UV and visible region, and a blue shift at near band edge is formed with doping. The room temperature magnetic measurement result into weak ferromagnetism but pure ZnO is diamagnetic. However, the temperature dependent magnetic measurement using zero-field and field cooling at dc magnetizing field 500 Oe induces long-range ferromagnetic ordering. It results into antiferromagnetic Neel temperature of ZFLaO53 at around 42 K. The magnetic hysteresis is also measured at 200, 100, 50 and 10 K measurement that indicate enhancement in ferromagnetism at low temperature. Overall, the La doping into Zn 0.95 Fe 0.05 O results into enhanced antiferromagnetic interaction as well as lattice defects/vacancies. The role of the oxygen vacancy as the dominant defects in doped ZnO must form Bound magnetic polarons has been described. - Graphical abstract: The long-range ferromagnetic order in Zn 0.92 Fe 0.05 La 0.03 O nanoparticles at low temperature measurements involves oxygen vacancy as the medium of magnetic interactions. - Highlights: • The La and Fe doping

  20. Novel gas sensor with dual response under CO(g) exposure: Optical and electrical stimuli

    Science.gov (United States)

    Rocha, L. S. R.; Cilense, M.; Ponce, M. A.; Aldao, C. M.; Oliveira, L. L.; Longo, E.; Simoes, A. Z.

    2018-05-01

    In this work, a lanthanum (La) doped ceria (CeO2) film, which depicted a dual gas sensing response (electric and optical) for CO(g) detection, was obtained by the microwave-assisted hydrothermal (HAM) synthesis and deposited by the screen-printing technique, in order to prevent deaths by intoxication with this life-threatening gas. An electric response under CO(g) exposure was obtained, along with an extremely fast optical response for a temperature of 380 °C, associated with Ce+4 reduction and vacancy generation. A direct optical gap was found to be around 2.31 eV from UV-Vis results, which corresponds to a transition from valence band to 4f states. Due to the anomalous electron configuration of cerium atoms with 4f electrons in its reduced state, they are likely to present an electric conduction based on the small polaron theory with a hopping mechanism responsible for its dual sensing response with a complete reversible behaviour.

  1. Investigation of the relaxor behavior of sol gel processed lanthanum lead titanium ceramics

    International Nuclear Information System (INIS)

    Limame, K.; Sayouri, S.; Yahyaoui, M.M.; Housni, A.; Jaber, B.

    2016-01-01

    A series of La doped lead titanate samples, with composition Pb_1_−_xLa_xTi_1_−_x_/_4O_3 (PLTx), where x=0.00; 0.02; 0.04; 0.06; 0.07; 0.08; 0.10; 0.12; 0.14; 0.16; 0.18; 0.21 and 0.22 was prepared using the sol–gel process. Addition of La gives rise to the two well-known phenomena: diffuseness and relaxation around the ferro-to-paraelectric transition; the two parameters related to these phenomena, and which give a satisfactory interpretation of them, have been estimated using the Uchino's quadratic law. This diffuse phase transition (DPT) has been investigated with the help of the Landau–Devonshire cluster theory and the model of Cheng et al., to show that polar regions may be generated around the DPT and far from the temperature, T_m, of the maximum of the dielectric permittivity, which have as a direct consequence a non vanishing polarization even if T>T_m.

  2. Investigation of the relaxor behavior of sol gel processed lanthanum lead titanium ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Limame, K. [Centre Régional des Metiers de l' Education et de la Formation (CRMEF) de Fès, Rue deKuwait, BP 49, Fès (Morocco); Laboratoire de Physique Théorique et Appliquée, (LPTA), FSDM, B.P. 1796, Fès-Atlas, Fès (Morocco); Sayouri, S., E-mail: ssayouri@gmail.com [Laboratoire de Physique Théorique et Appliquée, (LPTA), FSDM, B.P. 1796, Fès-Atlas, Fès (Morocco); Yahyaoui, M.M. [Laboratoire de Physique Théorique et Appliquée, (LPTA), FSDM, B.P. 1796, Fès-Atlas, Fès (Morocco); Housni, A. [Laboratoire de Physique Théorique et Appliquée, (LPTA), FSDM, B.P. 1796, Fès-Atlas, Fès (Morocco); Institut Supérieur des Professions Infirmières et Techniques de Santé (ISPITS), Fès (Morocco); Jaber, B. [Centre National pour la Recherche Scientifique et Technique (CNRST), Angle Avenue Allal El Fassi avenue des FAR, Quartie Hay Ryad, BP8027 Nation Unies, Rabat (Morocco)

    2016-08-01

    A series of La doped lead titanate samples, with composition Pb{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} (PLTx), where x=0.00; 0.02; 0.04; 0.06; 0.07; 0.08; 0.10; 0.12; 0.14; 0.16; 0.18; 0.21 and 0.22 was prepared using the sol–gel process. Addition of La gives rise to the two well-known phenomena: diffuseness and relaxation around the ferro-to-paraelectric transition; the two parameters related to these phenomena, and which give a satisfactory interpretation of them, have been estimated using the Uchino's quadratic law. This diffuse phase transition (DPT) has been investigated with the help of the Landau–Devonshire cluster theory and the model of Cheng et al., to show that polar regions may be generated around the DPT and far from the temperature, T{sub m}, of the maximum of the dielectric permittivity, which have as a direct consequence a non vanishing polarization even if T>T{sub m}.

  3. Negative pressure driven valence instability of Eu in cubic Eu{sub 0.4}La{sub 0.6}Pd{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Abhishek [S N Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata-700098 (India); Mazumdar, Chandan; Ranganathan, R [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata-700064 (India)], E-mail: abhishek.phy@gmail.com, E-mail: chandan.mazumar@saha.ac.in

    2009-05-27

    We report the change in the valency of Eu-ions in the binary intermetallic cubic compound EuPd{sub 3} induced by La doping at rare-earth sites. Doping of La generates negative chemical pressure in the lattice, resulting in a significant increase of the lattice parameter without altering the simple-cubic structure of the compound. Results of dc-magnetic measurements suggest that this increase in the lattice parameter is associated with the valence transition of Eu-ions from Eu{sup 3+} to a mixed-valent state. As Eu{sup 2+}-ions possess a large magnetic moment, this valence transition significantly modifies the magnetic behavior of the compound. In contrast to introducing boron at the vacant body center site of the unit cell to change the valency of Eu-ions, as in the case of EuPd{sub 3}B, our results suggest it can also be altered by doping a rare-earth ion of larger size at the lattice site of Eu in EuPd{sub 3}.

  4. Negative pressure driven valence instability of Eu in cubic Eu0.4La0.6Pd3

    International Nuclear Information System (INIS)

    Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R

    2009-01-01

    We report the change in the valency of Eu-ions in the binary intermetallic cubic compound EuPd 3 induced by La doping at rare-earth sites. Doping of La generates negative chemical pressure in the lattice, resulting in a significant increase of the lattice parameter without altering the simple-cubic structure of the compound. Results of dc-magnetic measurements suggest that this increase in the lattice parameter is associated with the valence transition of Eu-ions from Eu 3+ to a mixed-valent state. As Eu 2+ -ions possess a large magnetic moment, this valence transition significantly modifies the magnetic behavior of the compound. In contrast to introducing boron at the vacant body center site of the unit cell to change the valency of Eu-ions, as in the case of EuPd 3 B, our results suggest it can also be altered by doping a rare-earth ion of larger size at the lattice site of Eu in EuPd 3 .

  5. All-perovskite transparent high mobility field effect using epitaxial BaSnO{sub 3} and LaInO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Useong; Park, Chulkwon; Kim, Young Mo; Ju, Chanjong; Park, Jisung; Char, Kookrin, E-mail: kchar@phya.snu.ac.kr [Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Ha, Taewoo; Kim, Jae Hoon [Department of Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Namwook; Yu, Jaejun [Center for Theoretical Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2015-03-01

    We demonstrate an all-perovskite transparent heterojunction field effect transistor made of two lattice-matched perovskite oxides: BaSnO{sub 3} and LaInO{sub 3}. We have developed epitaxial LaInO{sub 3} as the gate oxide on top of BaSnO{sub 3}, which were recently reported to possess high thermal stability and electron mobility when doped with La. We measured the dielectric properties of the epitaxial LaInO{sub 3} films, such as the band gap, dielectric constant, and the dielectric breakdown field. Using the LaInO{sub 3} as a gate dielectric and the La-doped BaSnO{sub 3} as a channel layer, we fabricated field effect device structure. The field effect mobility of such device was higher than 90 cm{sup 2} V{sup −1} s{sup −1}, the on/off ratio was larger than 10{sup 7}, and the subthreshold swing was 0.65 V dec{sup −1}. We discuss the possible origins for such device performance and the future directions for further improvement.

  6. Lead-Free Antiferroelectric Silver Niobate Tantalate with High Energy Storage Performance.

    Science.gov (United States)

    Zhao, Lei; Liu, Qing; Gao, Jing; Zhang, Shujun; Li, Jing-Feng

    2017-08-01

    Antiferroelectric materials that display double ferroelectric hysteresis loops are receiving increasing attention for their superior energy storage density compared to their ferroelectric counterparts. Despite the good properties obtained in antiferroelectric La-doped Pb(Zr,Ti)O 3 -based ceramics, lead-free alternatives are highly desired due to the environmental concerns, and AgNbO 3 has been highlighted as a ferrielectric/antiferroelectric perovskite for energy storage applications. Enhanced energy storage performance, with recoverable energy density of 4.2 J cm -3 and high thermal stability of the energy storage density (with minimal variation of ≤±5%) over 20-120 °C, can be achieved in Ta-modified AgNbO 3 ceramics. It is revealed that the incorporation of Ta to the Nb site can enhance the antiferroelectricity because of the reduced polarizability of B-site cations, which is confirmed by the polarization hysteresis, dielectric tunability, and selected-area electron diffraction measurements. Additionally, Ta addition in AgNbO 3 leads to decreased grain size and increased bulk density, increasing the dielectric breakdown strength, up to 240 kV cm -1 versus 175 kV cm -1 for the pure counterpart, together with the enhanced antiferroelectricity, accounting for the high energy storage density. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Review on dielectric properties of rare earth doped barium titanate

    International Nuclear Information System (INIS)

    Ismail, Fatin Adila; Osman, Rozana Aina Maulat; Idris, Mohd Sobri

    2016-01-01

    Rare earth doped Barium Titanate (BaTiO_3) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO_3 (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO_3 downshifted the Curie temperature (T_C). Transition temperature also known as Curie temperature, T_C where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO_3, Er-doped BaTiO_3, Sm-doped BaTiO_3, Nd-doped BaTiO_3 and Ce-doped BaTiO_3 had been proved to increase and the transition temperature or also known as T_C also lowered down to room temperature as for all the RE doped BaTiO_3 except for Er-doped BaTiO_3.

  8. Influence of Lanthanum Doping on the Structural and Optical Properties of Hematite Nanopowders

    Science.gov (United States)

    Justus, J. Sharmila; Dharma Roy, S. Dawn; Raj, A. Moses Ezhil

    2016-10-01

    Rare-earth elements are an attractive class of dopant elements, as they give easily trivalent cations that possibly altering the structure and other properties of the parent nanoparticles and creating multifunctional materials because of their f-electronic configurations. Herein, experimental evidence has been given for a better understanding of the factors that dictate the interactions of La doping on the structure and optical properties of iron oxide nanoparticles. For that, lanthanum doped hematite (α-Fe2O3) nanoparticles were prepared by a facile solution method using iron (III) chloride (FeCl3) as starting precursor and sodium hydroxide (NaOH) as reducing agent without templates at low temperature. As-prepared powders were subsequently calcined in air for 3 hr at 800 °C. Xray diffraction (XRD) technique was used to study the nanocrystal formation of α-Fe2O3 and Fourier Transform Raman (FT-Raman) spectral information identified the chemical bond structure of the nanoparticles. Morphology study of the nanoparticles was identified using Scanning Electron Microscope (SEM) and the incorporated La content was recognized from the Energy Dispersive X-ray Spectroscopy (EDS) analysis. The optical absorption spectrum was recorded in the wavelength range of 200-2000 nm and the optical parameters such as absorption coefficient and optical band gap energy of pure and doped Fe2O3 nanoparticles were determined. Obtained results are interpreted by considering the impregnation of trivalent La cations that replaced Fe cations of the host structure.

  9. Doping effect on the physical properties of Ca10Pt3As8(Fe2As2)5 single crystals

    Science.gov (United States)

    Pan, Jiayun; Karki, Amar; Plummer, E. W.; Jin, Rongying

    2017-12-01

    Ca10Pt3As8(Fe2As2)5 is a unique parent compound for superconductivity, which consists of both semiconducting Pt3As8 and metallic FeAs layers. We report the observation of superconductivity induced via chemical doping in either Ca site using rare-earth (RE) elements (RE  =  La, Gd) or Fe site using Pt. The interlayer distance and the normal-state physical properties of the doped system change correspondingly. The coupled changes include (1) superconducting transition temperature T c increases with increasing both doping concentration and interlayer distance, (2) our T c value is higher than previously reported maximum value for Pt doping in the Fe site, (3) both the normal-state in-plane resistivity and out-of-plane resistivity change from non-metallic to metallic behavior with increasing doping concentration and T c, and (4) the transverse in-plane magnetoresistance (MRab) changes from linear-field dependence to quadratic behavior upon increasing T c. For La-doped compound with the highest T c (~35 K), upper critical fields (Hc2ab , Hc2c ), coherence lengths (ξ ab, ξ c), and in-plane penetration depth (λ ab) are estimated. We discuss the relationship between chemical doping, interlayer distance, and physical properties in this system.

  10. Dopant-site-dependent scattering by dislocations in epitaxial films of perovskite semiconductor BaSnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Useong; Park, Chulkwon; Kim, Rokyeon; Mun, Hyo Sik; Kim, Hoon Min; Kim, Namwook; Yu, Jaejun; Char, Kookrin, E-mail: kchar@phya.snu.ac.kr [Center for Strongly Correlated Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Ha, Taewoo; Kim, Jae Hoon [Department of Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Hyung Joon; Kim, Tai Hoon; Kim, Kee Hoon [Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-05-01

    We studied the conduction mechanism in Sb-doped BaSnO{sub 3} epitaxial films, and compared its behavior with that of the mechanism of its counterpart, La-doped BaSnO{sub 3}. We found that the electron mobility in BaSnO{sub 3} films was reduced by almost 7 times when the dopant was changed from La to Sb, despite little change in the effective mass of the carriers. This indicates that the scattering rate of conduction electrons in the BaSnO{sub 3} system is strongly affected by the site at which the dopants are located. More importantly, we found that electron scattering by threading dislocations also depends critically on the dopant site. We propose that the large enhancement of scattering by the threading dislocations in Sb-doped BaSnO{sub 3} films is caused by the combination effect of the change in the distribution of Sb impurities in the films, the formation of the Sb impurity clusters near the threading dislocations, and the conduction electron clustering near the Sb impurities.

  11. Chemical compatibility and properties of suspension plasma-sprayed SrTiO3-based anodes for intermediate-temperature solid oxide fuel cells

    Science.gov (United States)

    Zhang, Shan-Lin; Li, Cheng-Xin; Li, Chang-Jiu

    2014-10-01

    La-doped strontium titanate (LST) is a promising, redox-stable perovskite material for direct hydrocarbon oxidation anodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this study, nano-sized LST and Sm-doped ceria (SDC) powders are produced by the sol-gel and glycine-nitrate processes, respectively. The chemical compatibility between LST and electrolyte materials is studied. A LST-SDC composite anode is prepared by suspension plasma spraying (SPS). The effects of annealing conditions on the phase structure, microstructure, and chemical stability of the LST-SDC composite anode are investigated. The results indicate that the suspension plasma-sprayed LST-SDC anode has the same phase structure as the original powders. LST exhibits a good chemical compatibility with SDC and Mg/Sr-doped lanthanum gallate (LSGM). The anode has a porosity of ∼40% with a finely porous structure that provides high gas permeability and a long three-phase boundary for the anode reaction. Single cells assembled with the LST-SDC anode, La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte, and La0.8Sr0.2CoO3-SDC cathode show a good performance at 650-800 °C. The annealing reduces the impedances due to the enhancement in the bonding between the particles in the anode and interface of anode and LSGM electrolyte, thus improving the output performance of the cell.

  12. Electronic structures near surfaces of perovskite type oxides

    International Nuclear Information System (INIS)

    Hara, Toru

    2005-01-01

    This work is intended to draw attention to the origin of the electronic structures near surfaces of perovskite type oxides. Deep states were observed by ultraviolet photoelectron spectroscopic measurements. The film thickness dependent electronic structures near surfaces of (Ba 0.5 Sr 0.5 )TiO 3 thin films were observed. As for the 117-308 nm thick (Ba 0.5 Sr 0.5 )TiO 3 films, deep states were lying at 0.20, 0.55, and 0.85 eV below the quasi-fermi level, respectively. However, as for the 40 nm thick (Ba 0.5 Sr 0.5 )TiO 3 film, the states were overlapped. The A-site doping affected electronic structures near surfaces of SrTiO 3 single crystals. No evolution of deep states in non-doped SrTiO 3 single crystal was observed. However, the evolution of deep states in La-doped SrTiO 3 single crystal was observed

  13. Degradation and Mineralization of Benzohydroxamic Acid by Synthesized Mesoporous La/TiO2

    Directory of Open Access Journals (Sweden)

    Xianping Luo

    2016-10-01

    Full Text Available Rare earth element La-doped TiO2 (La/TiO2 was synthesized by the sol-gel method. Benzohydroxamic acid was used as the objective pollutant to investigate the photocatalytic activity of La/TiO2. The physicochemical properties of the prepared materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, specific surface area and porosity, scanning electron microscopy and transmission electron microscopy. As a result, the doping of La could inhibit the crystal growth of TiO2, increase its specific surface area and expand its response to visible light, thus improving its photocatalytic activity. La/TiO2 with the doping ratio of 0.75% calcined at 500 °C, showing the highest photocatalytic activity to degrade benzohydroxamic acid under the irradiation of 300 W mercury lamp. About 94.1% of benzohydroxamic acid with the original concentration at 30 mg·L−1 was removed after 120 min in a solution of pH 4.4 with an La/TiO2 amount of 0.5 g·L−1. Furthermore, 88.5% of the total organic carbon was eliminated after 120 min irradiation. In addition, after four recycling runs, La/TiO2 still kept high photocatalytic activity on the photodegradation of benzohydroxamic acid. The interfacial charge transfer processes were also hypothesized.

  14. Synthesis and photocatalytic properties of visible light responsive La/TiO2-graphene composites

    International Nuclear Information System (INIS)

    Khalid, N.R.; Ahmed, E.; Hong Zhanglian; Ahmad, M.

    2012-01-01

    Highlights: ► Synthesis of La/TiO 2 -graphene composites by two-step hydrothermal method. ► Efficient charge separation due to La doping and graphene incorporation. ► Enhanced photocatalytic activity of composite catalyst for MB degradation under visible-light. - Abstract: La/TiO 2 -graphene composites used as photocatalyst were prepared by two-step hydrothermal method. The as-prepared composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The results of optical properties of La/TiO 2 -graphene composites exhibit extended light absorption in visible-light region and possess better charge separation capability as compared to pure TiO 2 . The photocatalytic activity measurement demonstrate that La/TiO 2 -graphene composites exhibited an enhanced photocatalytic activity for methylene blue (MB) degradation under visible-light irradiation compared to pure TiO 2 , which was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of graphene and the large surface contact between graphene and La/TiO 2 nanoparticles.

  15. Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique

    KAUST Repository

    Han, Wei

    2013-07-08

    There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ∼100 ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti 3+. Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material. © 2013 Macmillan Publishers Limited. All rights reserved.

  16. Ferroelectric properties of full plasma-enhanced ALD TiN/La:HfO{sub 2}/TiN stacks

    Energy Technology Data Exchange (ETDEWEB)

    Chernikova, A. G.; Kuzmichev, D. S.; Negrov, D. V.; Kozodaev, M. G.; Markeev, A. M. [Moscow Institute of Physics and Technology, Institutskii per. 9, 141700 Dolgoprudny, Moscow Region (Russian Federation); Polyakov, S. N. [Technological Institute for Superhard and Novel Carbon Materials, Tsentral' naya Str. 7a, 142190 Troitsk, Moscow (Russian Federation)

    2016-06-13

    We report the possibility of employment of low temperature (≤330 °C) plasma-enhanced atomic layer deposition for the formation of both electrodes and hafnium-oxide based ferroelectric in the metal-insulator-metal structures. The structural and ferroelectric properties of La doped HfO{sub 2}-based layers and its evolution with the change of both La content (2.1, 3.7 and 5.8 at. %) and the temperature of the rapid thermal processing (550–750 °C) were investigated in detail. Ferroelectric properties emerged only for 2.1 and 3.7 at. % of La due to the structural changes caused by the given doping levels. Ferroelectric properties were also found to depend strongly on annealing temperature, with the most robust ferroelectric response for lowest La concentration and intermediate 650 °C annealing temperature. The long term wake-up effect and such promising endurance characteristics as 3 × 10{sup 8} switches by bipolar voltage cycles with 30 μs duration and ± 3 MV/cm amplitude without any decrease of remnant polarization value were demonstrated.

  17. 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.

  18. Band gap and mobility of epitaxial perovskite BaSn1 -xHfxO3 thin films

    Science.gov (United States)

    Shin, Juyeon; Lim, Jinyoung; Ha, Taewoo; Kim, Young Mo; Park, Chulkwon; Yu, Jaejun; Kim, Jae Hoon; Char, Kookrin

    2018-02-01

    A wide band-gap perovskite oxide BaSn O3 is attracting much attention due to its high electron mobility and oxygen stability. On the other hand, BaHf O3 was recently reported to be an effective high-k gate oxide. Here, we investigate the band gap and mobility of solid solutions of BaS n1 -xH fxO3 (x =0 -1 ) (BSHO) as a basis to build advanced perovskite oxide heterostructures. All the films were epitaxially grown on MgO substrates using pulsed laser deposition. Density functional theory calculations confirmed that Hf substitution does not create midgap states while increasing the band gap. From x-ray diffraction and optical transmittance measurements, the lattice constants and the band-gap values are significantly modified by Hf substitution. We also measured the transport properties of n -type La-doped BSHO films [(Ba ,La ) (Sn ,Hf ) O3 ] , investigating the feasibility of modulation doping in the BaSn O3/BSHO heterostructures. The Hall measurement data revealed that, as the Hf content increases, the activation rate of the La dopant decreases and the scattering rate of the electrons sharply increases. These properties of BSHO films may be useful for applications in various heterostructures based on the BaSn O3 system.

  19. The Importance of Rare-Earth Additions in Zr-Based AB2 Metal Hydride Alloys

    Directory of Open Access Journals (Sweden)

    Kwo-Hsiung Young

    2016-07-01

    Full Text Available Effects of substitutions of rare earth (RE elements (Y, La, Ce, and Nd to the Zr-based AB2 multi-phase metal hydride (MH alloys on the structure, gaseous phase hydrogen storage (H-storage, and electrochemical properties were studied and compared. Solubilities of the RE atoms in the main Laves phases (C14 and C15 are very low, and therefore the main contributions of the RE additives are through the formation of the RENi phase and change in TiNi phase abundance. Both the RENi and TiNi phases are found to facilitate the bulk diffusion of hydrogen but impede the surface reaction. The former is very effective in improving the activation behaviors. −40 °C performances of the Ce-doped alloys are slightly better than the Nd-doped alloys but not as good as those of the La-doped alloys, which gained the improvement through a different mechanism. While the improvement in ultra-low-temperature performance of the Ce-containing alloys can be associated with a larger amount of metallic Ni-clusters embedded in the surface oxide, the improvement in the La-containing alloys originates from the clean alloy/oxide interface as shown in an earlier transmission electron microscopy study. Overall, the substitution of 1 at% Ce to partially replace Zr gives the best electrochemical performances (capacity, rate, and activation and is recommended for all the AB2 MH alloys for electrochemical applications.

  20. 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.

  1. 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

  2. Parallel charge sheets of electron liquid and gas in La0.5Sr0.5TiO3/SrTiO3 heterostructures

    Science.gov (United States)

    Renshaw Wang, X.; Sun, L.; Huang, Z.; Lü, W. M.; Motapothula, M.; Annadi, A.; Liu, Z. Q.; Zeng, S. W.; Venkatesan, T.; Ariando

    2015-12-01

    We show here a new phenomenon in La0.5Sr0.5TiO3/SrTiO3 (LSTO/STO) heterostructures; that is a coexistence of three-dimensional electron liquid (3DEL) and 2D electron gas (2DEG), separated by an intervening insulating LSTO layer. The two types of carriers were revealed through multi-channel analysis of the evolution of nonlinear Hall effect as a function of film thickness, temperature and back gate voltage. We demonstrate that the 3D electron originates from La doping in LSTO film and the 2D electron at the surface of STO is due to the polar field in the intervening insulating layer. As the film thickness is reduced below a critical thickness of 6 unit cells (uc), an abrupt metal-to-insulator transition (MIT) occurs without an intermediate semiconducting state. The properties of the LSTO layer grown on different substrates suggest that the insulating phase of the intervening layer is a result of interface strain induced by the lattice mismatch between the film and substrate. Further, by fitting the magnetoresistance (MR) curves, the 6 unit cell thick LSTO is shown to exhibit spin-orbital coupling. These observations point to new functionalities, in addition to magnetism and superconductivity in STO-based systems, which could be exploited in a multifunctional context.

  3. Electrochemical approach to evaluate the mechanism of photocatalytic water splitting on oxide photocatalysts

    International Nuclear Information System (INIS)

    Matsumoto, Yasumichi; Unal, Ugur; Tanaka, Noriyuki; Kudo, Akihiko; Kato, Hideki

    2004-01-01

    Photoelectrochemical measurements of TiO 2 , NaTaO 3 , and Cr or Sb doped TiO 2 and SrTiO 3 photocatalysts were carried out in H 2 and O 2 saturated electrolytes in order to evaluate the reverse reactions during water photolysis. The poor activity of TiO 2 as a result of reverse photoreactions of O 2 reduction and H 2 oxidation was revealed with the respective high cathodic and anodic photocurrents. The rise in the photocurrents at NaTaO 3 after La doping was in harmony with the doping-induced increase in the photocatalytic activity. NiO loading suppresses the O 2 photoreverse reactions, which declines photocatalytic activity, and/or promotes the photo-oxidation of water, because the O 2 photo-reduction current was scarcely observed near the flatband potential. Photocurrents of O 2 reduction and H 2 oxidation were observed under visible light for the Cr and Sb doped SrTiO 3 and TiO 2 , respectively. These phenomena are in harmony with the previous reports on the photocatalysts examined with sacrificial reagents

  4. Interface analysis of Ge ultra thin layers intercalated between GaAs substrates and oxide stacks

    Energy Technology Data Exchange (ETDEWEB)

    Molle, Alessandro, E-mail: alessandro.molle@mdm.infm.i [Laboratorio Nazionale MDM, CNR-INFM, Via C. Olivetti 2, 20041 Agrate Brianza (Italy); Lamagna, Luca; Spiga, Sabina [Laboratorio Nazionale MDM, CNR-INFM, Via C. Olivetti 2, 20041 Agrate Brianza (Italy); Fanciulli, Marco [Laboratorio Nazionale MDM, CNR-INFM, Via C. Olivetti 2, 20041 Agrate Brianza (MI) (Italy); Dipartimento di Scienza dei Materiali, Universita di Milano Bicocca, Milano (Italy); Brammertz, Guy; Meuris, Marc [IMEC, 75 Kapeldreef, B-3001 Leuven (Belgium)

    2010-01-01

    Capping III-V compound surfaces with Ge ultra-thin layer might be a viable pathway to passivate the electrically active interface traps which usually jeopardize the integration of III-V materials in metal-oxide-semiconductor devices. As the physical nature of such traps is intrinsically related to the chemical details of the interface composition, the structural and compositional features of the Ge/GaAs interface were thoroughly investigated in two different configurations, the atomic layer deposition of La-doped ZrO{sub 2} films on Ge-capped GaAs and the ultra-high vacuum based molecular beam deposition of GeO{sub 2}/Ge double stack on in situ prepared GaAs. In the former case, the intercalation of a Ge interface layer is shown to suppress the concentration of interface Ga-O, As-O and elemental As bonding which were significantly detected in case of the direct oxide deposition on GaAs. In the latter case, the incidence of two different in situ surface preparations, the Ar sputtering and the atomic H cleaning, on the interface composition is elucidated and the beneficial role played by the atomic H exposure in reducing the semiconductor-oxygen bonds at the interface level is demonstrated.

  5. The synthesis, characterization and optical properties of Si4+ and Pr4+ doped Y6 MoO12 compounds: environmentally benign inorganic pigments with high NIR reflectance

    International Nuclear Information System (INIS)

    George, Giable; Reddy, M.L.P.

    2010-01-01

    Full text: Much interest has attended roofing materials with high solar reflectance and high thermal emittance, so that interiors stay cool, thereby reducing the demand for air conditioned buildings. The heat producing region of the infrared radiations ranges from 700-1100 nm. Replacing conventional pigments with 'cool pigments' that absorb less NIR radiation can provide coatings similar in color to that of conventional roofing materials, but with higher solar reflectance. NIR reflective pigments have been used in the military, construction, plastics and ink industries. Complex inorganic pigments based on mixed metal oxides (eg., chromium green, cobalt blue, cadmium stannate, lead chromate, cadmium yellow and chrome titanate yellow), which have been used in camouflage, absorb visible light but reflect the NIR portion of incident radiation. However, many of these pigments are toxic and there is a need to develop novel colored, NIR-reflecting inorganic pigments that are less hazardous to the environment. In this work, a series of NIR reflective colored pigments of formula Y 6-x M x MoO 12+δ (where M Si 4+ or Pr 4+ and x ranges from 0 to 1.0) were synthesized by traditional solid-state route and applied to asbestos cement roofing material so as to evaluate their use as 'cool pigments'. The phase purity of the calcined pigment samples were determined using powder X-ray diffraction. The diffuse reflectance of the powdered pigment samples were measured using a UV-Vis-NIR Spectrometer. The Lab color coordinates were evaluated by CIE 1976 color scale. Replacing Si 4+ for Y 3+ in Y 6 MoO 12 changed the color from light-yellow to dark-yellow and the band gap decreased from 2.60 to 2.45 eV due to O 2p -Mo 4d charge transfer transitions. In contrast, replacing Pr 4+ for Y 3+ changed the color from light yellow to dark brown and the band gap shifted from 2.60 to 1.90 eV. The coloring mechanism is based on the introduction of an additional 4f 1 electron energy level of Pr 4

  6. Surface properties and dye loading behavior of Zn{sub 2}SnO{sub 4} nanoparticles hydrothermally synthesized using different mineralizers

    Energy Technology Data Exchange (ETDEWEB)

    Annamalai, Alagappan; Eo, Yang Dam [Department of Advanced Technology Fusion, Konkuk University, 1 Hwayang-dong, Kwangjin-gu, Seoul 143-701 (Korea, Republic of); Im, Chan [Department of Chemistry, Konkuk University, 1 Hwayang-dong, Kwangjin-gu, Seoul 143-701 (Korea, Republic of); Lee, Man-Jong, E-mail: leemtx@konkuk.ac.kr [Department of Advanced Technology Fusion, Konkuk University, 1 Hwayang-dong, Kwangjin-gu, Seoul 143-701 (Korea, Republic of)

    2011-10-15

    We present for the first time the influence of different mineralizers on the isoelectric point (IEP) of zinc stannate (Zn{sub 2}SnO{sub 4}) nanoparticles hydrothermally prepared using three different mineralizers, viz., Na{sub 2}CO{sub 3}, KOH and tert-butyl amine, and the effect of the IEPs on the dye loading behavior of Zn{sub 2}SnO{sub 4} based photoelectrodes in dye sensitized solar cells (DSSCs). To produce highly crystalline, uniform sized Zn{sub 2}SnO{sub 4} nanoparticles, hydrothermal processing parameters, such as reaction temperature, time, and the mineralizers used have been critically adjusted. The structural and morphological features of the as-synthesized Zn{sub 2}SnO{sub 4} nanoparticles have been observed using both scanning and transmission electron microscopy. For the surface state characterization of shape- and size-controlled Zn{sub 2}SnO{sub 4} nanoparticles, the IEPs of Zn{sub 2}SnO{sub 4} surfaces were determined through zeta potential measurements. The IEPs were found to be 5.7, 7.4 and 8.1 for Zn{sub 2}SnO{sub 4} nanoparticles formed using Na{sub 2}CO{sub 3}, KOH and tert-butyl amine, respectively, suggesting that the surface properties of Zn{sub 2}SnO{sub 4} nanoparticles can be manipulated through the choice of the mineralizers used during the hydrothermal reaction. The amount of N719 dye loading on the surfaces of Zn{sub 2}SnO{sub 4} electrodes having different IEPs was also evaluated. It was revealed that the higher the IEP, the higher the dye loading amount, which means that the IEP mainly affects the dye loading at the dye-metal oxide interface. - Highlights: {yields} The effect of various mineralizers on the isoelectric point of Zn{sub 2}SnO{sub 4} was discussed. {yields} The IEP of Zn{sub 2}SnO{sub 4} can be modified by the choice of mineralizer. {yields} Change in IEP affects the surface properties and the morphology of Zn{sub 2}SnO{sub 4} particles. {yields} Modified surface affects the N719 dye loading behaviour of the Zn{sub 2

  7. Surface properties and dye loading behavior of Zn2SnO4 nanoparticles hydrothermally synthesized using different mineralizers

    International Nuclear Information System (INIS)

    Annamalai, Alagappan; Eo, Yang Dam; Im, Chan; Lee, Man-Jong

    2011-01-01

    We present for the first time the influence of different mineralizers on the isoelectric point (IEP) of zinc stannate (Zn 2 SnO 4 ) nanoparticles hydrothermally prepared using three different mineralizers, viz., Na 2 CO 3 , KOH and tert-butyl amine, and the effect of the IEPs on the dye loading behavior of Zn 2 SnO 4 based photoelectrodes in dye sensitized solar cells (DSSCs). To produce highly crystalline, uniform sized Zn 2 SnO 4 nanoparticles, hydrothermal processing parameters, such as reaction temperature, time, and the mineralizers used have been critically adjusted. The structural and morphological features of the as-synthesized Zn 2 SnO 4 nanoparticles have been observed using both scanning and transmission electron microscopy. For the surface state characterization of shape- and size-controlled Zn 2 SnO 4 nanoparticles, the IEPs of Zn 2 SnO 4 surfaces were determined through zeta potential measurements. The IEPs were found to be 5.7, 7.4 and 8.1 for Zn 2 SnO 4 nanoparticles formed using Na 2 CO 3 , KOH and tert-butyl amine, respectively, suggesting that the surface properties of Zn 2 SnO 4 nanoparticles can be manipulated through the choice of the mineralizers used during the hydrothermal reaction. The amount of N719 dye loading on the surfaces of Zn 2 SnO 4 electrodes having different IEPs was also evaluated. It was revealed that the higher the IEP, the higher the dye loading amount, which means that the IEP mainly affects the dye loading at the dye-metal oxide interface. - Highlights: → The effect of various mineralizers on the isoelectric point of Zn 2 SnO 4 was discussed. → The IEP of Zn 2 SnO 4 can be modified by the choice of mineralizer. → Change in IEP affects the surface properties and the morphology of Zn 2 SnO 4 particles. → Modified surface affects the N719 dye loading behaviour of the Zn 2 SnO 4 based DSSCs.

  8. Muon spin relaxation and rotation studies of the filled skutterudite alloys praseodymium osmium ruthenium antimonide and praseodymium lanthanum osmium antimonide

    Science.gov (United States)

    Shu, Lei

    Some filled skutterudite compounds have recently been found to exhibit very interesting properties. The first Pr-based heavy-fermion superconductor, PrOs4Sb12, is an intriguing material due to the unusual properties of both its normal and superconducting states. Comprehensive muon spin rotation and relaxation studies and magnetic susceptibility measurements, described in this dissertation, have been performed to investigate the microscopic properties of PrOs4Sb12 and its Ru and La doped alloys. The temperature dependence of penetration depth measured in the vortex state of PrOs4Sb12 using transverse-field muon spin rotation (TF-muSR) is weaker than those measured by radiofrequency measurements. A scenario based on two-band superconductivity in PrOs4Sb 12, is proposed to resolve this difference. TF-muSR experiments also suggest the suppression of superfluid density with Ru doping, probably due to impurity scattering. In addition, magnetic susceptibility data as well as analysis of the muSR data in PrOs4Sb12 reveal a nearly linear relation of mu+ Knight shift vs. magnetic susceptibility. This suggests that the muon charge does not affect the crystalline electric field splitting of Pr3+ near neighbors. Additional evidence comes from the fact that the superconducting transition temperature Tc measured from muSR is consistent with the bulk superconducting values. Zero-field muon spin relaxation (ZF-muSR) experiments have been carried out in the Pr(Os1-xRux) 4Sb12 and Pr1-yLayOs 4Sb12 alloy systems to investigate the time-reversal symmetry (TRS) breaking found in an earlier ZF-muSR study of the end compound PrOs 4Sb12. The results from measurements at KEK, Japan, suggest that Ru doping is considerably more efficient than La doping in suppressing TRS breaking superconducting in PrOs4Sb12. However, we think that the spontaneous local field that indicates TRS breaking detected by ZF-muSR may depend on sample quality if those fields are from inhomogeneity in the

  9. Antiferromagnetic order in the ladder compound SrCu{sub 2}O{sub 3}: Cu-NMR/NQR measurements

    Energy Technology Data Exchange (ETDEWEB)

    Ohsugi, S.; Kitaoka, Y.; Azuma, M.; Fujishiro, Y.; Takano, M.

    1999-12-01

    The authors carried out the extensive Cu-nuclear magnetic and quadrupole resonance (NMR/NQR) experiments on the Zn(Ni)-doped ladder compound SrCu{sub 2}O{sub 3} (Sr123), Sr(Cu{sub 1{minus}x}M{sub x}){sub 2}O{sub 3} (M = Zn and Ni) with x {le} 0.02 and the La-doped Sr123, Sr{sub 1{minus}x}La{sub x}Cu{sub 2}O{sub 3} with {alpha} {le} 0.03. A spin-correlation length {xi}{sub s}/a (a: the lattice spacing between the Cu sites along the leg) of nonmagnetic impurity-induced staggered polarization (IISP) estimated from a quasi-one-dimensional (Q1D) IISP along the two legs in the 0.1--2% Zn-doped Sr123 was found to be independent of temperature (T) and scaled to an mean impurity distance D{sub AV} with the relation of {xi}{sub s}/a = 2.5 + D{sub AV}. The {xi}{sub s}/a's are much longer in x = 0.001 ({xi}{sub s}/a {approximately} 50) and 0.005 ({xi}{sub s}/a {approximately} 12) than an instantaneous spin-correlation length {xi}{sub 0}/a {approximately} 3--8 in Sr123. The formula of Neel T, T{sub N} (WC-Q1D) = J exp({minus}D{sub AV}/({xi}{sub s}/a)) (J = 2,000 K) based on the weakly interladder-coupled (WC) Q1D model explains the experimental T{sub N} values quantitatively.

  10. Lanthanum doped titania decorated with silver plasmonic nanoparticles with enhanced photocatalytic activity under UV-visible light

    Science.gov (United States)

    Dal'Toé, Adrieli T. O.; Colpani, Gustavo Lopes; Padoin, Natan; Fiori, Márcio Antônio; Soares, Cíntia

    2018-05-01

    Lanthanum doped titanium dioxide decorated with silver plasmonic nanoparticles (Ag-La/TiO2 NPs) materials were prepared using a simple ultrasound-assisted wet impregnation method followed by silver photodeposition. The obtained photocatalysts with different Ag contents were characterized by XRD, FE-SEM, EDX, TEM, BET, XPS, DRS and PL techniques. Moreover, the size distribution of the nanoparticles aggregates was assessed. The characterization analysis revealed that La doping slightly changed the crystalline phase of TiO2, increased the amount of surface hydroxyl groups and interacted with TiO2 nanoparticles via Ti-O-La bond, while Ag photodeposition enhanced the absorption of visible light due to the effects of localized surface plamon resonance and significantly decreased electronic recombination rate by the Schottky junction. Furthermore, the combination of Ag-La induced the formation of oxygen vacancies, which increased the amount of adsorbed surface hydroxyl groups in Ag-La/TiO2. In addition, Ag-La possibly decreased the semiconductor surface energy, which acted positively in the reduction of NPs aggregation. These features along with better textural properties (greater surface areas) played a fundamental role in the enhancement of the photocatalytic activity of Ag-La/TiO2 composites for the decolorization of methylene blue under UV-visible irradiation compared to the mono-metallic (La/TiO2 and Ag/TiO2) modified photocatalysts. Finally, a mechanism for the transfer of charge carriers in Ag-La/TiO2 photocatalyst under UV-visible irradiation was proposed.

  11. Physicochemical compatibility of SrCeO3 with potential SOFC cathodes

    International Nuclear Information System (INIS)

    Tolchard, J.; Grande, T.

    2007-01-01

    The chemical and physical compatibility of SrCeO 3 is investigated with respect to LaMO 3 (M=Mn, Fe, Co) and La 2-x Sr x NiO 4 (x=0, 0.8), via the reaction of fine-grained powder compacts and solid-state diffusion couples. Compositions were chosen so as to give predictive insight into possible candidate materials for all-oxide electrochemical devices. Results show the primary reaction in these systems to be the dissolution of SrO from SrCeO 3 into the LaMO 3 /La 2-x Sr x NiO 4 , and corresponding formation of La-doped CeO 2 . Reaction kinetics are observed to be relatively fast, with element profiles suggesting the diffusion of Sr 2+ in ceria to be surprisingly rapid. It is demonstrated that perovskite starting materials represent poor candidates for use with SrCeO 3 , reacting completely to form Ruddlesden-Popper/K 2 NiF 4 type oxides. Reaction with La 2 NiO 4 is less pronounced, and formation of secondary phases suppressed for the composition La 1.2 Sr 0.8 NiO 4 . It is thus concluded that Ruddlesden-Popper type oxides represent good candidate materials for use with a SrCeO 3 -based electrolytes when doped with appropriate levels of Sr. - Graphical abstract: Assessment of the SrCeO 3 proton conductor shows this material to have poor chemical compatibility with LaMO 3 perovskite systems, but predicts coexistence with Ruddlesden-Popper type oxides

  12. Synthesis of N and La co-doped TiO{sub 2}/AC photocatalyst by microwave irradiation for the photocatalytic degradation of naphthalene

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Dandan; Wu, Zhansheng, E-mail: wuzhans@126.com; Tian, Fei; Ye, Bang-Ce; Tong, Yanbin, E-mail: tongyanbin@sina.com

    2016-08-15

    La and N co-doped TiO{sub 2} nanoparticles supported on activated carbon (TiO{sub 2}/AC) were synthesized through a microwave-assisted sol–gel method for the synergistic removal of naphthalene solution by photocatalytic degradation. Results showed that the La and N ions were incorporated into the TiO{sub 2} framework in both the anatase and rutile phases of TiO{sub 2} for single doped and co-doped samples, which narrowed the band gap of TiO{sub 2} from 2.82 to 2.20 eV. The PL spectra of the samples showed a decrease in the recombination centers when N and La were introduced in TiO{sub 2}/AC. The 0.001La-N-TiO{sub 2}/AC photocatalyst exhibited the highest degradation efficiency of 93.5% for naphthalene under visible light within 120 min. This result was attributed to a synergistic effect involving the efficient inhibition of the recombination of photogenerated electrons and holes, the increase in surface hydroxyl, surface area, volume pores, and the increase of uptake in the visible light region. In addition, the high apparent rate constant indicated that La and N co-doping result in the increase of photoactivity. This study demonstrated the co-doped TiO{sub 2}/AC is a highly efficient photocatalyst for the removal of naphthalene. The results provided valuable information on the mechanism of naphthalene decomposition. - Highlights: • N, La codoped TiO{sub 2}/AC catalysts were synthesized by microwave-assisted. • N and La doping inhibit the recombination of photogenerated electrons and holes. • 0.001La-N-TiO{sub 2}/AC obtains photodegradation efficiency of 93.5% for naphthalene. • The photocatalysts possess good photochemical stability and reusability.

  13. Decoupling of magnetism and electric transport in single-crystal (Sr1‑x A x )2IrO4 (A  =  Ca or Ba)

    Science.gov (United States)

    Zhao, H. D.; Terzic, J.; Zheng, H.; Ni, Y. F.; Zhang, Y.; Ye, Feng; Schlottmann, P.; Cao, G.

    2018-06-01

    We report a systematical structural, transport and magnetic study of Ca or Ba doped Sr2IrO4 single crystals. Isoelectronically substituting Ca2+ (up to 15%) or Ba2+ (up to 4%) ion for the Sr2+ ion provides no additional charge carriers but effectively changes the lattice parameters in Sr2IrO4. In particular, 15% Ca doping considerably reduces the c-axis and the unit cell by nearly 0.45% and 1.00%, respectively. These significant, anisotropic compressions in the lattice parameters conspicuously cause no change in the Néel temperature which remains at 240 K, but drastically reduces the electrical resistivity by up to five orders of magnitude or even precipitates a sharp insulator-to-metal transition at lower temperatures, i.e. the vanishing insulating state accompanies an unchanged Néel temperature in (Sr1‑x A x )2IrO4. This observation brings to light an intriguing difference between chemical pressure and applied pressure, the latter of which does suppress the long-range magnetic order in Sr2IrO4. This difference reveals the importance of the Ir1–O2–Ir1 bond angle and homogenous volume compression in determining the magnetic ground state. All results, along with a comparison drawn with results of Tb and La doped Sr2IrO4, underscore that the magnetic transition plays a nonessential role in the formation of the charge gap in the spin–orbit-tuned iridate.

  14. The phase diagram and magnetic properties of Co and Ti co-doped (1−x)BiFeO_3–xLaFeO_3 solid solutions

    International Nuclear Information System (INIS)

    Wu, Jiangtao; Xu, Jun; Li, Nan; Jiang, Yaqi; Xie, Zhaoxiong

    2015-01-01

    Single phase Co and Ti co-doped Bi_1_−_xFeO_3−La_xFeO_3 (x = 0–1) solid solutions were prepared by the sol–gel method. Room temperature x-ray powder diffraction (XRD) patterns showed that the structures of as-prepared Bi_1_−_xLa_xFe_0_._9_0Co_0_._0_5Ti_0_._0_5O_3 solid solutions transformed from rhombohedral R3c to tetragonal P4mm and then to orthorhombic Pnma, with increasing La concentration from 0 to 1. In situ high-temperature XRD (HTXRD) analysis further revealed that rhombohedral structure R3c (x ≤ 0.16) and tetragonal structure P4mm (0.17 ≤ x ≤ 0.40) changed to orthorhombic Pnma along with increasing temperature, and the phase transition temperature decreased with the increase of La doping concentration. However, the orthorhombic structure Pnma (x ≥ 0.41) kept stable even when the temperature reached 850 °C. The phase diagram of as-prepared binary solid solutions of Bi_1_−_xLa_xFe_0_._9_0Co_0_._0_5Ti_0_._0_5O_3(x = 0–1) was drawn on the basis of XRD and HTXRD analysis. Magnetic measurement revealed that the magnetic properties are greatly enhanced with the increase of La content. - Highlights: • Single phase Co and Ti co-doped (1−x)BiFeO_3–xLaFeO_3 (x = 0–1) solid solutions were synthesized. • The phase transitions were investigated by tuning composition and temperature. • Phase diagram was constructed according to the results of XRD for the first time. • The magnetization of solid solution can be enhanced when increasing La content.

  15. The effect of point defects on ferroelastic phase transition of lanthanum-doped calcium titanate ceramics

    International Nuclear Information System (INIS)

    Ni, Yan; Zhang, Zhen; Wang, Dong; Wang, Yu; Ren, Xiaobing

    2013-01-01

    Highlights: ► The effect of point defects on phase transitions in Ca (1−x) La 2x/3 TiO 3 was studied. ► When x = 0.45, normal ferroelastic phase transition happens. ► When x = 0.7, a “glassy-like” frozen process appears. ► Point defects weaken the thermodynamic stability of ferroelastic phase. ► Point defects induce a “glassy-like” frozen process. -- Abstract: In the present paper, La-doped CaTiO 3 is studied to investigate the effect of point defects on ferroelastic phase transition of the ceramics. The dynamic mechanical measurements show that the transition temperature of the orthorhombic to tetragonal phase transition of Ca (1−x) La 2x/3 TiO 3 decreases with increasing dopant (La) concentration x. The samples with the dopant content of x = 0.45 and 0.7 exhibit different structure evolution features during their transition processes as revealed by in situ powder X-ray diffraction (XRD) measurement. Moreover, when x = 0.7, the storage modulus shows a frequency-dependent minimum at T g , which can be well fitted with the Vogel–Fulcher relation, and the corresponding internal friction also exhibits a frequency-dependent peak within the same temperature regime. These results thus indicate that doping La suppresses ferroelastic phase transition in CaTiO 3 and induces a “glassy-like” behavior in Ca (1−x) La 2x/3 TiO 3 , which is similar to “strain glass” in Ni-doped Ti 50−x Ni 50+x

  16. Synthesis, structural, optical and Raman studies of pure and lanthanum doped ZnSe nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pushpendra, E-mail: push.nac@gmail.com [Department of Physics, Faculty of Science, Banaras Hindu University, Varanasi 221005 (India); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 11529, Taiwan (China); Singh, Jai [Department of Physics, Faculty of Science, Banaras Hindu University, Varanasi 221005 (India); Department of Materials Science and Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Pandey, Mukesh Kumar [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 11529, Taiwan (China); Jeyanthi, C.E. [Research and Development Centre, Bharathiar University, Coimbatore 641 046 (India); Siddheswaran, R. [Department of Materials Science and Engineering, University of Concepcion, Concepcion (Chile); Paulraj, M. [Department of Physics, Faculty of Physical sciences and Mathematics, University of Concepcion, Casilla 160, Concepcion (Chile); Hui, K.N. [Department of Materials Science and Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Hui, K.S., E-mail: kshui@hanyang.ac.kr [Department of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

    2014-01-01

    Graphical abstract: - Highlights: • Template-free synthesis of ZnSe and ZnSe:La nanoparticles was developed at low temperature 100 °C. • Cubic ZnSe and ZnSe:La nanoparticles were obtained by chemical route. • As-synthesized ZnSe:La nanoparticles showed higher emission intensity than ZnSe nanoparticles. • Band gap (E{sub g}) of ZnSe nanoparticles was bigger than ZnSe nanoparticles due to nanosized effect. - Abstract: In this work, a simple, effective and reproducible chemical synthetic route for the production of high-quality, pure ZnSe nanoparticles (NPs), and lanthanum-doped ZnSe (ZnSe:La) NPs is presented. The wide bandgap, luminescent pure ZnSe and ZnSe:La NPs has been synthesized at a low temperature (100 °C) in a single template-free step. The size and optical bandgap of the NPs was analyzed from powder X-ray diffraction (XRD), UV–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM). A broad photoluminescence (PL) emission across the visible spectrum has been demonstrated by a systematic blue-shift in emission due to the formation of small nanoparticles. Here, contribution to emission intensity from surface states of NPs increases with La doping. TEM data revealed that the average size of ZnSe and ZnSe:La NPs is 14 and 8 nm, respectively. On the other hand, band gap energy E{sub g} of ZnSe and ZnSe:La NPs were found to be 3.59 eV and 3.65 eV, respectively. Results showed that hydrazine hydrate played multiple roles in the formation of ZnSe and ZnSe:La NPs. A possible reaction mechanism for the growth of NPs is also discussed.

  17. Effect of light rare earth doping in 123 high temperature supercoductors

    Directory of Open Access Journals (Sweden)

    M. Mirzadeh

    2006-09-01

    Full Text Available   We have studied the structural and electrical properties of Gd(Ba2-xLaxCu3O7+δ [Gd(BaLa123], Gd(Ba2-xNdxCu3O7+δ [Gd(BaNd123], and Nd(Ba2-xPrxCu3O7+δ [Nd(BaPr123] compounds with 0.0≤x≤0.8 prepared by the standard solid-state reaction. The XRD patterns show that all of the samples with x≤0.5 are isosructure 123 phase, but in Gd(BaNd123 and Nd(BaPr123 there are several impurity peaks in the XRD patterns for x≥0.6. We estimated the xcsolubility=1.1, 0.6 and 0.55 in Gd(BaLa123, Nd(BaPr123, and Gd(BaNd123, respectively. The resistivity increases with the increase of doping. The decrease of Tc with the increase of Pr doping is faster than Nd and La doping. The normal-state resistivity is fitted for two and three dimensional variable range hopping (2D&amp3D-VRH and Coulomb gap (CG regimes, separately. Our results indicate that the dominant mechanism for x≥xcSIT is 3D-VRH. The broadening of magnetoresistance have been investigated by TAFC and AH models. The pinning energy and Josephson coupling energy, decrease with the increase of applied magnetic field as U~H-β, these values also decrease with doping concentration Pr is more effective than Nd and La.

  18. Structure, chemistry and luminescence properties of dielectric La{sub x}Hf{sub 1-x}O{sub y} films

    Energy Technology Data Exchange (ETDEWEB)

    Kaichev, V.V., E-mail: vvk@catalysis.ru [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation); Novosibirsk State University, Novosibirsk (Russian Federation); Smirnova, T.P.; Yakovkina, L.V. [Nikolaev Institute of Inorganic Chemistry, Novosibirsk (Russian Federation); Ivanova, E.V.; Zamoryanskaya, M.V. [Ioffe Physical-Technical Institute, St. Petersburg (Russian Federation); Saraev, A.A. [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation); Novosibirsk State University, Novosibirsk (Russian Federation); Pustovarov, V.A. [Ural State Technical University, Ekaterinburg (Russian Federation); Perevalov, T.V.; Gritsenko, V.A. [Novosibirsk State University, Novosibirsk (Russian Federation); Rzhanov Institute of Semiconductor Physics, Novosibirsk (Russian Federation)

    2016-06-01

    Dielectric films of La{sub 2}O{sub 3}, HfO{sub 2}, and La{sub x}Hf{sub 1-x}O{sub y} were synthesized by metal-organic chemical vapor deposition. Structural, chemical, and luminescence properties of the films were studied using X-ray photoelectron spectroscopy, methods of X-ray diffraction and selected area electron diffraction, high-resolution transmission electron microscopy, and a cathodoluminescence technique. It was found that doping of hafnium oxide with lanthanum leads to the formation of a continuous series of solid solutions with a cubic structure. This process is accompanied by the formation of oxygen vacancies in the HfO{sub 2} lattice. Cathodoluminescence spectra of the La{sub x}Hf{sub 1-x}O{sub y}/Si films exhibited a wide band with the maximum near 2.4–2.5 eV, which corresponds to the blue emission. Quantum-chemical calculations showed that this blue band is due to oxygen vacancies in the HfO{sub 2} lattice. - Highlights: • HfO{sub 2} and solid solution La{sub x}Hf{sub 1-x}O{sub y} films were synthesized by MOCVD. • The continuous series of solid solutions with a cubic structure was formed at La doping of HfO{sub 2}. • Cathodoluminescence band at 2.4–2.5 eV is observed due to the oxygen vacancies in La{sub x}Hf{sub 1-x}O{sub y}. • The cathodoluminescence decreases in intensity when the La concentration increases.

  19. Dielectric behaviors of Pb1-3x/2LaxTiO3 derived from mechanical activation

    International Nuclear Information System (INIS)

    Soon, H.P.; Xue, J.M.; Wang, J.

    2004-01-01

    To investigate the origin of ultrahigh relative permittivity that has been observed for lanthanum-doped lead titanate, Pb 1-3x/2 La x TiO 3 (PLT-A) with x ranging from 0.10 to 0.25 were synthesized by mechanical activation of constituent oxides. Their sintered density, grain size and relative permittivity demonstrated a steady increase with increasing of La doping. Upon thermal annealing in oxygen, the relative permittivity of Pb 0.70 La 0.2 TiO 3 (PLT-A20) at T c showed an initial rise and a peak at 4h of annealing, and then a steady fall with further increase in annealing time. In contrast, when annealed in nitrogen for 4 h, a significant rise in relative permittivity was observed, although the increase rate falls with prolonged annealing. The observed dependence of relative permittivity and dielectric loss for PLT-A20 on the initial annealing in both oxygen and nitrogen demonstrated the domination of space charge polarization as a result of PbO loss through evaporation from the surface region. While the high activation energy for Pb 2+ and O 2- diffusion through the surface scale slows down the rate of PbO loss through evaporation, excess loss of PbO adversely affect space charge polarization, leading to a fall in relative permittivity of PLT-A20, upon prolonged annealing in oxygen. In addition to PbO loss, prolonged annealing in nitrogen generated oxygen vacancies, which played an important role in affecting the relative permittivity

  20. Electronically conductive perovskite-based oxide nanoparticles and films for optical sensing applications

    Science.gov (United States)

    Ohodnicki, Jr., Paul R; Schultz, Andrew M

    2015-04-28

    The disclosure relates to a method of detecting a change in a chemical composition by contacting a electronically conducting perovskite-based metal oxide material with a monitored stream, illuminating the electronically conducting perovskite-based metal oxide with incident light, collecting exiting light, monitoring an optical signal based on a comparison of the incident light and the exiting light, and detecting a shift in the optical signal. The electronically conducting perovskite-based metal oxide has a perovskite-based crystal structure and an electronic conductivity of at least 10.sup.-1 S/cm, where parameters are specified at the gas stream temperature. The electronically conducting perovskite-based metal oxide has an empirical formula A.sub.xB.sub.yO.sub.3-.delta., where A is at least a first element at the A-site, B is at least a second element at the B-site, and where 0.8perovskite-based oxides include but are not limited to La.sub.1-xSr.sub.xCoO.sub.3, La.sub.1-xSr.sub.xMnO.sub.3, LaCrO.sub.3, LaNiO.sub.3, La.sub.1-xSr.sub.xMn.sub.1-yCr.sub.yO.sub.3, SrFeO.sub.3, SrVO.sub.3, La-doped SrTiO.sub.3, Nb-doped SrTiO.sub.3, and SrTiO.sub.3-.delta..

  1. Calcium stanate (CaSnO_3) doped with Fe"3"+, Co"2"+ ou Cu"2"+ applied in the photodegradation of Remazol Golden Yellow and in the reduction of NO with CO or NH_3

    International Nuclear Information System (INIS)

    Santos, Guilherme Leocardio Lucena dos

    2017-01-01

    Calcium stannate, CaSnO_3, is orthorhombic perovskite-type that presents technological applications as catalysts and photocatalysts. In this work, undoped CaSnO_3 and doped with Fe"3"+, Co"2"+ or Cu"2"+ were obtained by the modified Pechini method and applied in photodegradation of the textile dye Remazol Golden Yellow and as catalysts in the reduction reaction of nitrogen monoxide (NO). Furthermore, these materials were deposited on the ZrO_2 support or Pd"2"+-doped or Pd impregnated and evaluated in the reduction of NO with CO and NO with NH_3. The catalysts were characterized by thermogravimetric analysis (TG/DTA), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), infrared spectroscopy (IR), Raman spectroscopy, analysis of the surface area by the BET method, scanning electron microscopy with field emission (FE-SEM) and transmission electron microscopy (TEM). XRD patterns showed a small change in the long range-order for the doped samples due to partial substitution of cations. The Raman spectra indicated that the incorporation of Fe"3"+, Co"2"+ and Cu"2"+ in the CaSnO_3 lattice promoted a symmetry breaking, which was confirmed by the change of the band gap values of the samples. The photocatalytic tests of RNL dye were performed in the reactor using a UVC lamp (λ = 254 nm). The catalytic tests were carried out in a reactor containing a gaseous mixture with stoichiometric amounts of nitrogen monoxide (NO) and carbon monoxide (CO) in helium in the temperature range of 300 °C to 700 °C or in a reactor containing a mixture of NO and ammonia (NH_3) in helium in the temperature range of 250 °C to 500 °C. The results of the photocatalytic evaluation showed that CaSnO_3 doping with transition metals increased the photocatalytic efficiency of the material, especially for the Cu"2"+ (76% of discoloration), which was related to the while the decrease in the intensity of the photoluminescence spectrum as a function of doping. The catalytic tests of NO

  2. Calcium stanate (CaSnO{sub 3}) doped with Fe{sup 3+}, Co{sup 2+} ou Cu{sup 2+} applied in the photodegradation of Remazol Golden Yellow and in the reduction of NO with CO or NH{sub 3}; Estanatos de calcio (CaSnO{sub 3}) dopados com Fe{sup 3+}, Co{sup 2+} ou Cu{sup 2+} aplicados na fotodegradacao de Remazol Amarelo Ouro e na reducao de NO com CO ou NH{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Guilherme Leocardio Lucena dos

    2017-11-01

    Calcium stannate, CaSnO{sub 3}, is orthorhombic perovskite-type that presents technological applications as catalysts and photocatalysts. In this work, undoped CaSnO{sub 3} and doped with Fe{sup 3+}, Co{sup 2+} or Cu{sup 2+} were obtained by the modified Pechini method and applied in photodegradation of the textile dye Remazol Golden Yellow and as catalysts in the reduction reaction of nitrogen monoxide (NO). Furthermore, these materials were deposited on the ZrO{sub 2} support or Pd{sup 2+}-doped or Pd impregnated and evaluated in the reduction of NO with CO and NO with NH{sub 3}. The catalysts were characterized by thermogravimetric analysis (TG/DTA), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), infrared spectroscopy (IR), Raman spectroscopy, analysis of the surface area by the BET method, scanning electron microscopy with field emission (FE-SEM) and transmission electron microscopy (TEM). XRD patterns showed a small change in the long range-order for the doped samples due to partial substitution of cations. The Raman spectra indicated that the incorporation of Fe{sup 3+}, Co{sup 2+} and Cu{sup 2+} in the CaSnO{sub 3} lattice promoted a symmetry breaking, which was confirmed by the change of the band gap values of the samples. The photocatalytic tests of RNL dye were performed in the reactor using a UVC lamp (λ = 254 nm). The catalytic tests were carried out in a reactor containing a gaseous mixture with stoichiometric amounts of nitrogen monoxide (NO) and carbon monoxide (CO) in helium in the temperature range of 300 °C to 700 °C or in a reactor containing a mixture of NO and ammonia (NH{sub 3}) in helium in the temperature range of 250 °C to 500 °C. The results of the photocatalytic evaluation showed that CaSnO{sub 3} doping with transition metals increased the photocatalytic efficiency of the material, especially for the Cu{sup 2+} (76% of discoloration), which was related to the while the decrease in the intensity of the

  3. Nanostructured Thermoelectric Oxides for Energy Harvesting Applications

    KAUST Repository

    Abutaha, Anas I.

    2015-11-24

    As the world strives to adapt to the increasing demand for electrical power, sustainable energy sources are attracting significant interest. Around 60% of energy utilized in the world is wasted as heat. Different industrial processes, home heating, and exhausts in cars, all generate a huge amount of unused waste heat. With such a huge potential, there is also significant interest in discovering inexpensive technologies for power generation from waste heat. As a result, thermoelectric materials have become important for many renewable energy research programs. While significant advancements have been done in improving the thermoelectric properties of the conventional heavy-element based materials (such as Bi2Te3 and PbTe), high-temperature applications of thermoelectrics are still limited to one materials system, namely SiGe, since the traditional thermoelectric materials degrade and oxidize at high temperature. Therefore, oxide thermoelectrics emerge as a promising class of materials since they can operate athigher temperatures and in harsher environments compared to non-oxide thermoelectrics. Furthermore, oxides are abundant and friendly to the environment. Among oxides, crystalline SrTiO3 and ZnO are promising thermoelectric materials. The main objective of this work is therefore to pursue focused investigations of SrTiO3 and ZnO thin films and superlattices grown by pulsed laser deposition (PLD), with the goal of optimizing their thermoelectric properties by following different strategies. First, the effect of laser fluence on the thermoelectric properties of La doped epitaxial SrTiO3 films is discussed. Films grown at higher laser fluences exhibit better thermoelectric performance. Second, the role of crystal orientation in determining the thermoelectric properties of epitaxial Al doped ZnO (AZO) films is explained. Vertically aligned (c-axis) AZO films have superior thermoelectric properties compared to other films with different crystal orientations. Third

  4. A novel bilayered Sr{sub 0.6}La{sub 0.4}TiO{sub 3}/La{sub 0.8}Sr{sub 0.2}MnO{sub 3} interconnector for anode-supported tubular solid oxide fuel cell via slurry-brushing and co-sintering process

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yanjie; Wang, Shaorong; Liu, Renzhu; Wen, Tinglian; Wen, Zhaoyin [CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS), 1295 Dingxi Road, Shanghai 200050 (China)

    2011-02-01

    Considering that conventional lanthanum chromate (LaCrO{sub 3}) interconnector is hard to be co-sintered with green anode, we have fabricated a novel bilayered interconnector which consists of La-doped SrTiO{sub 3} (Sr{sub 0.6}La{sub 0.4}TiO{sub 3}) and Sr-doped lanthanum manganite (La{sub 0.8}Sr{sub 0.2}MnO{sub 3}). Sr{sub 0.6}La{sub 0.4}TiO{sub 3} is conductive and stable in reducing atmosphere, locating on the anode side; while La{sub 0.8}Sr{sub 0.2}MnO{sub 3} is on the cathode side. A slurry-brushing and co-sintering method is applied: the Sr{sub 0.6}La{sub 0.4}TiO{sub 3} and La{sub 0.8}Sr{sub 0.2}MnO{sub 3} slurries are successively brushed onto green anode specimen, followed by co-firing course to form a dense bilayered Sr{sub 0.6}La{sub 0.4}TiO{sub 3}/La{sub 0.8}Sr{sub 0.2}MnO{sub 3} interconnector. For operating with humidified hydrogen and oxygen at 900 C, the ohmic resistances between anode and cathode/interconnector are 0.33 {omega} cm{sup 2} and 0.186 {omega} cm{sup 2}, respectively. The maximum power density is 290 mW cm{sup -2} for a cell with interconnector, and 420 mW cm{sup -2} for a cell without it, which demonstrates that nearly 70% of the power output can be achieved using this bilayered Sr{sub 0.6}La{sub 0.4}TiO{sub 3}/La{sub 0.8}Sr{sub 0.2}MnO{sub 3} interconnector. (author)

  5. Effects of Nd-addition on the structural, hydrogen storage, and electrochemical properties of C14 metal hydride alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wong, D.F. [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Department of Chemical Engineering, Wayne State University, Detroit, MI 48202 (United States); Young, K., E-mail: kwo.young@basf.com [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Department of Chemical Engineering, Wayne State University, Detroit, MI 48202 (United States); Nei, J.; Wang, L. [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Ng, K.Y.S. [Department of Chemical Engineering, Wayne State University, Detroit, MI 48202 (United States)

    2015-10-25

    Nd-addition to the AB{sub 2}-based alloy Ti{sub 12}Zr{sub 22.8−x}V{sub 10}Cr{sub 7.5}Mn{sub 8.1}Co{sub 7.0}Ni{sub 32.2}Al{sub 0.4}Nd{sub x} is studied for its effects on the structure, gaseous-phase hydrogen storage, and electrochemical properties. This study follows a series of Cu, Mo, Fe, Y, Si, and La doping studies in similar AB{sub 2}-based alloys. Limited solubility of Nd in the main Laves phase promotes the formation of secondary phases (AB and Zr{sub 7}Ni{sub 10}) to provide catalytic effects and synergies for improved capacity and high-rate dischargeability (HRD) performance. The main C14 storage phase has smaller lattice constants and cell volumes, and these effects reduce the storage capacity at higher Nd levels. Different hydrogen absorption mechanisms can occur in these multi-component, multi-phase alloys depending on the interfaces of the phases, and they have effects on the alloy properties. Higher Nd-levels improve the HRD performance despite having lower bulk diffusion and surface exchange current. Magnetic susceptibility measurements indicate large percentage of larger metallic nickel clusters are present in the surface oxide of alloys with higher Nd-content, and AC impedance studies show very low charge-transfer resistance with high catalytic capability in the alloys. The −40 °C charge-transfer resistance of 8.9 Ω g in this Nd-series of alloys is the lowest measured out of the studies investigating doped AB{sub 2}-based MH alloys for improved low-temperature characteristics. The improvement in HRD and low-temperature performance appears to be related to the proportion of the highly catalytic NdNi-phase at the surface, which must offset the increased bulk diffusion resistance in the alloy. - Graphical abstract: Schematics of hydrogen flow and corresponding PCT isotherms in funneling mode. - Highlights: • Structural and hydrogen storage properties of Nd-substituted AB{sub 2} metal hydride are reported. • Nd contributes to the lowest

  6. Fundamental aspects of regenerative cerium oxide nanoparticles and their applications in nanobiotechnology

    Science.gov (United States)

    Patil, Swanand D.

    Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of cerium oxide nanoparticles increases with decrease in particle size. Also Raman allowed mode shift to lower energies and the peak at 464 cm-1 becomes broader and asymmetric. The size dependent changes in cerium oxide were correlated to increase in oxygen vacancy concentration in the cerium oxide lattice. The doping of cerium oxide nanoparticles with trivalent elements introduces more oxygen vacancies and expands the cerium oxide lattice further (in addition to the lattice expansion due to the size effect). The lattice expansion is greater for La-doped cerium oxide nanoparticles compared to Nd-doping due to the larger ionic radius of La compared to Nd, the lattice expansion is directly proportional to the dopant concentration. The synthesized cerium oxide nanoparticles were used to develop an electrochemical biosensor of hydrogen peroxide (H2O2). The sensor was useful to detect H2O2 concentrations as low as 1muM in water. Also the preliminary testing of the sensor on tomato stem and leaf extracts indicated that the sensor can be used in practical applications such as plant physiological studies etc. The nanomolar concentrations of cerium oxide nanoparticles were also found to be useful in decreasing ROS (reactive oxygen species) mediated cellular damages in various in vitro cell cultures. Cerium oxide

  7. Processing, structure and magnetic properties correlation in co-precipitated Ca-ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Abasht, Behzad, E-mail: abasht@gmail.com [Space Thruster Research Institute, Iranian Space Research Center, Tabriz (Iran, Islamic Republic of); Department of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Beitollahi, Ali; Mirkazemi, Seyyed Mohammad [Department of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

    2016-12-15

    study, the calcium hexaferrite has been synthesized using co-precipitation method. • M-phase was present only in the La-doped sample at about 1200 °C. • The value of maximum magnetization is relatively high due to M-phase formation. • The effect of La amount on the magnetic properties has been discussed.

  8. Impurity-induced staggered polarization and antiferromagnetic order in spin-12 Heisenberg two-leg ladder compound SrCu2O3: Extensive Cu NMR and NQR studies

    Science.gov (United States)

    Ohsugi, S.; Tokunaga, Y.; Ishida, K.; Kitaoka, Y.; Azuma, M.; Fujishiro, Y.; Takano, M.

    1999-08-01

    We report characteristics of impurity-induced staggered polarization (IISP) and antiferromagnetic long-range order (AF-LRO) in the gapped spin-1/2 Heisenberg two-leg ladder compound SrCu2O3 (Sr123). We have carried out comprehensive NMR and NQR investigations on three impurity-doped systems, Sr(Cu1-xMx)2O3 (M=Zn, Ni) with xIISP along the leg was found to be much longer than ξ0/a in x=0.001 and 0.005. The notable result is that ξs/a that was found to be T independent is scaled to mean distances DAV=1/(2x) between the Zn and Ni impurities and DAV=1/x between the La impurities. When DAV=500 for x=0.001 (Zn doping), ξs/a~50 is estimated. The significantly broadened NQR spectrum has provided unambiguous evidence for the AF-LRO in the Zn and Ni doping (x=0.01 and 0.02). Rather uniform AF moments at the middle Cu sites between the impurities are estimated to be about 0.04μB at 1.4 K along the a axis. By assuming that exponential decay constants of AF moments are equivalent to ξs/a's for the IISP, the size of an AF moment next to the impurity is deduced as SAF~1/4. We propose that these exponential distributions of IISP and AF moments along the two-leg suggest that an interladder interaction is in a weakly coupled quasi-one-dimensional (WC-Q1D) regime. The formula of TN=J0exp(-DAV/(ξs/a)) based on the WC-Q1D model explains TN(exp)=3 K (x=0.01) and 5.8 K (x=0.02) quantitatively and predicts to be as small as TN=0.09 K for x=0.001 using J0=2000 K. On the other hand, there is no evidence of AF-LRO for the La doping (x=0.02 and 0.03) down to 1.4 K, nevertheless their ξs/a's are almost equivalent to those in the Zn and Ni doping (x=0.01 and 0.02). We remark that the Q1D-IISP is dramatically enhanced by the interladder interaction even though so weak, once the impurity breaks up the quantum coherence in the short-range resonating valence bond (RVB) state with the gap. On the one hand, we propose that TN is determined by a strength of the interladder interaction and a size

  9. Anabolik Steroidlerin Genotoksik ve Sitotoksik Etkilerinin İnsan Periferal Lenfosit Kültüründe Mikronükleus Test Tekniğiyle Araştırılması

    Directory of Open Access Journals (Sweden)

    Deniz ALTUN ÇOLAK

    2016-10-01

    Full Text Available Özet. Spor tarihi boyunca genç yaştaki bir çok sporcunun doping amacıyla anabolik-androjenik steroidleri yoğun olarak kullandığı bilinmektedir. Bu çalışmayla, kullanımı yasaklanmış olsa da yapılan araştırmalarda illegal olarak halen sıkça kullanılmakta olan Nandrolone Decanoate (Deca-durabolin® ve Stanozolol (Winstrol doping maddelerinin olası genotoksik, mutajenik ve sitotoksik etkilerinin insan kan kültüründe in vitro mikronükleus testi ile belirlenmesi amaçlanmıştır. Bu amaçla doping maddelerinin farklı konsantrasyonları (1, 10, 25, 50, 75 ve 100 mM hazırlanmış ve kan kültürüne uygulanmıştır. Genotoksik etki için mikronükleus frekansları, sitotoksik etki için ise Nükleer Bölünme İndeksi (NBİ hesaplanmıştır. Elde edilen veriler, çözücü olarak kullanılan dimetil sülfoksit (DMSO ile hazırlanan negatif kontrol grubuyla ve genotoksik etkisi çok iyi bilinen Etil metansülfonat (EMS ile hazırlanmış pozitif kontrol grubuyla karşılaştırılmıştır. Bu sonuçlara göre; çalışmamızda kullandığımız doping maddelerinden Nandrolone Decanoate özellikle son iki konsantrasyonda (75 ve 100 mM  insan periferal lenfositlerinde mikronükleus frakansını istatistiksel olarak anlamlı (p< 0,05 bir şekilde artırmıştır. Ayrıca NBİ oranlarına bakıldığında da özellikle son iki konsantrasyonda kontrol grubuna göre önemli düşüşler tespit edilmiştir. Bununla birlikte diğer doping maddesi olan Stanozolol ise sadece son konsantrasyonda (100 mM anlamlı artışlara neden olmuşken NBİ değerini etkilememiştir. Tüm elde ettiğimiz sonuçlardan her iki doping maddesinin de yüksek konsantrasyonlarda genotoksik ve sitotoksik etkiler yaratabileceği bu nedenle kullanımlarının tehlikeli olabileceği sonucuna ulaşılmıştır.Anahtar Kelimeler: Genotoksisite, Lenfosit kültürü, Mikronükleus, Nandrolone Decanoate, Stanozolol Abstract. Throughout the sports history

  10. Blood composition of the reindeer . II. Blood chemistry

    Directory of Open Access Journals (Sweden)

    Mauri Nieminen

    1983-05-01

    kokonaisvalkuainen (63 - 87 g/l, albumiini (39 - 43 g/l, globuliinit (23 - 44 g/l, urea (5,7 - 9 mmol/1, kokonaislipidit (2,7 - 5,2 g/l, triglyseridit (0,17 - 0.33 mmol/1, rasvahapot (0,89 - 1,54 g/l, kalsium (2,2 - 2,6 mmol/1, fosfori (1,6 - 2,2 mmol/I, magnesium (0,8 - 1,2 mmol/1 ja kupari (6,7-18 (Jmol/l olivat korkeimmillaan kesallå ja syksylla ja laskivat talvella. Alhaisimmat pitoisuudet mitattiin nålkiintyneille vaatimille kevaalla. Seerumin korkeat ureapitoisuudet ja CPK, LDH ja SAP aktiivisuudet kuvastivat kehon valkuaisten ja kudosten hajoamista nalkiintymisen aikana. Vuodenajoilla ja ravinnolla ei ollut vaikutusta seerumin T4-, kreatiniini-, natrium- ja kloridipitoisuuksiin. Korkeat ruumiinpainot ja veren kemialliset arvot mitattiin vaatimille, joita ruokittiin sailorehulla ja melassileikkeellå talvella.Renblod. II. Blodkemi.Abstract in Swedish / Sammandrag: Den kemiska sammansattningen av blodet hos 578 halvvilda vajor undesoktes under år 1973 — 1979 med hanvisning till ålder, årstid, kalvning och nåringstillstånd. Viktokningen var storst, 400 g/dygn, vid en ålder av 4 — 8 veckor. Detta återspeglades aven i de hoga varden av serumthyroxin (TV, alkalfosfatas (SAP, kreatininfosfokinas (CPK och i blodsockerhalten. Den låga SAP-aktiviteten under vintern var ett tecken på att tillvåxten stannat. Vårdet av pH i venblodet var 7,46 och koagulationskapaciteten (21 sek, 100% var mycket hog under sommaren och hosten. 15 olika åggviteåmnen och 15 fettsyror skiljdes ur serum. Halten av åggviteåmnen i serum var 58 g/1 vid en ålder av 20 dygn och 87 g/1 hos vajorna på hosten. Skillnaden berodde på forandringen i globulinmångden. Foråndringarna hos immunoglobulinerna påvisar, att kalven får sin motståndsformåga efter fodseln ur vajans mjolk och att kalven sjålv borjar producera gammaglobuliner forst då den nått en ålder av 4 veckor. Den nyfodda kalvens serumlipider (2,9 g/1, triglycerider (0,29 mmol/1, och kolesterol (1,6 mmol/1 var tåmligen låga och