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Sample records for ca sc ti

  1. Particle-hole configurations and energy spectra of 42Ca, 42Sc and 42Ti nuclei

    International Nuclear Information System (INIS)

    Shell-model calculations are performed to investigate the level structure in 42Ca, 42Sc and 42Ti nuclei. The shell model states are expressed for two-particle, particle-hole and three-particle one-hole configurations in terms of coupled two-particle states. We have used the modified surface-delta interaction, pairing and Coulomb interaction in this calculation. The configurations considered are 1f7/2, 2p3/2 and 1d3/2 Single-particle energies and parameters of the interaction are determined by least-squares fitting procedure. The resulting two-body matrix elements are applied to calculate the energy spectra of two-particle states and three-particle one-hole states in 42Ca, 42Sc and 42Ti nuclei

  2. No-Core Shell Model for 48-Ca, 48-Sc and 48-Ti

    Energy Technology Data Exchange (ETDEWEB)

    Popescu, S; Stoica, S; Vary, J P; Navratil, P

    2004-10-26

    The authors report the first no-core shell model results for {sup 48}Ca, {sup 48}Sc and {sup 48}Ti with derived and modified two-body Hamiltonians. We use an oscillator basis with a limited {bar h}{Omega} range around 40/A{sup 1/3} = 11 MeV and a limited model space up to 1 {bar h}{Omega}. No single-particle energies are used. They find that the charge dependence of the bulk binding energy of eight A = 48 nuclei is reasonably described with an effective Hamiltonian derived from the CD-Bonn interaction while there is an overall underbinding by about 0.4 MeV/nucleon. However, resulting spectra exhibit deficiencies that are anticipated due to: (1) basis space limitations and/or the absence of effective many-body interactions; and, (2) the absence of genuine three-nucleon interactions. They introduce phenomenological modifications to obtain fits to total binding and low-lying spectra. The resulting no-core shell model opens a path for applications to experiments such as the double-beta ({beta}{beta}) decay process.

  3. Particle-hole configurations and energy spectra of sup 4 sup 2 Ca, sup 4 sup 2 Sc and sup 4 sup 2 Ti nuclei

    CERN Document Server

    Kim, M W

    1996-01-01

    Shell-model calculations are performed to investigate the level structure in sup 4 sup 2 Ca, sup 4 sup 2 Sc and sup 4 sup 2 Ti nuclei. The shell model states are expressed for two-particle, particle-hole and three-particle one-hole configurations in terms of coupled two-particle states. We have used the modified surface-delta interaction, pairing and Coulomb interaction in this calculation. The configurations considered are 1f sub 7 sub / sub 2 , 2p sub 3 sub / sub 2 and 1d sub 3 sub / sub 2 Single-particle energies and parameters of the interaction are determined by least-squares fitting procedure. The resulting two-body matrix elements are applied to calculate the energy spectra of two-particle states and three-particle one-hole states in sup 4 sup 2 Ca, sup 4 sup 2 Sc and sup 4 sup 2 Ti nuclei.

  4. The Feasibility of direct measurement of the {sup 44}Ti(α, p){sup 47}V and {sup 40}Ca(α, p){sup 43}Sc reactions in forward kinematics at astrophysically relevant temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Al-Abdullah, T. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Dresden (Germany); The Hashemite University, Physics Department, P.O. Box 150459, Zarqa (Jordan); Akhmadaliev, S.; Bemmerer, D.; Sobiella, M. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Dresden (Germany); Ayranov, M. [Directorate-General for Energy, European Commission, Luxembourg (Luxembourg); Dressler, R.; Schumann, D.; Stowasser, T. [Paul Scherrer Institute, Laboratory of Radiochemistry and Environmental Chemistry, Villigen PSI (Switzerland); Elekes, Z. [Institute for Nuclear Research of the Hungarian Academy of Sciences (MTA ATOMKI), Debrecen (Hungary); Kivel, N. [Paul Scherrer Institute, Nuclear Energy and Safety, Hot Laboratory Division, Villigen PSI (Switzerland); Schmidt, K.; Takacs, M.P. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Dresden (Germany); Technische Universitaet Dresden, Institute of Nuclear and Particle Physics, Dresden (Germany); Zuber, K. [Technische Universitaet Dresden, Institute of Nuclear and Particle Physics, Dresden (Germany)

    2014-09-15

    Understanding the synthesis of radioactive {sup 44}Ti in the α-rich freeze-out following core-collapse supernovae may help to better interpret such explosive events. The γ-ray lines from the decay of {sup 44}Ti have been observed by space-based γ-ray telescopes from two supernova remnants. It is believed that the {sup 44}Ti(α, p){sup 47}V reaction dominates the destruction of {sup 44}Ti, while the {sup 40}Ca(α, p){sup 43}Sc reaction removes fuel from the main {sup 44}Ti production reaction {sup 40}Ca(α, γ){sup 44}Ti. Here we report on a possible technique to determine both reaction rates at astrophysically relevant energies in forward kinematics. The first reaction will be performed using a 1-10 MBq {sup 44}Ti target. Two important concerns are considered to make this study possible: The amount of stable Ti in the radioactive target, which will be prepared via spallation reactions at Paul Scherrer Institute (PSI), and the degree of radioactive contaminations in the experimental setup due to sputtered {sup 44}Ti atoms after intensive irradiations. Several online and offline measurements in parallel with Monte Carlo simulations were performed to investigate these issues. (orig.)

  5. The Feasibility of direct measurement of the 44Ti(α, p)47V and 40Ca(α, p)43Sc reactions in forward kinematics at astrophysically relevant temperatures

    International Nuclear Information System (INIS)

    Understanding the synthesis of radioactive 44Ti in the α-rich freeze-out following core-collapse supernovae may help to better interpret such explosive events. The γ-ray lines from the decay of 44Ti have been observed by space-based γ-ray telescopes from two supernova remnants. It is believed that the 44Ti(α, p)47V reaction dominates the destruction of 44Ti, while the 40Ca(α, p)43Sc reaction removes fuel from the main 44Ti production reaction 40Ca(α, γ)44Ti. Here we report on a possible technique to determine both reaction rates at astrophysically relevant energies in forward kinematics. The first reaction will be performed using a 1-10 MBq 44Ti target. Two important concerns are considered to make this study possible: The amount of stable Ti in the radioactive target, which will be prepared via spallation reactions at Paul Scherrer Institute (PSI), and the degree of radioactive contaminations in the experimental setup due to sputtered 44Ti atoms after intensive irradiations. Several online and offline measurements in parallel with Monte Carlo simulations were performed to investigate these issues. (orig.)

  6. Photoionization study of Ne-like K9+, Ca10+, Sc11+, Ti12+, V13+, Cr14+, Mn15+, and Fe16+ ions using the screening constant by unit nuclear charge method

    Science.gov (United States)

    Goyal, Arun; Khatri, Indu; Sow, Malick; Sakho, Ibrahima; Aggarwal, Sunny; Singh, A. K.; Mohan, Man

    2016-08-01

    Photoionization of the 2s22p6 (1S0) ground state of the Ne-like (Z=19-29) ions is presented in this paper. Resonance energies and total natural width of the 2s2p6np 1P series of the Ne-like K9+, Ca10+, Sc11+, Ti12+, V13+, Cr14+, Mn15+, and Fe16+are reported. All the calculations are made using the Screening constant by unit nuclear charge (SCUNC) formalism. New data for Ne-like K9+, Sc11+, Ti12+, V13+, Cr14+, and Mn15+ions are tabulated. Good agreements are found with available literature data.

  7. Yield measurements in the reactions 48Ca(p,γ)49Sc and 48Ca(p,n)48Sc

    International Nuclear Information System (INIS)

    Absolute cross sections for the reactions 48Ca(p,γ)49Sc and 48Ca(p,n)48Sc have been measured for proton bombarding energies from 0.76 MeV to 2.20 MeV. The results are in satisfactory agreement with predictions of the Hauser-Feshback statistical model of nuclear reactions. In particular, the predicted flattening out of the (p,γ) cross section above the threshold for the (p,n3) channel is consistent with the data

  8. 47Ca production for 47Ca/47Sc generator system using electron linacs

    International Nuclear Information System (INIS)

    In this work we have studied the feasibility of photonuclear production of 47Ca from 48Ca for 47Ca/47Sc generators. Photon flux distribution for electron beams of different energies incident on a tungsten converter was calculated using the MCNPX radiation transport code. The 47Ca production rate dependence on electron beam energy was found and 47Ca/47Sc yields were estimated for a 40 MeV electron beam. It was shown that irradiating enriched targets with a 40 MeV, 1 mA beam will result in tens of MBq g−1 (few mCi g−1) activity of 47Sc. The results of the simulations were benchmarked by irradiating 22.5 g of CaCl2 powder with a 39 MeV electron beam incident on a tungsten converter. Measured 47Ca/47Sc activities were found to be in very good agreement with the predictions. - Highlights: • We have evaluated the 47Ca production rate using 48Ca(γ,n)47Ca reaction for different electron beam energies and have constructed “parent”-“daughter” activity curves to estimate 47Sc yields. • We have shown the advantages of irradiating a 48Ca target in comparison to natural calcium target • To verify the predicted yield values we have irradiated 22.5 g of calcium chloride (natCaCl2) powder using 39 MeV, 12.5 μA electron beam and found the results to be in a good agreement with the simulations • We have shown that irradiating a 48Ca target with a 40 MeV 1 mA beam will result in tens of MBq g−1 (~ mCi g−1) activity of 47Sc

  9. Cyclotron production of high purity 44m,44Sc with deuterons from 44CaCO3 targets

    International Nuclear Information System (INIS)

    Introduction: Due to its longer half-life, 44Sc (T1/2 = 3.97 h) as a positron emitter can be an interesting alternative to 68Ga (T1/2 = 67.71 min). It has been already proposed as a PET radionuclide for scouting bone disease and is already available as a 44Ti/44Sc generator. 44Sc has an isomeric state, 44mSc (T1/2 = 58.6 h), which can be co-produced with 44Sc and that has been proved to be considered as an in-vivo PET generator 44mSc/44Sc. This work presents the production route of 44mSc/44Sc generator from 44Ca(d,2n), its extraction/purification process and the evaluation of its performances. Methods: Irradiation was performed in a low activity target station using a deuteron beam of 16 MeV, which favors the number of 44mSc atoms produced simultaneously to 44Sc. Typical irradiation conditions were 60 min at 0.2 μA producing 44 MBq of 44Sc with a 44Sc/44mSc activity ratio of 50 at end of irradiation. Separations of the radionuclides were performed by means of cation exchange chromatography using a DGA® resin (Triskem). Then, the developed process was applied with bigger targets, and could be used for preclinical studies. Results: The extraction/purification process leads to a radionucleidic purity higher than 99.99% (43Sc, 46Sc, 48Sc < DL). 44mSc/44Sc labeling towards DOTA moiety was performed in order to get an evaluation of the specific activities that could be reached with regard to all metallic impurities from the resulting source. Reaction parameters of radiolabeling were optimized, reaching yields over 95%, and leading to a specific activity of about 10–20 MBq/nmol for DOTA. A recycling process for the enriched 44Ca target was developed and optimized. Conclusion: The quality of the final batch with regard to radionucleidic purity, specific activity and metal impurities allowed a right away use for further radiopharmaceutical evaluation. This radionucleidic pair of 44mSc/44Sc offers a quite interesting PET radionuclide for being further evaluated as an in

  10. Structural, elastic and thermodynamic properties of Ti2SC

    Indian Academy of Sciences (India)

    Hongzhi Fu; Wenfang Liu; Tao Gao

    2011-12-01

    The structural parameters, elastic constants and thermodynamic properties of Ti2SC were investigated under pressure and temperature by using first-principles plane-wave pseudopotential density functional theory within the generalized gradient approximation. The obtained results are in agreement with the available experimental data. The bulk moduli along the - and -axes, $B_{a}$ and $B_{c}$, almost linearly increase with pressure, and the former is always smaller than the latter. The ratio of $B_{c}/B_{a}$ has a trend of gradual increase as the pressure increases. It is found that the elastic constants, anisotropy and Debye temperature of Ti2SC increase with pressure, while axial compressibility along the - and -axes decreases with pressure. The thermal properties including the equation of state, the Grüneisen parameter , the anisotropies $\\Delta_{p}, \\Delta_{S1}$ and $\\Delta_{S2}$, and the heat capacity are estimated at various pressures and temperatures.

  11. First-principles study of Sc-doping effect on the stability, electronic structure and photocatalytic properties of Sr2TiO4

    International Nuclear Information System (INIS)

    The stability, electronic structure and photocatalytic properties of the Sc-doped Sr2TiO4 are investigated by first-principles calculations based on the density functional theory. The calculated results reveal that due to the electronic changes from doping, the stability of Sr2Sc0.125Ti0.875O4 is weakened after Sc doping. Meanwhile, because the increase value of lattice parameter a is larger than that of lattice parameter c, the value of c/a decreases to 3.209 and is smaller than that of undoped Sr2TiO4. The band gap of Sr2Sc0.125Ti0.875O4 has a narrowing about 0.25 eV compared with that of undoped Sr2TiO4, resulting in the red-shift of absorption spectra edge. Particularly, the dispersion of the conduction bands and valence bands of Sr2Sc0.125Ti0.875O4 is enhanced after doping, which is preferable for the photocatalytic performance. In addition, a new weak absorption appears in the visible light region, which would somehow contribute to the photocatalytic activity of Sr2Sc0.125Ti0.875O4. - Highlights: • The Sc-doped Sr2TiO4 are thermodynamically stable. • The dispersion of the band structure of Sr2Sc0.125Ti0.875O4 is enhanced. • A new weak absorption appears in the visible light region. • The Sc doping can contribute to the photocatalytic activity of Sr2Sc0.125Ti0.875O4

  12. Enhanced hardness in epitaxial TiAlScN alloy thin films and rocksalt TiN/(Al,Sc)N superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Bivas [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Lawrence, Samantha K.; Bahr, David F. [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Schroeder, Jeremy L.; Birch, Jens [Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Sands, Timothy D. [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2014-10-13

    High hardness TiAlN alloys for wear-resistant coatings exhibit limited lifetimes at elevated temperatures due to a cubic-AlN to hexagonal-AlN phase transformation that leads to decreasing hardness. We enhance the hardness (up to 46 GPa) and maximum operating temperature (up to 1050 °C) of TiAlN-based coatings by alloying with scandium nitride to form both an epitaxial TiAlScN alloy film and epitaxial rocksalt TiN/(Al,Sc)N superlattices on MgO substrates. The superlattice hardness increases with decreasing period thickness, which is understood by the Orowan bowing mechanism of the confined layer slip model. These results make them worthy of additional research for industrial coating applications.

  13. Thermodynamic properties of CaTiF5(s)

    International Nuclear Information System (INIS)

    Calcium titanofluoride CaTiF5(s) was prepared by solid-state reaction of CaF2(s) with TiF3(s) and characterized by X-ray diffraction method. The standard molar isobaric heat capacity (Cp,mo) of CaTiF5(s) was determined by a power compensated differential scanning calorimeter in the temperature from 230K to 710K. A solid-state galvanic cell with CaF2 as electrolyte was used to determine the standard molar Gibbs energy of formation (ΔfGmo) of CaTiF5 in the temperature range from 803K to 1005K. The galvanic cell can be depicted as:(-)Pt,O2(g,101.325kPa)/{CaO(s)+CaF2(s)}//CaF2//{CaTiF5(s)+CaTiO3(s)}/O2 (g,101.325kPa),Pt(+)The second law analysis of present data were carried out to derive the standard entropy Smo(298.15K) and the enthalpy of formation ΔfHmo (298.15K) and the values derived are 68.7J.K-1.mol-1 and -2848.4kJ.mol-1, respectively

  14. Piezoelectric and Dielectric Properties of Multilayered BaTiO3/(Ba,Ca)TiO3/CaTiO3 Thin Films.

    Science.gov (United States)

    Zhu, Xiao Na; Gao, Ting Ting; Xu, Xing; Liang, Wei Zheng; Lin, Yuan; Chen, Chonglin; Chen, Xiang Ming

    2016-08-31

    Highly oriented multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films were fabricated on Nb-doped (001) SrTiO3 (Nb:STO) substrates by pulsed laser deposition. The configurations of multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films are designed with the thickness ratio of 1:1:1 and 2:1:1 and total thickness ∼300 nm. Microstructural characterization by X-ray diffraction indicates that the as-deposited thin films are highly c-axis oriented and large in-plane strain is determined in BaTiO3 and CaTiO3 layers. Piezoresponse force microscopy (PFM) studies reveal an intense in-plane polarization component, whereas the out-of-plane shows inferior phase contrast. The optimized combination is found to be the BaTiO3-(Ba0.85Ca0.15)TiO3-CaTiO3 structure with combination ratio 2:1:1, which displays the largest domain switching amplitude under DC electric field, the largest room-temperature dielectric constant ∼646, a small dielectric loss of 0.03, and the largest dielectric tunability of ∼50% at 400 kV/cm. These results suggest that the enhanced dielectric and tunability performance are greatly associated with the large in-plane polarization component and domain switching. PMID:27514235

  15. Structural, electronic and elastic properties of M2SC (M = Ti, Zr, Hf) compounds

    International Nuclear Information System (INIS)

    Using ab initio calculations, we have studied the structural, electronic and elastic properties of M2SC, with M = Ti, Zr and Hf. Geometrical optimization of the unit cell are in good agreement with the available experimental data. The band structures show that all three materials are conducting. The analysis of the site and momentum projected densities shows that the bonding is achieved through a hybridization of M-atom d states with S and C-atom p states. The Md-Sp bonds are lower in energy and are stiffer than Md-Cp bonds. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young's moduli and Poisson's ratio for ideal polycrystalline M2SC aggregates. We estimated the Debye temperature of M2SC from the average sound velocity. This is a quantitative theoretical prediction of the elastic properties of Ti2SC, Zr2SC, and Hf2SC compounds, and it still awaits experimental confirmation

  16. The first principle study of Ni2ScGa and Ni2TiGa

    International Nuclear Information System (INIS)

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni2TiGa and Ni2ScGa alloys in the cubic L21 structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C11, C12 and C44. We calculated elastic constants in L21 structure for Ni2TiGa and Ni2ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni2TiGa, Ni 3d states and Sc 3d states for Ni2ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni2TiGa, 0.76 states/eV Cell for Ni2ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L21 phase is unstable since the phonon calculations have imagine modes

  17. Electronic structure of new mixed Ti13MC13 nanocrystallites (M = Sc, V, ..., Cu)

    International Nuclear Information System (INIS)

    The electron structure of the series of new Ti13MC13 metal-carbon molecular nanocrystallites is studied through the ab initio self-consistent discrete variation method. The third order metals (Sc, V, ..., Cu) are considered as the M-elements. The regularities of forming the electron structure, chemical bonds, charge distributions and atomic magnetic moments in the Ti13MC13 in dependence on the M-atom type and its position in the source Ti14C13 nanocrystallite are forecasted. The obtained results are compared with the electron states calculations of the 3d-admixtures in the crystalline titanium carbide

  18. Strength of the $E_{\\text{p}}$=1.842 MeV resonance in the $^{40}$Ca(p,$\\gamma$)$^{41}$Sc reaction revisited

    CERN Document Server

    Schmidt, Konrad; Anders, Michael; Bemmerer, Daniel; Caciolli, Antonio; Dietz, Mirco; Elekes, Zoltán; Junghans, Arnd R; Menzel, Marie-Luise; Schwengner, Ronald; Wagner, Andreas; Zuber, Kai

    2014-01-01

    The strength of the $E_{\\rm p} = 1.842$ MeV resonance in the $^{40}$Ca(p,$\\gamma$)$^{41}$Sc reaction is determined with two different methods: First, by an absolute strength measurement using calcium hydroxide targets, and second, relative to the well-determined strength of the resonance triplet at $E_\\alpha$ = 4.5 MeV in the $^{40}$Ca($\\alpha$,$\\gamma$)$^{44}$Ti reaction. The present new value of $\\omega\\gamma=(0.192\\pm0.017)$ eV is 37% (equivalent to $3.5\\sigma$) higher than the evaluated literature value. In addition, the ratio of the strengths of the 1.842 MeV $^{40}$Ca(p,$\\gamma$)$^{41}$Sc and 4.5 MeV $^{40}$Ca($\\alpha$,$\\gamma$)$^{44}$Ti resonances has been determined to be $0.0229\\pm0.0018$. The newly corrected strength of the 1.842-MeV resonance can be used in the future as a normalization point for experiments with calcium targets.

  19. Phase diagram of the system Ca-Ti-O at 1200 K

    OpenAIRE

    Jacob, KT; Gupta, Sapna

    2009-01-01

    Phase relations in the system Ca-Ti-O have been established by equilibration of several samples at 1200 K for prolonged periods and identification of phases in quenched samples by optical and scanning electron microscopy, XRD and EDS. Samples representing 20 compositions in the ternary system were analyzed. There was negligible solid solubility of Ca in the phases along the binary Ti-O, and of Ti in CaO. Four ternary oxides were identified: CaTiO3, Ca4Ti3O10 and Ca3Ti2O7 containing tetravalen...

  20. Apparent vanishing of ferroelectricity in nanostructured BiScO3PbTiO3

    OpenAIRE

    Amorín, H.; R. Jiménez; Ricote, J.; Hungría, T; de Castro, A.; Algueró, M.

    2010-01-01

    Abstract Nanostructured ceramics of high-temperature piezoelectric 0.375BiScO 3 -0.625PbTiO 3 were prepared by spark plasma sintering of nanocrystalline powders obtained by mechanosynthesis. The macroscopic electrical properties were characterized on dense ceramics with decreasing average grain size down to 28 nm. Results indicate that the electric field is screened by the electrically insulating grain boundaries at the nanoscale, which needs to be considered when discussing size effects i...

  1. Cross section measurement for 45Sc(p,γ)46Ti

    International Nuclear Information System (INIS)

    The cross section of the reaction 45Sc(p,γ)46Ti has been measured over the bombarding energy range 0.7 - 4.2 MeV. This energy range is appropriate for calculating the interaction rate in a stellar interior over the temperature range 109 - 1010K. The results are compared with predictions of the statistical model of nuclear reactions. Stellar interaction rates are calculated

  2. Microstructure and transformation behavior of Ni24.7Ti50.3Pd25 high temperature shape-memory alloy with Sc micro-addition

    International Nuclear Information System (INIS)

    NiTiPd shape-memory alloys (SMAs) are potential functional materials for use as solid-state actuators in the temperature range 100–250 °C. The present study investigates the effect of 1.0 at.% Sc micro-addition to Ni24.7Ti50.3Pd25 alloy, Sc replacing either Ti or Ni. Results show that all the three alloys studied have stable transformation behavior on stress-free thermal cycling and hence, are suitable for cyclic actuation applications. However, the addition of Sc to NiTiPd alloy leads to decrease of transformation temperatures, the magnitude of decrease being greater for the alloy with Sc replacing Ni. The martensite finish (Mf) temperature of 181 °C for the NiTiPd alloy decreased to 139 °C for Sc replacing Ti and 83 °C for Sc replacing Ni. Also, the indentation modulus of NiTiPdSc (Sc replacing Ni) alloy is found to be significantly low compared to the other alloys. Analysis indicates that the observed differences in the alloy properties are related to the solubility of Sc in the NiTiPd matrix. While the quaternary NiTiPdSc alloy, Sc replacing Ti, has a single phase microstructure, the alloy with Sc replacing Ni shows the presence of Sc-rich and TiPd-type second phases in the microstructure. TEM examination revealed that the TiPd-type phase has a distinct rod-like morphology (30–50 nm) arranged in a grid-like structure. The transformation and indentation behavior of the alloys is elucidated using thermodynamic calculations of frictional energy and an electronic structure based analysis. - Highlights: • TEM of Ni23.7Ti50.3Pd25Sc1 showed distinct grid of TiPd-type phase nanorods < 50 nm. • Stress-free thermal cycling of all the three alloys showed stable transformation behavior. • Ni24.7Ti49.3Pd25Sc1 and Ni23.7Ti50.3Pd25Sc1 showed single and multiphase structures. • Sc micro-addition (1 at.%) to Ni24.7Ti50.3Pd25 alloy decreased TTs significantly. • Ni23.7Ti50.3Pd25Sc1 exhibited lower modulus of 67 GPa to 85 GPa of Ni24.7Ti50.3Pd25

  3. Microstructural and high temperature deformation characterization of Ti-45Al-3Nb-(Cr, Mn, Mo, Sc) alloy

    International Nuclear Information System (INIS)

    Research highlights: → Complex microalloying increased remarkably the high temperature strength of Ti-45Al-3Nb alloy. → Strength increase was attributed to microstructural refinement, dispersive and solution strengthening effects. → The ductility of Ti45Al3Nb was remarkably enhanced owing to improvement of inhomogeneous distribution of electron cloud. - Abstract: The effect of complex microalloying by combinative additions of Nb, Sc, Mn, Cr and Mo to the directionally solidified Ti-45Al alloys on microstructures and mechanical properties has been examined in the present study. It is shown that a respective microstructure of fully lamellar for Ti-45Al-3Nb and Ti-45Al-3Nb-0.5Sc and basket weave type for Ti-45Al-3Nb-2Cr-2Mo-1Mn-0.5Sc were observed. The high temperature strength of Ti-45Al-3Nb alloy is improved via dispersive strengthening effect of fine Ti3(Al,Sc) dispersoids and solution strengthening effect from the other alloying elements. Enhanced ductility of Ti-45Al-3Nb alloy was achieved by Cr, Mn and Mo combinative additions.

  4. Preparation of CaCu3Ti4O12 using a wet chemical method

    International Nuclear Information System (INIS)

    CaCu3Ti4O12 was synthesized starting from a solution of TiO2 to which Ca and Cu nitrates were added. Due to the differences in the solubilities of the Ca, Cu and Ti, initial variations from ideal stoichiometry and a high solution pH was necessary to obtain stoichiometric CaCu3Ti4O12 precipitates. As precipitated samples were amorphous with CuO phases observed after drying of the precipitates at 300 degree C. CaCu3Ti4O12 phases was observed after heat treatment at 1000 degree C. XRD studies show the presence of CuO and TiO2 in addition to the CaCu3Ti4O12 for non-stoichiometric samples. Observations under the SEM show the presence of Cu rich and Ti rich phases in addition to the CaCu3Ti4O12. (Author)

  5. Scandium(iii) complexes of monophosphorus acid DOTA analogues: a thermodynamic and radiolabelling study with (44)Sc from cyclotron and from a (44)Ti/(44)Sc generator.

    Science.gov (United States)

    Kerdjoudj, R; Pniok, M; Alliot, C; Kubíček, V; Havlíčková, J; Rösch, F; Hermann, P; Huclier-Markai, S

    2016-01-19

    The complexation ability of DOTA analogs bearing one methylenephosphonic (DO3AP) or methylenephosphinic (DO3AP(PrA) and DO3AP(ABn)) acid pendant arm toward scandium was evaluated. Stability constants of their scandium(iii) complexes were determined by potentiometry combined with (45)Sc NMR spectroscopy. The stability constants of the monophosphinate analogues are somewhat lower than that of the Sc-DOTA complex. The phosphorus acid moiety interacts with trivalent scandium even in very acidic solutions forming out-of-cage complexes; the strong affinity of the phosphonate group to Sc(iii) precludes stability constant determination of the Sc-DO3AP complex. These results were compared with those obtained by the free-ion selective radiotracer extraction (FISRE) method which is suitable for trace concentrations. FISRE underestimated the stability constants but their relative order was preserved. Nonetheless, as this method is experimentally simple, it is suitable for a quick relative comparison of stability constant values under trace concentrations. Radiolabelling of the ligands with (44)Sc was performed using the radioisotope from two sources, a (44)Ti/(44)Sc generator and (44m)Sc/(44)Sc from a cyclotron. The best radiolabelling conditions for the ligands were pH = 4, 70 °C and 20 min which were, however, not superior to those of the parent DOTA. Nonetheless, in vitro behaviour of the Sc(iii) complexes in the presence of hydroxyapatite and rat serum showed sufficient stability of (44)Sc complexes of these ligands for in vivo applications. PET images and ex vivo biodistribution of the (44)Sc-DO3AP complex performed on healthy Wistar male rats showed no specific bone uptake and rapid clearance through urine. PMID:26675416

  6. The consistency of the data for neutron fission averaged cross-sections of threshold reactions: A study on the cross-section of 46Ti(n,p)46Sc, 47Ti(n,p)47Sc, 48Ti(n,p)48Sc and 64Zn(n,p)64Cu reactions

    International Nuclear Information System (INIS)

    The consistency of the published values for fission averaged cross-sections of threshold reactions induced in a nuclear reactor is analyzed. The influence of the literature data involved in the determination of these cross-sections is discussed. Renormalizations based on cross-sections value for the standard reactions, isotopic abundances of the precursors and radiation emission probabilities of the radionuclide under study and the monitor, are applied to the evaluation of the cross-sections for the reactions: 46Ti(n,p)46Sc; 47Ti(n,p)47Sc; 48Ti(n,p)48Sc; and 64Zn(n,p)64Cu. - Highlights: • Some published data on cross-sections averaged over a fission spectrum are analyzed. • The reactions were 46Ti(n,p)46Sc; 47Ti(n,p)47Sc; 48Ti(n,p)48Sc and 64Zn(n,p)64Cu. • Renormalization as a function of five critical parameters was performed. • Averages of the renormalized values were calculated and the results discussed

  7. Fundamental studies of H2 interaction with MAl3 clusters [M = Li, Sc, Ti, Zr

    International Nuclear Information System (INIS)

    Highlights: • A first-principles calculation on H2 interaction and saturation on stable MAl3 clusters [M = Li, Sc, Ti, Zr] is performed. • Transition metals have negative electron charge density while Al atom has positive in MAl3 from NBO charge analysis. • H2 undergoes dissociative chemisorption on the M atop site resulting in M–H–Al bridge bond. • H2 saturation on M atop site results initially chemisorption and then physisorption with 3-centered Kubas interaction. • External electric field applied on TiAl3H4 leads to more polarization, H2 bond elongation and increased adsorption energy. -- Abstract: Complex metal hydride is a promising hydrogen storage material for automobile applications due to its reversible storage capacity. The presence of transition metal halide is found to improve significantly the kinetics of H2 adsorption and desorption processes. Experimental studies have indicated the formation of distorted MAl3 phase where M = Sc, Ti, Zr. In this study, a first-principles density functional study has been performed to investigate the hydrogen interaction and saturation on stable tetrahedral MAl3 clusters [M = Li, Sc, Ti, and Zr] by employing spin-polarized hybrid and non-local density functionals. On saturation, the first H2 molecule undergoes chemisorption in the transition metals while further loading results in physisorption with the Kubas-type H2 interaction. Activation energy barrier for the H2 dissociation over the cluster is calculated to be ∼0.2 eV for the transition metals. Effect of external electric field on the MAl3H4 cluster with molecular H2 is studied which leads to polarization of physisorbed H2 and the cluster. The results offer an explanation for catalysts role in improving the kinetics of H2 sorption process in complex metal hydrides

  8. Doping of BiScO3-PbTiO3 Ceramics for Enhanced Properties

    Science.gov (United States)

    Sehirlioglu, Alp; Sayir, Ali; Dynys, Fred

    2008-01-01

    High-temperature piezoelectrics are a key technology for aeronautics and aerospace applications such as fuel modulation to increase the engine efficiency and decrease emissions. The principal challenge for the insertion of piezoelectric materials is the limitation on upper use temperature which is due to low Curie-Temperature (T(sub c) and increasing electrical conductivity. BiScO3 -PbTiO3 (BS-PT) system is a promising candidate for improving the operating temperature for piezoelectric actuators due to its high TC (>400 C). Effects of Zr and Mn doping of the BS-PT ceramics have been studied and all electrical and electromechanical properties for Sc-deficient and Ti-deficient BS- PT ceramics are reported as a function of electrical field and temperature. Donor doping with Zr and Mn (in Sc deficient compositions) increased the DC-resistivity and decreased tan at all temperatures. Resulting ceramics exhibited saturated hysteresis loops with low losses and showed no dependence on the applied field (above twice the coercive field) and measurement frequency.

  9. Synthesis and characterization of CTO (CaTiO3)

    International Nuclear Information System (INIS)

    The objective of this work is to study the ceramic material CTO (CaTiO3) by X-Ray Diffraction. The composites of CTO are widely used in dielectric resonators in communication systems. The CTO was prepared by solid state method in a planetary high energy ball milling (Fritsch Pulverisette 5). Stoichiometric quantities of CaCO3 (Aldrich 99%) and TiO2 (Merck 99%) were dry milled during 4h with a rotational speed of 370 rpm and then calcined at 1000 deg C for 3h. After, the CTO was studied by X-ray diffraction (XRD). The refinement showed that the CTO was formed with 100% mass, the graph of Williamson-Hall showed a homogeneous sample, with a contraction in the crystal lattice and a reasonably small particle size. (author)

  10. Computational investigation on MB n (M = Li-Cs, Be-Ba, Sc-La and Ti; n = 28 and 38).

    Science.gov (United States)

    Xu, Qianhui; Liu, Chang; Yang, Le; Jin, Peng; Tang, Chengchun; Chen, Zhongfang

    2016-08-01

    Differing from the weakly antiaromatic B80 buckyball, the medium-sized C 1-B28 and D 2h -B38, as well as their mono- to tetra-anions, are highly aromatic, as indicated by the negative nucleus-independent chemical shifts (NICSs) at their cage centers. The interior cavities and high aromaticity of the B28 and B38 cages render them very promising hosts to accommodate diverse metal atoms. Accordingly, we carried out systematic density functional theory (DFT) computations on the structures, stabilities and electronic properties of metalloborofullerenes MB n (M = Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La and Ti; n = 28 and 38). Among them, besides the recently reported M@B38(M = Sc, Y and Ti) [Lu et al. (2015) Phys Chem Chem Phys 17:20897-20902], Ti@B28 and M@B38 (M = Ca and La) also favor endohedral structures with large binding energies, and are suggested promising targets for experimental applications. Note that Ti@B28 is the first endohedral derivative based on the new B28 fullerene, and La@B38 features the largest metal size inside a B38 cage thus far. These endohedral derivatives, as exemplified by Ca@B38, may exhibit σ and π double aromaticity over the whole cage surface, indicating their considerable stability. In contrast, the other metals prefer to reside at the exterior cage surface, due mainly to the mismatch of their sizes with the boron cages, though the size match is not the only factor to determine their doping form. Furthermore, the infrared absorption spectra and (11)B nuclear magnetic resonance spectra of the three new M@B n complexes were computed to assist future experimental characterization. Graphical Abstract Putting more metals into medium-sized boron cages! PMID:27424298

  11. Interface enhanced functionalities in BaTiO3/CaTiO3 superlattices

    Science.gov (United States)

    Wu, Xifan

    2014-03-01

    Interface engineering of oxide thin films has led to the development of many intriguing physical properties and new functionalities, in which the oxygen rotation and tilting take an crucial role. The oxygen octahedral tilt has been considered to be a coherent motion in the oxide thin-films, based on which the tilt is often neglected in the modeling of ABO3 superlattices. However, combined with state-of-art experimental high-resolution electron microscopic image, our first-principles results clearly show that oxygen octahedral tilt should be more appropriately defined by the tilting angles of two individual pyramids. Each pyramid will tilt rather independently as a function of its local chemical environment. Considering the oxygen octahedral rotation at the same time, the new picture of oxygen octahedral tilting will induce a novel interface effect, in which an unstable structure in bulk CaTiO3 will be stabilized at the interface in BaTiO3/CaTiO3 superlattice. This novel interface effect induces large polarizations both in-plane and out-of-plane with a corresponding enhanced piezoelectricity. The above scenario successfully explains the recent experimental discoveries in BaTiO3/CaTiO3 superlattices by H. Lee's and P. Evan's groups respectively.

  12. Development of single chain variable fragment (scFv) antibodies against surface proteins of 'Ca. Liberibacter asiaticus'.

    Science.gov (United States)

    Yuan, Qing; Jordan, Ramon; Brlansky, Ronald H; Minenkova, Olga; Hartung, John

    2016-03-01

    'Candidatus Liberibacter asiaticus' is the causal agent of citrus huanglongbing, the most serious disease of citrus worldwide. We have developed and applied immunization and affinity screening methods to develop a primary library of recombinant single chain variable fragment (scFv) antibodies in an M13 vector, pKM19. The antibody population is enriched for antibodies that bind antigens of 'Ca. Liberibacter asiaticus'. The primary library has more than 10(7) unique antibodies and the genes that encode them. We have screened this library for antibodies that bind to specifically-chosen proteins that are present on the surface of 'Ca. Liberibacter asiaticus'. These proteins were used as targets for affinity-based selection of scFvs that bind to the major outer membrane protein, OmpA; the polysaccharide capsule protein KpsF; a protein component of the type IV pilus (CapF); and, two flagellar proteins FlhA and FlgI. These scFvs have been used in ELISA and dot blot assays against purified protein antigens and 'Ca. Liberibacter asiaticus' infected plant extracts. We have also recloned many of these scFvs into a plasmid expression vector designed for the production of scFvs. Screening of these scFvs was more efficient when phage-bound, rather than soluble scFvs, were used. We have demonstrated a technology to produce antibodies at will and against any protein target encoded by 'Ca. Liberibacter asiaticus'. Applications could include advanced diagnostic methods for huanglongbing and the development of immune labeling reagents for in planta applications. PMID:26744234

  13. Interface interaction and wetting of Sc2O3 exposed to Cu-Al and Cu-Ti melts

    International Nuclear Information System (INIS)

    Scandia is a thermodynamically stable oxide and could be used as a structural material for a crucible in order to avoid a melt contamination. In the present study wetting experiments of Cu-Al and Cu-Ti melts on Scandia substrate were preformed at 1423 K by a sessile drop method. It was established that Al and Ti additions lead to the improved wetting and that the final contact angle decreases with increasing the additives concentration. For Al containing melts, the contact angle changes gradually with time, and a relatively thick interaction layer, which consists of Al2O3, Sc2O3, and metallic channels, was formed at the Sc2O3/Cu-Al interface. For Ti containing melts, the final contact angle is achieved already during heating, and an extremely thin layer based on a Ti-Sc-O compound was detected by AES at the Sc2O3/Cu-Ti interface. The results of a thermodynamic analysis, which takes into account the formation free energy of the oxides, involved in the systems, and the thermodynamic properties of the liquid solutions are in a good agreement with the experimental observations. (orig.)

  14. Luminescence and energy transfer in Ca3Sc2Si3O12:Ce3+,Mn2+ white LED phosphors

    International Nuclear Information System (INIS)

    Expanded emission spectra ranging from green to red are reported in Ca3Sc2Si3O12 (CSS):Ce3+,Mn2+ silicate garnets. Mn2+ may occupy Ca2+ site (Mn2+(I)) to generate a yellow emission band at 574 nm or Sc3+ site (Mn2+(II)) with red emission band at 680 nm. Efficient energy transfers from the green emitting Ce3+ to both Mn2+(I) and Mn2+(II) occur upon blue excitation into Ce3+. Concentration dependence of Mn2+ emission is analyzed based on Ce3+–Mn2+ energy transfer, steady state rate equations, and fluorescence lifetimes. Energy transfer efficiency (ηT) and rate (W) are calculated with values as high as 45% and 14.01×106 s−1, respectively. - Highlights: ► Mn2+ can occupy Ca2+ site to generate a yellow emission band at 574 nm in Ca3Sc2Si3O12 (CSS). ► Mn2+ can also occupy Sc3+ site to generate a red emission band at 680 nm in CSS. ► Remarkable energy transfers (ETs) from Ce3+ to Mn2+ occur upon blue excitation into Ce3+ in CSS. ► Full color emissions are obtained based on Ce3+–Mn2+ ETs in CSS:Ce3+,Mn2+.

  15. Structures in the system CaTiO{sub 3}/SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Ball, C.J.; Begg, B.D.; Cookson, D.J.; Thorogood, G.J.; Vance, E.R. [ANSTO, Menai, New South Wales (Australia). Materials Div.

    1998-09-01

    At room temperature the sequence of phases with increasing amounts of strontium in the system CaTiO{sub 3}/SrTiO{sub 3} is orthorhombic (Pnma), orthorhombic (Bmmb), tetragonal (I4/mcm), and cubic (Pm3m). All phase boundaries shift toward smaller strontium contents with increase of temperature. Volume changes resulting from phase transformations are small for all compositions. Shape changes are greatest ({approximately}0.3%) for the Bmmb/I4/mcm transition, but would probably be accommodated by microtwinning and so are unlikely to affect the mechanical integrity of a specimen.

  16. The first principle study of Ni{sub 2}ScGa and Ni{sub 2}TiGa

    Energy Technology Data Exchange (ETDEWEB)

    Özduran, Mustafa [Ahi Evran Üniversitesi Fen Edebiyat Fakültesi Fizik Bölümü, Kırşehir (Turkey); Turgut, Kemal [Yüksek Lisans Öğrencisi, Kırşehir (Turkey); Arikan, Nihat [Ahi Evran Üniversitesi Eğitim Fakültesi İlköğretim Bölümü, Kırşehir (Turkey); İyigör, Ahmet; Candan, Abdullah [Ahi Evran Üniversitesi Merkezi Araştırma Laboratuvarı, Kırşehir (Turkey)

    2014-10-06

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni{sub 2}TiGa and Ni{sub 2}ScGa alloys in the cubic L2{sub 1} structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C{sub 11}, C{sub 12} and C{sub 44}. We calculated elastic constants in L2{sub 1} structure for Ni{sub 2}TiGa and Ni{sub 2}ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni{sub 2}TiGa, Ni 3d states and Sc 3d states for Ni{sub 2}ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni{sub 2}TiGa, 0.76 states/eV Cell for Ni{sub 2}ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L2{sub 1} phase is unstable since the phonon calculations have imagine modes.

  17. Cross-plane thermal conductivity of (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices

    Science.gov (United States)

    Saha, Bivas; Koh, Yee Rui; Comparan, Jonathan; Sadasivam, Sridhar; Schroeder, Jeremy L.; Garbrecht, Magnus; Mohammed, Amr; Birch, Jens; Fisher, Timothy; Shakouri, Ali; Sands, Timothy D.

    2016-01-01

    Reduction of cross-plane thermal conductivity and understanding of the mechanisms of heat transport in nanostructured metal/semiconductor superlattices are crucial for their potential applications in thermoelectric and thermionic energy conversion devices, thermal management systems, and thermal barrier coatings. We have developed epitaxial (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices with periodicity ranging from 1 nm to 240 nm that show significantly lower thermal conductivity compared to the parent TiN/(Al,Sc)N superlattice system. The (Ti,W)N/(Al,Sc)N superlattices grow with [001] orientation on the MgO(001) substrates with well-defined coherent layers and are nominally single crystalline with low densities of extended defects. Cross-plane thermal conductivity (measured by time-domain thermoreflectance) decreases with an increase in the superlattice interface density in a manner that is consistent with incoherent phonon boundary scattering. Thermal conductivity values saturate at 1.7 W m-1K-1 for short superlattice periods possibly due to a delicate balance between long-wavelength coherent phonon modes and incoherent phonon scattering from heavy tungsten atomic sites and superlattice interfaces. First-principles density functional perturbation theory based calculations are performed to model the vibrational spectrum of the individual component materials, and transport models are used to explain the interface thermal conductance across the (Ti,W)N/(Al,Sc)N interfaces as a function of periodicity. The long-wavelength coherent phonon modes are expected to play a dominant role in the thermal transport properties of the short-period superlattices. Our analysis of the thermal transport properties of (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices addresses fundamental questions about heat transport in multilayer materials.

  18. Biological properties of nanostructured Ti incorporated with Ca, P and Ag by electrochemical method

    Energy Technology Data Exchange (ETDEWEB)

    Li, Baoe; Hao, Jingzu; Min, Yang [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Xin, Shigang [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Guo, Litong [School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou 221116 (China); He, Fei [National Key Laboratory of C1 Chemical Industry, Tianjin University, Tianjin 300072 (China); Liang, Chunyong; Wang, Hongshui [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Li, Haipeng, E-mail: lhpcx@163.com [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)

    2015-06-01

    TiO{sub 2} nanotube arrays were synthesized on Ti surface by anodic oxidation. The elements of Ca and P were simultaneously incorporated during nanotubes growth in SBF electrolyte, and then Ag was introduced to nanotube arrays by cathodic deposition, which endowed the good osseointegration and antibacterial property of Ti. The bioactivity of the Ti surface was evaluated by simulated body fluid soaking test. The biocompatibility was investigated by in vitro cell culture test. And the antibacterial effect against Staphylococcus aureus was examined by the bacterial counting method. The results showed that the incorporation of Ca, P and Ag elements had no significant influence on the formation of nanotube arrays on Ti surface during electrochemical treatment. Compared to the polished or nanotubular Ti surface, TiO{sub 2} nanotube arrays incorporated with Ca, P and Ag increased the formation of bone-like apatite in simulated body fluid, enhanced cell adhesion and proliferation, and inhibited the bacterial growth. Based on these results, it can be concluded that the nanostructured Ti incorporated with Ca, P and Ag by electrochemical method has promising applications as implant material. - Highlights: • Nanotube arrays were prepared on Ti surface by anodic oxidation. • Ca, P and Ag were incorporated to nanotube arrays by electrochemical method. • Ca, P and Ag endowed Ti with good osseointegration and antibacterial property. • The beneficial effect of electrochemical treatment on Ti implant was demonstrated.

  19. Biological properties of nanostructured Ti incorporated with Ca, P and Ag by electrochemical method

    International Nuclear Information System (INIS)

    TiO2 nanotube arrays were synthesized on Ti surface by anodic oxidation. The elements of Ca and P were simultaneously incorporated during nanotubes growth in SBF electrolyte, and then Ag was introduced to nanotube arrays by cathodic deposition, which endowed the good osseointegration and antibacterial property of Ti. The bioactivity of the Ti surface was evaluated by simulated body fluid soaking test. The biocompatibility was investigated by in vitro cell culture test. And the antibacterial effect against Staphylococcus aureus was examined by the bacterial counting method. The results showed that the incorporation of Ca, P and Ag elements had no significant influence on the formation of nanotube arrays on Ti surface during electrochemical treatment. Compared to the polished or nanotubular Ti surface, TiO2 nanotube arrays incorporated with Ca, P and Ag increased the formation of bone-like apatite in simulated body fluid, enhanced cell adhesion and proliferation, and inhibited the bacterial growth. Based on these results, it can be concluded that the nanostructured Ti incorporated with Ca, P and Ag by electrochemical method has promising applications as implant material. - Highlights: • Nanotube arrays were prepared on Ti surface by anodic oxidation. • Ca, P and Ag were incorporated to nanotube arrays by electrochemical method. • Ca, P and Ag endowed Ti with good osseointegration and antibacterial property. • The beneficial effect of electrochemical treatment on Ti implant was demonstrated

  20. Combined embedding of N-doping and CaCO{sub 3} surface modification in the TiO{sub 2} photoelectrodes for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Park, Su Kyung; Yun, Tae Kwan [Department of Chemistry, Keimyung University, Daegu 704-701 (Korea, Republic of); Bae, Jae Young, E-mail: jybae@kmu.ac.kr [Department of Chemistry, Keimyung University, Daegu 704-701 (Korea, Republic of); Won, Yong Sun, E-mail: yswon@pknu.ac.kr [Department of Chemical Engineering, Pukyong National University, Busan 608-739 (Korea, Republic of)

    2013-11-15

    A successive embedding of N-doping and CaCO{sub 3} surface modification was carried out in the TiO{sub 2} photoelectrodes for dye-sensitized solar cells (DSSCs). The combined effect was revealed with the great increase of the open-circuit voltage (V{sub oc}), short-circuit current (J{sub sc}), and photoelectric conversion efficiency (η) of the prepared cells; the efficiency (η) was improved from 5.42% of a commercial TiO{sub 2} photoelectrode to 7.47% of an unmodified N-doped electrode, and to 9.03% of a N-doped and CaCO{sub 3} surface modified electrode. An enhanced photoresponse in N-doped TiO{sub 2} nanoparticles generate more photo-excited electrons in adsorbed dye, as supported by measured UV–vis diffuse reflectance spectra and incident photon to current conversion efficiency (IPCE). A successive CaCO{sub 3} surface modification then form a barrier on the surface of N-doped TiO{sub 2} particles, suppressing charge recombination of photo-generated electrons from N-doped TiO{sub 2} to dye or electrolyte, and thus extending their life time in the electrode, as supported by electron impedance spectroscopy (EIS). Furthermore, the higher basicity of the CaCO{sub 3} modified TiO{sub 2} facilitates the dye adsorption, as supported by the direct measurement of the amount of adsorbed dye.

  1. Local structure in BaTi O3-BiSc O3 dipole glasses

    Science.gov (United States)

    Levin, I.; Krayzman, V.; Woicik, J. C.; Bridges, F.; Sterbinsky, G. E.; Usher, T.-M.; Jones, J. L.; Torrejon, D.

    2016-03-01

    Local structures in cubic perovskite-type (B a0.6B i0.4) (T i0.6S c0.4) O3 solid solutions that exhibit reentrant dipole glass behavior have been studied with variable-temperature x-ray/neutron total scattering, extended x-ray absorption fine structure, and electron diffraction methods. Simultaneous fitting of these data using a reverse Monte Carlo algorithm provided instantaneous atomic configurations, which have been used to extract local displacements of the constituent species. The smaller Bi and Ti atoms exhibit probability density distributions that consist of 14 and 8 split sites, respectively. In contrast, Ba and Sc feature single-site distributions. The multisite distributions arise from large and strongly anisotropic off-center displacements of Bi and Ti. The cation displacements are correlated over a short range, with a correlation length limited by chemical disorder. The magnitudes of these displacements and their anisotropy, which are largely determined by local chemistry, change relatively insignificantly on cooling from room temperature. The structure features a nonrandom distribution of local polarization with low-dimensional polar clusters that are several unit cells in size. In situ measurements of atomic pair-distribution function under applied electric field were used to study field-induced changes in the local structure; however, no significant effects besides lattice expansion in the direction of the field could be observed up to electric-field values of 4 kV m m-1 .

  2. Phase Formation and Vibrational Characterization of Pb (Ca) TiO3 Ceramics

    International Nuclear Information System (INIS)

    Ca doped PbTiO3 ceramics were prepared by conventional solid solution method and heated at 7000C for 3 hours. X-ray diffraction analyses were carried out to determine phase formation. Vibrational frequencies of Pb1-x Cax TiO3 ceramics and constituent polycrystalline phase of CaTiO3 molecules were observed by FTIR spectrum of 400cm-1 to 4000cm-1 region and molecular orientations of Ca doped Pb TiO3 ceramics were also investigated by FT-Raman spectroscopy within the Raman shift ranges of 400 to 4000cm-1 region.

  3. Cerium-, terbium- and europium-activated CaScAlSiO6 as a full-color emitting phosphor

    International Nuclear Information System (INIS)

    We reported a single-phased CaScAlSiO6:Ce3+, Tb3+, Eu3+ as a potential full-color emitting phosphor for the application in fluorescent lamps. The CaScAlSiO6:Ce3+, Tb3+, Eu3+ phosphor exhibits three bands under 254 nm excitation: one band situated at 380 nm is attributed to the 5d→4f transitions of Ce3+ ions, the second band with sharp lines peaked at 542 nm is assigned to the 5D4→7FJ transitions of Tb3+ ions, the third band in the orange–red region (580–700 nm) is originated from 5D0→7FJ transitions of Eu3+ ions. The Commission Internationale de I’Eclairage (CIE) chromaticity coordinates (0.30, 0.30) and high color rendering index (CRI=88) can be achieved upon excitation of 254 nm light. It is suggested that CaScAlSiO6:Ce3+, Tb3+, Eu3+ can serve as a potential single-phased full-color emitting phosphor for phosphor-converted fluorescent lamps. -- Highlights: • A novel full-color emitting phosphor CaScAlSiO6:Ce3+, Tb3+, Eu3+ are synthesized and investigated. • The obtained phosphor exhibits three emission bands. • The CIE chromaticity coordinates (0.30, 0.30) and high color rendering index CRI=88 can be achieved. • These results indicated that CSAS:Ce3+, Tb3+, Eu3+ is a promising single-composition full-color emitting phosphor

  4. Hydrogen Storage Properties of Ti1.2Fe+xCa Hydrogen Storage Alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The hydrogen storage properties of Ti1.2Fe+xCa (x=1%, 3% and 5% in mass fraction) alloys was investigated. Results show that the modified alloys can be activated without any thermal treatment at room temperature due to the addition of Ca and excess Ti in the alloys. Hydrogen storage properties of these modified alloys vary with Ca amount and reaction temperature. In addition, the influence mechanism of the addition of Ca and excessive Ti on the activation behavior and hydrogen storage capacity of the alloys was discussed.

  5. Anodic-hydrothermal preparation of prism-shaped CaTiO3 structure on titanium surface

    International Nuclear Information System (INIS)

    The prism-shaped perovskite structure of CaTiO3 on titanium surface was fabricated by an anodic-hydrothermal method. Firstly, the TiO2 film was formed on Ti substrate by electrochemical anodization. Secondly, the anodized TiO2/Ti substrate was used as a template for the hydrothermal synthesis of CaTiO3 coating. The samples were characterized with X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectrum. The experimental results show that anodic TiO2 substrate and alkali environment are key factors for the formation of prism-shaped CaTiO3, and the NaOH concentrations plays an important role in determining the size and shape of CaTiO3 structures. Meanwhile, the CaTiO3 surfaces possess the better deposition ability of Ca and P in vitro.

  6. Dust depletion of Ca and Ti in QSO absorption line systems

    CERN Document Server

    Guber, C R

    2016-01-01

    To explore the role of titanium- and calcium-dust depletion in gas in and around galaxies we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope and spectroscopically analyze 34 absorption-line systems at z<=0.5 to measure column densities (or limits) for CaII and TiII. We complement our UVES data set with previously published absorption-line data on Ti/Ca for redshifts up to z~3.8. Our absorber sample contains 110 absorbers (DLAs, sub-DLAs & LLSs). We compare our Ti/Ca findings with results from the Milky Way and the Magellanic Clouds and discuss the properties of Ti/Ca absorbers in the general context of quasar absorption-line systems.Our analysis indicates that there are two distinct populations of absorbers with either high or low Ti/Ca ratios with a separation at [Ti/Ca}]~1. While the calcium dust depletion in most of the absorbers appe...

  7. Surface rumpling of cubic CaTiO3 from density functional theory

    Institute of Scientific and Technical Information of China (English)

    Yang Kun; Wang Chun-Lei; Li Ji-Chao; Zhang Chao; Wu Qing-Zao; Zhang Yan-Fei; Yin Na; Liu Xue-Yan

    2006-01-01

    In this paper, the structure of cubic CaTiO3 (001) surfaces with CaO and TiO2 terminations has been studied from density functional calculations. It has been found that the Ca atom has the largest relaxation for both kinds of terminations, and the rumpling of the CaO-terminated surface is much larger than that of TiO2-terminated surface.Also we have found that the metal atom relaxes much more prominently than the O atom does in each layer. The CaO-terminated surface is slightly more energetically favourable than the TiO2-terminated surface from the analysis of the calculated surface energy.

  8. Spectral variations of Ca3Sc2Si3O12:Ce phosphors via substitution and energy transfer

    Institute of Scientific and Technical Information of China (English)

    LIU Yuanhong; ZHUANG Weidong; LIU Ronghui; HU Yunsheng; HE Huaqiang; ZHANG Shusheng; GAO Wei

    2012-01-01

    The luminescence intensity of emission peak at around 525 nm decreased in the Ce3+ and Er3+ co-doped Ca3Sc2Si3O12 phosphors.Mg2+ ion,which was likely incorporated into the Sc3+ position of the host crystal,was co-doped to adjust the crystal field and compensate for the excess positive charge due to the doping of Ce3+.The green emission belonged to the 5d→4f transition of Ce3+ moved toward longer wavelength by addition of Mg2+ in Ce3+ and Er3+ co-doped Ca3Sc2Si3O12 phosphor,which could increase the brightness of the phosphor.However,the position of weakening of luminescence intensity at around 525 nm remained basically unchanged by increasing the amount of Mg2+.The results showed that the weakening of luminescence intensity at around 525 nm caused by the absorption of Er3+,which had littleinfluence on the environment of the crystal field.

  9. Fe and Mg solubility in the Ca site of zirconolite, CaZrTi2O7

    International Nuclear Information System (INIS)

    Full text: The solid solubility of Fe in the Ca site of zirconolite appears to be approximately the same whether it is incorporated as the divalent or trivalent species. Divalent Fe was encouraged by using an argon firing atmosphere and direct substitution in the Ca site [Ca(1x)FexZrTi2O7] and trivalent Fe by the use of an air atmosphere and Al compensation in the Ti site [Ca(1x)FexZrTi(2-x)A1xO7]. The anticipated valences were confirmed by X-ray near-edge, X-ray photoelectron and Moessbauer spectroscopies. Changing the firing atmosphere from argon to air and vice versa also changed the Fe valences, but scanning electron microscopy showed that small amounts of second phase, Fe-bearing materials were present. The possible reasons for the apparently similar solid solubilities of divalent and trivalent Fe in the Ca site are discussed. Solid state magic-angle nuclear magnetic resonance was used to study Mg speciation in the Ca and Ti sites of zirconolite

  10. Dielectric properties of CaCu2.9Co0.1Ti4O12 and CaCu3Ti3.9Co0.1O12 ceramics synthesized by semi-wet route

    Indian Academy of Sciences (India)

    K D Mandal; Alok Kumar Rai; Laxman Singh; Om Parkash

    2012-06-01

    The effect of Co+2 doping on Cu+2 and Ti+4 sites in calcium copper titanate, CaCu3Ti4O12, has been examined. The doped compositions, CaCu3−CoTi4O12 and CaCu3Ti4−CoO12 ( = 0.10) ceramics, were prepared by novel semi-wet route. In this method, calcium, copper and cobalt salts were taken in solution form and TiO2 was used in solid form. XRD analysis confirmed the formation of single-phase materials. Structure of CaCu3Ti4O12 does not change on doping with cobalt either on Cu-site or Ti-site and it remains cubic. Scanning electron micrographs (SEM) show average grain size of CaCu2.9Co0.1Ti4O12 to be larger than CaCu3Ti3.9Co0.1O12 ceramic. Energy dispersive X-ray spectroscopy (EDX) studies confined the purity of parent and Co-doped CaCu3Ti4O12 ceramics. Dielectric constant (r) and dielectric loss (tan ) of CaCu2.9Co0.1Ti4O12 is comparatively higher than that of CaCu3Ti3.9Co0.1O12 ceramic at all measured frequencies and temperatures.

  11. Processing and characterization of CaTiO3 perovskite ceramics

    Directory of Open Access Journals (Sweden)

    Guilherme Gralik

    2014-06-01

    Full Text Available Calcium titanate (CaTiO3 ceramics with perovskite structure were produced by solid state reaction. Calcium carbonate (CaCO3 and titanium dioxide (TiO2 were mixed (in molar ratios 1/1 and 3/2, and the obtained mixtures were calcined at 1150 °C in successive thermal cycles. The obtained samples were characterized by differential thermal analysis, thermogravimetry, X-ray diffraction, measurement of particle size distribution and linear thermal shrinkage. XRD results indicated that the samples have perovskite CaTiO3 structure with small amount of secondary CaO and TiO2 phases, and their phase composition depends on the heat treatment conditions. The measured values of electrical resistivity were within the characteristic range of insulating materials and approach values corresponding to semiconducting ceramics.

  12. TiN/(Al,Sc)N metal/dielectric superlattices and multilayers as hyperbolic metamaterials in the visible spectral range

    Science.gov (United States)

    Saha, Bivas; Naik, Gururaj V.; Saber, Sammy; Akatay, Cem; Stach, Eric A.; Shalaev, Vladimir M.; Boltasseva, Alexandra; Sands, Timothy D.

    2014-09-01

    Hyperbolic metamaterials (HMMs) based on metal/dielectric multilayers have garnered attention in recent years due to their extraordinary optical properties emanating from hyperbolic dispersion of isofrequency surfaces. We have developed a new class of epitaxial metal/dielectric superlattice HMMs based on transition-metal nitrides—titanium nitride (TiN) and aluminum scandium nitride (AlxSc1-xN)—that could potentially lead to better HMM performance without requiring any traditional plasmonic materials such as gold (Au) and silver (Ag). Our results suggest that the TiN/(Al,Sc)N superlattices grown on (001) MgO substrates are nominally monocrystalline and pseudomorphic, exhibiting sharp interfaces with interface roughnesses of about one to two atomic layers. HMMs deposited on (0001) sapphire substrates grow in 111 orientation with local epitaxy inherent to individual grains, while on (001) Si substrates, the HMMs are polycrystalline. The HMM properties extracted with effective medium theory along with nonlocal field corrections indicate that the TiN/(Al,Sc)N superlattices grown on MgO substrates have both transverse negative (type-I) and transverse positive (type-II) hyperbolic dispersion of the isofrequency surfaces in the visible to near-IR spectral regions. The carrier concentration of TiN layers was varied deliberately by tuning the deposition conditions, thereby shifting the spectral range of both type-I and type-II HMM dispersions. The epitaxial thin-film-based HMMs developed here mark the beginning of a new generation of optical metamaterials with enhanced electromagnetic properties.

  13. Photoluminescence and CO2 absorption on lanthanum doped CaTiO3 nanoparticles

    International Nuclear Information System (INIS)

    Ca1-xLaxTiO3 powders were prepared by the polymeric precursor method. X-ray diffraction (XRD), FT-Raman spectroscopy, transmission electron microscopy (TEM), and N2 and CO2 adsorption were used for the microstructural and surface characterization of the powders. Room temperature photoluminescence (PL) was observed in Ca1-xLaxTiO3 amorphous particles. The PL intensity of these powders was found to be dependent on the lanthanum molar concentration. (author)

  14. Enhancing the photoluminescence intensity of CaTiO3:Eu3+ red phosphors with magnesium

    Institute of Scientific and Technical Information of China (English)

    张杰强; 范艳伟; 陈朝阳; 王军华; 赵鹏君; 郝斌

    2015-01-01

    Red phosphors MgxCa1–xTiO3:Eu3+ (0Ca0.6TiO3:0.03Eu3+ was 4.26 times of that of phosphor CaTiO3:0.03Eu3+. Based on these results, it implied that the PL intensity of phosphorCaTiO3:0.03Eu3+ could be significantly enhanced by introducing Mg2+ into CaTiO3 host lattices and the phosphor Mg0.4Ca0.6TiO3:0.03Eu3+ might be the promising red-emitting phosphor in making tricolor phosphor converted white-LEDs.

  15. Effectively CO2 photoreduction to CH4 by the synergistic effects of Ca and Ti on Ca-loaded TiSiMCM-41 mesoporous photocatalytic systems

    Science.gov (United States)

    Jo, Seung Won; Kwak, Byeong Sub; Kim, Kang Min; Do, Jeong Yeon; Park, No-Kuk; Ryu, Si Ok; Ryu, Ho-Jung; Baek, Jeom-In; Kang, Misook

    2015-11-01

    TixSiMCM-41 is a mesoporous photocatalyst with a tetragonal framework and high structural regularity. In this study, Ca was introduced to the TixSiMCM-41 surfaces to improve CO2 absorption. The catalytic performance of mesoporous Ca/TixSiMCM-41 was superior to that of the reported Ca/TixSiO2 nano-sized composite catalyst. The photoreduction of CO2 to CH4 improved remarkably over the Ca(10.0 wt.%)/Ti35Si65MCM-41 catalyst, producing 82.0 μmol g-1cat L-1 after an 8 h reaction. A model for the enhanced photoactivity over Ca/TixSiMCM-41 was suggested, and the results were attributed to the effective charge separation and inhibited recombination of the photogenerated electron-hole pairs over Ca/TixSiMCM-41.

  16. Mixed interface and charge neutrality in the oxide heterostructure DyScO3/SrTiO3

    International Nuclear Information System (INIS)

    Oxide interfaces have attracted considerable attention in recent years due to the emerging novel behavior, which does not exist in the corresponding parent bulk compounds, e.g. joining two simple band insulators LaAlO3 and SrTiO3 with different polarity can induce new properties ranging from conductivity to magnetism, even to superconductivity. The electrostatic potential diverges due to the polar discontinuity at the interface. But intermixing at the interface, defects, or formation of a polarization in the substrate can help to avoid the divergence of the electrostatic potential. We carried out density functional theory calculations based on the full-potential linearized augmented planewave (FLAPW) method as implemented in the FLEUR code (www.flapw.de) for studying sharp and intermixed DyScO3/SrTiO3 interfaces. DyScO3 layers induce the same polarity as the lanthanum aluminate. Experimental evidence for intermixing was reported for this system. We investigated both scenarios avoiding the polar catastrophe, either by forming a mixed layer at the interface or by formation of a polarization in the SrTiO3 substrate.

  17. Sodium scandium diphosphate, NaScP2O7, isotypic with α-NaTi(IIIP2O7

    Directory of Open Access Journals (Sweden)

    Zdirad Žák

    2009-12-01

    Full Text Available Crystals of the title compound, NaScP2O7, were grown by a flux method. The crystal structure is isotypic with those of α-NaTiP2O7, NaYbP2O7 and NaLuP2O7, and is closely related to that of NaYP2O7. The structural set-up consists of a three-dimensional framework of P2O7 units that are corner-shared by ScO6 octahedra, forming tunnels running parallel to [010]. The Na atoms are situated in the tunnels and are surrounded by nine O atoms in a distorted environment.

  18. Thermoelastic properties of ScB2, TiB2, YB4 and HoB4

    DEFF Research Database (Denmark)

    Waskowska, A.; Gerward, L.; Staun Olsen, J.;

    2011-01-01

    modulus 180-200GPa), while TiB2 may be classified as superhard (bulk modulus about 260GPa). We report here first experimental and theoretical determinations of the bulk modulus for HoB4 (195(5) and 198.2GPa, respectively), and first experimental values of the bulk modulus for ScB2 (196(2)GPa) and YB4 (185......(4)GPa). No pressure-induced phase transformations are observed in any of the above borides up to about 20GPa. A continuous temperature-driven orthorhombic distortion is observed for HoB4 below 285K. Values of the thermal expansion coefficient are reported for ScB2 and HoB4 at 293, 200 and 100K...

  19. Wear Behavior of Cold Pressed and Sintered Al2O3/TiC/CaF2Al2O3/TiC Laminated Ceramic Composite

    Institute of Scientific and Technical Information of China (English)

    Xuefeng YANG; Jian CHENG; Peilong SONG; Shouren WANG; Liying YANG; Yanjun WANG; Ken MAO

    2013-01-01

    A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance,such as low friction coefficient and low wear rate.Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure.Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear.Al2O3/TiC ceramic was also cold pressed and sintered for comparison.Friction analysis of the two ceramics was then conducted via a wear-and-tear machine.Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum,respectively.Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite.Under the friction load,the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits.This process formed a smooth,self-lubricating film,which led to better anti-wear properties.Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.

  20. Clustering of O–X, X = (Ag, Al, Ga, Sn, Sc, Zn, Zr) point defects in hexagonal Ti: Formation mechanism and ductility variations

    International Nuclear Information System (INIS)

    The interactions of prime interstitial and alloying elements in hexagonal Ti were investigated using a density functional theory calculations. The binding energies of oxygen with all substitution elements whose solubility limit in α-Ti is greater than 3 at% were calculated. The investigations performed reveal no attraction between Zn, Zr, Ag and O, and strong O–Sc and O–Sn binding. It was found that the O–X clustering mechanism is based on a direct and long-range O–X interaction, both controlled by valence structure and electronegativity of substitational elements. The single crystal and isotropic elastic constants together with Pugh's plasticity criterion were calculated for Ti with multiple point defects to evaluate their impact on mechanical properties. The results obtained reveal that a low concentration of O improves ductility in Ti + Sc solid solutions and increases the brittleness of Ti + Sn alloys. The diverse effect on ductility is due to different chemical bond types in the vicinity of O. The results show that the interstitial-substitational elements clustering effect may be used to optimize mechanical properties of α-Ti alloys. - Highlights: • DFT calculations were performed to investigate the point defects binding in α-Ti. • Sn and Sc exhibit the highest attraction to O in α-Ti lattice. • O–X interaction is controlled by short- and long range interactions. • Oxygen can suppress or enhance ductility of α-Ti-X solid solutions

  1. Isothermal cross-sections of Hf-Sc-Ga(800 deg C) and Hf-Ti-Ga (750 deg C) phase diagrams

    International Nuclear Information System (INIS)

    Isothermal cross sections of Hf-Sc-Ga (800 deg C) and Hf-Ti-Ga (750 deg C) state diagrams are plotted. The existence of two ternary Hfsub(0.1-0.8)Scsub(0.9)-sub(0.2)Ga and Hfsub(0.8)Scsub(0.2)Gasub(3) phases is stated in the Hf-Sc-Ga system. The crystal structure of these compounds investigated by the powder method belongs to the structural α-MoB and ZrAl3 types respectively. Continuous rows of (Hf, Sc5Ga5, (Hf, Ti)Ga3 and (Hf, Ti)Ga2 solid solutions are formed in the investigated systems. Essential quantity of the third component dissolve binary Sc5Ga4, Sc2Ga3 (15 and 30 at % Hf respectively), Hf5Ga4, HfGa2 (20, 10 at. % Sc), Hf5Ga4, HfGa, Hf5Ga3, Hf2Ga3 (48, 30, 46, 20 at. % Ti) gallides

  2. A simple solvothermal process to synthesize CaTiO3 microspheres and its photocatalytic properties

    International Nuclear Information System (INIS)

    Highlights: • This paper presents a facile hydrothermal route to self-assemble CaTiO3 nanosheets into microspheres without any surfactants or template and discusses the photocatalytic performance of the large-scale structure. • The growth mechanism for spherical CaTiO3 is proposed to be a self assembly-nanosheets building units further oriented growth mechanism. • The molar ratio of water/ethanol is crucial for the formation of spherical CaTiO3. In addition, CaTiO3 microspheres were stable during the photocatalytic reaction and more convenient to store and handle as a micrometre-scale structure. • The present work not only helps understanding of the growth behavior of 3D CaTiO3 microspheres in a solution synthetic system, but also provides an efficient approach to enhance the photocatalytic properties of CaTiO3 catalysts by the controllable design of desirable structure and morphology. - Abstract: Novel CaTiO3 microspheres composed of nanosheets have been successfully prepared via a very simple solvothermal process in ethanol aqueous solution without any template or surfactant. The microstructure and morphology are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The effects of the reaction time, reaction temperature, and molar ratio of ethanol/water on the formation of the spherical structure have been investigated. CaTiO3 microspheres assembled by nanosheet units have been obtained by controlling the molar ratio of water/ethanol. The growth mechanism has been proposed based on the results of time-dependent experiments. It is proposed that amorphous particles transformed to nanosheets, and nanosheets self assembly into solid microspheres, then nanosheets building units further oriented growth along [1 1 0] direction result in the formation of nanosheets building units, and finally form the microsphere composed of nanosheets. CaTiO3

  3. Substitution of Ti3+ and Ti4+ in hibonite (CaAl12O19)

    OpenAIRE

    Doyle, PM; Schofield, PF; Berry, AF; Walker, AM; Knight, KS

    2014-01-01

    The structures of eight synthetic samples of hibonite, with variable Ti oxidation state and Ti concentration (2.4–15.9 wt% TiO2) that span the range reported for natural hibonite found in meteorites, were determined by Rietveld refinements of neutron powder diffraction data. Ti3+ was found to exclusively occupy the octahedral face-sharing M4 site irrespective of the presence or absence of Ti4+. Ti4+ partitions between the trigonal bipyramidal M2 site and the M4 site. The ratio (Ti4+ on M2):(T...

  4. A new approach to targetry and cyclotron production of 45Ti by proton irradiation of 45Sc

    Directory of Open Access Journals (Sweden)

    Fazaeli Yousef

    2014-01-01

    Full Text Available Titanium-45 with a half-life of 3.09 hours decays by emission of positrons (85% and the electron capture process (15%. These properties make this radionuclide useful in the diagnosis of tumors by positron emission tomography. In this study, after having considered the excitation functions for the 45Sc(p, n45Ti reaction using TALYS and ALICE/ASH codes and after the comparison with other experimental data, 45Ti was produced by dint of the pressing method and a newly designed and manufactured shuttle and capsule, resulting in an experimental yield of 403.3 MBq/mAh. Essential target thickness and physical yield were calculated. The scandium oxide target was irradiated at a 20 mA current and a 21 MeV proton beam energy for 1 hour.

  5. First-principles study of hydrogen storage on Ti (Sc)-decorated boron-carbon-nitride sheet

    Energy Technology Data Exchange (ETDEWEB)

    Song Nahong [College of Computer and Information Engineering, Henan University of Economics and Law, Zhengzhou 450002 (China); Wang Yusheng [College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou, Henan 450011 (China); Center of Clean Energy and Quantum Structures, School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450052 (China); Sun Qiang [Center of Clean Energy and Quantum Structures, School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450052 (China); Jia Yu, E-mail: xxwysheng@163.com [Center of Clean Energy and Quantum Structures, School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450052 (China)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer The gravimetric densities of H{sub 2} are 7.6 wt% and 7.8 wt%, respectively. Black-Right-Pointing-Pointer The average adsorption energy of hydrogen molecule is in the range of 0.4-0.56 eV/H{sub 2} (0.13-0.27 eV/H{sub 2}). Black-Right-Pointing-Pointer It can operate under ambient thermodynamic conditions. - Abstract: Ab initio first-principles calculations are carried out to investigate Ti (Sc)-decorated two-dimensional boron-carbon-nitride (BC{sub 2}N) sheets for their application as hydrogen storage materials. The results show that with four H{sub 2} molecules attached to per metal atom the Ti (Sc)-decorated BC{sub 2}N can store up to 7.6 wt% (7.8 wt%) of hydrogen in molecular form. The Kubas interaction and the polarization mechanism lead to the adsorption energy within the range of 0.4-0.56 eV/H{sub 2} (0.13-0.27 eV/H{sub 2}), which is suitable for ambient temperature hydrogen storage.

  6. Judd–Ofelt analysis of Tm3+ doped in CaSc2O4 ceramic samples

    International Nuclear Information System (INIS)

    The Judd–Ofelt analysis is applied to light-scattering ceramic CaSc2O4 doped with Tm3+. The calibration of the Judd–Ofelt parameters is performed by two approaches: (i) using the known magnetic-dipole contribution to the transition intensity of 3H6→3H5; (ii) using the radiative lifetime of an energy level supposed to decay mainly radiatively (1G4 or 3F4). The following results were obtained: Ω2=1.55×10−20 cm2; Ω4=1.71×10−20 cm2; Ω6=0.98×10−20 cm2, using the first approach; Ω2=1.70×10−20 cm2, Ω4=1.84×10−20 cm2, Ω6=1.13×10−20 cm2 (calibration using 1G4); Ω2=1.57×10−20 cm2, Ω4=1.70×10−20 cm2, Ω6=1.04×10−20 cm2 (calibration using 3F4). The obtained Judd–Ofelt parameters are used to calculate the radiative lifetimes and quantum efficiencies of several Tm3+ levels, spontaneous emission probabilities and branching ratios of various Tm3+ transitions. A fairly good agreement was obtained between the results of these methods. - Highlights: • Judd–Ofelt (JO) analysis of ceramic Tm:CaSc2O4 is presented. • Two calibration methods are developed for the JO parameters of Tm3+ in ceramic media. • The calibration methods yield close results. • Radiative lifetimes, branching ratios, and quantum efficiencies are obtained

  7. Excitation functions for production of 46Sc by deuteron and proton beams in natTi: A basis for additional monitor reactions

    International Nuclear Information System (INIS)

    Highlights: • Compilation of experimental cross section data for the natTi(d,x)46Sc process. • Compilation of experimental cross section data for the natTi (p,x)46Sc process. • Critical selection of datasets. • Spline fit and recommended cross section values to selected datasets. • Comparison with theoretical results (TENDL2013 on-line library). - Abstract: An objective of a new Coordinated Research Program launched recently by IAEA is to strengthen and broaden the cross section database for monitoring of charged particle beams given in IAEA-TECDOC-1211. One of the suggestions is to complement the widely used natTi(d,x)48V monitor reaction by the natTi(d,x)46Sc reaction having a maximum in a somewhat higher energy. After compilation of the data sets for this reaction available in literature and unpublished data from our earlier experiments, a selection of 20 sets is proposed for statistical fitting and extraction of recommended values. A similar analysis is presented for the natTi(p,x)46Sc reaction where 16 datasets are finally selected

  8. Excitation functions for production of {sup 46}Sc by deuteron and proton beams in {sup nat}Ti: A basis for additional monitor reactions

    Energy Technology Data Exchange (ETDEWEB)

    Hermanne, A., E-mail: aherman@vub.ac.be [Cyclotron Department, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussel (Belgium); Tárkányi, F.; Takács, S.; Ditrói, F. [Institute of Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Amjed, N. [Department of Physics, Government College University Lahore, 54000 Lahore (Pakistan)

    2014-11-01

    Highlights: • Compilation of experimental cross section data for the {sup nat}Ti(d,x){sup 46}Sc process. • Compilation of experimental cross section data for the {sup nat}Ti (p,x){sup 46}Sc process. • Critical selection of datasets. • Spline fit and recommended cross section values to selected datasets. • Comparison with theoretical results (TENDL2013 on-line library). - Abstract: An objective of a new Coordinated Research Program launched recently by IAEA is to strengthen and broaden the cross section database for monitoring of charged particle beams given in IAEA-TECDOC-1211. One of the suggestions is to complement the widely used {sup nat}Ti(d,x){sup 48}V monitor reaction by the {sup nat}Ti(d,x){sup 46}Sc reaction having a maximum in a somewhat higher energy. After compilation of the data sets for this reaction available in literature and unpublished data from our earlier experiments, a selection of 20 sets is proposed for statistical fitting and extraction of recommended values. A similar analysis is presented for the {sup nat}Ti(p,x){sup 46}Sc reaction where 16 datasets are finally selected.

  9. Structure of 55Ti and 49Ca from relativistic one-neutron knockout

    CERN Document Server

    Maierbeck, P; Krücken, R; Kröll, T; Alvarez-Pol, H; Aksouh, F; Aumann, T; Behr, K; Benjamim, E A; Benlliure, J; Bildstein, V; Böhmer, M; Boretzky, K; García-Borge, M J; Brünle, A; Bürger, A; Caamaño, M; Casarejos, E; Chatillon, A; Chulkov, L V; Cortina-Gil, D; Enders, J; Eppinger, K; Fästermann, T; Friese, J; Fabbietti, L; Gascón, M; Geissel, H; Gerl, J; Górska, M; Hansen, P G; Jonson, B; Kanungo, R; Kiselev, O; Kojouharov, I; Klimkiewicz, A; Kurtukian, T; Kurz, N; Larsson, K; Bleis, T Le; Mahata, K; Maier, L; Nilsson, T; Nociforo, C; Nyman, G; Pascual-Izarra, C; Perea, A; Pérez, D; Prochazka, A; Rodriguez-Tajes, C; Rossi, D; Schaffner, H; Schrieder, G; Schwertel, S; Simon, H; Sitár, B; Stanoiu, M; Sümmerer, K; Tengblad, O; Weick, H; Winkler, S; Brown, B A; Otsuka, T; Tostevin, J; Rae, W D M

    2008-01-01

    Results are presented from a one-neutron knockout reaction at relativistic energies on 50Ca and 56Ti using the GSI FRS as a two-stage magnetic spectrometer and the Miniball array for gamma-ray detection. Inclusive and exclusive longitudinal momentum distributions and cross-sections were measured enabling the determination of the orbital angular momentum of the populated states. First-time observation of the 3.35(15) MeV nu f7/2-hole state in 49Ca and the 955(6) keV nu p3/2-hole state in 55Ti is reported. The measured data clearly indicates that the ground state of 55Ti is a 1/2- state, in agreement with shell-model calculations using the GXPF1A interaction that predict a sizable N=34 gap in 54Ca.

  10. Strong irradiation tolerance to amorphization in delta-Sc{sub 4}Ti{sub 3}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J., E-mail: zhangjian@xmu.edu.cn [School of Energy, Xiamen University, Xiamen, Fujian 361005 (China); Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Patel, M.K. [Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996 (United States); Wang, Y.Q.; Tang, M. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Won, J. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon 305-806 (Korea, Republic of); Valdez, J.A. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Sickafus, K.E. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996 (United States)

    2015-04-15

    Polycrystalline delta-phase Sc{sub 4}Ti{sub 3}O{sub 12} was irradiated under two separate conditions, with 200 keV Ne{sup +} or 600 keV Kr{sup 3+} at cryogenic temperature (∼77 K) to examine its radiation tolerance to amorphization. Irradiated samples were characterized using grazing incidence X-ray diffraction and cross-sectional transmission electron microscopy. An order-to-disorder (O–D) structural transformation was observed under both ion beam irradiation conditions, but the threshold irradiation doses to produce the O–D transformation differ significantly. The order to disorder phase transformation was completed by a fluence of 2 × 10{sup 19} Ne/m{sup 2} (or a peak dose of ∼0.7 dpa) with Ne irradiation, while it was not accomplished until a fluence of 5 × 10{sup 20} Kr/m{sup 2} (or a peak dose of ∼93 dpa) with Kr irradiation. This observation was interpreted in terms of greater probability of defect survivability in dilute Ne versus dense Kr ion cascades. More interesting aspect in this study, in the basis of so-called “chemical effects”, Ti-bearing oxide Sc{sub 4}Ti{sub 3}O{sub 12} should be readily amorphous when exposed to ion irradiation, but no amorphization was observed even after 93 displacements per atom in Kr irradiation. These observations exhibit that the temperature–composition (T–C) phase diagram is a good indicator for radiation tolerance, especially for amorphization.

  11. Enhanced Efficiency of Dye-Sensitized Solar Cells by Trace Amount Ca-Doping in TiO2 Photoelectrodes

    Directory of Open Access Journals (Sweden)

    Mengmei Pan

    2015-01-01

    Full Text Available Trace amount Ca-doped TiO2 films were synthesized by the hydrothermal method and applied as photoanodes of dye-sensitized solar cells (DSSCs. To prepare Ca-doped TiO2 film electrodes, several milliliters of Ca(NO32 solution was added in TiO2 solution during the hydrolysis process. The improvements of DSSCs were confirmed by photocurrent density-voltage (J-V characteristics, electrochemical impedance spectroscopy (EIS measurements. Owing to the doping effect of Ca, the Ca-doped TiO2 thin film shows power conversion efficiency of 7.45% for 50 ppm Ca-doped TiO2 electrode, which is higher than that of the undoped TiO2 film (6.78% and the short-circuit photocurrent density (Jsc increases from 13.68 to 15.42 mA·cm−2. The energy conversion efficiency and short-circuit current density (Jsc of DSSCs were increased due to the faster electron transport in the Ca-doped TiO2 film. When Ca was incorporated into TiO2 films, the electrons transport faster and the charge collection efficiency ηcc is higher than that in the undoped TiO2 films.

  12. First-Principles Investigation of Vibrational Properties of CaTiO3 Crystal

    Science.gov (United States)

    Medeiros, Subenia; Araujo, Maeva

    2014-03-01

    The structural, electronic, vibrational, and optical properties of perovskite CaTiO3 in the cubic, orthorhombic, and tetragonal phase are calculated in the framework of density functional theory (DFT) with different exchange-correlation potentials by CASTEP package. The calculated band structure shows an indirect band gap of 1.88 eV at the Γ-R points in the Brillouin zone to the cubic structure, a direct band gap of 2.41 eV at the Γ- Γ points to the orthorhombic structure, and an indirect band gap of 2.31 eV at theM - Γ points to the tetragonal phase. I have concluded that the bonding between Ca and TiO2 is mainly ionic and that the TiO2 entities bond covalently. Unlike some perovskites the CaTiO3 does not exhibit a ferroelectric phase transition down to 4.2 K. It is still known that the CaTiO3 has a static dielectric constant that extrapolates to a value greater than 300 at zero temperature, and the dielectric response is dominated by low frequency (ν ~ 90cm-1) polar optical modes in which cation motion opposes oxygen motion. Our calculated lattice parameters, elastic constants, optical properties, and vibrational frequencies are found to be in good agreement with the available theoretical and experimental values. The results for the effective mass in the electron and hole carriers are also presented in this work.

  13. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-31

    Density functional theory is used to study the electronic properties of the oxide heterointerfaceCaHfO3/SrTiO3. Structural relaxation is carried out with and without O vacancies. As compared to related interfaces, strongly reduced octahedral distortions are found. Stoichiometric interfaces between the wide band gap insulatorsCaHfO3 and SrTiO3 turn out to exhibit an insulating state. However, interface metallicity is introduced by O vacancies, in agreement with experiment. The reduced octahedral distortions and necessity of O deficiency indicate a less complicated mechanism for the creation of the interfacial electron gas.

  14. Neutron activation determination of LaAL03CaTiO3 matrix

    International Nuclear Information System (INIS)

    The article suggests that the control upon lanthanum aluminate calcium titanate (LaALO3CaTiO3) in conformity with the All-Union State Standard should be carried out through applying a nuclear-physical analysis which shortens the time considerably and consequently is more agreeable for industrial conditions than the control accomplished by chemical methods. The matrix elements LaAlO3CaTiO3 were determined through a neutron-activation method. The experimental data show that the difference between the results obtained from the chemical and neutron-activation analyses is within the limits of error

  15. Theoretical study on the possibility of bipolar doping of ScN

    OpenAIRE

    Soto, G.; Moreno-Armenta, M. G.; Reyes-Serrato, A.

    2008-01-01

    Scandium nitride (ScN) is a semiconducting transition metal nitride for which there are not identified dopants. We present local density functional calculations, in supercell approach, for ScN doped with O and C in N-sites and Ca and Ti in Sc-sites. Small additions of these atoms have the effect of shifting the Fermi level within the electronic band structure. O and Ti bring occupied states in bottom of conduction band, while C and Ca produces holes in top of valence band. Based on the theory...

  16. Biomimetic Ca-P coating on pre-calcified Ti plates by electrodeposition method

    International Nuclear Information System (INIS)

    A new electrodeposition method was presented for Ca-P coating on pre-calcified titanium (PTi) plates at room temperature. The biomimetic coating morphology was investigated by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) results indicated that the functional TiOx layer with groups of -Ca and -OH was formed on PTi surface after pre-calcified chemical treatment. The TiOx layer showed a lower water contact angle and lower surface energy than those of pure titanium surfaces, and the PTi surface natures are benefited by coupling biomimetic Ca-P layer with bioactivity in the electrodeposition process. Moreover, the crystallization of Ca-P precipitate and the bond strength of coating to PTi substrates were improved significantly by post-treatments. Our results suggest this new coating process and its subsequent application to biomedical implant devices.

  17. Nature of bonding in CaTiO3 and SrTiO3: A Compton scattering study

    International Nuclear Information System (INIS)

    Compton profile measurements for CaTiO3 and SrTiO3 perovskite compounds have been undertaken using 20 Ci 137Cs Compton spectrometer. To understand the nature of bonding in both the compounds, we have analyzed the Compton line shape in terms of equal-valence-electron-density profiles. Electron momentum densities, energy bands and density of states computed using linear combination of the atomic orbitals method (within the framework of density functional theory) are analyzed using the experimental Compton line shapes. It is seen that the recently developed second order generalized gradient approximation gives a better description of momentum densities than the local density approximation. Moreover, bonding in both the ceramic compounds has also been discussed in terms of Mulliken's population analysis. - Highlights: ► First ever Compton profiles for CaTiO3 and SrTiO3 have been measured. ► Nature of bonding is compared between both isoelectronic compounds. ► For the first time theoretical band gaps agree with available experimental data. ► Mulliken's population is interpreted using EVED experimental profiles. ► SO-GGA CPs are found to be in better agreement with experimental CPs than LDA.

  18. Structural and electrical properties of nonstoichiometric semiconducting pyrochlores in Ca-Ce-Ti-Nb-O system

    International Nuclear Information System (INIS)

    Research highlights: → Nonstoichiometric semiconducting pyrochlores, CaCexTiNbO7-δ (x = 0.5-1.0) system have been synthesized by the conventional solid state route. → CaCe0.7TiNbO6.55, crystallizes into a pure cubic pyrochlore structure by accommodating smaller Ti ions on the A site. → The impedance analysis indicates relaxor behavior of these compounds due to disorder in the system. - Abstract: A series of quaternary nonstoichiometric cubic pyrochlores with varying cerium content in Ca-Ce-Ti-Nb-O system has been synthesized through solid state route. The powder X-ray diffraction and Rietveld analysis indicate that smaller Ti cation occupies the A site by displacing the A and O' ions causing displacive disorder in the cubic pyrochlore structure. The electrical conductivity measurements reveal that they exhibit semiconductor behavior in a broad temperature range (30-600 deg. C) and the conductivity increases with increase in Ce content. The X-ray photoelectron spectroscopy (XPS) analysis corroborates the presence of Ce in 3+ state. The impedance analysis reveals two types of conduction processes from the frequency dependent conductivity plots, i.e. low frequency conduction due to short range hopping and high frequency conduction due to the localized reorientation hopping mechanism. The relaxational properties indicate that hopping frequency is dependent on cerium concentration and is a measure of degree of disorder in the system.

  19. Dielectric properties of CaTiO3 coatings prepared by plasma spraying

    Czech Academy of Sciences Publication Activity Database

    Sedláček, J.; Ctibor, Pavel; Kotlan, J.; Pala, Zdeněk

    2013-01-01

    Roč. 29, č. 5 (2013), s. 384-389. ISSN 0267-0844 Institutional support: RVO:61389021 Keywords : Plasma * Ceramics * CaTiO3 * Permittivity * Resistivity Subject RIV: JG - Metallurgy Impact factor: 1.510, year: 2013 http://www.ingentaconnect.com/content/maney/se/2013/00000029/00000005/art00012

  20. Formation mechanism of CaTiO3 hollow crystals with different microstructures.

    Science.gov (United States)

    Yang, Xianfeng; Fu, Junxiang; Jin, Chongjun; Chen, Jian; Liang, Chaolun; Wu, Mingmei; Zhou, Wuzong

    2010-10-13

    The crystal growth of CaTiO(3) hollow crystals with different microstructures has been investigated. In a water-free poly(ethylene glycol) 200 (PEG-200) solution, CaTiO(3) nanocubes formed first. The nanocubes underwent an oriented self-assembly into spherical particles, enhanced by the surface-adsorbed polymer molecules. Since the growth of nanocubes and their aggregation took place simultaneously, the nanocubes in the outer shells were larger than those in the cores. Disappearance of the small nanocubes in the cores of the spheres during an Ostwald ripening process led to spherical hollow crystals. Addition of a small amount of water (1.25 vol %) in the polymer solution enhanced surface recrystallization of the aggregated spheres, forming a cubic morphology. The orthorhombic distortion of the perovskite CaTiO(3) structure did not have a significant effect on the nanocube aggregation, resulting in a domain structure in the shells. Single-crystalline hollow cubes were produced with a slightly higher water content, e.g., 5 vol %. This process of (1) aggregation of nanocubes and (2) surface crystallization followed by (3) surface-to-core extension of recrystallization gives a good example of the reversed crystal growth route in ceramic materials. The proposed formation mechanism of the hollow CaTiO(3) crystals would enable us to control the microstructures of these materials and to explain the formation of many other hollow crystals. PMID:20843080

  1. Microstructure and transformation behavior of Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} high temperature shape-memory alloy with Sc micro-addition

    Energy Technology Data Exchange (ETDEWEB)

    Ramaiah, K.V., E-mail: kvramaiah@nal.res.in [Materials Science Division, CSIR-National Aerospace Laboratories, Bangalore 560 017 (India); Saikrishna, C.N. [Materials Science Division, CSIR-National Aerospace Laboratories, Bangalore 560 017 (India); Gouthama [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208 016 (India); Bhaumik, S.K. [Materials Science Division, CSIR-National Aerospace Laboratories, Bangalore 560 017 (India)

    2015-08-15

    NiTiPd shape-memory alloys (SMAs) are potential functional materials for use as solid-state actuators in the temperature range 100–250 °C. The present study investigates the effect of 1.0 at.% Sc micro-addition to Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} alloy, Sc replacing either Ti or Ni. Results show that all the three alloys studied have stable transformation behavior on stress-free thermal cycling and hence, are suitable for cyclic actuation applications. However, the addition of Sc to NiTiPd alloy leads to decrease of transformation temperatures, the magnitude of decrease being greater for the alloy with Sc replacing Ni. The martensite finish (M{sub f}) temperature of 181 °C for the NiTiPd alloy decreased to 139 °C for Sc replacing Ti and 83 °C for Sc replacing Ni. Also, the indentation modulus of NiTiPdSc (Sc replacing Ni) alloy is found to be significantly low compared to the other alloys. Analysis indicates that the observed differences in the alloy properties are related to the solubility of Sc in the NiTiPd matrix. While the quaternary NiTiPdSc alloy, Sc replacing Ti, has a single phase microstructure, the alloy with Sc replacing Ni shows the presence of Sc-rich and TiPd-type second phases in the microstructure. TEM examination revealed that the TiPd-type phase has a distinct rod-like morphology (30–50 nm) arranged in a grid-like structure. The transformation and indentation behavior of the alloys is elucidated using thermodynamic calculations of frictional energy and an electronic structure based analysis. - Highlights: • TEM of Ni{sub 23.7}Ti{sub 50.3}Pd{sub 25}Sc{sub 1} showed distinct grid of TiPd-type phase nanorods < 50 nm. • Stress-free thermal cycling of all the three alloys showed stable transformation behavior. • Ni{sub 24.7}Ti{sub 49.3}Pd{sub 25}Sc{sub 1} and Ni{sub 23.7}Ti{sub 50.3}Pd{sub 25}Sc{sub 1} showed single and multiphase structures. • Sc micro-addition (1 at.%) to Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} alloy decreased TTs

  2. Ag- and Cu-doped multifunctional bioactive nanostructured TiCaPCON films

    Energy Technology Data Exchange (ETDEWEB)

    Shtansky, D.V., E-mail: shtansky@shs.misis.ru [National University of Science and Technology “MISIS”, Leninsky prospekt 4, Moscow 119049 (Russian Federation); Batenina, I.V.; Kiryukhantsev-Korneev, Ph.V.; Sheveyko, A.N.; Kuptsov, K.A. [National University of Science and Technology “MISIS”, Leninsky prospekt 4, Moscow 119049 (Russian Federation); Zhitnyak, I.Y.; Anisimova, N.Yu.; Gloushankova, N.A. [N.N. Blokhin Russian Cancer Research Center of RAMS, Kashirskoe shosse 24, Moscow 115478 (Russian Federation)

    2013-11-15

    A key property of multicomponent bioactive nanostructured Ti(C,N)-based films doped with Ca, P, and O (TiCaPCON) that can be improved further is their antibacterial effect that should be achieved without compromising the implant bioactivity and biocompatibility. The present work is focused on the study of structure, chemical, mechanical, tribological, and biological properties of Ag- and Cu-doped TiCaPCON films. The films with Ag (0.4–4 at.%) and Cu (13 at.%) contents were obtained by simultaneous sputtering of a TiC{sub 0.5}–Ca{sub 3}(PO{sub 4}){sub 2} target and either an Ag or a Cu target. The film structure was studied using X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman-shift and IR spectroscopy. The films were characterized in terms of their hardness, elastic modulus, dynamic impact resistance, friction coefficient and wear rate (both in air and normal saline), surface wettability, electrochemical behavior and Ag or Cu ion release in normal saline. Particular attention was paid to the influence of inorganic bactericides (Ag and Cu ions) on the bactericidal activity against unicellular yeast fungus Saccharomyces cerevisiae and gram-positive bacteria Lactobacillus acidophilus, as well as on the attachment, spreading, actin cytoskeleton organization, focal adhesions, and early stages of osteoblastic cell differentiation. The obtained results show that the Ag-doped films are more suitable for the protection of metallic surfaces against bacterial infection compared with their Cu-doped counterpart. In particular, an excellent combination of mechanical, tribological, and biological properties makes Ag-doped TiCaPCON film with 1.2 at.% of Ag very attractive material for bioengineering and modification of load-bearing metal implant surfaces.

  3. The solid phases interaction in Ca2TiSi2O8 - Sr2TiSi2O8 system

    International Nuclear Information System (INIS)

    The solid phases interaction in Ca2TiSi2O8 - Sr2TiSi2O8 system has been studied by x-ray diffraction and IR-spectroscopic methods in a temperature range of 700-1300 C. The concentration limits of the formation of solid solutions on the basis of CaTiSi2O8 and Sr2TiSi2O8 and regions of their combined existence were established. (author). 2 refs

  4. Effect of Nb and Sc doping on the phase transformation of sol-gel processed TiO2 nanoparticles.

    Science.gov (United States)

    Ahmad, A; Buzby, S; Ni, C; Ismat Shah, S

    2008-05-01

    Nb and Sc doped TiO2 nanoparticles were synthesized via sol-gel technique. Dopant concentration of each element was varied from 0.5 to 1.5 atomic%. The effect of metal ion doping and calcination temperatures on anatase to rutile phase transformation has been investigated. Samples were analyzed by various analytical methods such as X-ray diffraction (XRD), Transmission Electron Microscope (TEM), X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDS). XRD analyses showed that Nb and Sc doped samples calcined at 300 degrees C and 350 degrees C, respectively, were crystalline and had an anatase structure. Results showed that anatase was stable up to 700 degrees C annealing temperature for samples doped with 0.5 atomic% Nb. There was a sharp transition from anatase to rutile phase above 700 degrees C and complete rutile structure was obtained at 750 degrees C. However, the transformation from anatase to rutile was not so sharp in samples doped with 1.0 atomic% and 1.5 atomic% Nb. Results indicated that higher concentration of Nb helps to stabilize the anatase phase. For samples doped with 0.5 atomic% Sc, anatase phase is stable up to 650 degrees C. Transformation from anatase to rutile starts at temperature above 650 degrees C and 100% rutile phase was obtained at 800 degrees C while for samples doped with 1.0 atomic% and 1.5 atomic% Sc, the complete transformation from anatase to rutile takes place at an even higher temperature. Results indicate that increasing the calcination time from 0.5 to 2.0 hours at 500 degrees C does not affect the stability of anatase phase. However, TEM and XRD data showed that the increase in the annealing time leads to an increase in particles size. The rutile to anatase concentration ratio increased with temperature above the phase transformation temperature. The activation energy for the phase transformation from anatase to rutile for doped and undoped samples was also measured. There was a general rise in

  5. Magnetism and electronic structure of (001)- and (111)-oriented LaTiO{sub 3} bilayers sandwiched in LaScO{sub 3} barriers

    Energy Technology Data Exchange (ETDEWEB)

    Weng, Yakui; Dong, Shuai, E-mail: sdong@seu.edu.cn [Department of Physics and Jiangsu Key Laboratory of Advanced Metallic Materials, Southeast University, Nanjing 211189 (China)

    2015-05-07

    In this study, the magnetism and electronic structure of LaTiO{sub 3} bilayers along both the (001) and (111) orientations are calculated using the density functional theory. The band insulator LaScO{sub 3} is chosen as the barrier layer and substrate to obtain the isolating LaTiO{sub 3} bilayer. For both the (001)- and (111)-oriented cases, LaTiO{sub 3} demonstrates the G-type antiferromagnetism as the ground state, similar to the bulk material. However, the electronic structure is significantly changed. The occupied bands of Ti are much narrower in the (111) case, giving a nearly flat band. As a result, the exchange coupling between nearest-neighbor Ti ions is reformed in these superlattices, which will affect the Néel temperature significantly.

  6. Cyclotron production of {sup 44}Sc for clinical application

    Energy Technology Data Exchange (ETDEWEB)

    Krajewski, S.; Bilewicz, A. [Institute of Nuclear Chemistry and Technology, Warsaw (Poland); Cydzik, I. [Institute of Nuclear Chemistry and Technology, Warsaw (Poland); European Commission Joint Research Center, Ispra (Italy). Inst. for Health and Consumer Protection; Warsaw Univ. (Poland). Heavy Ion Lab.; Abbas, K. [European Commission Joint Research Center, Ispra (Italy). Institute for Transuranium Elements; Bulgheroni, A.; Simonelli, F.; Holzwarth, U. [European Commission Joint Research Center, Ispra (Italy). Inst. for Health and Consumer Protection

    2013-08-01

    {sup 44} is a promising {beta}{sup +}-emitter for molecular imaging with intermediate half-life of 4 h. Due to the chemical similarity of Sc{sup 3+} to the Lu{sup 3+} and Y{sup 3+} cations, {sup 44}Sc-DOTA bioconjugates are expected to demonstrate similar properties in vivo as the {sup 177}Lu- and {sup 90}Y-bioconjugates, what is important in planning the radionuclide therapy. {sup 44}Sc can be obtained from the {sup 44}Ti/{sup 44}Sc generator. An alternative method for {sup 44}Sc production can be the irradiation of {sup 44}Ca target at small cyclotrons. The aim of our work was to optimize the parameters of {sup 44}CaCO{sub 3} irradiation and to develop a simple procedure for {sup 44}Sc separation from the calcium target. For optimization study, {sup 44}CaCO{sub 3} targets were irradiated by protons in the energy range of 5.6-17.5 MeV with 9 MeV being found to be the best energy for {sup 44}Ca irradiations. A simple and fast separation procedure of {sup 44}Sc from calcium target was developed using chelating resin Chelex 100. DOTATATE conjugate was successfully radiolabelled with high yield at elevated temperature using the produced {sup 44}Sc. While {sup 44}CaCO{sub 3} is relatively expensive, the cost of {sup 44}Sc-DOTATATE production can be reduced by target recovery. Due to low proton energy required to produce GBq activity level of {sup 44}Sc, the availability of {sup 44}Sc radioisotope could be enhanced to open new opportunities for applications in medical imaging. (orig.)

  7. Cyclotron production of 44Sc for clinical application

    International Nuclear Information System (INIS)

    44 is a promising β+-emitter for molecular imaging with intermediate half-life of 4 h. Due to the chemical similarity of Sc3+ to the Lu3+ and Y3+ cations, 44Sc-DOTA bioconjugates are expected to demonstrate similar properties in vivo as the 177Lu- and 90Y-bioconjugates, what is important in planning the radionuclide therapy. 44Sc can be obtained from the 44Ti/44Sc generator. An alternative method for 44Sc production can be the irradiation of 44Ca target at small cyclotrons. The aim of our work was to optimize the parameters of 44CaCO3 irradiation and to develop a simple procedure for 44Sc separation from the calcium target. For optimization study, 44CaCO3 targets were irradiated by protons in the energy range of 5.6-17.5 MeV with 9 MeV being found to be the best energy for 44Ca irradiations. A simple and fast separation procedure of 44Sc from calcium target was developed using chelating resin Chelex 100. DOTATATE conjugate was successfully radiolabelled with high yield at elevated temperature using the produced 44Sc. While 44CaCO3 is relatively expensive, the cost of 44Sc-DOTATATE production can be reduced by target recovery. Due to low proton energy required to produce GBq activity level of 44Sc, the availability of 44Sc radioisotope could be enhanced to open new opportunities for applications in medical imaging. (orig.)

  8. Formation of CaO·TiO2-MgO·Al2O3 dual phase inclusion in Ti stabilized stainless steel

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The formation of CaO.TiO2-MgO.Al2O3 dual phase inclusion in 321 stainless steel was investigated in the laboratory. The result indicated that the condition for the formation of CaO.TiO2-MgO.Al2O3 in 321 steel is [Ca]>0.001wt%, [Ti]>0.1wt%, and[Al]>0.01wt%. The mechanism is the following: Al2O3 inclusion turns into CaO-Al2O3 after Ca-Si wire is fed into the molten steel;[Mg] is then obtained by reducing MgO in slag or crucible wall by [Al] and [Ti]; finally CaO-Al2O3 inclusion is changed into CaO.TiO2-MgO-Al2O3 by the reaction with [Mg], [Ti], and [O] in the molten steel simultaneously.

  9. Surface structures and osteoblast response of hydrothermally produced CaTiO{sub 3} thin film on Ti-13Nb-13Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin-Woo, E-mail: jinwoo@knu.ac.kr [Department of Periodontology, School of Dentistry, Kyungpook National University, 188-1, Samduk 2Ga, Jung-Gu, Daegu 700-412 (Korea, Republic of); Tustusmi, Yusuke [Department of Metals, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental Univeristy, Tokyo 101-0062 (Japan); Lee, Chong Soo; Park, Chan Hee [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Kim, Youn-Jeong; Jang, Je-Hee [Department of Periodontology, School of Dentistry, Kyungpook National University, 188-1, Samduk 2Ga, Jung-Gu, Daegu 700-412 (Korea, Republic of); Khang, Dongwoo; Im, Yeon-Min [School of Materials Science and Engineering, Gyeongsang National University, Jinju 600-701 (Korea, Republic of); Doi, Hisashi; Nomura, Naoyuki; Hanawa, Takao [Department of Metals, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental Univeristy, Tokyo 101-0062 (Japan)

    2011-06-15

    This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating calcium ions (Ca) obtained by hydrothermal treatment with or without post heat-treatment in the Ti-13Nb-13Zr alloy. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. In vitro biocompatibility of the Ca-containing surfaces was assessed in comparison with untreated surfaces using a pre-osteoblast cell line. Hydrothermal treatment produced a crystalline CaTiO{sub 3} layer. Post heat-treatment at 400 deg. C for 2 h in air significantly decreased water contact angles in the CaTiO{sub 3} layer (p < 0.001). The Ca-incorporated alloy surfaces displayed markedly increased cell viability and ALP activity compared with untreated surfaces (p < 0.001), and also an upregulated expression of various integrin genes ({alpha}1, {alpha}2, {alpha}5, {alpha}v, {beta}1 and {beta}3) at an early incubation time-point. Post heat-treatment further increased attachment and ALP activity in cells grown on Ca-incorporated Ti-13Nb-13Zr alloy surfaces. The results indicate that the Ca-incorporated oxide layer produced by hydrothermal treatment and a simple post heat-treatment may be effective in improving bone healing in Ti-13Nb-13Zr alloy implants by enhancing the viability and differentiation of osteoblastic cells.

  10. Surface structures and osteoblast response of hydrothermally produced CaTiO3 thin film on Ti-13Nb-13Zr alloy

    International Nuclear Information System (INIS)

    This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating calcium ions (Ca) obtained by hydrothermal treatment with or without post heat-treatment in the Ti-13Nb-13Zr alloy. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. In vitro biocompatibility of the Ca-containing surfaces was assessed in comparison with untreated surfaces using a pre-osteoblast cell line. Hydrothermal treatment produced a crystalline CaTiO3 layer. Post heat-treatment at 400 deg. C for 2 h in air significantly decreased water contact angles in the CaTiO3 layer (p < 0.001). The Ca-incorporated alloy surfaces displayed markedly increased cell viability and ALP activity compared with untreated surfaces (p < 0.001), and also an upregulated expression of various integrin genes (α1, α2, α5, αv, β1 and β3) at an early incubation time-point. Post heat-treatment further increased attachment and ALP activity in cells grown on Ca-incorporated Ti-13Nb-13Zr alloy surfaces. The results indicate that the Ca-incorporated oxide layer produced by hydrothermal treatment and a simple post heat-treatment may be effective in improving bone healing in Ti-13Nb-13Zr alloy implants by enhancing the viability and differentiation of osteoblastic cells.

  11. Phase transitions and physical properties in Ca-modified Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 solid solutions

    International Nuclear Information System (INIS)

    The influence on the relaxor state and phase transitions are studied when Sr in 0.4Na1/2Bi1/2 TiO3-0.4SrTiO3-0.2PbTiO3 is gradually replaced by Ca. The concentration dependence of the tetragonal cell volume confirms replacement of Sr by Ca in the lattice, while tetragonality remains independent of Ca concentration in a certain concentration range. The stability of the relaxor state and temperature of phase transition is also weakly dependent on Ca at low concentrations of Ca, and steeply increases starting from a certain Ca concentration. The stability of the phase transition and polarization at low concentrations of Ca and simultaneous steep decreasing of dielectric permittivity values with increasing Ca content is explained assuming that in this concentration range Ca resides inside polar nanoregions, preventing their reorientation in weak external electric field

  12. Synthesis of anatase nanoparticles with extremely wide solid solution range and ScTiNbO6 with α-PbO2 structure

    International Nuclear Information System (INIS)

    Anatase-type nanoparticles ScXTi1-2XNbXO2 with wide solid solution range (X=0-0.35) were hydrothermally formed at 180 deg. C for 5 h. The lattice parameters a0 and c0, and the optical band gap of anatase gradually and linearly increased with the increase of the content of niobium and scandium from X=0 to 0.35. Their photocatalytic activity and adsorptivity by the measurement of the concentration of methylene blue (MB) that remained in the solution in the dark or under UV-light irradiation were evaluated. The anatase phase existed stably up to 900 deg. C for the samples with X=0.25-0.30 and 750 deg. C for that with X=0.35 during heat treatment in air. The phase with α-PbO2 structure and the rutile phases coexisted in the samples with X=0.25-0.30 after heated at temperatures above 900-950 deg. C. The α-PbO2 structure having composition ScTiNbO6 with possibly some cation order similar to that seen in wolframite existed as almost completely single phase after heat treatment at temperatures 900-1500 deg. C through phase transformation from anatase-type ScTiNbO6. - Graphical abstract: Anatase-type ScXTi1-2XNbXO2 solid solutions with wide solid solution range (X=0-0.35) were hydrothermally formed as nanoparticles from the precursor solutions of Sc(NO3)3, TiOSO4, NbCl5 at 180 deg. C for 5 h using the hydrolysis of urea. Anatase-type ScTiNbO6 was synthesized under hydrothermal condition. ScTiNbO6 having α-PbO2 structure with possibly some cation order similar to that seen in wolframite was formed through phase transformation above 900 deg. C.

  13. Correlated rattling-ion origins of dielectric properties in reentrant dipole glasses BaTiO{sub 3}-BiScO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Krayzman, Victor; Levin, Igor, E-mail: igor.levin@nist.gov; Woicik, Joseph C. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Bridges, Frank [Department of Physics, University of California, Santa Cruz, California 95064 (United States)

    2015-11-09

    The local structure of the pseudo-cubic solid solution 0.6BaTiO{sub 3}-0.4BiScO{sub 3}, which exhibits reentrant dipole-glass behavior, has been determined using the Reverse Monte Carlo method to simultaneously fit (1) neutron and X-ray total scattering data (including the corresponding real-space pair-distribution functions), (2) Bi and Sc extended X-ray absorption fine structure, and (3) patterns of diffuse scattering in electron diffraction. These structural refinements revealed the multi-site probability density distributions for both Bi (14-sites) and Ti (8 sites), whereas Ba and Sc featured normal unimodal distributions. Bi atoms are displaced along both the 〈111〉 and 〈100〉 directions, while Ti atoms are shifted along 〈111〉. Correlated dynamic hopping of Bi and Ti over their corresponding split sites combined with chemical disorder is proposed as the origin of the strong frequency dispersion observed in dielectric measurements. The existence of split sites also explains the reentrant dipole-glass behavior reported for this system.

  14. Correlated rattling-ion origins of dielectric properties in reentrant dipole glasses BaTiO3-BiScO3

    International Nuclear Information System (INIS)

    The local structure of the pseudo-cubic solid solution 0.6BaTiO3-0.4BiScO3, which exhibits reentrant dipole-glass behavior, has been determined using the Reverse Monte Carlo method to simultaneously fit (1) neutron and X-ray total scattering data (including the corresponding real-space pair-distribution functions), (2) Bi and Sc extended X-ray absorption fine structure, and (3) patterns of diffuse scattering in electron diffraction. These structural refinements revealed the multi-site probability density distributions for both Bi (14-sites) and Ti (8 sites), whereas Ba and Sc featured normal unimodal distributions. Bi atoms are displaced along both the 〈111〉 and 〈100〉 directions, while Ti atoms are shifted along 〈111〉. Correlated dynamic hopping of Bi and Ti over their corresponding split sites combined with chemical disorder is proposed as the origin of the strong frequency dispersion observed in dielectric measurements. The existence of split sites also explains the reentrant dipole-glass behavior reported for this system

  15. Growth of Araucaria angustifolia in the Embrapa/Epagri forest reserve, Caçador, SC, Brazil Crescimento de Araucaria angustifolia na Reserva Florestal Embrapa/ Epagri, Caçador, SC

    Directory of Open Access Journals (Sweden)

    Patricia Póvoa de Mattos

    2010-06-01

    Full Text Available Araucaria Forest is one of most threatened phyto-physiognomies in the Atlantic Forest domain,
    presenting great ecological-economical importance. Nevertheless, there are still lacks of knowledge concerning growth and dynamic of important species, as Araucaria angustifolia. The objective of this work was to recover  the past growth of Araucaria angustifolia, native from Caçador, SC, Brazil, by measuring growth rings and to estimate the average periodic diametric increment. The growth rings were counted and measured, using a stereoscope microscope, in increment cores of 0.5 cm collected from 32 adult trees. The measurements were done with LINTAB measuring table, with 0.01 mm of precision. The samples sizes were irregular, varying from 4.2 to 20.2 cm long. The trees presented average diameter breast height (DBH of 76.3 cm, varying from 10.7 to 141.3 cm. The periodic diameter increment from the last 10 years was 0.4 cm, varying from 0.11 to 1.15 cm. It was observed differences among trees, but there was a tendency of reduction of growth rhythm in larger trees, being more
    evident in trees with more than 110 cm of DBH.A Floresta Ombrófila Mista (FOM é uma das fitofisionomias mais ameaçadas da área de domínio da
    Mata Atlântica, apresentando grande importância ecológico-econômica. Apesar disso, ainda existem lacunas de conhecimento sobre a produtividade primária, o crescimento e a dinâmica de espécies importantes, como a Araucaria angustifolia. O presente trabalho tem por objetivo estudar o crescimento anual de Araucaria angustifolia, nativa do Município de Caçador, SC, pela medição dos anéis de crescimento. A contagem e medição dos anéis de crescimento foram feitas com o auxílio de um microscópio estereoscópico, em baguetas de 0,5 cm de diâmetro, coletadas de 32 árvores adultas. As medições foram feitas com o medidor de anéis de crescimento LINTAB, com precisão de 0,01 mm. O comprimento das amostras

  16. First principles study of the electron structures of CaCu3Mn4O12 and CaCu3Ti4O12

    International Nuclear Information System (INIS)

    The electronic structures of CaCu3Mn4O12 and CaCu3Ti4O12 are investigated from HF SCF LCAO calculation. In CaCu3Mn4O12, the band and the density of states show a spin asymmetric ferrimagnetic character with a small energy gap. The Mn spin is anti-aligned with the Cu spin, and the total spin moment is 9 μ B. Our calculation correctly reproduces the observed antiferromagnetic insulating character of CaCu3Ti4O12. The gap in the band structure, which is 2.15 eV, reasonably agrees with the experimental value 1.5 eV. The electron density populations at different planes show clearly that the electron density has symmetric character. A tilted Mn(Ti) orbital implies a typical tilted three-dimensional network of MnO6 (TiO6) octahedra due to doping of the Jahn-Teller ion Cu. There is no covalency between Ca, Cu and Mn(Ti) atoms. In contrast, there are stronger bonds and somewhat likely covalency between Cu and O atoms, and also between Mn(Ti) and O atoms

  17. Cr4 + :Gd3Sc2Ga3O12 passive Q-switch for the Cr3 + :LiCaAlF6 laser

    Science.gov (United States)

    Kuo, Yen-Kuang; Yang, Yang; Birnbaum, Milton

    1994-05-01

    A Cr4+:Gd3Sc2Ga3O12 (Cr4+:GSGG) broad-band saturable absorber has been demonstrated to be an excellent passive Q-switch for the flashlamp-pumped tunable Cr3+:LiCaAlF6 (Cr:LiCAF) laser at room temperature. A single Q-switched laser output pulse of 11 mJ in energy and 37 ns in duration at 778 nm was obtained in a nonoptimized laser.

  18. The phase stability of Ca2TiO4 and related Ruddlesden-Popper phases

    Science.gov (United States)

    Ramadan, Amr H. H.; Hesselmann, Linda; De Souza, Roger A.

    2015-11-01

    The Ruddlesden-Popper phases of the Ca-Ti-O system, Can+1TinO3n+1, are investigated by means of atomistic simulations employing empirical pair potentials. The stability of the phases is examined in terms of various reaction schemes: the formation from the binary oxides, the addition of the perovskite oxide to a given phase, and the reaction between perovskite and rock-salt oxides. The energies of these reactions are compared with results previously obtained for the Ruddlesden-Popper phases of the Sr-Ti-O system. The importance of the disproportionation reaction of the various R-P phases in both Ca and Sr systems is also emphasized. The results obtained are in good agreement with experimental observations regarding both systems.

  19. Alpha clustering in Ti isotopes: 40,44,48Ca + α resonant scattering

    Directory of Open Access Journals (Sweden)

    Bailey Sam

    2016-01-01

    Full Text Available Measurements were made of the 4He(40,44,48Ca,α resonant scattering reactions at 180° and up to Ec.m. ~ 11.5MeV, using the Thick Target Inverse Kinematics technique. These measurements are discussed, with a focus on assessing their usefulness for investigating α-clustering in medium mass 44,48,52Ti nuclei.

  20. (Zn, Ca) Solid-Solution Behavior and Its Effect on Luminescence Properties in Ca1- xZnx TiO3: 0.002Pr3+ Phosphors

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Nominal composition of Ca1 - xZnxTiO3: 0. 002Pr3 + ( x = 0. 000 ~ 0. 200) phosphors were prepared by conventional solid reaction route. XRD and PL measurements were used to investigate the solid-solution structure and luminescence properties of Zn-doped Ca1- xZnxTiO3:0. 002Pr3 + phosphors. The effect of solid-solution structure formed by substitution between Ca2 + and Zn2 + ions on the luminescent properties was analyzed. The results reveal that, with the increase of Zn substitution content below 0.010, lattice parameters and the intensity of excitation peak at both 260 and 330 nm as well as the corresponding 610 nm emission intensity are monotonously decreased quickly in a similar tendency. Also, the evolution of luminescence intensity and crystal cell parameters against Zn doping concentration are in good agreement.Above results are closely related with the structure change within Ca1- xZnxTiO3:0. 002Pr3 + solid-solution phase formed by the Zn ions substitution for the Ca sites. Present study reveals that the solid-solution structure formed by substitution between Ca2 + and Zn2 + ions has significant effect on the luminescence properties of single phase Ca1- xZnxTiO3:0.002Pr3 +phosphors.

  1. Impact of symmetry on the ferroelectric properties of CaTiO3 thin films

    Science.gov (United States)

    Biegalski, Michael D.; Qiao, Liang; Gu, Yijia; Mehta, Apurva; He, Qian; Takamura, Yayoi; Borisevich, Albina; Chen, Long-Qing

    2015-04-01

    Epitaxial strain is a powerful tool to induce functional properties such as ferroelectricity in thin films of materials that do not possess ferroelectricity in bulk form. In this work, a ferroelectric state was stabilized in thin films of the incipient ferroelectric, CaTiO3, through the careful control of the biaxial strain state and TiO6 octahedral rotations. Detailed structural characterization was carried out by synchrotron x-ray diffraction and scanning transmission electron microscopy. CaTiO3 films grown on La0.18Sr0.82Al0.59Ta0.41O3 (LSAT) and NdGaO3 (NGO) substrates experienced a 1.1% biaxial strain state but differed in their octahedral tilt structures. A suppression of the out-of-plane rotations of the TiO6 octahedral in films grown on LSAT substrates resulted in a robust ferroelectric I4 mm phase with remnant polarization ˜5 μC/cm2 at 10 K and Tc near 140 K. In contrast, films grown on NGO substrates with significant octahedral tilting showed reduced polarization and Tc. These results highlight the key role played by symmetry in controlling the ferroelectric properties of perovskite oxide thin films.

  2. Impact of symmetry on the ferroelectric properties of CaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Biegalski, Michael D.; Qiao, Liang [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Gu, Yijia; Chen, Long-Qing [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16801 (United States); Mehta, Apurva [Stanford Synchrotron Lightsource SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); He, Qian; Borisevich, Albina [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Takamura, Yayoi, E-mail: ytakamura@ucdavis.edu [Department of Chemical Engineering and Materials Science, University of California Davis, Davis, California 95616 (United States)

    2015-04-20

    Epitaxial strain is a powerful tool to induce functional properties such as ferroelectricity in thin films of materials that do not possess ferroelectricity in bulk form. In this work, a ferroelectric state was stabilized in thin films of the incipient ferroelectric, CaTiO{sub 3}, through the careful control of the biaxial strain state and TiO{sub 6} octahedral rotations. Detailed structural characterization was carried out by synchrotron x-ray diffraction and scanning transmission electron microscopy. CaTiO{sub 3} films grown on La{sub 0.18}Sr{sub 0.82}Al{sub 0.59}Ta{sub 0.41}O{sub 3} (LSAT) and NdGaO{sub 3} (NGO) substrates experienced a 1.1% biaxial strain state but differed in their octahedral tilt structures. A suppression of the out-of-plane rotations of the TiO{sub 6} octahedral in films grown on LSAT substrates resulted in a robust ferroelectric I4 mm phase with remnant polarization ∼5 μC/cm{sup 2} at 10 K and T{sub c} near 140 K. In contrast, films grown on NGO substrates with significant octahedral tilting showed reduced polarization and T{sub c}. These results highlight the key role played by symmetry in controlling the ferroelectric properties of perovskite oxide thin films.

  3. Surface chemical changes of CaTiO3:Pr3+ upon electron beam irradiation

    International Nuclear Information System (INIS)

    Surface chemical changes of CaTiO3:Pr3+ phosphor material and their effect on the red emission intensity of the 1D2→3H4 transition of Pr3+, upon electron beam irradiation are presented. Red emission at 613 nm was obtained upon probing the surface with a 2 keV electron beam. The surface chemical changes and Pr3+ red emission were monitored using an Auger Electron Spectroscopy (AES) and Cathodoluminescence (CL) spectrometer, respectively. The CL intensity decreased with a decrease in O on the surface at 1×10−8 Torr base pressure and decreased with an increase in O on the surface at 1×10−6 Torr O2. The X-ray Photoelectron Spectroscopy (XPS) revealed that CL degradation at 1×10−6 Torr O2 is due to the formation of CaO and CaOx as well as TiO2/Ti2O3 non-luminescent species on the surface.

  4. Hibonite, Ca2/Al, Ti/24O38, from the Leoville and Allende chondritic meteorites.

    Science.gov (United States)

    Keil, K.; Fuchs, L. H.

    1971-01-01

    Hibonite was discovered in light-colored, Ca-Al-Ti-rich and Si-Fe-poor, achondritic inclusions of the Leoville and Allende HL-group chondrites. Two varieties of hibonite occur: one emits a bright red-orange luminescence under electron bombardment and has high amounts of Al2O3 (87.7; 87.9) and low amounts of MgO (0.65; 0.8) and TiO2 (0.68; 0.8). The other emits a bright blue luminescence and is low in Al2O3 (78.7; 79.2) and high in MgO (3.3; 3.7) and TiO2 (6.5; 7.9) (in wt. %). The oxide CaO is about the same in both varieties. It is suggested that the change in the color of the visible luminescence results from changes in composition. The origin of hibonite which occurs in complex mineral assemblages together with anorthite, gelhenite, wollastonite, aluminous diopside, andradite, Ca-pyroxene, perovskite, spinel, taenite, chromite, and pentlandite, and in close proximity to nodules containing calcite, whewellite, forsterite and many of the aforementioned phases, is discussed. The proposition that hibonite and associated phases originated by contact metamorphism and metasomatism of calcite-dolomite bearing assemblages cannot, at this time, be completely ruled out.

  5. New low loss A{sub 9}B{sub 9}O{sub 31} (A = La; B = Ti, Mg, Sc, Fe, Al, Ga) ceramics for microwave applications

    Energy Technology Data Exchange (ETDEWEB)

    Muhammad, Raz [Materials Research Laboratory, Department of Physics, University of Peshawar, 25120 (Pakistan); Iqbal, Yaseen, E-mail: dryaseeniqbal@yahoo.co.uk [Materials Research Laboratory, Department of Physics, University of Peshawar, 25120 (Pakistan); Reaney, Ian M. [Department of Materials Science and Engineering, University of Sheffield, S1 3JD (United Kingdom)

    2015-10-15

    A{sub n}B{sub n}O{sub 3n+2} (n = 4.5) type layered perovskite ceramics with general formula A{sub 9}B{sub 9}O{sub 31} (A = La; B = Ti, Mg, Sc, Fe, Al, Ga) were prepared via a mixed oxide solid state sintering route. X-ray diffraction analysis revealed single phase La{sub 9}(TiB){sub 9}O{sub 31} (B = Ti, Mg, Sc, Fe, Al, Ga) solid solutions with orthorhombic (Pnma) symmetry when sintered at 1500–1650 °C for 4–12 h. The temperature coefficient of resonance frequency (τ{sub f}) was influenced by the polarizability of B-site cations while relative permittivity (ε{sub r}) and quality factor (Q × f{sub o}) were dependent on the relative density. The samples investigated in the present study exhibited reasonable ε{sub r} (39–48.3), high Q × f{sub o} (11823–19070 GHz) and near zero τ{sub f} (−1.28 to −22.16 ppm/°C). These ceramics might be potential candidates for microwave devices. - Highlights: • New A{sub 9}B{sub 9}O{sub 31} (A = La; B = Ti, Mg, Sc, Fe, Al, Ga) type compounds were processed. • All the compositions formed single phase ceramics with orthorhombic (Pnma) symmetry. • The dielectric properties were strongly influenced by the processing condition. • The best dielectric properties achieved were ε{sub r} = 42, Q{sub f} = 17216 GHz and τ{sub f} ∼ −1.3 ppm/°C. • Sc- and Fe-based compounds meet the bench mark for MW applications.

  6. Importance of spin-orbit coupling in power factor calculations for half-Heusler ANiB (A=Ti, Hf, Sc, Y; B=Sn, Sb, Bi)

    OpenAIRE

    Guo, San-Dong

    2015-01-01

    We investigate the spin-orbit coupling (SOC) effects on the electronic structures and semi-classic transport coefficients of half-Heusler $\\mathrm{ANiB}$ (A=Ti, Hf, Sc, Y; B=Sn, Sb, Bi) by using generalized gradient approximation (GGA). Calculated results show that SOC splits the valence bands at high symmetry $\\Gamma$ point, and modifies the outline of $\\Gamma$-centered valence bands, which has remarkable effects on the electron transport properties. Thermoelectric properties are performed t...

  7. Synthesis of CaTiO3 from calcium titanyl oxalate hexahydrate (CTO) as precursor employing microwave heating technique

    Indian Academy of Sciences (India)

    B M Patil; R S Srinivasa; S R Dharwadkar

    2007-06-01

    Calcium titanate, CaTiO3, an important microwave dielectric material and one of major phases in synroc (synthetic rock), a titanate ceramic with potential application for fixation of high level nuclear waste was synthesized from calcium titanyl oxalate [CaTiO (C2O4)2.6H2O] (CTO) by employing microwave heating technique. CTO heated in microwave heating system in air at 500°C for 1 h gave a perovskite, CaTiO3. The product obtained by heating of CTO in the same system at 700°C for the same duration was however, much more crystalline. CaTiO3 obtained by the present method was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET surface area measurement.

  8. Construction of monoenergetic neutron calibration fields using 45Sc(p, n) 45Ti reaction at JAEA

    International Nuclear Information System (INIS)

    The 8 and 27 keV monoenergetic neutron calibration fields have been developed by using 45Sc(p, n)45Ti reaction. Protons from a 4-MV Pelletron accelerator are used to bombard a thin scandium target evaporated onto a platinum disc. The proton energies are finely adjusted to the resonance to generate the 8 and 27 keV neutrons by applying a high voltage to the target assemblies. The neutron energies were measured using the time-of-flight method with a lithium glass scintillation detector. The neutron fluences at a calibration point located at 50 cm from the target were evaluated using Bonner spheres. A long counter was placed at 2.2 m from the target and at 60 deg. to the direction of the proton beam in order to monitor the fluence at the calibration point. Fluence and dose equivalent rates at the calibration point are sufficient to calibrate many types of the neutron survey metres. (authors)

  9. Quantum criticality in CaRuO{sub 3} - Influence of Ti substitution

    Energy Technology Data Exchange (ETDEWEB)

    Baran, A. [Faculty of Manufacturing Technologies, Technical University of Kosice, Presov (Slovakia); Zorkovska, A. [Institute of Geotechnics Slovak Academy of Science, Kosice (Slovakia); Kajnakova, M.; Feher, A. [Centre of Low Temperature Physics, P. J. Safarik University and Slovak Academy of Science, Kosice (Slovakia); Sebek, J.; Santava, E. [Institute of Physics Academy of Science of Czech Republic, Prague (Czech Republic); Bradaric, I. [Condensed Matter Physics Laboratory, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade (Serbia)

    2012-08-15

    Thermodynamic and transport properties of the CaRu{sub 1-x}Ti{sub x}O{sub 3} system with x = 0, 0.03, 0.07, 0.10, and 0.15 in magnetic field up to 9 T have been studied. The unconventional temperature dependences of magnetic susceptibility, specific heat, and electrical resistivity observed for CaRuO{sub 3} are typical for non-Fermi liquids and they support the assumption about the proximity of the system to the quantum critical point. The analysis of the experimental results suggests the electronic phase separation in CaRuO{sub 3} into ferromagnetic itinerant regions coexisting with strongly correlated ones. Substitution by titanium seems to push the system towards ferromagnetism, and drives it away from the quantum criticality. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Solid state reaction synthesis and photoluminescence properties of Dy{sup 3+} doped Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12} phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Long, Qiang; Wang, Chuang; Li, Yanyan; Ding, Jianyan; Wang, Xicheng; Wang, Yuhua, E-mail: wyh@lzu.edu.cn

    2015-11-15

    Highlights: • Ca{sub 3−x}Sc{sub 2}Si{sub 3}O{sub 12}:xDy{sup 3+} (0.01 ≤ x ≤ 0.03) was successfully synthesized under a reducing atmosphere. • The thermal stability of the Ca{sub 2.975}Sc{sub 2}Si{sub 3}O{sub 12}:0.025Dy{sup 3+} is superior to commercial phosphors in theory and experiment. • The optimal chromaticity coordinates of Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} is (x = 0.3425, y = 0.3343) upon 350 nm excitation. - Abstract: The white emission phosphor Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} was synthesized by the solid-state reaction. Phase analysis and characteristic luminescence properties are investigated by X-ray diffraction and photoluminescence spectra measurement. Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} phosphor shows strong absorption in 350–410 nm region and exhibits white emission with CIE chromaticity coordinates of (0.3425, 0.3343). Its emission intensity at 250 °C remained 74% of that measured at room temperature. Moreover, the activation energy is also calculated through the Arrhenius equation. The result shows that the thermostability of Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} is superior than that of commercial phosphor Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Ce{sup 3+}. The outstanding luminescent properties indicate that Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} could be a potential white light emission phosphor.

  11. The structure and piezoelectric properties of (Ca1-xSrx)Bi4Ti4O15 ceramics

    International Nuclear Information System (INIS)

    In this paper, the structure and piezoelectric properties of (Ca1-xSrx)Bi4Ti4O15 ceramics (x=0-1.0) are investigated. The formation of single orthorhombic phase is verified by XRD. The dependence of dielectric and piezoelectric properties on x is also determined. The results show that the excellent properties could be found in the composition of x=0.4. In that composition, d33=14.9, TC=677 deg. C and the DC resistivity is decuplely higher than that of BST (SrBi4Ti4O15) and CBT (CaBi4Ti4O15)

  12. A simple solvothermal process to synthesize CaTiO{sub 3} microspheres and its photocatalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Weixia [State Key Lab of Silicon Materials & School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Department of Material Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen, 333001 (China); Song, Bin, E-mail: bzsong@zju.edu.cn [Department of Physics, Zhejiang University, Hangzhou, 310027 (China); Meng, Weijie; Zhao, Gaoling; Han, Gaorong [State Key Lab of Silicon Materials & School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2015-09-15

    Highlights: • This paper presents a facile hydrothermal route to self-assemble CaTiO{sub 3} nanosheets into microspheres without any surfactants or template and discusses the photocatalytic performance of the large-scale structure. • The growth mechanism for spherical CaTiO{sub 3} is proposed to be a self assembly-nanosheets building units further oriented growth mechanism. • The molar ratio of water/ethanol is crucial for the formation of spherical CaTiO{sub 3}. In addition, CaTiO{sub 3} microspheres were stable during the photocatalytic reaction and more convenient to store and handle as a micrometre-scale structure. • The present work not only helps understanding of the growth behavior of 3D CaTiO{sub 3} microspheres in a solution synthetic system, but also provides an efficient approach to enhance the photocatalytic properties of CaTiO{sub 3} catalysts by the controllable design of desirable structure and morphology. - Abstract: Novel CaTiO{sub 3} microspheres composed of nanosheets have been successfully prepared via a very simple solvothermal process in ethanol aqueous solution without any template or surfactant. The microstructure and morphology are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The effects of the reaction time, reaction temperature, and molar ratio of ethanol/water on the formation of the spherical structure have been investigated. CaTiO{sub 3} microspheres assembled by nanosheet units have been obtained by controlling the molar ratio of water/ethanol. The growth mechanism has been proposed based on the results of time-dependent experiments. It is proposed that amorphous particles transformed to nanosheets, and nanosheets self assembly into solid microspheres, then nanosheets building units further oriented growth along [1 1 0] direction result in the formation of nanosheets building units, and finally form the

  13. Structural and luminescence study of Ce3+ and Tb3+ doped Ca3Sc2Si3O12 garnets obtained by freeze-drying synthesis method

    Science.gov (United States)

    Velázquez, J. J.; Fernández-González, R.; Marrero-Jerez, J.; Rodríguez, V. D.; Lukowiak, A.; Chiappini, A.; Chiasera, A.; Ferrari, M.; Núñez, P.

    2015-08-01

    Ca3Sc2Si3O12 garnets doped with Ce3+ and Tb3+ ions were synthesized by a freeze-drying precursor method. The structural characterization was performed by X-ray diffraction (XRD) and Raman spectroscopy. Scanning Electron Microscopy (SEM) images of the calcined material were studied. High temperature treatments and doping with RE3+ ions resulted in a reduction of the secondary phases (Sc2O3) and an increase of the mean size of the nanocrystals, from 75 to 149 nm. These effects were confirmed by means of Raman spectra. Moreover, luminescence features of Ce3+ and Tb3+ doped samples indicated that these ions are effectively incorporated into the crystalline phase. In addition, the energy transfer processes between Ce3+ and Tb3+ ions in codoped garnets have been studied.

  14. Testing sol-gel CaTiO3 coatings for biocompatible applications

    International Nuclear Information System (INIS)

    In the present work, CaTiO3 films with thicknesses of 4 μm have been prepared by sol-gel spin-coating process. The films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy and scanning electron microscopy-energy disperse X-ray spectroscopy to study the chemical, structural and morphological changes produced by annealing treatments. Polycrystalline coatings with a perovskite structure were obtained at temperatures of 800 deg. C. These films grown on mirror-like surfaces show good adherence and develop a rough microstructured surface. The biomimetic properties were assayed by evaluating the growth of apatite in simulated body fluids (SBF). We conclude that the coatings are of potential interest in order to enhance the surface properties of Ti-based prosthetic alloys

  15. PHOTOCATALYTIC ACTIVITY OF TiO2 NANO SUPPORTED ON MEMBRANE CELLULOSE ACETATE/NATA DE COCO (CA/NDC IN PHOTODEGRADATION OF METHYLENE BLUE

    Directory of Open Access Journals (Sweden)

    Roro Ernia Prawithasari

    2015-12-01

    Full Text Available Study of synthesis and effectiveness of membrane catalyst of cellulose acetate/nata de coco-TiO2 nano (CA/NDC-TiO2 nano in photodegradation of methylene blue in batch system has been investigated. TiO2nanoparticles were synthesized by hydrothermal method followed by calcination at 450oC. Scanning Electron Microscopy (SEM images indicate nano TiO2 has been successfully synthesized with average particle diameter as 88,63±4,37 nm. X-ray diffraction pattern (XRD of nano TiO2 shows some characteristic peaks of anatase TiO2 were still existed. Membrane photocatalyst of CA/NDC- nano TiO2 was prepared via phase inversion method by mixing TiO2 nanoparticles with CA casting solution. Thermogravimetric analysis shows three decomposition steps of CA/NDC-nano membrane as well as CA/NDC membrane. Photodegradation of methylene blue was conducted with nano-TiO2 particles and CA/NDC-TiO2 membrane for 50 minutes in batch system. The absorbance changes were measured by spectrophotometer at wavelength of 664.6 nm. The result shows the photodegradation rections tended to follow second order reaction. According to the rate constant value, k, the photocatalytic effectivity using CA-NDC/nano TiO2 membrane and nano TiO2photocatalysts in metilen blue photodegradation, statistically were not significantly different.

  16. Spectroscopic study of 44Ti by reactions 40Ca(α,γ)44Ti, 40Ca(7Li,p2nγ)44Ti and 42Ca(α,2nγ)44Ti

    International Nuclear Information System (INIS)

    The first reaction allowed to populate states of excitation energies between 9.2 and 9.8 MeV and to measure their γ-decays to low-lying states in 44Ti. Moreover this reaction helps in measuring the mean lifetime of 12 states by using the Doppler shift attenuation method. The second reaction was used to find the levels predicted by the shell model and among them the highest spin allowed Jsup(π)=12+. The third reaction helps in measuring the mean lifetime tau=3.0+-0.6 ns of the Jsup(π)=(12+) state at Esub(x)=8.040 MeV. In this measurement the delayed coincidence technique with a pulsed beam was used. A confrontation of the experimental and theoretical studies on the 44Ti nucleus is presented in this work

  17. Partial conductivities in perovskites CaZr1- x Sc x O3-α ( x = 0.03-0.20) in an oxidation atmosphere

    Science.gov (United States)

    Gorelov, V. P.; Balakireva, V. B.; Kuz'min, A. V.

    2016-01-01

    Partial (ionic, proton, and hole) conductivities of oxides CaZr1- x Sc x O3-α( x = 0.03-0.20) with the perovskite structure in air atmosphere have been studied as functions of temperature in the range of 600-900°C and partial water-vapor pressure in the range of {P_{{H_2}O}}= 40-2500 Pa. The influence of the humidity of the atmosphere on the relative change in the concentration of oxygen vacancies as a function of temperature has been estimated.

  18. Ab-initio Study of Structural Phase Transitions, Electronic and Optical Properties of the Double Perovskite A2ScSbO6 (A=Sr,Ca)

    OpenAIRE

    Ray, Rajyavardhan; Himanshu, A. K.; Bandyopadhyay, S K; Sen, Pintu; Kumar, Uday; Sinha, T. P.

    2013-01-01

    First principles study of the electronic structures and optical properties of recently synthesized double perovskite $A_2ScSbO_6$ $(A=Sr, Ca)$ have been performed within the framework of density functional theory using WIEN2k. With increasing temperature, the $Sr$ compound has three phase transitions at ${\\rm 400K}$, ${\\rm 550K}$ and ${\\rm 650K}$ approximately, leading to the following sequence of phases: $P21/n \\rightarrow I2/m \\rightarrow I4/m \\rightarrow Fm\\bar{3}m$. Starting from the mono...

  19. Dielectric and electromechanical properties of LiNbO3-modified (BiNa)TiO3-(BaCa)TiO3 lead-free piezoceramics

    Science.gov (United States)

    Zaman, Arif; Hussain, Ali; Malik, Rizwan Ahmed; Maqbool, Adnan; Nahm, Sahn; Kim, Myong-Ho

    2016-05-01

    The dielectric and electromechanical properties of LiNbO3-modified (1-x) [0.91Na0.5Bi0.5TiO3-0.09Ba0.70Ca0.30TiO3]-xLiNbO3 (abbreviated as (BiNa)TiO3-(BaCa)TiO3-LN) lead-free piezoceramics were investigated. The electrical properties revealed that the addition of LiNbO3 (LN) induces a phase transition from a non-ergodic relaxor to an ergodic relaxor in the (BiNa)TiO3-(BaCa)TiO3-LN system. A large electrostrain of ~0.418% with a normalized strain of ~690 pm V-1 at 6 kV mm-1 was observed at the coexistence of the non-ergodic relaxor and ergodic relaxor phases for LN 0.020, where a field-assisted reversible phase transition between metastable ferroelectric and stable ergodic relaxor phases occurs. Subsequently, a gradual enhancement in the temperature stability of the dielectric constant was observed. At 3 mol.% LN, a nearly constant temperature and a frequency-invariant permittivity of ɛ r ~ 3300 over a broad temperature range of 147 °C-306 °C was observed along with small losses from room temperature up to 400 °C.

  20. Microwave dielectric properties of 0.95MgTiO3-0.05CaTiO3 for application in dielectric resonator antenna

    International Nuclear Information System (INIS)

    In this paper, the microwave dielectric properties of 0.95MgTiO3-0.05CaTiO3 ceramics have been studied for application in dielectric resonator antenna design. ZnO was selected as liquid sintering aids to lower the sintering temperature of 0.95MgTiO3-0.05CaTiO3. The X-ray diffraction pattern exhibited single phase for ceramics up to 1.0 wt.%. The maximum dielectric constant was obtained for samples after 0.25 wt.% ZnO addition and 1290 deg. C for 4 h sintering. A near-zero temperature coefficient of resonant frequency (τf) of -4.9 ppm/deg. C was obtained for 0.95MgTiO3-0.05CaTiO3 ceramics with 0.25 wt.% ZnO sintered at 1250 deg. C for 4 h. The dielectric resonator antenna measured at 9.58 GHz exhibited a 5.92% bandwidth (return loss <-10 dB) of center frequency

  1. Performance of Ca1-xSrxTiO3 as barriers in dielectric barrier discharges with different Sr content

    International Nuclear Information System (INIS)

    Plasma assisted catalytic technology, which uses synergetic technologies between the catalyst and plasma, has attracted much attention over the past several years. Theoretically, permittivity of a dielectric barrier influences the transferred charge of a microdischarge; thus high permittivity can improve the plasma reaction in a dielectric barrier discharge (DBD) plasma reactor. Despite the increased interest in the chemical processes, very little has been reported concerning the influence of materials of a dielectric barrier on DBD plasma reactions, since a high permittivity barrier generally exhibits low fracture strength and low dielectric strength making it break down under strong current pulses. In the present study, Ca1-xSrxTiO3 (0.1 ≤ x ≤ 0.4) which possesses a high permittivity and a high fracture strength was prepared by liquid phase sintering and was used as a dielectric barrier for the destruction of carbon dioxide by a DBD plasma reaction. The permittivity of Ca1-xSrxTiO3 (0.1 ≤ x ≤ 0.4) increased with increasing SrTiO3 content; however, the observed CO2 conversion became greatest using Ca0.8Sr0.2TiO3 and then decreased with increasing SrTiO3 content. These results imply that the reactivity of CO2 destruction does not monotonously increase with increased permittivity of the Ca1-xSrxTiO3 barriers. Both amplitude and density of the current pulses ignited by Ca0.8Sr0.2TiO3 were much greater than that of Ca0.6Sr0.4TiO3. Further, it was confirmed that a plasma reaction uniformly proceeded using the Ca0.8Sr0.2TiO3 barrier, but proceeded non-uniformly using the Ca0.6Sr0.4TiO3 barrier by observing the carbon deposition profiles on the surfaces of the barriers

  2. Density functional study of the structural and magnetic properties of Al12X(X=Sc, Ti, V, Gr, Mn, Fe, Co, Ni, Cu, Zn) clusters

    International Nuclear Information System (INIS)

    Started from the four types 13-atom high-symmetric (Ih, Oh , D5h, D3h) close-packed structures and by replacing a 3d group atom in the unequivalent position, the structural and magnetic properties of the doped Al12X (X=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) clusters are systematically studied by u- sing the density-functional theory. Our results show that: except Al12Cr and Al12Fe, all the other Al12X clusters prefer to the Ih-replacing geometry as the ground-state structure, and with replacing surface atom for the early 3d elements (X=Sc, Ti, V, Mn) but the central atom for the late 3d elements (X=Co, Ni, Cu, Zn); Al12Cr and Al12Fe prefer to the Oh structure with replacing a surface atom as the ground- state; The energy-closed isomers can be found clearly for the doped clusters for most 3d elements (X= Ti, V, Cr, Fe, Co, Zn); Magnetism enhancement effect can be found in general for all these doped clusters as comparing with the pure Al13 cluster. (authors)

  3. Sodium scandium diphosphate, NaScP2O7, isotypic with α-NaTi(III)P2O7

    OpenAIRE

    Zdirad Žák; Jan Cempírek; Radek Škoda

    2009-01-01

    Crystals of the title compound, NaScP2O7, were grown by a flux method. The crystal structure is isotypic with those of α-NaTiP2O7, NaYbP2O7 and NaLuP2O7, and is closely related to that of NaYP2O7. The structural set-up consists of a three-dimensional framework of P2O7 units that are corner-shared by ScO6 octahedra, forming tunnels running parallel to [010]. The Na atoms are situated in the tunnels and are surrounded by nine O atoms in a distorted environment.

  4. Characterisation of Sol-Gel Synthesis of Phase Pure CaTiO3 Nano Powders after Drying

    Science.gov (United States)

    Mallik, P. K.; Biswal, G.; Patnaik, S. C.; Senapati, S. K.

    2015-02-01

    According to a few recent studies, calcium titanate (CT) is a material that is similar to hydroxyapatite in biological properties. However, calcium titanate is not currently being used in the biomedical applications as to hydroxyapatite. The objective is to prepare nano calcium titanate powders from the equimolar solution of calcium oxide, ethanol and Titanium (IV) isopropoxide via sol-gel synthesis. The phase analysis and morphology of powder particles were studied by X-ray diffraction (XRD), while the composition and size of powder particles were determined by Transmission electron microscope (TEM) attached with energy dispersive x-ray spectrometer (EDS). As results, XRD confirm the presence of phase pure crystalline CaTiO3 after drying at 100°C for 24 hours, while TEM analysis confirms about 13 nm sizes of CaTiO3 particles and some agglomerated particle of 20-30 nm. Moreover, EDS analysis indicates that the approximately stoichiometric Ca/Ti ratio 1:1 was obtained in the CaTiO3 powders. Finally, it can be concluded that described sol-gel synthesis could be novel method for the production of nano CaTiO3 particles at lower temperature compared to any other methods of production.

  5. Sol–gel synthesis and photoluminescence of CaTi1–ZrO3 : Pr3+ phosphors

    Indian Academy of Sciences (India)

    Lixia Lin; Bing Yan

    2010-02-01

    CaTi1–ZrO3 : Pr3+ phosphors have been synthesized by sol–gel and solid state methods, with = 1/300, 2/300, 3/300, 4/300, 5/300, 6/300, 7/300, respectively. Powder X-ray diffraction (XRD), UV-visible absorption spectra, photoluminescent spectra (PL), and scanning electron microscopy (SEM) images are used to characterize the powder samples. The inverse absorption at 610 nm appearing in the UV-visible absorption spectra is due to the ${}^{1}D_{2} \\rightarrow {}^{3}H_{4}$ characteristic emission of Pr3+. Changes in the emission spectra at 610 nm were agreed with those in UV-visible absorption spectra. The strongest red excitation obtained from CaTi1–ZrO3 : Pr3+ ( = 4/300) and CaTi1–ZrO3 : Pr3+ ( = 5/300) possesses the strongest emission at 610 nm, similar to the intensities of Ca(Ti1–Zr)O3 : Pr3+ ( = 3/300, 4/300, 6/300), which may be corresponded to the cell parameters of CaTi1–ZrO3 : Pr3+.

  6. Discovery of a New Garnet Mineral, Ca_3Ti_2(SiAl_2)O_(12): An Alteration Phase in Allende

    OpenAIRE

    Ma, Chi; Krot, Alexander N.

    2013-01-01

    During a nanomineralogy investigation of the Allende CV3 carbonaceous chondrite, a new Ti-rich silicate, Ca_3Ti_2(SiAl_2)O_(12) with the Ia-3d garnet structure, was identified in the Type B1 Ca,Al-rich inclusion (CAI) Egg-3. Field-emission SEM with EDS and electron back-scatter diffraction and electron microprobe were used to characterize the composition and structure. Synthetic Ca_3Ti_2(SiAl_2)O_(12) is not reported. We present here the natural occurrence of Ca_3Ti_2(SiA...

  7. Synthesis and characterization of CCTO (CaCu3Ti4O12)

    International Nuclear Information System (INIS)

    The objective of this work is to study the ceramic material CCTO (CaCu3Ti4O12) by X-Ray Diffraction. The CCTO is a material with a giant dielectric constant at room temperature and good temperature stability over a wide temperature and frequency ranges. The preparation method has a great influence on the structure and dielectric properties of this material. The CCTO was prepared by solid state method in a planetary high energy ball milling (Fritsch Pulverisette 5). Stoichiometric quantities of CaCO3 (Aldrich 99%), TiO2 (Merck 99%) and CuO (Analar 98%) were dry milled during 30h with a rotational speed of 370 rpm and then calcined at 1050 deg C for 12h. After, the CCTO was studied by X-ray diffraction (XRD). The refinement showed that the CCTO was formed with 100% mass, the graph of Williamson-Hall showed a homogeneous sample, with a contraction in the crystal lattice and a reasonably small particle size. (author)

  8. Natural CaO-TiO2-SiO2 based ceramics

    Directory of Open Access Journals (Sweden)

    Jelena Pantić

    2011-06-01

    Full Text Available Lešnica river deposits consist of a large number of minerals of different grain sizes including sphene. Since it is very difficult to obtain pure monophase titanite by different synthetic routes (sol-gel, coprecipitation, combustion, spray pyrolysis and hydrothermal method, the aim of this work was to study the structure of the sphene from the Lešnica river deposits and possibility of using it as a natural precursor for CaO-TiO2-SiO2 based ceramics. The sphene from Lešnica was analyzed by different methods: tristimulus colorimetry, infrared spectroscopy, electron microprobe and X-ray single crystal diffraction. It was confirmed that Al, Fe, Mn and P are present in the sphene structure and proposed that corresponding structural formula could be: (Ca2+1.008 Mn2+0.0021.010(Ti4+0.901 Fe3+0.033 Al3+0.060 P5+0.0010.995 Si4+1.024 O2-5.

  9. Study of synergistic effect of Sc and C co-doping on the enhancement of visible light photo-catalytic activity of TiO2

    Science.gov (United States)

    Nasir, Muhammad; Lei, Juying; Iqbal, Waheed; Zhang, Jinlong

    2016-02-01

    Scandium and carbon co-doped TiO2 catalyst was prepared through a simple sol-gel synthesis method by using scandium nitrate as scandium dopant precursor, glucose as carbon precursor and tetrabutyl orthotitanate as titanium precursor and calcined them at 450 °C for 3 h. The characterizations of the prepared samples were accomplished through X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence spectroscopy (PL), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET). The X-ray diffraction results of the samples showed the decrease in the crystal size of the sample with the subsequent increase in the specific surface area as shown by Brunauer-Emmett-Teller. The UV-visible diffuse reflectance spectroscopy displayed the blue shift in the absorption together with the photoluminescence spectroscopy revealed the decrease in the recombination of electrons and holes by the addition of the scandium and then after the certain optimum value, the further increase of the scandium further increased the recombination of electrons and holes. The photo-catalytic activity of the samples was investigated with the help of photo-catalytic degradation of Acid orange 7 under visible light irradiation. The degradation of Acid orange 7 was highly increased for the Sc and C co-doped samples compared to the single C doped sample. And the sample 0.2 Sc/C-TiO2 had the maximum increase. The enhanced photo-catalytic performance was due the decrease of the crystal size, increase of the surface area, increase in the surface hydroxyl groups, and increase of the lifetime of the electrons and holes because of the synergistic effect of the Sc and C co-doping in TiO2.

  10. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect.

    Science.gov (United States)

    Naveed-Ul-Haq, M; Shvartsman, Vladimir V; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C

    2016-01-01

    The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 - 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 -CoFe2O4 bulk composites with similar content of the ferrite phase. PMID:27555563

  11. Study of the synthesis of TiO2 layers on macroporous ceramic supports in supercritical (SC) CO2 for processing radioactive aqueous effluents in dynamic mode

    International Nuclear Information System (INIS)

    Public and military nuclear industry generates a significant amount of radioactive liquid waste which must be treated before being released into the environment. Decontamination methods alternative to the industrial techniques (evaporation, chemical treatment) are being developed, such as column treatments or coupled filtration/sorption processes. Current researches mainly focus on the development and shaping of specific sorbents. In this context, the objectives of this thesis were first to study the synthesis of TiO2 layers on macroporous ceramic supports in supercritical (SC) CO2 and then to evaluate their potential for radionuclide extraction in these alternative processes. A robust synthesis method has been developed, based on the thermal decomposition of titanium isopropoxide in SC CO2 in the temperature range between 150 C and 350 C. Nano-structured TiO2 films were formed on the macroporous supports (ceramic foams, tubular α-alumina supports) with good adhesion, already at 150 C. The effect of the synthesis temperature on sorbents physico-chemical characteristics and sorption properties has been studied with TiO2 powders prepared under the same conditions as the supported films. The best sorption performance were observed for the powder prepared at 150 C, owing to its higher density of surface sites in comparison with powders prepared at either 250 C or 350 C. Consequently, this synthesis temperature (150 C) was selected for a detailed study of the composite sorbents (TiO2/support), in order to assess their sorption performance in continuous treatment processes. The sorption experiments have shown that a column of alumina macroporous foam (Φpore = 400μm) coated with TiO2 was suitable for processing effluents in dynamic mode with high throughputs. Both macro-pore sizes and column height were revealed as important parameters to be controlled. For the coupled filtration/sorption treatment, TiO2 membranes exhibit good mechanical strength and are able to

  12. Density functional theory study of Mo-doped M@(BN)48 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) clusters

    Science.gov (United States)

    Liang, Wenjuan; Jia, Jianfeng; Lv, Jin; Wu, Haishun

    2016-03-01

    The structure and magnetic properties of Mo-doped M@(BN)48 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) clusters were calculated at BPW91/LanL2DZ level. The magnetic nature of the clusters M@(BN)48 significantly changed when doping with Mo atom, except for Co@(BN)48. Only the magnetic moment for the CrMo@(BN)48 cluster was decreased to zero. Thus, M@(BN)48 clusters can be selected as the model system to detect Mo atom by the change of the magnetic moment.

  13. Study on uranium recovery from tungsten residue. Separation of U from Fe, Mn, Zr, Ti, Th, and Sc with mixture of N235 and TBP

    International Nuclear Information System (INIS)

    Mixture of N235 and TBP was applied for the separation of UFe/MnZrTiThSc by extracting U and Fe from hydrochloric acid medium. Then, acetic acid was utilized to scrub impurities from the loaded organic phase. The extraction was investigated at different concentrations of TBP, N235, hydrochloric acid, metal ions and extraction times. And the scrubbing of metal impurities was studied at different concentrations of acetic acid and scrubbing times. Finally, a process for uranium recovery from tungsten residue has been developed, generating with a final product U3O8 of 99.7 % purity and an overall uranium recovery of 91.8 %. (author)

  14. Judd–Ofelt and energy-transfer analysis of Er3+ doped in CaSc2O4 ceramic samples

    International Nuclear Information System (INIS)

    A Judd–Ofelt analysis of Er3+ in CaSc2O4 ceramic samples is performed. The Judd–Ofelt parameters are found (Ω2=3.88×10−20 cm2, Ω4=1.83×10−20 cm2, Ω6=0.83×10−20 cm2) and the radiative lifetimes of Er3+ energy levels and the branching ratios of Er3+ transitions are calculated. The luminescence lifetimes of metastable energy levels are obtained experimentally and the quantum efficiencies of these levels are calculated. The luminescence kinetics of the thermalized levels (2H11/2, 4S3/2) at various Er3+ concentrations is used to characterize the cross-relaxation processes that influence these green-emitting levels. The decays of these levels are well described by the Inokuti–Hirayama model for dipole–dipole interaction. The CDA microparameter was found to be 6.7×10−39 cm6 s−1. - Highlights: • Judd–Ofelt analysis is performed on light-scattering ceramic Er:CaSc2O4. • Quantum efficiencies of (2H11/2, 4S3/2) and 4I11/2 levels of Er3+ are estimated. • Energy-transfer microparameter for cross-relaxation of (2H11/2, 4S3/2) is obtained

  15. Synthesis condition and structural/luminescent properties of CaTiO{sub 3}:Eu{sup 3+} red phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Orihashi, Takuya; Adachi, Sadao, E-mail: adachi@el.gunma-u.ac.jp

    2015-10-15

    Eu{sup 3+}-activated CaTiO{sub 3} red phosphor is synthesized by the solid-state reaction method and its structural and optical properties are investigated using X-ray diffraction analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL lifetime measurements. The effects of calcination condition (temperature, duration, and Eu dopant concentration) on the structural and Eu{sup 3+} emission properties are studied in detail. Temperature dependences of the PL intensity and decay time at T = 20–300 K are measured and analyzed on the basis of the thermal quenching model. It has been found that CaTiO{sub 3} can be formed at activation energy of ∼0.4 eV, which is considerably lower than the thermal activation energy (∼1.0 eV) of Eu{sup 3+} in the CaTiO{sub 3} host. Thermal quenching of the Eu{sup 3+} emission has also been observed to occur at an energy of ∼0.25 eV, determined from the temperature-dependent luminescence intensity and decay time analyses. The schematic energy-level diagram for Eu{sup 3+} in the CaTiO{sub 3} host is also proposed for the sake of a better understanding of the PL and PLE processes in this phosphor system. - Highlights: • Optimization was made for synthesizing CaTiO{sub 3}:Eu{sup 3+} red phosphor using the solid-state reaction method. • Eu{sup 3+} concentration was optimized to obtain high efficient red phosphor. • Temperature-dependent Eu{sup 3+} emission properties were measured and analyzed in detail. • An energy-level scheme for Eu{sup 3+} ion in CaTiO{sub 3} was proposed.

  16. Non-stoichiometry of Li2TiO3 under hydrogen atmosphere condition

    International Nuclear Information System (INIS)

    Li2TiO3 is one of the most promising candidates for solid breeder materials. In order to control the grain growth at the time of high temperature use, the development of Li2TiO3 which has oxide additive is needed. In the present paper, the structure and the non-stoichiometry of Li2TiO3 added with some different oxides have been extensively investigated by means of thermogravimetry and X-ray diffractometry (XRD). In the case of the Li2TiO3 samples used in this study, Li2TiO3 powder and oxide powder (CaO, ZrO2, Sc2O3) in small quantity were mixed in the following molecular ratio: CaO/Li2TiO3 = 0.20%, ZrO2/Li2TiO3 = 0.44% or Sc2O3/Li2TiO3 0.40%. These samples are designated as Ca-Li2TiO3, Zr-Li2TiO3, and Sc-Li2TiO3, respectively. Ca-Li2TiO3 and Zr-Li2TiO3 exist as double phases, and Sc-Li2TiO3 exists as a single phase. In thermogravimetry, Ca-Li2TiO3 has fewer oxygen defects than the other kinds of Li2TiO3 in the hydrogen atmosphere. The overall results suggest that the oxide additives are able to control not only the growth of the grain size but also the amount of oxygen defects

  17. First-Principles Calculations of Structural, Electronic and Optical Properties of CaTiO3 Crystal

    Science.gov (United States)

    Medeiros, Subênia; Silva, Jusciane; Albuquerque, Eudenilson; Freire, Valder

    2013-03-01

    The structural, electronic, vibrational, and optical properties of perovskite CaTiO3 in the cubic, orthorhombic, and tetragonal phase are calculated in the framework of density functional theory (DFT) with different exchange-correlation potentials by CASTEP package. The calculated band structure shows an indirect band gap of 1.88 eV at the Γ-R points in the Brillouin zone to the cubic structure, a direct band gap of 2.41 eV at the Γ - Γ points to the orthorhombic structure, and an indirect band gap of 2.31 eV at the M' Γ points to the tetragonal phase. I have concluded that the bonding between Ca and TiO2 is mainly ionic and that the TiO2 entities bond covalently. Unlike some perovskites the CaTiO3 does not exhibit a ferroelectric phase transition down to 4.2 K. It is still known that the CaTiO3 has a static dielectric constant that extrapolates to a value greater than 300 at zero temperature. Our calculated lattice parameters, elastic constants, optical properties, and vibrational frequencies are found to be in good agreement with the available theoretical and experimental values. The results for the effective mass in the electron and hole carriers are also presented in this work.

  18. Crystal-field study for the orthorhombic Yb3+ centers in Ca3Sc2Ge3O12 and Lu3Ga5O12 garnets

    International Nuclear Information System (INIS)

    Highlights: • Optical and EPR spectra for CaSGG:Yb3+ and LuGG:Yb3+ garnets were explained. • The reliability and standardization of fitted CFPs were performed and discussed. • The unavailability of SPM for LuGG:Yb3+ garnet was found and analyzed briefly. - Abstract: The crystal-field modeling based on superposition model (SPM) for the orthorhombic Yb3+ centers in Ca3Sc2Ge3O12 (CaSGG) and Lu3Ga5O12 (LuGG) garnets has been employed to explain their recent experimental optical spectroscopy. Furthermore, the electron paramagnetic resonance (EPR) principal g values for orthorhombic Yb3+ centers in LuGG garnet have been interpreted and the predicted g factors for CaSGG:Yb3+ garnet are also given. Both calculated optical spectra and EPR g factors for the two Yb3+-doped garnets could be regarded as in reasonable agreement with the experimental ones. Two important facts about reliability and standardization of the fitted phenomenological crystal-field parameters (CFPs) have been discussed and the unexpected unavailability of direct parametric modeling by SPM for LuGG:Yb3+ garnet is also found and analyzed briefly

  19. Influence of titanium precursor on photoluminescent emission of micro-cube-shaped CaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mazzo, Tatiana Martelli, E-mail: tatimazzo@gmail.com [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Avenida Almameda Saldanha da Gama, 89, Ponta da Praia, CEP 11030-400 Santos, SP (Brazil); Santilli do Nascimento Libanori, Gabriela [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Avenida Almameda Saldanha da Gama, 89, Ponta da Praia, CEP 11030-400 Santos, SP (Brazil); Moreira, Mario Lucio [Instituto de Física e Matemática, Universidade Federal de Pelotas, P.O. Box 354, Campus do Capão do Leão, 96001-970 Pelotas, RS (Brazil); Avansi Jr, Waldir [Departamento de Física, Universidade Federal de São Carlos, Jardim Guanabara, 13565-905 São Carlos, SP (Brazil); Mastelaro, Valmor Roberto [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, Arnold Schimidt, 13566-590 São Carlos, SP (Brazil); Varela, José Arana; Longo, Elson [INCTMN/LIEC, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, R. Francisco Degni, 55, Bairro Quitandinha, 14801-907 Araraquara, SP (Brazil)

    2015-09-15

    For this research, we studied the influence of titanium tetrachloride (TC) and titanium tetraisopropoxide (TTP) precursors on CaTiO{sub 3} (CTO) synthesis by employing a microwave-assisted hydrothermal (MAH) method regarding their respective short-, medium- and long-range features to determine if the use of different titanium precursors enhances the structural evolution of the material. The growth mechanism for the formation of the micro-cube-shaped CTO is proposed to obtain nanoparticle aggregation of self-assembly nanoplates. The disorder coupled to the oxygen vacancies of [TiO{sub 5}]–[TiO{sub 6}] in complex clusters in the CTO 1 powder and twists in bonding between the [TiO{sub 6}]–[TiO{sub 6}] complex clusters in the CTO 2 powder were mainly responsible for photoluminescent (PL) emission. - Highlights: • Different titanium precursors enhance the structural evolution of the material. • [TiO{sub 5}]–[TiO{sub 6}] and twists in bonding [TiO{sub 6}]–[TiO{sub 6}] were responsible for PL emission. • Micro-cube shaped was formed by nanoparticle aggregation of self-assembly nanoplates.

  20. Influence of titanium precursor on photoluminescent emission of micro-cube-shaped CaTiO3

    International Nuclear Information System (INIS)

    For this research, we studied the influence of titanium tetrachloride (TC) and titanium tetraisopropoxide (TTP) precursors on CaTiO3 (CTO) synthesis by employing a microwave-assisted hydrothermal (MAH) method regarding their respective short-, medium- and long-range features to determine if the use of different titanium precursors enhances the structural evolution of the material. The growth mechanism for the formation of the micro-cube-shaped CTO is proposed to obtain nanoparticle aggregation of self-assembly nanoplates. The disorder coupled to the oxygen vacancies of [TiO5]–[TiO6] in complex clusters in the CTO 1 powder and twists in bonding between the [TiO6]–[TiO6] complex clusters in the CTO 2 powder were mainly responsible for photoluminescent (PL) emission. - Highlights: • Different titanium precursors enhance the structural evolution of the material. • [TiO5]–[TiO6] and twists in bonding [TiO6]–[TiO6] were responsible for PL emission. • Micro-cube shaped was formed by nanoparticle aggregation of self-assembly nanoplates

  1. Solid state synthesis and structural refinement of polycrystalline LaCa1-TiO3 ceramic powder

    Indian Academy of Sciences (India)

    O P Shrivastava; Narendra Kumar; I B Sharma

    2004-04-01

    Perovskite structure based ceramic precursors have a characteristic property of substitution in the ``A" site of the ABO3 structure. This makes them a potential material for nuclear waste management in synthetic rock (SYNROC) technology. In order to simulate the mechanism of rare earth fixation in perovskite, La Ca1-TiO3 (where = 0.05) has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and La as starting materials. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The ceramic phase has been characterized by its powder diffraction pattern. Step analysis data has been used to determine the structure of solid solution of lanthanum substituted calcium titanate. The SEM and EDAX analyses also confirm that the CaTiO3 can act as a host for lanthanum. X-ray data has been interpreted using CRYSFIRE and POWDERCELL softwares. The ℎ, , values for different lattice planes have been generated from the experimental data. The lanthanum substituted perovskite crystallizes in orthorhombic symmetry with space group (#62). Following unit cell parameters have been calculated: = 5.410, = 7.631, = 5.382. The calculated and observed values of corresponding intensities, 2, and density show good agreement. GSAS based calculation for bond distances Ti–O, Ca–O, La–O and bond angles Ti–O–Ca, Ca–O–Ca, La–O–Ti have been reported.

  2. High tunability of the soft mode in strained SrTiO{sub 3}/DyScO{sub 3} multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kadlec, C; Kadlec, F; Nemec, H; Kuzel, P [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Schubert, J; Panaitov, G [Institute of Bio and Nanosystems, Research Center Juelich, D-52425 Juelich (Germany)], E-mail: kuzelp@fzu.cz

    2009-03-18

    SrTiO{sub 3}/DyScO{sub 3} epitaxial multilayers with variable number and thickness (10-100 nm) of bilayers deposited on DyScO{sub 3} substrates were investigated by means of time-domain terahertz spectroscopy at room temperature. A tensile strain develops in the SrTiO{sub 3} films and shifts the eigenfrequency of the ferroelectric soft mode down by {approx}25-45 cm{sup -1} with respect to the value found for single crystals. In all films the soft mode strongly hardens upon the electrical bias and a linear coupling to a silent excitation of relaxation type at 10 cm{sup -1} is observed. We show that the change in the THz and sub-THz response of the layers with an increasing field is determined solely by the soft mode eigenfrequency and we propose a phenomenological model describing the origin of the tunability and the peculiar properties of the ferroelectric soft mode in the terahertz spectral range.

  3. Microwave dielectric properties of layered Mg0.93Ca0.07TiO3-(Ca0.3Li0.14Sm0.42)TiO3 ceramics

    International Nuclear Information System (INIS)

    Microwave dielectric properties of the layered functionally graded materials (FGMs) ceramics with Mg0.93Ca0.07TiO3 (MCT) and (Ca0.3Li0.14Sm0.42)TiO3 (CLST) were investigated as a function of sintering times at 1350 deg. C. The stable and uniform interfaces of the FGMs specimens were confirmed by X-ray diffraction and SEM photographs study. As a sintering time increased, Qf values of the FGMs specimens were decreased, whereas dielectric constants of the specimens did not changed remarkably. The change of Qf values could be attributed to the compositional inhomogeneity at the interfacial region resulted from the active ionic diffusion. From the EPMA work, active diffusion of Mg2+ (r=0.72 Angst) and Ti4+ (r=0.605 Angst) was detected in the interface of FGMs specimens with an increase of sintering time

  4. Microwave synthesis and sintering characteristics of CaCu3Ti4O12

    Indian Academy of Sciences (India)

    P Thomas; L N Sathapathy; K Dwarakanath; K B R Varma

    2007-12-01

    CaCu3Ti4O12 (CCTO) was synthesized and sintered by microwave processing at 2.45 GHz, 1.1 kW. The optimum calcination temperature using microwave heating was determined to be 950°C for 20 min to obtain cubic CCTO powders. The microwave processed powders were sintered to 94% density at 1000°C/60 min. The microstructural studies carried out on these ceramics revealed the grain size to be in the range 1–7 m. The dielectric constants for the microwave sintered (1000°C/60 min) ceramics were found to vary from 11000–7700 in the 100 Hz–100 kHz frequency range. Interestingly the dielectric loss had lower values than those sintered by conventional sintering routes and decreases with increase in frequency.

  5. Anomalous current-voltage behavior of CaCu3Ti4O12 ceramics

    International Nuclear Information System (INIS)

    This letter reports on an investigation of dc current-voltage measured in CaCu3Ti4O12 ceramics. The experimental results show unusual I-V behaviors associated with the electrically inhomogeneous nature of the grains (mixture of semiconducting and insulating regions) and dependence on delay time. The data strongly suggest that both the localization of current in the conductive region and local Joule self-heating effects are essential elements to explain the abrupt drop in the electric field. In addition, the hysteresis behavior recorded during the I-V measurements shows strong dependence on delay time, i.e., the time needed for the polarization phenomena to occur

  6. Chemical solution deposition of CaCu3Ti4O12 thin film

    Indian Academy of Sciences (India)

    Viswanathan S Saji; Han Cheol Choe

    2010-06-01

    CaCu3Ti4O12 (CCTO) thin film was successfully deposited on boron doped silica substrate by chemical solution deposition and rapid thermal processing. The phase and microstructure of the deposited films were studied as a function of sintering temperature, employing X-ray diffractometry and scanning electron microscopy. Dielectric properties of the films were measured at room temperature using impedance spectroscopy. Polycrystalline pure phase CCTO thin films with (220) preferential orientation was obtained at a sintering temperature of 750°C. There was a bimodal size distribution of grains. The dielectric constant and loss factor at 1 kHz obtained for a film sintered at 750°C was ∼ 2000 and tan ∼ 0.05.

  7. Inelastic neutron scattering and lattice dynamics of NaNbO3 and Sr0.70Ca0.30TiO3

    Indian Academy of Sciences (India)

    S K Mishra; R Mittal; N Choudhury; S L Chaplot; D Pandey

    2008-11-01

    NaNbO3 and (Sr,Ca)TiO3 exhibit an unusual complex sequence of temperature- and pressure-driven structural phase transitions. We have carried out lattice dynamical studies to understand the phonon modes responsible for these phase transitions. Inelastic neutron scattering measurements using powder samples were carried out at the Dhruva reactor, which provide the phonon density of states. Lattice dynamical models have been developed for SrTiO3 and CaTiO3 which have been fruitfully employed to study the phonon spectra and vibrational properties of the solid solution (Sr,Ca)TiO3.

  8. Synthesis of Cr-doped CaTiSiO5 ceramic pigments by spray drying

    International Nuclear Information System (INIS)

    Cr-doped CaTiSiO5 was synthesized by spray drying and conventional ceramic method in order to assess its potential as ceramic pigment. The evolution of the phase composition with thermal treatment was investigated by X-ray powder diffraction (XRPD) and thermal analyses (DTA-TGA-EGA). Powder morphology and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction, respectively. The color efficiency of pigments was evaluated by optical spectroscopy (UV-vis-NIR) and colorimetric analysis (CIE Lab). Results proved that spray drying is an efficient procedure to prepare highly reactive pigment precursors. The spray-dried powders consist of hollow spherical particles with aggregate size in the 1-10 μm range, developing a brown coloration. Optical spectra reveal the occurrence of Cr(III) and Cr(IV), both responsible for the brown color of this pigment. The former occupies the octahedral site of titanite, in substitution of Ti(IV), while the latter is located at the tetrahedral site, where replaces Si(IV)

  9. Improvement in antibacterial properties of Ti by electrodeposition of biomimetic Ca-P apatite coat on anodized titania

    Energy Technology Data Exchange (ETDEWEB)

    Gad El-Rab, Sanaa M.F. [Biotechnology Department, Faculty of Science, Taif University, Taif (Saudi Arabia); Botany Department, Faculty of Science, Asuit University, Asuit (Egypt); Fadl-allah, Sahar A., E-mail: Sahar.fadlallah@yahoo.com [Materials and Corrosion Lab (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Chemistry Department, Faculty of Science, Cairo University, Cairo (Egypt); Montser, A.A. [Materials and Corrosion Lab (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Chemistry Department, Faculty of Science, South-Valley University (Egypt)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Ca-P coating on titania titanium surface was directly fabricated successfully by electrochemical deposition. Black-Right-Pointing-Pointer Treatment the titanium surface by TiO{sub 2} could improve the adhesion strength between the Ca-P coating and the surface. Black-Right-Pointing-Pointer Anodization treatment in phosphoric acid is benefit to inhibit the oral bacteria. Black-Right-Pointing-Pointer According to the electrochemical corrosion test, corrosion resistance of Ti was improved by both anodization and electrodeposition of the Ca-P/titania coating. Black-Right-Pointing-Pointer Ca-P/titania sample is believed to be a functional biomaterial which combines antibacterial activity and good corrosion resistance in bioenvironment. - Abstract: Titanium metal (Ti) with antibacterial function was successfully developed in the present study by electrodeposition of biomimetic Ca-P coat in simple supersaturated calcium and phosphate solution (SCPS). The electrochemical behavior and corrosion resistance of Ca-P deposited on anodized titanium (AT) have been investigated in SCPS by using electrochemical impedance spectroscopy (EIS). The plate-counting method was used to evaluate the antibacterial performance against Staphylococcus aureus (ATCC6538). In vitro antibacterial activity study indicated a significantly reduced number of bacteria S. aureus on Ca-P/AT plate surface when compared with that on Ti or AT surfaces and the corresponding antibacterial mechanism is discussed. The morphology and chemical structure of different titanium samples were systematically investigated by scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX). The study confirmed that the antibacterial properties of the samples were related to chemical composition of sample surface.

  10. Room temperature magnetic and dielectric properties of cobalt doped CaCu3Ti4O12 ceramics

    International Nuclear Information System (INIS)

    CaCu3Ti4−xCoxO12 (x = 0, 0.2, 0.4) ceramics were prepared by a conventional solid state reaction, and the effects of cobalt doping on the room temperature magnetic and dielectric properties were investigated. Both X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the presence of Cu and Co rich phase at grain boundaries of Co-doped ceramics. Scanning electron microscopy micrographs of Co-doped samples showed a striking change from regular polyhedral particle type in pure CaCu3Ti4O12 (CCTO) to sheet-like grains with certain growth orientation. Undoped CaCu3Ti4O12 is well known for its colossal dielectric constant in a broad temperature and frequency range. The dielectric constant value was slightly changed by 5 at. % and 10 at. % Co doping, whereas the second relaxation process was clearly separated in low frequency region at room temperature. A multirelaxation mechanism was proposed to be the origin of the colossal dielectric constant. In addition, the permeability spectra measurements indicated Co-doped CCTO with good magnetic properties, showing the initial permeability (μ′) as high as 5.5 and low magnetic loss (μ″ < 0.2) below 3 MHz. And the interesting ferromagnetic superexchange coupling in Co-doped CaCu3Ti4O12 was discussed

  11. Self-healing of defects in CaO coatings on V-5%Cr-5%Ti in liquid lithium

    International Nuclear Information System (INIS)

    In-situ electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt % dissolved Ca was measured as a function of time at temperatures between 250 and 600 degrees C. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at >360 degrees C

  12. 1 Hz linewidth Ti:sapphire laser as local oscillator for 40Ca+ optical clocks

    Science.gov (United States)

    Bian, Wu; Huang, Yao; Guan, Hua; Liu, Peiliang; Ma, Longsheng; Gao, Kelin

    2016-06-01

    A Ti:sapphire laser at 729 nm is frequency stabilized to an ultra-stable ultra-low thermal expansion coefficient (ULE) cavity by means of Pound-Drever-Hall method. An acousto-optic modulator is used as the fast frequency feedback component. 1 Hz linewidth and 2 × 10-15 frequency stability at 1-100 s are characterized by optical beating with a separated Fabry-Perot cavity stabilized diode laser. Compared to the universal method that the error signal feedback to inject current of a diode laser, this scheme is demonstrated to be simple and also effective for linewidth narrowing. The temperature of zero coefficient of the thermal expansion of the ULE cavity is measured with the help of a femto-second frequency comb. And the performance of the laser is well defined by locking it to the unperturbed clock transition line-center of 4 S1/2-3 D5/2 clock transition of a single laser cooled 40Ca+ ion. A Fourier-transform limited resonance of 6 Hz (Δv/v = 1.5 × 10-14) is observed. This laser is also used as the local oscillator for the comparison experiment of two 40Ca+ ion optical clocks and improves the stability of comparison for an order of magnitude better than the previous results.

  13. Judd–Ofelt and energy-transfer analysis of Er{sup 3+} doped in CaSc{sub 2}O{sub 4} ceramic samples

    Energy Technology Data Exchange (ETDEWEB)

    Georgescu, Şerban [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Ştefan, Angela [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); University of Bucharest, Faculty of Physics, 405 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Toma, Octavian, E-mail: octavian.toma@inflpr.ro [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania)

    2015-11-15

    A Judd–Ofelt analysis of Er{sup 3+} in CaSc{sub 2}O{sub 4} ceramic samples is performed. The Judd–Ofelt parameters are found (Ω{sub 2}=3.88×10{sup −20} cm{sup 2}, Ω{sub 4}=1.83×10{sup −20} cm{sup 2}, Ω{sub 6}=0.83×10{sup −20} cm{sup 2}) and the radiative lifetimes of Er{sup 3+} energy levels and the branching ratios of Er{sup 3+} transitions are calculated. The luminescence lifetimes of metastable energy levels are obtained experimentally and the quantum efficiencies of these levels are calculated. The luminescence kinetics of the thermalized levels ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) at various Er{sup 3+} concentrations is used to characterize the cross-relaxation processes that influence these green-emitting levels. The decays of these levels are well described by the Inokuti–Hirayama model for dipole–dipole interaction. The C{sub DA} microparameter was found to be 6.7×10{sup −39} cm{sup 6} s{sup −1}. - Highlights: • Judd–Ofelt analysis is performed on light-scattering ceramic Er:CaSc{sub 2}O{sub 4}. • Quantum efficiencies of ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) and {sup 4}I{sub 11/2} levels of Er{sup 3+} are estimated. • Energy-transfer microparameter for cross-relaxation of ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) is obtained.

  14. Judd–Ofelt analysis of Ho{sup 3+} doped in ceramic CaSc{sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Georgescu, Şerban [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Ştefan, Angela [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); University of Bucharest, Faculty of Physics, 405 Atomistilor Street, 077125 Măgurele-Ilfov (Romania); Toma, Octavian, E-mail: octavian.toma@inflpr.ro [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Voiculescu, Ana-Maria [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania)

    2015-06-15

    A Judd–Ofelt analysis was performed on a calcium scandate (CaSc{sub 2}O{sub 4}) ceramic sample doped with 2 at% Ho{sup 3+}. Using the measured lifetime of {sup 5}I{sub 7} level to calibrate the absorption spectrum, the Judd–Ofelt parameters were obtained: Ω{sub 2} = 3.78×10{sup −20} cm{sup 2}, Ω{sub 4} = 5.17×10{sup −20} cm{sup 2}, and Ω{sub 6} = 1.92×10{sup −20} cm{sup 2}. The electric-dipole and magnetic-dipole transition probabilities, radiative lifetimes and luminescence branching ratios were calculated. The quantum efficiency of the green emitting levels ({sup 5}F{sub 4}, {sup 5}S{sub 2}) was found: 54%. The calibration method also allowed the estimation of the ‘effective’ thickness of the ceramic sample: approximately eight times greater than the geometric thickness. - Highlights: • Jud–Ofelt analysis is performed on a Ho(2 at%):CaSc{sub 2}O{sub 4} translucent ceramic sample. • The intensity parameters were calibrated using the lifetime of the {sup 5}I{sub 7} Ho{sup 3+} level. • The luminescence lifetimes of Ho{sup 3+} metastable levels were measured. • Transition rates, radiative lifetimes and quantum efficiencies were calculated. • The quantum efficiency calculated for the green-emitting levels ({sup 5}F{sub 4},{sup 5}S{sub 2}) is 54%.

  15. Studies of the effects of TiCl3 in LiBH4/CaH2/TiCl3 reversible hydrogen storage system

    International Nuclear Information System (INIS)

    Highlights: ► We systematically studied the effects of TiCl3 in LiBH4/CaH2/TiCl3 hydrogen storage system. ► It is found that adding 0.25 TiCl3 produces fully reversible hydrogen absorption and desorption and a lower desorption temperature. ► LiCl experiences four different states, i.e. “formed-solid solution-molten solution-precipitation”, in the whole desorption process of the system. ► The incorporation of LiCl into LiBH4 forms more viscous molten LiBH4·LiCl, leading to fast kinetics. ► The precipitation and re-incorporation of LiCl into LiBH4 lead to a fully reversible complex hydrogen storage system. - Abstract: In the present study, the effects of TiCl3 on desorption kinetics, absorption/desorption reversibility, and related phase transformation processes in LiBH4/CaH2/TiCl3 hydrogen storage system was studied systematically by varying its concentration (x = 0, 0.05, 0.15 and 0.25). The results show that LiCl forms during ball milling of 6LiBH4/CaH2/xTiCl3 and that as temperature increases, o-LiBH4 transforms into h-LiBH4, into which LiCl incorporates, forming solid solution of LiBH4·LiCl, which melts above 280 °C. Molten LiBH4·LiCl is more viscous than molten LiBH4, preventing the clustering of LiBH4 and the accompanied agglomeration of CaH2, and thus preserving the nano-sized phase arrangement formed during ball milling. Above 350 °C, the molten solution LiBH4·LiCl further reacts with CaH2, precipitating LiCl. The main hydrogen desorption reaction is between molten LiBH4·LiCl and CaH2 and not between molten LiBH4 and CaH2. This alters the hydrogen reaction thermodynamics and lowers the hydrogen desorption temperature. In addition, the solid–liquid nano-sized phase arrangement in the nano-composites improves the hydrogen reaction kinetics. The reversible incorporation/precipitation of LiCl at the hydrogen reaction temperature and during temperature cycling makes the 6LiBH4/CaH2/0.25TiCl3 nano-composite a fully reversible hydrogen

  16. Study of new sheep bone and Zn/Ca ratio around TiAlV screw: PIXE-RBS analysis

    International Nuclear Information System (INIS)

    This study reports on in vivo particle induced X-ray emission (PIXE) measurements combined with Rutherford backscattering spectroscopy (RBS) analyses of new remodeled sheep bone formed around TiAlV screws. The implants (screws) were anodized by a modified TiMaxTM process. The interface between the implant and the bone was carefully investigated. [Zn]/[Ca] in-depth composition profiles as well as Ca, Fe elemental maps were recorded. The thickness of new bone formed around the screw reached 300-400 μm. Osteon and Osteoid phases were identified in the new bone. A higher [Zn]/[Ca] ratio was observed in the new bone as compared to the mature bone. Blood vessels were observed in the bone in close contact with the screw. This study shows the potential of ion beam analysis for biological and biomedical characterization

  17. Enhanced Mechanical Properties of MgZnCa Bulk Metallic Glass Composites with Ti-Particle Dispersion

    Directory of Open Access Journals (Sweden)

    Pei Chun Wong

    2016-05-01

    Full Text Available Rod samples of Mg60Zn35Ca5 bulk metallic glass composites (BMGCs dispersed with Ti particles have been successfully fabricated via injection casting. The glass forming ability (GFA and the mechanical properties of these Mg-based BMGCs have been systematically investigated as a function of the volume fraction (Vf of Ti particles. The results showed that the compressive ductility increased with Vf. The mechanical performance of these BMGCs, with up to 5.4% compressive failure strain and 1187 MPa fracture strength at room temperature, can be obtained for the Mg-based BMGCs with 50 vol % Ti particles, suggesting that these dispersed Ti particles can absorb the energy of the crack propagations and can induce branches of the primary shear band into multiple secondary shear bands. It follows that further propagation of the shear band is blocked, enhancing the overall plasticity.

  18. Influence of Ti{sup 4+} on the magnetic state of CaRu{sub 1-x}Ti{sub x}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Zorkovska, A. [Centre of Low Temperature Physics of the Faculty of Science UPJS and Institute of Experimental Physics SAS, 04154 Kosice (Slovakia)]. E-mail: anna.zorkovska@upjs.sk; Baran, A. [Centre of Low Temperature Physics of the Faculty of Science UPJS and Institute of Experimental Physics SAS, 04154 Kosice (Slovakia); Bradaric, I. [' Vinca' Institute of Nuclear Sciences, 11001 Belgrade (Serbia and Montenegro); Savic, I. [Faculty of Physics, University of Belgrade, 11000 Belgrade (Serbia and Montenegro); Sebek, J. [Institute of Physics AS CR, 18221 Prague (Czech Republic); Santava, E. [Institute of Physics AS CR, 18221 Prague (Czech Republic); Svoboda, P. [Faculty of Mathematics and Physics, Charles University, DES, 12116 Prague (Czech Republic); Marincev, D. [Department of Physics, Military Academy, 11000 Belgrade (Serbia and Montenegro); Kohout, S. [Physik Inst. der Universitaet Zuerich, CH 80-57 Zurich (Switzerland); Keller, H. [Physik Inst. der Universitaet Zuerich, CH 80-57 Zurich (Switzerland); Feher, A. [Centre of Low Temperature Physics of the Faculty of Science UPJS and Institute of Experimental Physics SAS, 04154 Kosice (Slovakia)

    2007-09-15

    In order to shed more light on the character of magnetic correlations at low temperatures in CaRuO{sub 3}, the delicate effect of substituting nonmagnetic Ti{sup 4+} for Ru{sup 4+} in low concentrations (0.5-15%) has been investigated by magnetization, AC-susceptibility and specific heat measurements. Despite the clear features in magnetic measurement data at 34K no specific heat anomaly has been observed, nevertheless, two temperature regions with different magnetic characters have been identified. In pure CaRuO{sub 3} significant low-temperature upturn of C/T is visible below 15K. This feature is suppressed by Ti substitution.

  19. Investigation of various reactions for the direct synthesis of TiCr2 intermetallic compound from the TiO2–Cr2O3–Ca system

    International Nuclear Information System (INIS)

    Highlights: ► A new processing route was applied for the synthesis of TiCr2 intermetallic powder directly by the Calciothermic co-reduction of TiO2–Cr2O3 oxides. ► Various reactions in the TiO2–Cr2O3–Ca system are investigated. ► According to EDS analyses the formation of TiCr2 compound is a mutual diffusion process that needs time for its formation. ► After activation the obtained intermetallic powder showed capability for hydrogen storage. - Abstract: A new processing route was applied for the synthesis of TiCr2 intermetallic powder directly by the Calciothermic co-reduction of TiO2–Cr2O3 oxides. Differential thermal analysis (DTA) and X-ray diffraction (XRD) were used to determine the various reactions. According to DTA results heating the mixture up to about 675 °C resulted in an endothermic peak. This endothermic peak indicates the formation of a solid solution formation by the reaction of TiO2 with Cr2O3. As the temperature increased to about 950 °C the Ca started to melt (at approximately 847 °C) resulting to an exothermic peak due to the reaction of Ca with Cr2O3 forming Cr metal. The formation of CaTiO3 formed by the reaction of CaO with TiO2 decreased the amount of TiO2 in the mixture of starting materials. When the mixture was heated up to 1058 °C, Ca reacted with TiO2 forming Ti as indicated by an exothermic reaction forming Ti. Finally, when the holding time at 1200 °C and the amount of Ca were increased, the TiCr2 intermetallic was formed while the CaTiO3 compound was gradually disintegrated into CaO and Ti and the amount of oxygen content in samples was decreased. The obtained intermetallic powder showed the capability of hydrogen storage after being activated.

  20. Preparation and Electrical Properties of CaCu3Ti4O12 Thin Ceramic Sheets via Water-based Tape Casting

    Directory of Open Access Journals (Sweden)

    LI Wei, XIONG Zhao-Xian, XUE Hao

    2014-11-01

    Full Text Available Thin ceramic sheet of CaCu3Ti4O12 has a great significance for preparation of multiplayer ceramic chip capacitors. In this work, a simple plan was made to achieve CaCu3Ti4O12 thin ceramic sheets with excellent dielectric properties. Thin ceramic sheets of CaCu3Ti4O12 were prepared via water-based tape casting at various sintering temperatures. The CaCu3Ti4O12 samples sintered at 1080℃ exhibit a great performance on dielectric properties with high permittivity (εr=98605 and low dielectric loss (tanδ=0.028 which are better than those of samples prepared by conventional dry pressing. Meanwhile, the complex impedance spectra were measured to explain the mechanism of special electrical behaviors of CaCu3Ti4O12 ceramics. These testing results indicate that the CaCu3Ti4O12 ceramics via tape casting exhibits a better performance of giant permittivity and lower dielectric loss than other reports, which provides a possibility for the application of the CaCu3Ti4O12 in modern micro-electronics technology.

  1. Extraction properties of Sc3, Ti4, Zr4, Hf4, Th4 and U4 acid di-(2-ethylhexyl) phosphates

    International Nuclear Information System (INIS)

    Extraction properties of Sc3, Ti4, Zr4, Hf4, Th4 and U4 acid di-(2-ethylhexyl) phosphates (M1-D2EHPA) relatively to Eu3, Fe3, Ga3 (M2) are studied. An acid salt is considered as an organic reagent, where M1 plays the role of electron acceptor substituent resulting in redistribution of electron density on donor atoms of functional groups. Variations of electron density on oxygen atoms of POO-groups conditioned by M1 metal are supposed to be determined, mainly, by its nature, while extracted M2 metal depending on its nature ''choses'' any non-equivalent bonds differing by the character with M1 of POO-group for interaction that manifests in extraction properties of M1-D2EHPA relatively to M2

  2. Large Electric-Field Modulation of Magnetic Properties in Fe Films on BiScO3-PbTiO3 Ceramics

    Directory of Open Access Journals (Sweden)

    Jing Wang

    2010-01-01

    Full Text Available Based on the magneto-optical Kerr effect, we report the electric-field modulation of the magnetic properties in Fe/BiScO3-PbTiO3 (BSPT film-on-ceramic substrate structure. The Fe films are directly grown on the fully-poled BSPT ceramic substrates by magnetron sputtering. An electric field applied parallel to the prepolarization direction of the piezoelectric BSPT can induce a reversible increase in the coercive field Hc of about 30%, whereas an electric field antiparallel to the prepolarization direction can cause a persistent, tremendous decrease (as large as 97% in Hc, and a small reversal electric field can resume it back. The strain induced by the inverse piezoelectric effect is the primary mechanism behind. This large modulation of the coercive field by the electric field could inspire further exploration of electric-field-controlled magnetic switching in multiferroic heterostructures.

  3. Radiation damage effects in the perovskite CaTiO3 and resistance of materials to amorphization

    International Nuclear Information System (INIS)

    We combine classical and quantum-mechanical simulations to study the structural changes in CaTiO3 under irradiation. We identify common defects, and suggest that their stability is related to the covalent character of Ti-O bonding. We address the issue of resistance to amorphization by radiation damage, and propose that a complex material is amorphizable by radiation damage if it is able to form a covalent network. On a more detailed level, we suggest that resistance to amorphization is defined by the competition between the short-range covalent and long-range ionic forces

  4. Investigation of structural and optical properties of CaTiO{sub 3} powders doped with Mg{sup 2+} and Eu{sup 3+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Larissa H., E-mail: larissahelena2009@gmail.com [Institute of Chemistry, State University of São Paulo, 14800-900, Araraquara, São Paulo (Brazil); Savioli, Julia [Department of Chemistry, Federal University of São Carlos, 13565-905, São Carlos, São Paulo (Brazil); Moura, Ana P. de [Institute of Chemistry, State University of São Paulo, 14800-900, Araraquara, São Paulo (Brazil); Nogueira, Içamira C. [Department of Chemistry, Federal University of São Carlos, 13565-905, São Carlos, São Paulo (Brazil); Li, Maximo S. [Institute of Physics, University of São Paulo, P.O. Box, 13566-590, São Carlos, São Paulo (Brazil); Longo, Elson; Varela, José A. [Institute of Chemistry, State University of São Paulo, 14800-900, Araraquara, São Paulo (Brazil); Rosa, Ieda L.V. [Department of Chemistry, Federal University of São Carlos, 13565-905, São Carlos, São Paulo (Brazil)

    2015-10-25

    In this work, CaTiO{sub 3} powders doped with Mg{sup 2+} ions and CaTiO{sub 3} powders co-doped with Mg{sup 2+} and Eu{sup 3+} ions were prepared by the polymeric precursor method (PPM). These powders were characterized by different characterization techniques to study the influence of Mg{sup 2+} doping as well as Mg{sup 2+} and Eu{sup 3+} co-doping in structural and optical properties of CaTiO{sub 3} perovskite-type structure. The Rietveld refinement and Micro-Raman analyses suggested the substitution Mg{sup 2+} and Eu{sup 3+} ions in the A-site of CaTiO{sub 3} perovskite. The influence of Mg{sup 2+} doping can be detected by the displacement of calcium and oxygen atomic positions when compared to the non-doped CaTiO{sub 3} powder. When Eu{sup 3+} ions are added to the A-site of this perovskite the excess of positive charge can be compensated by the formation of calcium vacancies. Luminescence data showed that Ca{sub 1-x}Mg{sub x}TiO{sub 3} and Ca{sub 1x}Mg{sub x/2}Eu{sub 2y/3}TiO{sub 3} powders are potential materials for fabrication of lighting devices based on near-UV and blue LED using an excitation wavelength of 397 and/or 450 nm. - Highlights: • CaTiO{sub 3} co-doped with Mg{sup 2+} and Eu{sup 3+} were obtained by the Polymeric Precursor Method. • Incorporation of Mg{sup 2+} and Eu{sup 3+} ions in the CaTiO{sub 3} lattice. • Enhancement of the Eu{sup 3+} photoluminescence.

  5. Effects of Ti-Based Additives on the Hydrogen Storage Properties of a LiBH4/CaH2 Destabilized System

    Directory of Open Access Journals (Sweden)

    Hongwei Yang

    2010-01-01

    Full Text Available The hydrogen storage properties of a destabilized LiBH4/CaH2 system ball-milled with TiCl3, TiF3, and TiO2 additives have been investigated. It is found that the system with TiCl3 additive has a lower dehydrogenation temperature than the ones with other additives. Further study shows that a higher amount of TiCl3 is more effective in reducing the desorption temperature of the LiBH4/CaH2 system, since it leads to a lower activation energy of dehydrogenation. The activations energies for mixtures containing 4, 10, and 25 mol% of TiCl3 are 141, 126, and 110 kJ/mol, respectively. However, the benefits of higher amounts of TiCl3 are offset by a larger reduction in hydrogen capacity of the mixtures.

  6. Study of 40Ca(3He,t)40Sc and 9Be(3He,t)9B reactions

    International Nuclear Information System (INIS)

    The objective of this research thesis is to perform additional experiments for a better definition of the interaction occurring during the (3He,t) charge exchange reaction, notably in the case of transitions between different layers, and in the case of a target nucleus with a non null spin. In this respect, this thesis addresses the study of 40Ca and 9Be nuclei. After a description of experimental devices and of the obtained performance, the author reports the development of microscopic calculation model within the framework of the DWBA (Distorted Wave Born Approximation). Experimental results are then presented, analysed and discussed

  7. Fabrication and performance testing of CaO insulator coatings on V-5%Cr-5%Ti in liquid lithium

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.H.; Dragel, G. [Argonne National Lab., Chicago, IL (United States)

    1995-04-01

    Corrosion resistance of structural materials, and the magnetohydrodynamic (MHD) force and its influence on thermal hydraulics and corrosion, are major concerns in the design of liquid-metal blankets for magnetic fusion reactors (MFRs). The objective of this study is to develop in-situ stable coatings at the liquid-metal/structural-material interface, with emphasis on coatings that can be converted to an electrically insulating film to prevent adverse currents that are generated by the MHD force from passing through the structural walls. The electrical resistance of CaO coatings produced on V-5Cr-5Ti by exposure of the alloy to liquid Li that contained 0.5 - 8.5 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degree}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420{degree}C to produce a CaO coating.

  8. Temperature driven nano-domain evolution in lead-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics

    Science.gov (United States)

    Lu, Shengbo; Xu, Zhengkui; Su, Shi; Zuo, Ruzhong

    2014-07-01

    Hierarchical micro- and nanoscale domain structures in Pb-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics were investigated by transmission electron microscopy. In situ heating and cooling studies of domain structure evolution reveal an irreversible domain transformation from a wedge-shaped rhombohedral nanodomain structure to a lamellar tetragonal domain structure, which could be associated with strong piezoelectricity in Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics.

  9. Temperature driven nano-domain evolution in lead-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics

    International Nuclear Information System (INIS)

    Hierarchical micro- and nanoscale domain structures in Pb-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics were investigated by transmission electron microscopy. In situ heating and cooling studies of domain structure evolution reveal an irreversible domain transformation from a wedge-shaped rhombohedral nanodomain structure to a lamellar tetragonal domain structure, which could be associated with strong piezoelectricity in Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics.

  10. Electronic stopping powers for Be, Ca and Ti in SiC

    International Nuclear Information System (INIS)

    Energy loss of ions in matter is fundamental to many applications dependent on the transport of ions in matter. In spite of a long history of studies, the electronic stopping power is not adequately described over all ranges of ions, energies and targets, particularly in the case of heavy ions or compound targets. In this study, stopping powers for Be, Ca and Ti in SiC have been determined using a time-of-flight energy elastic recoil detection analysis (ToF-E ERDA) set-up. In transmission geometry, the energy loss of heavy ions in a self-supporting SiC foil was measured over a continuous range of energies using the ToF data that was tagged by a Si detector with and without the stopping foil. By essentially calibrating the Si detector for each channel over the measured energy region based on TOF spectrometry, measurement uncertainties of less than 4% are achieved. In comparing with the experimental data, both the SRIM (stopping and range of ions in matter) code and the binary theory provide reasonable predictions

  11. Crystallographic and electronic structure of the Ca2TiMnO6 double perovskite

    International Nuclear Information System (INIS)

    In this work, we report synthesis and crystalline structure study of the Ca2TiMnO6 complex perovskite, by X-ray diffraction experiments and through the application of the Rietveld refinement using the GSAS code. Results revealed the crystallization of the system in a tetragonal perovskite with the characteristic structure given by I4/m (#87) space group and lattice parameters a=5.339(4) Å and c=7.736(6) Å. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system, by the Density Functional Theory (DFT) and using the Full-potential Linearized Augmented Plane Waves (FP-LAPW) method. The exchange-correlation potential was treated using the Generalized Gradient Approximation (GGA). All calculations were carried-out using spin polarization. For the up spin orientation the compound has a semiconducting behavior and for down spin polarization it behaves like a conductor. The calculated effective magnetic moment in cell was 4.02 μB, which is close to the expected value calculated from Hund's rules

  12. High temperature superconductor step-edge Josephson junctions using Ti-Ca-Ba-Cu-O

    Science.gov (United States)

    Ginley, David S.; Hietala, Vincent M.; Hohenwarter, Gert K. G.; Martens, Jon S.; Plut, Thomas A.; Tigges, Chris P.; Vawter, Gregory A.; Zipperian, Thomas E.

    1994-10-25

    A process for formulating non-hysteretic and hysteretic Josephson junctions using HTS materials which results in junctions having the ability to operate at high temperatures while maintaining high uniformity and quality. The non-hysteretic Josephson junction is formed by step-etching a LaAlO.sub.3 crystal substrate and then depositing a thin film of TlCaBaCuO on the substrate, covering the step, and forming a grain boundary at the step and a subsequent Josephson junction. Once the non-hysteretic junction is formed the next step to form the hysteretic Josephson junction is to add capacitance to the system. In the current embodiment, this is accomplished by adding a thin dielectric layer, LaA1O.sub.3, followed by a cap layer of a normal metal where the cap layer is formed by first depositing a thin layer of titanium (Ti) followed by a layer of gold (Au). The dielectric layer and the normal metal cap are patterned to the desired geometry.

  13. Orientación de láminas delgadas de (Pb, CaTiO3

    Directory of Open Access Journals (Sweden)

    Mendiola, J.

    1999-06-01

    Full Text Available Calcium modified PbTiO3 thin films have been prepared on platinized Si, MgO and SrTiO3 substrates. The films were deposited from a sol-gel solution with a concentration of 0.3 M and with a 10% excess of PbO. Two deposits of this solution on the substrates were made by spin-coating, crystallizing each of them by a Rapid Thermal Processing. The resulting films present a single (Pb,CaTiO3 perovskite phase. All the films are textured, but the films deposited on MgO and SrTiO3 show a preferred orientation in the polar direction of the perovskite. As a result of this orientation, pyroelectric coefficients were measured, without any poling, for the films on MgO and SrTiO3. Pyroelectric measurements indicate the application of these films in infrarred sensors.Se han preparado láminas delgadas de PbTiO3 modificado con calcio sobre substratos de Si, MgO y SrTiO3 electrodados con Pt. Las películas se depositaron a partir de una solución sintetizada por sol-gel, con concentración 0.3 M y con un 10 % en exceso de PbO. En cada lámina se hicieron dos depósitos de la solución sobre el substrato mediante la técnica de “spin-coating”, cristalizando cada uno de ellos con un tratamiento térmico rápido. Todas las láminas resultantes presentaban como única fase cristalina la perovskita de (Pb,CaTiO3. Las láminas presentaron una cierta textura, observándose una orientación preferente en la dirección polar en el caso de las películas depositas sobre MgO y SrTiO3. Como resultado de esta orientación, se midieron coeficientes piroeléctricos, sin polarización previa, en las láminas sobre MgO y SrTiO3. Las medidas piroeléctricas de estos materiales evidencian su utilidad en dispositivos para sensores de infrarrojo.

  14. Electronic properties of TiO2 doped with Sc, Y, La, Zr, Hf, V, Nb and Ta

    Science.gov (United States)

    Pan, J. W.; Li, C.; Zhao, Y. F.; Liu, R. X.; Gong, Y. Y.; Niu, L. Y.; Liu, X. J.; Chi, B. Q.

    2015-05-01

    The segregation of dopant inevitably affects the thermodynamic stability and electronic properties of transition metal (TM) doped TiO2 which were studied using first principles calculations. Here we show that the thermodynamic stability of doped systems is related with the doped position which is different for the considered TM dopants. The second phase could appear in V-doped TiO2 due to the Vsbnd Osbnd V bonding. The thermodynamic stability and electronic properties of the doped systems will be slightly infected by dopant concentration. Moreover, the band gaps are approximately proportional to the Mulliken population values of TMsbnd O bond.

  15. Persistent deNOx Ability of CaAl2O4:(Eu, Nd/TiO2-xNy Luminescent Photocatalyst

    Directory of Open Access Journals (Sweden)

    Li Huihui

    2011-01-01

    Full Text Available Abstract CaAl2O4:(Eu, Nd/TiO2-xNy composite luminescent photocatalyst was successfully synthesized by a simple planetary ball milling process. Improvement of photocatalytic deNOx ability of TiO2-xNy, together with the persistent photocatalytic activity for the decomposition of NO after turning off the light were realized, by coupling TiO2-xNy with long afterglow phosphor, CaAl2O4:(Eu, Nd. The novel persistent photocatalytic behavior was related to the overlap between the absorption wavelength of TiO2-xNy and the emission wavelength of the CaAl2O4:(Eu, Nd. It was found that CaAl2O4:(Eu, Nd/TiO2-xNy composites provided the luminescence to persist photocatalytic reaction for more than 3 h after turning off the light. Graphical Abstract CaAl2O4:(Eu, Nd/TiO2-xNy composite luminescent photocatalyst with persistent deNOx activity after turning off the light was successfully synthesized by a simple planetary ball milling process. The novel persistent photocatalytic behavior was related to the overlap between the absorption wavelength of TiO2-xNy and the emission wavelength of the CaAl2O4:(Eu, Nd. Additional file 1 Click here for file

  16. Fusion and quasifission dynamics in the reactions $^{48}$Ca+$^{249}$Bk and $^{50}$Ti+$^{249}$Bk using TDHF

    CERN Document Server

    Umar, A S; Simenel, C

    2016-01-01

    Background: Synthesis of superheavy elements (SHE) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHE have been recently produced with doubly-magic $^{48}$Ca beams. However, SHE synthesis experiments with single-magic $^{50}$Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for $Z=117,119$ superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in $^{48}$Ca,$^{50}$Ti+$^{249}$Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles. Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment. Results: Nucleu...

  17. Impedance-based interpretations in 2-dimensional electron gas conduction formed in the LaAlO3/SrxCa1-xTiO3/SrTiO3 system

    Science.gov (United States)

    Park, Chan-Rok; Moon, Seon Young; Park, Da-Hee; Kim, Shin-Ik; Kim, Seong-Keun; Kang, Chong-Yun; Baek, Seung-Hyub; Choi, Jung-Hae; Kim, Jin-Sang; Choi, Eunsoo; Hwang, Jin-Ha

    2016-06-01

    Frequency-dependent impedance spectroscopy was applied to the 2-dimensioanl conduction transport in the LaAlO3/SrxCa1-xTiO3/SrTiO3 system. The 2-dimensional conduction modifies the electrical/dielectric responses of the LaAlO3/SrxCa1-xTiO3/SrTiO3 depending on the magnitude of the interfacial 2-dimensional resistance. The high conduction of the 2-dimensional electron gas (2DEG) layer can be described using a metallic resistor in series with two parallel RC circuits. However, the high resistance of the 2-dimensional layer drives the composite system from a finite low resistor in parallel with the surrounding dielectrics composed of LaAlO3 and SrTiO3 materials to a dielectric capacitor. This change in the resistance of the 2-dimensional layers modifies the overall impedance enabled by the presence of the interfacial layer due to SrxCa1-xTiO3, which alters the charge transport of the 2-dimensional layer from metallic to semiconducting conduction. A noticeable change is observed in the capacitance Bode plots, indicating highly amplified dielectric constants compared with the pristine SrTiO3 substrates and SrxCa1-xTiO3 with a greater Ca content.

  18. Judd–Ofelt analysis of Tm{sup 3+} doped in CaSc{sub 2}O{sub 4} ceramic samples

    Energy Technology Data Exchange (ETDEWEB)

    Georgescu, Şerban [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Ştefan, Angela [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); University of Bucharest, Faculty of Physics, 405 Atomistilor Street, 077125 Măgurele-Ilfov (Romania); Voiculescu, Ana-Maria [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Toma, Octavian, E-mail: octavian.toma@inflpr.ro [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania)

    2015-10-15

    The Judd–Ofelt analysis is applied to light-scattering ceramic CaSc{sub 2}O{sub 4} doped with Tm{sup 3+}. The calibration of the Judd–Ofelt parameters is performed by two approaches: (i) using the known magnetic-dipole contribution to the transition intensity of {sup 3}H{sub 6}→{sup 3}H{sub 5}; (ii) using the radiative lifetime of an energy level supposed to decay mainly radiatively ({sup 1}G{sub 4} or {sup 3}F{sub 4}). The following results were obtained: Ω{sub 2}=1.55×10{sup −20} cm{sup 2}; Ω{sub 4}=1.71×10{sup −20} cm{sup 2}; Ω{sub 6}=0.98×10{sup −20} cm{sup 2}, using the first approach; Ω{sub 2}=1.70×10{sup −20} cm{sup 2}, Ω{sub 4}=1.84×10{sup −20} cm{sup 2}, Ω{sub 6}=1.13×10{sup −20} cm{sup 2} (calibration using {sup 1}G{sub 4}); Ω{sub 2}=1.57×10{sup −20} cm{sup 2}, Ω{sub 4}=1.70×10{sup −20} cm{sup 2}, Ω{sub 6}=1.04×10{sup −20} cm{sup 2} (calibration using {sup 3}F{sub 4}). The obtained Judd–Ofelt parameters are used to calculate the radiative lifetimes and quantum efficiencies of several Tm{sup 3+} levels, spontaneous emission probabilities and branching ratios of various Tm{sup 3+} transitions. A fairly good agreement was obtained between the results of these methods. - Highlights: • Judd–Ofelt (JO) analysis of ceramic Tm:CaSc{sub 2}O{sub 4} is presented. • Two calibration methods are developed for the JO parameters of Tm{sup 3+} in ceramic media. • The calibration methods yield close results. • Radiative lifetimes, branching ratios, and quantum efficiencies are obtained.

  19. The temperature dependence of the nuclear quadrupole interaction of {sup 44}Ti(EC){sup 44}Sc in rutile

    Energy Technology Data Exchange (ETDEWEB)

    Butz, T., E-mail: Tilman.Butz@gmail.com [Universitaet Leipzig, Fakultaet fuer Physik und Geowissenschaften (Germany); Vianden, R. [Helmholtz Institut fuer Strahlen- und Kernphysik (Germany)

    2013-05-15

    The temperature dependence of the Nuclear Quadrupole Interaction on {sup 44}Sc in rutile was measured by Time Differential Perturbed Angular Correlation in the temperature range from 300 K to 945 K. Whereas {omega}{sub Q} = eQV{sub zz}/4h with V{sub zz} denoting the largest component of the electric field gradient tensor in magnitude increases with increasing temperature, the asymmetry parameter {eta} remains essentially constant. This observation fits into the systematic with other probes provided the sign of V{sub zz} is negative.

  20. Influence of glass additives on the microwave dielectric properties of Ca5Nb2TiO12 ceramics

    International Nuclear Information System (INIS)

    Investigation was made to correlate the effect of composition and concentration of glass content on the sintering temperature and microwave dielectric properties of polycrystalline Ca5Nb2TiO12 ceramics. Glass systems, such as B2O3, SiO2, B2O3-SiO2, ZnO-B2O3, Al2O3-SiO2, Al2O3-B2O3-SiO2, BaO-B2O3-SiO2, MgO-B2O3-SiO2, ZnO-B2O3-SiO2, PbO-B2O3-SiO2, and 2MgO-Al2O3-5SiO2 were added to calcined Ca5Nb2TiO12 powder in different weight percentages. The structure and microstructure of the sintered ceramics were studied using powder X-ray diffraction and scanning electron microscopic methods. The specimens were characterized in the microwave frequency range (3-6 GHz). The study revealed that alumina and silica based glasses were more effective in improving the dielectric properties of Ca5Nb2TiO12 ceramics, whereas borate glasses are more suited for lowering the sintering temperature

  1. New perovskite-related oxides having high dielectric constant: Ln2Ba2CaZn2Ti3O14 (Ln = La and Pr)

    Indian Academy of Sciences (India)

    Pika Jha; Ashok K Ganguli

    2003-10-01

    Two new oxides, La2Ba2CaZn2Ti3O14 and Pr2Ba2CaZn2Ti3O14, have been synthesized by the ceramic route at 1100°C. These oxides crystallize in the disordered cubic structure with an `a’ lattice parameter of 3.9728 (2) and 3.9448 (5) respectively. These oxides show high dielectric constant (70 and 57) and low loss (0.003 and 0.013 at 100 kHz) for La2Ba2CaZn2Ti)3O14 and Pr2Ba2CaZn2Ti3O14 respectively. The dielectric constant is highly stable with frequency and temperature.

  2. Energy levels, radiative rates and electron impact excitation rates for transitions in He-like Cl XVI, K XVIII, Ca XIX and Sc XX

    International Nuclear Information System (INIS)

    We report calculations of energy levels, radiative rates and electron impact excitation cross sections and rates for transitions in He-like Cl XVI, K XVIII, Ca XIX and Sc XX. The GRASP (general-purpose relativistic atomic structure package) is adopted for calculating energy levels and radiative rates. To determine the collision strengths and subsequently the excitation rates, the Dirac atomic R-matrix code (DARC) is used. Oscillator strengths, radiative rates and line strengths are reported for all E1, E2, M1 and M2 transitions among the lowest 49 levels of each ion. Collision strengths are averaged over a Maxwellian velocity distribution and the effective collision strengths obtained listed over a wide temperature range up to 107.4 K. Comparisons are made with similar data obtained from the flexible atomic code (FAC) to highlight the importance of resonances, included in calculations with DARC, in the determination of effective collision strengths. Discrepancies between the collision strengths from DARC and FAC, particularly for forbidden transitions, are also discussed. Additionally, theoretical lifetimes are listed for all the 49 levels of the above four ions.

  3. Interplay of the strain and microstructure in ferroelectric epitaxial CaTiO3 Films

    Science.gov (United States)

    He, Qian; Liang, Qiao; Biegalski, Michael; Borisevich, Albina

    2014-03-01

    CaTiO3 (CTO) was predicted to become ferroelectric under lattice strain. However, other factors such as oxygen octahedral tilts or microstructural details can play a role. In this work, two 20 nm CTO films were grown on LSAT and NGO by PLD. They both show ferroelectricity, with Tc near 140 K on LSAT and near 70 K on NGO, and the remnant polarization at 10K of 5 and 2 μC/cm, respectively. This is surprising given that the strain of CTO on both substrates is similar. AC-STEM shows two major differences in microstructure between two CTO films: Firstly, the first few nm of CTO on NGO show perfect epitaxial growth, and after that grains start to develop, but the c-axis of CTO remains aligned with the c-axis of NGO, suggesting the presence of 180° grain boundaries only. However for CTO/LSAT, grains begin to develop at the interface and their c-axes have two possible orientations, resulting in both 180° and 90° grain boundaries. These grain boundaries are either dislocations or ferroelastic twins. Secondly, the octahedral tilt behavior at the film/substrate interface is different: CTO/LSAT has a 5-6 unit cell transition region from the untilted LSAT to the tilted CTO, which is not the case in CTO/NGO. The connection between the microstructure, substrate strain and connections to the ferroelectric properties will be discussed in detail. Research at ORNL supported by the MSE Division, BES, U.S. DOE, and through a user project supported by ORNL's CNMS, which is also sponsored by BES, U.S. DOE.

  4. Magnetic and ferroelectric response of Ca2TiMnO6 manganite-like perovskite

    Directory of Open Access Journals (Sweden)

    R. Ochoa Burgos

    2012-01-01

    Full Text Available Se reporta la síntesis y caracterización del nuevo material tipo manganita Ca2TiMnO6. Las muestras fueron producidas siguiendo los procedimientos usualmente utilizados para reacciones en estado sólido. Los análisis por difracción de rayos X y refinamiento Rietveld revelan una cristalización tetragonal de perovskita compleja del material (grupo espacial I4/m, número 87, con parámetros de red a=5.5858 °A y c= 7.7518 A° . Las propiedades magnéticas se estudiaron mediante un MPMS SQUID Quantum Design. A partir de las medidas de magnetización en función de la temperatura, se determinó la presencia una transición paramagnética-antiferromagnétic con temperatura de Néel TN=15,5 K. A partir de la aproximación de Curie-Weiss se obtuvieron los parámetros magnéticos característicos del material. Las curvas de magnetización en función del campo aplicado muestran la histéresis magnética característica de los sistemas magnéticamente ordenados. De las curvas de polarización eléctrica, con voltajes de hasta 560 V, se evidencia el carácter ferroeléctrico del material a temperatura ambiente.

  5. Structural properties of CaCu3Ti4O12 obtained by mechanical alloying

    International Nuclear Information System (INIS)

    Mechanical alloying has been used successfully to produce nanocrystalline powders of CaCu3Ti4O12 (CCTO), for the first time, using two different experimental procedures. The milled CCTO were studied by X-ray powder diffraction, infrared and Raman scattering spectroscopy. For two different milling procedures, CCTO was obtained after a couple of hours of milling (in average 30 h of milling, depending on the reaction procedure). The X-ray diffraction (XRD) patterns indicate that the crystallite size is within the range of 20-35 nm. After 100 h of milling the formation of CCTO was confirmed by X-ray powder diffraction in both procedures, with good stability. We also prepare the CCTO ceramic using the traditional procedure described in the literature and compared the physical properties of these samples with those ones obtained by milling process and good agreement was observed. The infrared and Raman scattering spectroscopy results suggest that the increase of the milling time leads to the formation of nanocrystalline CCTO, as seen by XRD analysis. These materials are attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile phones for example), where the decrease of the size of the devices are crucial. This milling process presents the advantage that melting is not necessary and the powder obtained is nanocrystalline with extraordinary mechanical properties. The material can be compacted and transformed in solid ceramic samples or used in others procedures of film preparation. The high efficiency of the process opens a way to produce commercial amount of nanocrystalline powders. Due to the nanocrystalline character of this powder, their mechanical properties have changed and for this reason a pressure of 1 GPa is enough to shape the sample into any geometry

  6. Phase equilibria in CaO–B2O3–TiO2 system at 1373 K and 1473 K

    International Nuclear Information System (INIS)

    Highlights: ► Phase equilibria in CaO–B2O3–TiO2 system at 1373 K and 1473 K were investigated using quenching method followed by XRD and SEM–EDS. ► Isothermal sections in CaO–B2O3–TiO2 system at 1373 K and 1473 K were experimentally constructed. ► The liquidus compositions of CaO–B2O3–TiO2 system at 1373 K and 1473 K were determined. -- Abstract: Phase equilibria in CaO–B2O3–TiO2 system at 1373 K and 1473 K were investigated using quenching method followed by X-ray diffraction and scanning electron microscopy (SEM) equipped with energy dispersive analysis (EDS). Isothermal sections in CaO–B2O3–TiO2 system at 1373 K and 1473 K were experimentally constructed. No ternary oxide compounds were found in this system. The liquidus composition of CaO–B2O3–TiO2 system at 1373 K and 1473 K were determined. The section at 1373 K contains one liquid region, three solid–liquid coexistence regions and five subsolid regions. The section at 1473 K contains one liquid region, five solid–liquid coexistence regions and three subsolidus regions

  7. Comparative dielectric studies of nanostructured BaTiO{sub 3}, CaCu{sub 3}Ti{sub 4}O{sub 12} and 0.5BaTiO{sub 3}⋅ 0.5CaCu{sub 3}Ti{sub 4}O{sub 12} nano-composites synthesized by modified sol–gel and solid state methods

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Laxman [Department of Chemistry, University of Ulsan, 93 Daehak-ro Nam-gu, Ulsan 680-749 (Korea, Republic of); Rai, Uma Shanker [Department of Chemistry, Centre of Advanced Study, Faculty of Science, Banaras Hindu University, Varanasi 221005, U.P. (India); Mandal, Kam Deo [Department of Chemistry, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005, U.P. (India); Sin, Byung Cheol; Lee, Hyung-il [Department of Chemistry, University of Ulsan, 93 Daehak-ro Nam-gu, Ulsan 680-749 (Korea, Republic of); Chung, Hoeil [Department of Chemistry, Hanyang University, Haengdang-dong 17, Seongdong-Gu, Seoul 133-791 (Korea, Republic of); Lee, Youngil, E-mail: nmryil@ulsan.ac.kr [Department of Chemistry, University of Ulsan, 93 Daehak-ro Nam-gu, Ulsan 680-749 (Korea, Republic of)

    2014-10-15

    BaTiO{sub 3} (BTO), CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) and 0.5BaTiO{sub 3}·0.5CaCu{sub 3}Ti{sub 4}O{sub 12} (BTO–CCTO), as a new nano-composite ceramic, were successfully designed and fabricated by a semi-wet gel route and a modified solid state method. The dielectric properties of the BTO–CCTO ceramic were compared to those of the BTO and CCTO ceramics at lower sintering temperatures and durations. The X-ray diffraction analysis revealed that the BTO and CCTO ceramics form a single crystalline phase and the average crystalline sizes calculated from X-ray diffraction data were in the range of 40–65 nm. The particle sizes of the BTO, CCTO, and BTO–CCTO ceramics obtained from transmission electron microscopy images were in the ranges of 40–65 nm, 80–110 nm, and 70–95 nm, respectively. The phase composition and microstructure were studied by X-ray diffraction and scanning electron microscopy. The energy dispersive X-ray results demonstrated the purity and stoichiometry of the BTO–CCTO nano-composite. The grain sizes of the BTO, CCTO and BTO–CCTO ceramics were found to be in the ranges of 500 nm–1 μm, 4–24 μm, and 250 nm–4 μm, respectively. The AC conductivity as a function of frequency confirmed the semiconducting nature of all of the ceramics and obeyed the Jonscher's power law. The impedance spectrum measurement result showed that the CCTO ceramic possessed an exceptional grain boundary resistance, which supports the internal barrier layer capacitance (IBLC) mechanism present in this ceramic and is responsible for the high ε{sub r} values. - Highlights: • Nanostructured BaTiO{sub 3}, CaCu{sub 3}Ti{sub 4}O{sub 12}, and 0.5BaTiO{sub 3}⋅ 0.5CaCu{sub 3}Ti{sub 4}O{sub 12} have been synthesized. • XRD and TEM analysis confirmed the formation of nanoparticles, 40–65 and 50–90 nm. • Impedance analysis shows high grain-boundary resistance present in CCTO ceramic. • AC conductivity as a function of frequency confirms the

  8. Validação dos sistemas de alerta Machardy e Colpam 40® para previsão da requeima do tomateiro em Caçador, SC Validation of the warning systems MacHardy and Colpam 40® to forecast late blight in tomato from Caçador municipality, Santa Catarina state (SC) Brazil

    OpenAIRE

    Walter Ferreira Becker

    2010-01-01

    Foram validados dois sistemas de alerta na requeima do tomateiro, no município de Caçador-SC em dois ciclos de cultivo. No primeiro ciclo, os métodos de MacHardy modificado e Colpam 40®, este com valor de severidade acumulado da doença (VS) igual a 10, como alerta para a pulverização de fungicidas de contato e comparados ao sistema convencional de calendário no híbrido Carmen e na cultivar Santa Clara. Em relação ao convencional, a indicação de pulverizações pelos sistemas de alerta permitiu ...

  9. Investigation into the use of CaZrO3 as a facecoat material in the investment casting of TiAl alloys

    International Nuclear Information System (INIS)

    Research was carried out to determine the interactions between the filler and stucco materials in CaZrO3 based facecoats during shell firing as well as between the facecoat and a TiAl alloy during the casting process. A ‘flash re-melting’ technique, which gives a similar heating profile to the actual investment casting process, was used to study the phase transformations in the shell moulds. The chemical inertness of the facecoat was then investigated using a sessile drop test using a Ti–45Al–2Nb–2Mn–0.2TiB alloy. In this study, the facecoat compositions and the interaction products between metal and shells were characterized using x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A severe interaction was found between CaZrO3 filler and Al2O3 stucco, which rapidly damaged the shell surface. As well as oxygen, zirconium and silicon ions from the shell moulds were also observed to penetrate into the TiAl metal to form (Ti, Zr)5(Al, Si)3 phases in the metal/shell interfacial areas. - Highlights: • To determine the interactions between CaZrO3 filler and stucco materials during shell firing. • To study the reaction between the CaZrO3 facecoat and TiAl alloy during casting. • The Al2O3 stucco can react with CaZrO3 filler to form (Zr, Ca)O2 and CaAlxOy at 1650 °C. • O, Zr and Si ions from the ceramic moulds were observed to penetrate into the TiAl metal. • The reaction products include (Ti, Zr)5(Al, Si)3 and ZrAl2 phase with high Ti ions solid solution

  10. Tuning of Photoluminescence by Cation Nanosegregation in the (CaMg) x (NaSc) 1–x Si 2 O 6 Solid Solution

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Zhiguo; Liu, Guokui; Wen, Jianguo; Mei, Zhigang; Balasubramanian, Mahalingam; Molokeev, Maxim S.; Peng, Licong; Gu, Lin; Miller, Dean J.; Liu, Quanlin; Poeppelmeier, Kenneth R.

    2016-02-03

    Controlled photoluminescence tuning is important for the optimization and modification of phosphor materials. Herein we report an isostructural solid solution of (CaMg)x(NaSc)1-xSi2O6 (0 < x < 1) in which cation nanosegregation leads to the presence of two dilute Eu2+ centers. The distinct nanodomains of isostructural (CaMg)Si2O6 and (NaSc)Si2O6 contain a proportional number of Eu2+ ions with unique, independent spectroscopic signatures. Density functional theory calculations provided a theoretical understanding of the nanosegregation and indicated that the homogeneous solid solution is energetically unstable. It is shown that nanosegregation allows predictive control of color rendering and therefore provides a new method of phosphor development.

  11. Analysis of the normal optical, Michel and molecular potentials on the $^{40}$Ca($^6$Li, d)$^{44}$ Ti reaction

    Indian Academy of Sciences (India)

    MAZUMDER UTTAM K; SOMADDER ANOCK; HOQUE ENAMUL; HAQUE YASMEEN; DAS SUSANTA K; SEN GUPTA H M

    2016-06-01

    Full finite-range (FFR) distorted-wave Born approximation (DWBA) method has been applied to analyse the angular distributions of cross-sections of the $^{40}$Ca($^{6}$Li, d)$^{44}$Ti reaction at 28 MeV incident energy for the 22 transitions involving both the bound and unbound states of $^{44}$Ti byusing the normal optical, Michel and molecular potentials. The extracted spectroscopic factors for the three optical potentials are compared with those of some previous studies of zero-range (ZR) calculations of the$^{40}$Ca($^{6}$Li, d)$^{44}$Ti reaction using the normal optical potential. The $\\chi^{2}$ values of all the levels are obtained for the three optical potentials to estimate the quality of the fits. Molecular and Michel potentials have been used for the first time to analyse the four-nucleon transfer reaction and it seems that the molecular potential fits the experimental data more satisfactorily for some of the states than the normal optical and Michel potentials.

  12. Investigation of laser cladding high temperature anti-wear composite coatings on Ti6Al4V alloy with the addition of self-lubricant CaF{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Zhan-Feng [School of Mechanical and Electric Engineering, Soochow University, 178 East Ganjiang Road, Suzhou 215006 (China); Liu, Xiu-Bo, E-mail: liuxiubo@suda.edu.cn [School of Mechanical and Electric Engineering, Soochow University, 178 East Ganjiang Road, Suzhou 215006 (China); Ren, Jia; Luo, Jian; Shi, Shi-Hong; Chen, Yao [School of Mechanical and Electric Engineering, Soochow University, 178 East Ganjiang Road, Suzhou 215006 (China); Shi, Gao-Lian; Wu, Shao-Hua [Suzhou Institute of Industrial Technology, Suzhou 215104 (China)

    2014-09-15

    Highlights: • A novel high temperature self-lubricating wear-resistant coating was fabricated. • TiC carbides and self-lubricant CaF{sub 2} were “in situ” synthesized in the coating. • The coating with the addition of CaF{sub 2} possessed superior properties than without. - Abstract: To improve the high-temperature tribological properties of Ti–6Al–4V alloy, γ-NiCrAlTi/TiC and γ-NiCrAlTi/TiC/CaF{sub 2} coatings were fabricated on Ti–6Al–4V alloy by laser cladding. The phase compositions and microstructure of the coatings were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). The tribological behaviors were evaluated using a ball-on-disk tribometer from ambient temperature to 600 °C under dry sliding wear conditions and the corresponding wear mechanisms were discussed. The results indicated that the γ-NiCrAlTi/TiC/CaF{sub 2} coating consisted of α-Ti, the “in situ” synthesized TiC block particles and dendrite, γ-NiCrAlTi solid solution and spherical CaF{sub 2} particles. The wear rates of γ-NiCrAlTi/TiC/CaF{sub 2} coating were decreased greatly owing to the combined effects of the reinforced carbides and continuous lubricating films. Furthermore, the friction coefficients of γ-NiCrAlTi/TiC/CaF{sub 2} coating presented minimum value of 0.21 at 600 °C, which was reduced by 43% and 50% compared to the substrate and γ-NiCrAlTi/TiC coating respectively. It was considered that the γ-NiCrAlTi/TiC/CaF{sub 2} coating exhibited excellent friction-reducing and anti-wear properties at high temperature.

  13. Investigation of laser cladding high temperature anti-wear composite coatings on Ti6Al4V alloy with the addition of self-lubricant CaF2

    International Nuclear Information System (INIS)

    Highlights: • A novel high temperature self-lubricating wear-resistant coating was fabricated. • TiC carbides and self-lubricant CaF2 were “in situ” synthesized in the coating. • The coating with the addition of CaF2 possessed superior properties than without. - Abstract: To improve the high-temperature tribological properties of Ti–6Al–4V alloy, γ-NiCrAlTi/TiC and γ-NiCrAlTi/TiC/CaF2 coatings were fabricated on Ti–6Al–4V alloy by laser cladding. The phase compositions and microstructure of the coatings were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). The tribological behaviors were evaluated using a ball-on-disk tribometer from ambient temperature to 600 °C under dry sliding wear conditions and the corresponding wear mechanisms were discussed. The results indicated that the γ-NiCrAlTi/TiC/CaF2 coating consisted of α-Ti, the “in situ” synthesized TiC block particles and dendrite, γ-NiCrAlTi solid solution and spherical CaF2 particles. The wear rates of γ-NiCrAlTi/TiC/CaF2 coating were decreased greatly owing to the combined effects of the reinforced carbides and continuous lubricating films. Furthermore, the friction coefficients of γ-NiCrAlTi/TiC/CaF2 coating presented minimum value of 0.21 at 600 °C, which was reduced by 43% and 50% compared to the substrate and γ-NiCrAlTi/TiC coating respectively. It was considered that the γ-NiCrAlTi/TiC/CaF2 coating exhibited excellent friction-reducing and anti-wear properties at high temperature

  14. Luminescence and energy transfer in Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Ce{sup 3+},Mn{sup 2+} white LED phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yongfu [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Zhang, Xia; Hao, Zhendong; Luo, Yongshi [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Wang, Xiaojun [Department of Physics, Georgia Southern University, Statesboro, GA 30460 (United States); Ma, Li, E-mail: lma@georgiasouthern.edu [Department of Physics, Georgia Southern University, Statesboro, GA 30460 (United States); Zhang, Jiahua, E-mail: zhangjh@ciomp.ac.cn [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2013-01-15

    Expanded emission spectra ranging from green to red are reported in Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12} (CSS):Ce{sup 3+},Mn{sup 2+} silicate garnets. Mn{sup 2+} may occupy Ca{sup 2+} site (Mn{sup 2+}(I)) to generate a yellow emission band at 574 nm or Sc{sup 3+} site (Mn{sup 2+}(II)) with red emission band at 680 nm. Efficient energy transfers from the green emitting Ce{sup 3+} to both Mn{sup 2+}(I) and Mn{sup 2+}(II) occur upon blue excitation into Ce{sup 3+}. Concentration dependence of Mn{sup 2+} emission is analyzed based on Ce{sup 3+}-Mn{sup 2+} energy transfer, steady state rate equations, and fluorescence lifetimes. Energy transfer efficiency ({eta}{sub T}) and rate (W) are calculated with values as high as 45% and 14.01 Multiplication-Sign 10{sup 6} s{sup -1}, respectively. - Highlights: Black-Right-Pointing-Pointer Mn{sup 2+} can occupy Ca{sup 2+} site to generate a yellow emission band at 574 nm in Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12} (CSS). Black-Right-Pointing-Pointer Mn{sup 2+} can also occupy Sc{sup 3+} site to generate a red emission band at 680 nm in CSS. Black-Right-Pointing-Pointer Remarkable energy transfers (ETs) from Ce{sup 3+} to Mn{sup 2+} occur upon blue excitation into Ce{sup 3+} in CSS. Black-Right-Pointing-Pointer Full color emissions are obtained based on Ce{sup 3+}-Mn{sup 2+} ETs in CSS:Ce{sup 3+},Mn{sup 2+}.

  15. Field induced domain switching as the origin of anomalous lattice strain along non-polar direction in rhombohedral BiScO{sub 3}-PbTiO{sub 3} close to the morphotropic phase boundary

    Energy Technology Data Exchange (ETDEWEB)

    Lalitha, K. V.; Ranjan, Rajeev, E-mail: rajeev@materials.iisc.ernt.in [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Fancher, Chris M.; Jones, Jacob L. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-08-03

    The lattice strain and domain switching behavior of xBiScO{sub 3}–(1-x)PbTiO{sub 3} (x = 0.40) was investigated as a function of cyclic field and grain orientation by in situ X-ray diffraction during application of electric fields. The electric field induced 200 lattice strain was measured to be five times larger than the 111 lattice strain in pseudorhombohedral xBiScO{sub 3}–(1-x)PbTiO{sub 3} (x = 0.40). It is shown that the anomalous 200 lattice strain is not an intrinsic phenomenon, but arises primarily due to stress associated with the reorientation of the 111 domains in dense polycrystalline ceramic.

  16. Field induced domain switching as the origin of anomalous lattice strain along non-polar direction in rhombohedral BiScO3-PbTiO3 close to the morphotropic phase boundary

    International Nuclear Information System (INIS)

    The lattice strain and domain switching behavior of xBiScO3–(1-x)PbTiO3 (x = 0.40) was investigated as a function of cyclic field and grain orientation by in situ X-ray diffraction during application of electric fields. The electric field induced 200 lattice strain was measured to be five times larger than the 111 lattice strain in pseudorhombohedral xBiScO3–(1-x)PbTiO3 (x = 0.40). It is shown that the anomalous 200 lattice strain is not an intrinsic phenomenon, but arises primarily due to stress associated with the reorientation of the 111 domains in dense polycrystalline ceramic

  17. First measurement of the nonlinear coefficient for Gd1-xLux Ca4O(BO3)3 and Gd1-xScxCa4O(BO3)3 crystals

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Mortensen, Jesper Liltorp; Germershausen, Sven; Tidemand-Lichtenberg, Peter; Buchhave, Preben; Gheorghe, Lucian; Lupei, Voicu; Loiseau, Pascal; Aka, Gerard

    2007-01-01

    The effective nonlinear coefficient and temperature acceptance bandwidth of three Lu and Sc co-doped GdCa4O(B03)3 type nonlinear crystals were measured. NCPM for SHG in to the blue-UV spectral region can be obtained by controlling the co-dopant concentration. Measurements were based on intra-cavi...

  18. Preparation and characterizations of Ba0.8Ca0.2TiO3 by complex polymerization method (CPM)

    International Nuclear Information System (INIS)

    Ba0.8Ca0.2TiO3 (BCT) was prepared by the complex polymerization method (CPM) using Ba0.8Ca0.2CO3 and [Ti[OCH(CH3)2]4 as starting materials. The powders were crystallized at several temperatures from 400 to 1200 deg. C using different times (from 1 to 8 h). The phase evolution and the physical properties were characterized by X-ray diffraction, Raman and IR spectroscopy. Such results indicate that the precursor Ba0.8Ca0.2CO3 used in the synthesis of Ba0.8Ca0.2TiO3 promotes an effective complexation of the ions Ca2+ in the matrix of BaTiO3. After heat treatment for 2 h at 600 deg. C the phase BCT was obtained with absence of the CaTiO3 or BaCO3 phases. The CPM is an efficient method in the synthesis of the BCT, using small reaction time and low temperature and cost for the preparation of these powders

  19. Preparation and characterizations of Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} by complex polymerization method (CPM)

    Energy Technology Data Exchange (ETDEWEB)

    Motta, F.V. [Laboratorio Interdisciplinar de Eletroquimica e Ceramica, CMDMC, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil)], E-mail: fabiana@liec.ufscar.br; Marques, A.P.A. [Laboratorio de Analise Termica e Materiais, Departamento de Quimica, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Escote, M.T. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil); Melo, D.M.A. [Laboratorio de Analise Termica e Materiais, Departamento de Quimica, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Ferreira, A.G. [Laboratorio de Ressonancia Magnetica Nuclear, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil); Longo, E. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil); Leite, E.R. [Laboratorio Interdisciplinar de Eletroquimica e Ceramica, CMDMC, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil); Varela, J.A. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil)

    2008-10-06

    Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} (BCT) was prepared by the complex polymerization method (CPM) using Ba{sub 0.8}Ca{sub 0.2}CO{sub 3} and [Ti[OCH(CH{sub 3}){sub 2}]{sub 4} as starting materials. The powders were crystallized at several temperatures from 400 to 1200 deg. C using different times (from 1 to 8 h). The phase evolution and the physical properties were characterized by X-ray diffraction, Raman and IR spectroscopy. Such results indicate that the precursor Ba{sub 0.8}Ca{sub 0.2}CO{sub 3} used in the synthesis of Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} promotes an effective complexation of the ions Ca{sup 2+} in the matrix of BaTiO{sub 3}. After heat treatment for 2 h at 600 deg. C the phase BCT was obtained with absence of the CaTiO{sub 3} or BaCO{sub 3} phases. The CPM is an efficient method in the synthesis of the BCT, using small reaction time and low temperature and cost for the preparation of these powders.

  20. Giant dielectric response and low dielectric loss in Al2O3 grafted CaCu3Ti4O12 ceramics

    International Nuclear Information System (INIS)

    This study sheds light on the effect of alumina on dielectric constant and dielectric loss of novel CaCu3Ti4O12 composite ceramics. Alumina, at several concentrations, was deposited on the surface of CaCu3Ti4O12 particles via sol-gel technique. The dielectric constant significantly increased for all frequencies and the dielectric loss substantially decreased for low and intermediate frequencies. These observations were attributed to the change in characteristics of grains and grain boundaries. It was found that the insulating properties of the grain boundaries are improved following the addition of Al2O3. The relative density of CaCu3Ti4O12/Al2O3 composite ceramics decreased compared to the pure CaCu3Ti4O12 and the grain size was greatly changed with the alumina content affecting the dielectric properties. With the addition of alumina into CaCu3Ti4O12, tighter interfaces formed. The 6%- and 10%-alumina ceramics showed the minimum dielectric loss and the maximum dielectric constant, respectively. Both the dielectric constant and loss tangent decreased in the 20%-alumina ceramic due to the formation of CuO secondary phase. It was revealed that Al serves as an electron acceptor decreasing the electron concentration, if Al3+ ions substitute for Ti4+ ions, and as an electron donor increasing the electron concentration, if Al3+ ions substitute for Ca2+ ions. We established a processing-microstructure-properties paradigm which opens new avenues for novel applications of CaCu3Ti4O12/Al2O3 composite ceramics

  1. Anomalous change in dielectric constant of CaCu3Ti4O12 under violet-to-ultraviolet irradiation

    International Nuclear Information System (INIS)

    The influence of light illumination on the dielectric constant of CaCu3Ti4O12 (CCTO) polycrystals is studied in this work. When exposed to 405-nm laser light, a reversible enhancement in the room temperature capacitance as high as 22% was observed, suggesting application of light-sensitive capacitance devices. To uncover the microscopic mechanisms mediating this change, we performed electronic structure measurements, using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. Together, these results suggest that the large capacitance enhancement is driven by oxygen vacancies induced by the irradiation.

  2. Magnetic phase separation in double layer ruthenates Ca3(Ru1−x Ti x )2O7

    OpenAIRE

    Jin Peng; Liu, J. Y.; J. Hu; Mao, Z. Q.; F. M. Zhang; Wu, X S

    2016-01-01

    A phase transition from metallic AFM-b antiferromagnetic state to Mott insulating G-type antiferromagnetic (G-AFM) state was found in Ca3(Ru1−x Ti x )2O7 at about x = 0.03 in our previous work. In the present, we focused on the study of the magnetic transition near the critical composition through detailed magnetization measurements. There is no intermediate magnetic phases between the AFM-b and G-AFM states, which is in contrasted to manganites where a similar magnetic phase transition takes...

  3. Detector de IR de lámina ferroeléctrica de (Pb,Ca)TiO3

    OpenAIRE

    Ramos, P.; Mendiola, J.; Jiménez, Ricardo; Calzada, M. L.; González, A; Tejedor, Paloma

    2002-01-01

    [ES] Se han obtenido depósitos multicapa de titanato de plomo modificado con calcio, (Pb0.76Ca0.24)TiO3, mediante un método de sol-gel, sobre substratos de Pt/MgO(100). El tratamiento térmico del substrato y la cristalización de las multicapas mediante tasas de calentamiento rápidas causan el desarrollo de una importante orientación preferente según el eje polar, perpendicular al mismo, lo que supone una autopolarización muy rentable para su empleo en detectores piroeléctricos de ra...

  4. Efficient Solar Energy Conversion Using CaCu3Ti4O12 Photoanode for Photocatalysis and Photoelectrocatalysis

    OpenAIRE

    H. S. Kushwaha; Niyaz A Madhar; B. Ilahi; Thomas, P; Aditi Halder; Rahul Vaish

    2016-01-01

    A highly efficient third generation catalyst, CaCu3Ti4O12 (CCTO) shows excellent photoelectrochemical (PEC) and photocatalytic ability. As only 4% part of the solar spectrum covers UV light, thus it is highly desirable to develop visible light active photocatalyst materials like CCTO for effective solar energy conversion. A direct band transition with a narrow band gap (1.5 eV) was observed. Under light irradiation, high photocurrent density was found to be 0.96 mA/cm2, indicating the visible...

  5. Large change in dielectric constant of CaCu3Ti4O12 under violet laser

    Science.gov (United States)

    Masingboon, C.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-03-01

    This work reports the influence of light illumination on the dielectric constant of CaCu3Ti4O12 (CCTO) polycrystals which exhibit giant dielectric constant. When the CCTO samples were exposed to 405-nm laser light, the enhancement in capacitance as high as 22% was observed for the first time, suggesting application of light-sensitive capacitance devices. To understand this change better microscopically, we also performed electronic-structure measurements using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. All these measurements suggest that this large change is driven by oxygen vacancy induced by the irradiation.

  6. Anomalous change in dielectric constant of CaCu3Ti4O12 under violet-to-ultraviolet irradiation

    Science.gov (United States)

    Masingboon, C.; Eknapakul, T.; Suwanwong, S.; Buaphet, P.; Nakajima, H.; Mo, S.-K.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-05-01

    The influence of light illumination on the dielectric constant of CaCu3Ti4O12 (CCTO) polycrystals is studied in this work. When exposed to 405-nm laser light, a reversible enhancement in the room temperature capacitance as high as 22% was observed, suggesting application of light-sensitive capacitance devices. To uncover the microscopic mechanisms mediating this change, we performed electronic structure measurements, using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. Together, these results suggest that the large capacitance enhancement is driven by oxygen vacancies induced by the irradiation.

  7. N = 3 - 3 Transitions of Ne-like Ions in the Iron Group, Especially Ca(10+) and Ti(12+)

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Y; Encarnacion, J L; Trabert, E

    2008-10-09

    The Ti XIII 2s{sup 2}2p{sup 5}3l-3l{prime} and 2s2p{sup 6}3l-3l{prime} transitions that have been discussed previously on the basis of beam-foil spectra and laser-produced plasmas in comparison to semi-empirically scaled computations have now been treated by accurate ab initio Multi-reference Moller-Plesset calculations. While most 2s{sup 2}2p{sup 5}3l-3l{prime} line identifications are supported by the new calculations, the 2s2p{sup 6}3l-3l{prime} transition arrays are revised. Theoretical level positions are given for all elements from Ca through Fe. The quality of the calculation is demonstrated on the beam-foil spectra of Ca.

  8. Performance of Ca{sub 1-x}Sr{sub x}TiO{sub 3} as barriers in dielectric barrier discharges with different Sr content

    Energy Technology Data Exchange (ETDEWEB)

    Li Ruixing; Tang Qing; Yin Shu; Sato Tsugio [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2007-09-07

    Plasma assisted catalytic technology, which uses synergetic technologies between the catalyst and plasma, has attracted much attention over the past several years. Theoretically, permittivity of a dielectric barrier influences the transferred charge of a microdischarge; thus high permittivity can improve the plasma reaction in a dielectric barrier discharge (DBD) plasma reactor. Despite the increased interest in the chemical processes, very little has been reported concerning the influence of materials of a dielectric barrier on DBD plasma reactions, since a high permittivity barrier generally exhibits low fracture strength and low dielectric strength making it break down under strong current pulses. In the present study, Ca{sub 1-x}Sr{sub x}TiO{sub 3} (0.1 {<=} x {<=} 0.4) which possesses a high permittivity and a high fracture strength was prepared by liquid phase sintering and was used as a dielectric barrier for the destruction of carbon dioxide by a DBD plasma reaction. The permittivity of Ca{sub 1-x}Sr{sub x}TiO{sub 3} (0.1 {<=} x {<=} 0.4) increased with increasing SrTiO{sub 3} content; however, the observed CO{sub 2} conversion became greatest using Ca{sub 0.8}Sr{sub 0.2}TiO{sub 3} and then decreased with increasing SrTiO{sub 3} content. These results imply that the reactivity of CO{sub 2} destruction does not monotonously increase with increased permittivity of the Ca{sub 1-x}Sr{sub x}TiO{sub 3} barriers. Both amplitude and density of the current pulses ignited by Ca{sub 0.8}Sr{sub 0.2}TiO{sub 3} were much greater than that of Ca{sub 0.6}Sr{sub 0.4}TiO{sub 3}. Further, it was confirmed that a plasma reaction uniformly proceeded using the Ca{sub 0.8}Sr{sub 0.2}TiO{sub 3} barrier, but proceeded non-uniformly using the Ca{sub 0.6}Sr{sub 0.4}TiO{sub 3} barrier by observing the carbon deposition profiles on the surfaces of the barriers.

  9. Ab-initio study of the magnetism, structure and spin dependent electronic states of Ti substituted MO (M = Mg, Ca, Sr)

    Science.gov (United States)

    Jaiganesh, G.; Jaya, S. Mathi

    2015-06-01

    The magnetism, structure and spin polarized electronic structure of Ti substituted MO (M = Mg, Ca, Sr) are studied using the ab-initio techniques within the framework of the density functional theory. Appropriately constructed supercell along with the full structural optimization of these cells is used for studying the influence of Ti substitution on the magnetism and electronic structure of these compounds. We find from our calculations that the Ti substituted MO compounds energetically favor magnetically ordered state. The Ti concentration is found to be important in deciding the magnetic order and we have observed antiferromagnetic order for the Ti concentration of 0.25. The Ti substituted MO compounds are thus an interesting class of materials that deserve further studies.

  10. Ab-initio study of the magnetism, structure and spin dependent electronic states of Ti substituted MO (M = Mg, Ca, Sr)

    International Nuclear Information System (INIS)

    The magnetism, structure and spin polarized electronic structure of Ti substituted MO (M = Mg, Ca, Sr) are studied using the ab-initio techniques within the framework of the density functional theory. Appropriately constructed supercell along with the full structural optimization of these cells is used for studying the influence of Ti substitution on the magnetism and electronic structure of these compounds. We find from our calculations that the Ti substituted MO compounds energetically favor magnetically ordered state. The Ti concentration is found to be important in deciding the magnetic order and we have observed antiferromagnetic order for the Ti concentration of 0.25. The Ti substituted MO compounds are thus an interesting class of materials that deserve further studies

  11. Structural characterization of Nd-doped Hf-zirconolite Ca 1-xNd xHfTi 2-xAl xO 7 ceramics

    Science.gov (United States)

    Caurant, Daniel; Loiseau, Pascal; Bardez, Isabelle

    2010-12-01

    Because of its high incorporation capacity and of the high thermal neutron capture cross-section of hafnium, Hf-zirconolite (CaHfTi 2O 7) ceramic can be envisaged as a potential waste form for minor actinides (Np, Am, Cm) and plutonium immobilization. In this work, Nd-doped Hf-zirconolite Ca 1-xNd xHfTi 2-xAl xO 7 ( x = 0; 0.01 and 0.2) ceramics have been prepared by solid state reaction. Neodymium has been used as trivalent actinide surrogate. The ceramic samples structure has been studied by X-ray diffraction and refined by the Rietveld method. This revealed that Nd 3+ ions only enter the Ca site, whereas part of Hf 4+ ions substitute titanium into Ti(1) sites and Al 3+ ions mainly occupy the Ti(2) split sites and Ti(3) sites of the zirconolite structure. Using various spectroscopic techniques (electron spin resonance, optical absorption and fluorescence), the environment of Nd 3+ cations in Hf-zirconolite has been studied and compared with that of Nd 3+ cations in Zr-zirconolite (CaZrTi 2O 7). Different local environments of Nd 3+ cations have been detected in Hf-zirconolite that can be attributed to the existence of an important disorder around Nd in the Ca site probably due to the statistical occupancy of the next nearest cationic site of neodymium (a split Ti site) by Ti 4+, Al 3+ cations and vacancies. No significant differences were observed concerning Nd 3+ cations environment and distribution in Hf- and Zr-zirconolite ceramics.

  12. CaTiO{sub 3}:Eu{sup 3+}, a potential red long lasting phosphor: Energy migration and characterization of trap level distribution

    Energy Technology Data Exchange (ETDEWEB)

    Som, S., E-mail: sudipta.som@gmail.com [Department of Physics, University of the Free State, Box 339, Bloemfontein 9300 (South Africa); Dutta, S. [Department of Applied Physics, Indian School of Mines, Dhanbad 826004 (India); Kumar, Vijay; Pandey, Anurag; Kumar, Vinod [Department of Physics, University of the Free State, Box 339, Bloemfontein 9300 (South Africa); Kunti, A.K.; Priya, J.; Sharma, S.K. [Department of Applied Physics, Indian School of Mines, Dhanbad 826004 (India); Terblans, J.J. [Department of Physics, University of the Free State, Box 339, Bloemfontein 9300 (South Africa); Swart, H.C., E-mail: swarthc@ufs.ac.za [Department of Physics, University of the Free State, Box 339, Bloemfontein 9300 (South Africa)

    2015-02-15

    Highlights: • CaTiO{sub 3}:Eu{sup 3+} long lasting afterglow red-light was obtained. • The afterglow lasted over 4 min after 397 nm irradiation. • Traps above room temperature were obtained with thermoluminescence measurements. • A possible afterglow mechanism was proposed. - Abstract: This paper comprises a promising approach for the development of a red-light emitting CaTiO{sub 3}:Eu{sup 3+} long-lasting phosphor. Eu{sup 3+} doped CaTiO{sub 3} phosphors were prepared by the solid state reaction method at 1000 °C. Red long-afterglow (LAG) originated from the f-f transitions of Eu{sup 3+} in the CaTiO{sub 3} and lasted for several minutes. Defect trap depth values from 0.62 up to 1.21 eV were obtained from thermoluminescence (TL) data. These defects were created due to charge compensation. These traps were responsible for the afterglow emission at room temperature. The decay curves and TL glow curves showed that the density of the traps with suitable depth has been significantly changed with an increase in dopant concentration. The depth and density of the traps can affect the LAG performance. The possible mechanism behind the LAG of Eu{sup 3+} in CaTiO{sub 3} was explained in detail on the basis of the trap distribution.

  13. CaTiO3:Eu3+, a potential red long lasting phosphor: Energy migration and characterization of trap level distribution

    International Nuclear Information System (INIS)

    Highlights: • CaTiO3:Eu3+ long lasting afterglow red-light was obtained. • The afterglow lasted over 4 min after 397 nm irradiation. • Traps above room temperature were obtained with thermoluminescence measurements. • A possible afterglow mechanism was proposed. - Abstract: This paper comprises a promising approach for the development of a red-light emitting CaTiO3:Eu3+ long-lasting phosphor. Eu3+ doped CaTiO3 phosphors were prepared by the solid state reaction method at 1000 °C. Red long-afterglow (LAG) originated from the f-f transitions of Eu3+ in the CaTiO3 and lasted for several minutes. Defect trap depth values from 0.62 up to 1.21 eV were obtained from thermoluminescence (TL) data. These defects were created due to charge compensation. These traps were responsible for the afterglow emission at room temperature. The decay curves and TL glow curves showed that the density of the traps with suitable depth has been significantly changed with an increase in dopant concentration. The depth and density of the traps can affect the LAG performance. The possible mechanism behind the LAG of Eu3+ in CaTiO3 was explained in detail on the basis of the trap distribution

  14. Efficient Solar Energy Conversion Using CaCu3Ti4O12 Photoanode for Photocatalysis and Photoelectrocatalysis

    Science.gov (United States)

    Kushwaha, H. S.; Madhar, Niyaz A.; Ilahi, B.; Thomas, P.; Halder, Aditi; Vaish, Rahul

    2016-01-01

    A highly efficient third generation catalyst, CaCu3Ti4O12 (CCTO) shows excellent photoelectrochemical (PEC) and photocatalytic ability. As only 4% part of the solar spectrum covers UV light, thus it is highly desirable to develop visible light active photocatalyst materials like CCTO for effective solar energy conversion. A direct band transition with a narrow band gap (1.5 eV) was observed. Under light irradiation, high photocurrent density was found to be 0.96 mA/cm2, indicating the visible light induced photocatalytic ability of CCTO. Visible light mediated photocatalytic and photoelectrocatalytic degradation efficiency of CaCu3Ti4O12 pellets (CCTO) was investigated for three classes of pharmaceutical waste: erythrosin (dye), ciprofloxacin (antibiotic) and estriol (steroid). It is found that the degradation process follows first order kinetic reaction in electrocatalysis, photocatalysis and photoelectrocatalysis and high kinetic rate constant was observed in photoelectrocatalysis. This was quite high in comparison to previously reported methods.

  15. Experimental demonstration of hybrid improper ferroelectricity and the presence of abundant charged walls in (Ca,Sr)3Ti2O7 crystals.

    Science.gov (United States)

    Oh, Yoon Seok; Luo, Xuan; Huang, Fei-Ting; Wang, Yazhong; Cheong, Sang-Wook

    2015-04-01

    On the basis of successful first-principles predictions of new functional ferroelectric materials, a number of new ferroelectrics have been experimentally discovered. Using trilinear coupling of two types of octahedron rotation, hybrid improper ferroelectricity has been theoretically predicted in ordered perovskites and the Ruddlesden-Popper compounds (Ca3Ti2O7, Ca3Mn2O7 and (Ca/Sr/Ba)3(Sn/Zr/Ge)2O7). However, the ferroelectricity of these compounds has never been experimentally confirmed and even their polar nature has been under debate. Here we provide the first experimental demonstration of room-temperature switchable polarization in bulk crystals of Ca3Ti2O7, as well as Sr-doped Ca3Ti2O7. Furthermore, (Ca, Sr)3Ti2O7 is found to exhibit an intriguing ferroelectric domain structure resulting from orthorhombic twins and (switchable) planar polarization. The planar domain structure accompanies abundant charged domain walls with conducting head-to-head and insulating tail-to-tail configurations, which exhibit a conduction difference of two orders of magnitude. These discoveries provide new research opportunities, not only for new stable ferroelectrics of Ruddlesden-Popper compounds, but also for meandering conducting domain walls formed by planar polarization. PMID:25581628

  16. AC Dielectric Properties and Positron Annihilation Study on Co and Ti Substitution Effect on Ca-Sr M-Hexaferrites

    Science.gov (United States)

    Mahmoud, K. R.; Eraky, M. R.

    2016-06-01

    The dependence of AC conductivity σ AC, dielectric constant έ, and dielectric loss tangent tan δ on frequency and composition have been investigated at room temperature for polycrystalline Ca0.5Sr0.5Co x Ti x Fe12 - 2 x O19 (where 0.0 ≤ x ≤ 0.8) hexaferrites. It was found that the parameters σ AC, ɛ ', and tan δ have maximum values at x = 0.4 of the Co and Ti substitution. The behavior of σ AC, ɛ ', and tan δ with frequency and composition was explained on the basis of the hopping conduction mechanism and the Koops model. Positron annihilation lifetime spectroscopy (PALS) was used to investigate the defects and changes in electron density for hexaferrite samples. The PAL parameters ( τ 1, I 1, τ 2, I 2, and mean lifetime) show that altering the doping percentage of the Co and Ti ions affects the size and concentration of defects. The results reveal that there are some large voids in the studied samples. The obtained results indicate the high sensitivity of the PALS technique to the enhanced structure changes with changing composition of the investigated samples and correlate the results with the measured electrical parameters.

  17. Ti doping-induced magnetic and morphological transformations in Sr- and Ca-substituted BiFeO3

    Science.gov (United States)

    Khomchenko, V. A.; Paixão, J. A.

    2016-04-01

    The investigation focuses on the crystal structure, microstructure, local ferroelectric and magnetic properties of the Bi0.9Sr0.1Fe1-x Ti x O3-δ (x  =  0.05, 0.1, 0.15; δ  =  (0.1  -  x)/2) multiferroics prepared by a solid-state reaction method. All the samples have been found to be isostructural with the pure BiFeO3 (the material crystallizes in a polar rhombohedral structure belonging to the space group R3c). It has been shown that the pattern of changes in the lattice parameters of the Bi0.9Sr0.1Fe1-x Ti x O3-δ samples can be interpreted as consistent with the doping-driven elimination of anion vacancies at x  ⩽  0.1 and the formation of cation vacancies at x  >  0.1. The readjustment of the defect structure associated with the mechanism of charge compensation in the aliovalent-substituted BiFeO3 is accompanied by correlated changes in the morphology, ferroelectric/ferroelastic domain structure and magnetic properties of the materials. In particular, it has been found that the deviation from the ideal (δ  =  0) cation-anion stoichiometry in the Bi0.9Sr0.1Fe1-x Ti x O3-δ system leads to a significant decrease in the average size of crystal grain and ferroelectric domains and gives rise to an antiferromagnetic-weak ferromagnetic transformation. Results of this study have been compared with those obtained for equally substituted samples of the Bi0.9Ca0.1Fe1-x Ti x O3-δ series (Khomchenko and Paixão 2015 J. Phys.: Condens. Matter 27 436002) to demonstrate how the variation in the chemical pressure introduced by the partial replacement of Bi3+ with bigger (Sr2+) and smaller (Ca2+) ions can affect the multiferroic behavior of Ti-doped bismuth ferrites.

  18. Dielectric properties, impedance analysis and modulus behavior of CaTiO3 ceramic prepared by solid state reaction

    International Nuclear Information System (INIS)

    Highlights: •A single phase orthorhombic CaTiO3 structure with sub-micron grains is produced. •The frequency exponent ‘s’ is temperature dependent and explained by CBH model. •The dielectric constant and loss tangent are frequency and temperature dependent. •The modulus plot reveals the presence of thermally activated dielectric relaxation. •Cole-cole plot reveals two primary relaxation processes exist in the sample. -- Abstract: Calcium titanate (CaTiO3) with the general formula for perovskites, ABO3, is of technological importance, particularly with regard to dielectric properties. In this work, CaTiO3 ceramic material was prepared by the conventional solid state reaction method. The dielectric properties, impedance characteristics and modulus behavior of the CaTiO3 ceramic material sintered at 1240 °C were investigated in the frequency range of 10−2–106 Hz and temperature range of 100–250 °C. The XRD analysis of the sintered CaTiO3 shows that it is an orthorhombic structure with lattice parameters a = 5.4398 Å, b = 7.6417 Å, and c = 5.3830 Å. The FESEM micrograph shows a significant difference in grain size distribution ranging from 0.26 to 2.32 μm. The AC conductivity, σAC, is found to increase with increasing temperature within the frequency range of 10−2–106 Hz confirming the hopping of electrons to be the conduction mechanism. Due to the decreasing values of the frequency exponent s with increasing temperature, the results of the σAC are discussed using the correlated barrier height (CBH) model. For dielectric studies, the dielectric constant, ε′ is found to decrease with increasing frequency. In the whole temperature range of 100–250 °C, high and low frequency plateau are observed. Each converges at high frequency (>105 Hz) for all the temperatures. The frequency dependence of loss tangent, tan δ, decreases with rise in temperature, with the loss tangent peak shifting to higher frequency. Due to its dielectric

  19. Dielectric properties, impedance analysis and modulus behavior of CaTiO{sub 3} ceramic prepared by solid state reaction

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Y.J., E-mail: yjeng_86@hotmail.com [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hassan, J., E-mail: jumiah@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hashim, M., E-mail: mansor@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

    2013-09-15

    Highlights: •A single phase orthorhombic CaTiO{sub 3} structure with sub-micron grains is produced. •The frequency exponent ‘s’ is temperature dependent and explained by CBH model. •The dielectric constant and loss tangent are frequency and temperature dependent. •The modulus plot reveals the presence of thermally activated dielectric relaxation. •Cole-cole plot reveals two primary relaxation processes exist in the sample. -- Abstract: Calcium titanate (CaTiO{sub 3}) with the general formula for perovskites, ABO{sub 3}, is of technological importance, particularly with regard to dielectric properties. In this work, CaTiO{sub 3} ceramic material was prepared by the conventional solid state reaction method. The dielectric properties, impedance characteristics and modulus behavior of the CaTiO{sub 3} ceramic material sintered at 1240 °C were investigated in the frequency range of 10{sup −2}–10{sup 6} Hz and temperature range of 100–250 °C. The XRD analysis of the sintered CaTiO{sub 3} shows that it is an orthorhombic structure with lattice parameters a = 5.4398 Å, b = 7.6417 Å, and c = 5.3830 Å. The FESEM micrograph shows a significant difference in grain size distribution ranging from 0.26 to 2.32 μm. The AC conductivity, σ{sub AC}, is found to increase with increasing temperature within the frequency range of 10{sup −2}–10{sup 6} Hz confirming the hopping of electrons to be the conduction mechanism. Due to the decreasing values of the frequency exponent s with increasing temperature, the results of the σ{sub AC} are discussed using the correlated barrier height (CBH) model. For dielectric studies, the dielectric constant, ε′ is found to decrease with increasing frequency. In the whole temperature range of 100–250 °C, high and low frequency plateau are observed. Each converges at high frequency (>10{sup 5} Hz) for all the temperatures. The frequency dependence of loss tangent, tan δ, decreases with rise in temperature, with the

  20. Probing charge transfer in a novel class of luminescent perovskite-based heterostructures composed of quantum dots bound to RE-activated CaTiO3 phosphors

    Science.gov (United States)

    Lewis, Crystal S.; Liu, Haiqing; Han, Jinkyu; Wang, Lei; Yue, Shiyu; Brennan, Nicholas A.; Wong, Stanislaus S.

    2016-01-01

    We report on the synthesis and structural characterization of novel semiconducting heterostructures composed of cadmium selenide (CdSe) quantum dots (QDs) attached onto the surfaces of novel high-surface area, porous rare-earth-ion doped alkaline earth titanate micron-scale spherical motifs, i.e. both Eu-doped and Pr-doped CaTiO3, composed of constituent, component nanoparticles. These unique metal oxide perovskite building blocks were created by a multi-pronged synthetic strategy involving molten salt and hydrothermal protocols. Subsequently, optical characterization of these heterostructures indicated a clear behavioral dependence of charge transfer in these systems upon a number of parameters such as the nature of the dopant, the reaction temperature, and particle size. Specifically, 2.7 nm diameter ligand-functionalized CdSe QDs were anchored onto sub-micron sized CaTiO3-based spherical assemblies, prepared by molten salt protocols. We found that both the Pr- and Eu-doped CaTiO3 displayed pronounced PL emissions, with maximum intensities observed using optimized lanthanide concentrations of 0.2 mol% and 6 mol%, respectively. Analogous experiments were performed on Eu-doped BaTiO3 and SrTiO3 motifs, but CaTiO3 still performed as the most effective host material amongst the three perovskite systems tested. Moreover, the ligand-capped CdSe QD-doped CaTiO3 heterostructures exhibited effective charge transfer between the two individual constituent nanoscale components, an assertion corroborated by the corresponding quenching of their measured PL signals.We report on the synthesis and structural characterization of novel semiconducting heterostructures composed of cadmium selenide (CdSe) quantum dots (QDs) attached onto the surfaces of novel high-surface area, porous rare-earth-ion doped alkaline earth titanate micron-scale spherical motifs, i.e. both Eu-doped and Pr-doped CaTiO3, composed of constituent, component nanoparticles. These unique metal oxide perovskite

  1. Influence of secondary phases on phase and microwave dielectric properties of new Ca2Ce2Ti5O16 ceramics

    International Nuclear Information System (INIS)

    Ca2Ce2Ti5O16 ceramics processed via mix oxide route was investigated. Phase composition and microwave dielectric properties were measured using X-ray diffraction and a cavity method, respectively. CeO2 and another unidentified phase (that vanishes at ≥1400°C) existed as secondary phases along with the parent Ca2Ce2Ti5O16 phase. The amount of the parent Ca2Ce2Ti5O16 phase increased with increasing sintering temperature from 1350°C to 1450 °C accompanied by a decrease in the apparent density. The density decreased but εr and Qufo increased with sintering temperature. An εr ∼87.2, Qufo ∼5915 GHz and τf ∼219 GHz was achieved for the sample sintered at 1450°C

  2. Electrical and microstructural properties of CaTiO3-doped K1/2Na1/2NbO3-lead free ceramics

    Indian Academy of Sciences (India)

    L Ramajo; R Parra; M A Ramírez; M S Castro

    2011-10-01

    Microstructure, electrical properties and dielectric behaviour of K1/2Na1/2NbO3 (KNN) and CaTiO3- modified K1/2Na1/2NbO3 (CTO-KNN) systems, were investigated. Discs doped with 0 to 0.55% mol of CaTiO3 (CTO) were sintered at 1125°C for 2 h. Although minority phases were found in doped samples, CaTiO3 was not detected. It was also observed that CTO changed the microstructure and grain size of KNN drastically. Also, the Curie temperature and permittivity values decreased. Addition of CTO between 0.15 and 0.45 mol% decreases the density and dielectric values. Samples prepared with higher content of CTO than 0.45 mol% showed better electrical properties.

  3. Metalloporphyrins with all the pyrrole nitrogens replaced with phosphorus atoms, MP(P)4 (M = Sc, Ti, Fe, Ni, Cu, Zn)

    International Nuclear Information System (INIS)

    Highlights: • First systematic DFT study of the MP(P)4 compounds with increasing number of d-electrons. • Complete substitution of pyrrole nitrogens by P-atoms does not change the ground spin state. • Complete substitution of pyrrole nitrogens by P-atoms results in a bowl-like shape. • Significant stabilization of the MP(P)4 LUMOs compared to the MP counterparts. • MP(P)4 HOMO/LUMO gaps are smaller than the MP HOMO/LUMO gaps. - Abstract: We performed first systematic DFT study of the structures and electronic features (frontier orbitals energies, HOMO/LUMO and optical gaps, IPs and EAs) of the MP(P)4 compounds, with increasing number of d-electrons: 3d14s2 (Sc) → 3d24s2 (Ti) → 3d64s2 (Fe) → 3d84s2 (Ni) → 3d104s1 (Cu) → 3d104s2 (Zn). We performed systematic comparison with the tetrapyrrole MP counterparts. Complete substitution of the pyrrole nitrogens by P-atoms does not change the calculated ground spin state of the compound. All the MP(P)4 species adopt a bowl-like shape, compared to generally planar or slightly distorted shapes of their MP counterparts. Significant positive charge accumulates on P-atoms in MP(P)4. Positive charges on the metals in MP(P)4 are noticeably lower than in the MP counterparts. The calculated MP(P)4 HOMO/LUMO gaps and optical gaps are noticeably smaller than the corresponding gaps in their MP counterparts, which is explained by stabilization of the MP(P)4 LUMOs

  4. Metalloporphyrins with all the pyrrole nitrogens replaced with phosphorus atoms, MP(P){sub 4} (M = Sc, Ti, Fe, Ni, Cu, Zn)

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, Aleksey E., E-mail: aleksey73kuznets@gmail.com

    2015-02-02

    Highlights: • First systematic DFT study of the MP(P){sub 4} compounds with increasing number of d-electrons. • Complete substitution of pyrrole nitrogens by P-atoms does not change the ground spin state. • Complete substitution of pyrrole nitrogens by P-atoms results in a bowl-like shape. • Significant stabilization of the MP(P){sub 4} LUMOs compared to the MP counterparts. • MP(P){sub 4} HOMO/LUMO gaps are smaller than the MP HOMO/LUMO gaps. - Abstract: We performed first systematic DFT study of the structures and electronic features (frontier orbitals energies, HOMO/LUMO and optical gaps, IPs and EAs) of the MP(P){sub 4} compounds, with increasing number of d-electrons: 3d{sup 1}4s{sup 2} (Sc) → 3d{sup 2}4s{sup 2} (Ti) → 3d{sup 6}4s{sup 2} (Fe) → 3d{sup 8}4s{sup 2} (Ni) → 3d{sup 10}4s{sup 1} (Cu) → 3d{sup 10}4s{sup 2} (Zn). We performed systematic comparison with the tetrapyrrole MP counterparts. Complete substitution of the pyrrole nitrogens by P-atoms does not change the calculated ground spin state of the compound. All the MP(P){sub 4} species adopt a bowl-like shape, compared to generally planar or slightly distorted shapes of their MP counterparts. Significant positive charge accumulates on P-atoms in MP(P){sub 4}. Positive charges on the metals in MP(P){sub 4} are noticeably lower than in the MP counterparts. The calculated MP(P){sub 4} HOMO/LUMO gaps and optical gaps are noticeably smaller than the corresponding gaps in their MP counterparts, which is explained by stabilization of the MP(P){sub 4} LUMOs.

  5. Ion-microprobe measurements of Mg, Ca, Ti and Fe isotopic ratios and trace element abundance in hibonite-bearing inclusions in primitive meteorites

    International Nuclear Information System (INIS)

    This thesis reports the isotopic abundances of Mg, Ca, and Ti and rare earth element (REE) abundances in 19 hibonite-bearing inclusions from primative meteorites. The isotopic ratios of Fe were measured in one of the samples, Lance HH-1. These measurements were made by means of secondary ion mass spectrometry (CAMECA IMS-3f). The novel hardware and software developments that made this work possible are described in detail. The samples were studied in thin section in order to investigate the relationship between the inclusions and their mineralogical environments. Inclusions from a number of different meteorites, specifically, Mighei, Murray, Murchison, Lance, Efremovka, Vigarano, Qingzhen, Dhajala, and Semarkona, were studied. The isotopes of Ca and Ti show large and correlated abundance anomalies in their most neutron-rich isotopes, 48Ca and 50Ti. The largest anomalies among the samples studied here are in the Murray inclusion MY-F6, with a 4.6% deficit in 48Ca and a 5.2% deficit in 50Ti, and Lance HH-1, with 3.3% and 6.0% deficits in 48Ca and 50Ti respectively. Correlated excesses of 48Ca and 50Ti, up to 2.4% and 1.4% respectively, are found in some other samples studied here. The fact that there is a correlation of isotopic anomalies in two different elements is clear evidence for a nucleosynthetic origin of these effects. Various possibilities for the origin of these isotopic anomalies are discussed and it is shown that a Cosmic Chemical Memory-like model of the incomplete mixing of dust grains from one or several supernovae is sufficient to explain the data. Magnesium isotopes show excesses of 26Mg, attributable to the in-situ decay of 26Al, in 7 of these inclusions

  6. Structure and Characteristics of Oxide Films Containing Ca and P on Ti Substrate

    Institute of Scientific and Technical Information of China (English)

    Fu LIU; Fuping WANG; Tadao Shimizu; Kaoru Igarashi; Liancheng ZHAO

    2005-01-01

    The ceramic coating was formed by using microarc oxidation (MAO) in the electrolytic solution ofβ-Glycerophosphate sodium salt pentahydrate (β-GP) and calcium acetate (CA). The microstructure, phase structure and phase composition were investigated with scanning electron microscopy (SEM), atomic force microscope (AFM), energy dispersive X-ray microanalyser (EDX), X-ray photoelectron spectroscopy (XPS), electron probe micro analyzer (EPMA) and X-ray diffraction (XRD). Investigation of the chemical composition of the coating with EDX revealed that Ca and P of high concentration existed in oxide films. XRD patterns indicated that the oxide film was composed of only anatase at low voltage discharge, and that rutile peaks appear in addition to anatase peak with increasing MAO voltage. Despite the existence of Ca and P, compounds concerning Ca and P were not detected in the oxide film.

  7. Ferroelectric phase transitions studies in 0.5Ba(Zr0.2Ti0.8) O3-0.5(Ba0.7Ca0.3)TiO3 ceramics

    OpenAIRE

    J.P.B. Silva; Queirós, E. C.; Tavares, P. B.; Sekhar, K C; Kamakshi, Koppole; Moreira, J. A.; Almeida, A; Pereira, M.; Gomes, M. J. M.

    2015-01-01

    The ferroelectric phase transitions in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT 50/50) ceramics,fabricatedbyasolidstatereaction,werestudiedbyusing X-Ray diffraction, Raman spectroscopy, and measuring electric polarization, dielectric permittivity and pyroelectric current. Xraydiffraction(XRD)confirmsthecoexistenceoftetragonal(T) andrhombohedral(R)phasesatroomtemperature.Thetemperature dependence of the Raman modes frequency reveals the existenceoftwophasetransitionscorrespondingtotherhom...

  8. Raman spectroscopy study of the interface structure in (CaCuO2)n/(SrTiO3)m superlattices

    OpenAIRE

    Di Castro, D.; Caramazza, S.; Innocenti, D.; Balestrino, G.; Marini, C.; Dore, P.; Postorino, P.

    2013-01-01

    Raman spectra of CaCuO2/SrTiO3 superlattices show clear spectroscopic marker of two structures formed in CaCuO2 at the interface with SrTiO3. For non-superconducting superlattices, grown in low oxidizing atmosphere, the 425 cm-1 frequency of oxygen vibration in CuO2 planes is the same as for CCO films with infinite layer structure (planar Cu-O coordination). For superconducting superlattices grown in highly oxidizing atmosphere, a 60 cm-1 frequency shift to lower energy occurs. This is ascrib...

  9. In vitro degradation, cytocompatibility and hemolysis tests of CaF2 doped TiO2-SiO2 composite coating on AZ31 alloy

    Science.gov (United States)

    Li, Bing; Chen, Yun; Huang, Wei; Yang, Wenzhong; Yin, Xiaoshuang; Liu, Ying

    2016-09-01

    In this study, a CaF2 doped TiO2-SiO2 composite coating was successfully coated onto AZ31 alloy by sol-gel method. Electrochemical tests, in vitro degradation, direct cellular experiment and hemolysis tests were conducted and the results showed that the CaF2 doped TiO2-SiO2 composite coating can not only improve the corrosion resistance, but also enhance the biocompatibility of AZ31 alloy. XRD, SEM and EDX were also performed to characterize the crystalline structures, morphologies and chemical compositions of the coatings.

  10. Measurement of Excitation Functions of 64Zn (n,p) 64Cu, 64Zn(n, Zn) 63Zn, 51V(n,alpha) 48Sc and 48Ti(n,p) 48Sc Reactions, Around 14-MeV Energy

    International Nuclear Information System (INIS)

    The cross-sections of the reactions 64Zn (n,p) 64Cu, 64Zn(n,Zn) 63Zn, 51V(n,alpha)48Sc and 48Ti (n,p) 48Sc around 14-MeV show large discrepancies in the literature. Accurate measurements of these excitation functions were made in the energy range 13.63-14.73 MeV applying the neutron activation technique using a neutron generator. Results were obtained with a statistical error less than 7%. These measured excitation functions were used to check the statistical multistep compound/ statistical multistep direct (SMC/SMD) reaction models using EXIFON code. The calculations are in good agreement with the measurements, specially for the (n,Zn) reactions

  11. Thermoelastic properties of ScB2, TiB2, YB4 and HoB4: Experimental and theoretical studies

    DEFF Research Database (Denmark)

    Waśkowska, A.; Gerward, Leif; Staun Olsen, J.;

    2011-01-01

    modulus 180–200 GPa), while TiB2 may be classified as superhard (bulk modulus about 260 GPa). We report here first experimental and theoretical determinations of the bulk modulus for HoB4 (195(5) and 198.2 GPa, respectively), and first experimental values of the bulk modulus for ScB2 (196(2) GPa) and YB4...... (185(4) GPa). No pressure-induced phase transformations are observed in any of the above borides up to about 20 GPa. A continuous temperature-driven orthorhombic distortion is observed for HoB4 below 285 K. Values of the thermal expansion coefficient are reported for ScB2 and HoB4 at 293, 200 and 100 K...

  12. Investigation into the use of CaZrO{sub 3} as a facecoat material in the investment casting of TiAl alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, C., E-mail: c.yuan@bham.ac.uk [School of Metallurgy and Materials, The University of Birmingham, B152TT (United Kingdom); Cheng, X. [School of Metallurgy and Materials, The University of Birmingham, B152TT (United Kingdom); School of Material Science and Engineering, Beihang University, No, 37 Xueyuan Street, Haidian District, Beijing 100191 (China); Withey, P.A. [School of Metallurgy and Materials, The University of Birmingham, B152TT (United Kingdom); Rolls-Royce plc. (United Kingdom)

    2015-04-01

    Research was carried out to determine the interactions between the filler and stucco materials in CaZrO{sub 3} based facecoats during shell firing as well as between the facecoat and a TiAl alloy during the casting process. A ‘flash re-melting’ technique, which gives a similar heating profile to the actual investment casting process, was used to study the phase transformations in the shell moulds. The chemical inertness of the facecoat was then investigated using a sessile drop test using a Ti–45Al–2Nb–2Mn–0.2TiB alloy. In this study, the facecoat compositions and the interaction products between metal and shells were characterized using x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A severe interaction was found between CaZrO{sub 3} filler and Al{sub 2}O{sub 3} stucco, which rapidly damaged the shell surface. As well as oxygen, zirconium and silicon ions from the shell moulds were also observed to penetrate into the TiAl metal to form (Ti, Zr){sub 5}(Al, Si){sub 3} phases in the metal/shell interfacial areas. - Highlights: • To determine the interactions between CaZrO{sub 3} filler and stucco materials during shell firing. • To study the reaction between the CaZrO{sub 3} facecoat and TiAl alloy during casting. • The Al{sub 2}O{sub 3} stucco can react with CaZrO{sub 3} filler to form (Zr, Ca)O{sub 2} and CaAl{sub x}O{sub y} at 1650 °C. • O, Zr and Si ions from the ceramic moulds were observed to penetrate into the TiAl metal. • The reaction products include (Ti, Zr){sub 5}(Al, Si){sub 3} and ZrAl{sub 2} phase with high Ti ions solid solution.

  13. Preparation of high dielectric constant thin films of CaCu3Ti4O12 by sol–gel

    Indian Academy of Sciences (India)

    Deepam Maurya; Devendra P Singh; D C Agrawal; Y N Mohapatra

    2008-02-01

    Preparation of sol–gel derived CaCu3Ti4O12 (CCTO) thin films using two different sols and their characterization including their dielectric response are reported. The properties of CCTO films depend heavily on solvents used to prepare the sols. Dielectric constant as high as ∼900 at 100 kHz could be obtained when acetic acid was used to prepare the sol; in contrast, use of hexanoic acid in the sol yielded films with a much lower dielectric constant. The variation in grain and grain boundary conductivities with temperature has been measured. Activation energies of 0.08 eV and 0.68 eV have been found for grain and grain boundary conduction, respectively.

  14. PDMS-SiO2-TiO2-CaO hybrid materials - Cytocompatibility and nanoscale surface features.

    Science.gov (United States)

    Almeida, J Carlos; Wacha, András; Gomes, Pedro S; Fernandes, M Helena R; Fernandes, M Helena Vaz; Salvado, Isabel M Miranda

    2016-07-01

    Two PDMS-SiO2-TiO2-CaO porous hybrid materials were prepared using the same base composition, precursors, and solvents, but following two different sol-gel procedures, based on the authors' previous works where for the first time, in this hybrid system, calcium acetate was used as calcium source. The two different procedures resulted in monolithic materials with different structures, microstructures, and surface wettability. Even though both are highly hydrophobic (contact angles of 127.2° and 150.6°), and present different filling regimes due to different surface topographies, they have demonstrated to be cytocompatible when tested with human osteoblastic cells, against the accepted idea that high-hydrophobic surfaces are not suitable to cell adhesion and proliferation. At the nanoscale, the existence of hydrophilic silica domains containing calcium, where water molecules are physisorbed, is assumed to support this capability, as discussed. PMID:27127030

  15. Study of structural evolution and photoluminescent properties at room temperature of Ca(Zr,Ti)O{sub 3} powders

    Energy Technology Data Exchange (ETDEWEB)

    Cavalcante, L.S. [Laboratorio Interdisciplinar de Eletroquimica e Ceramica-LIEC, Departamento de Quimica, Universidade Federal de Sao Carlos, P.O. Box 676, 13565-905 Sao Carlos, SP (Brazil)], E-mail: laeciosc@bol.com.br; Simoes, A.Z.; Espinosa, J.W.M. [Laboratorio Interdisciplinar em Ceramica, Departamento de Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista, P.O. Box 355, 14801-907 Araraquara, SP (Brazil); Santos, L.P.S. [Centro Federal de Educacao Tecnologica do Maranhao-CEFET, Departamento de Quimica, CEP 64009-700, Sao Luis, MA (Brazil); Longo, E.; Varela, J.A. [Laboratorio Interdisciplinar em Ceramica, Departamento de Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista, P.O. Box 355, 14801-907 Araraquara, SP (Brazil); Pizani, P.S. [Departamento de Fisica, Universidade Federal de Sao Carlos, P.O. Box 676, 13565-905 Sao Carlos, SP (Brazil)

    2008-09-22

    Calcium zirconate titanate, Ca(Zr{sub 0.05}Ti{sub 0.95})O{sub 3} (CZT) powders has been synthesized by the polymeric precursor method. The structural evolution and analysis of the CZT powders were monitored by the X-ray diffraction (XRD), Fourier transform Raman spectroscopy (FT-Raman) and ultraviolet-visible absorption spectroscopy (UV-vis). The decomposition of precursor resin was accompanied by evolution of thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTA). UV-vis measurements suggested that the presence of intermediary energy levels in the band gap are favorable for the intense and broad photoluminescence (PL) in structurally disordered CZT powders at room temperature. TGA and DTA have been employed to correlate the ranges of temperature with the structural order-disorder degree in the CZT lattice that are responsible by PL emission.

  16. Effect of orthorhombic distortion on dielectric and piezoelectric properties of CaBi4Ti4O15 ceramics

    International Nuclear Information System (INIS)

    High temperature bismuth layered piezoelectric and ferroelectric ceramics of CaBi4Ti4O15 (CBT) have been prepared using the solid state route. The formation of single phase material with orthorhombic structure was verified from x-ray diffraction and Raman spectroscopy. The orthorhombic distortion present in the CBT ceramic sintered at 1200 deg. C was found to be maximum. A sharp phase transition from ferroelectric to paraelectric was observed in the temperature dependent dielectric studies of all CBT ceramics. The Curie's temperature (Tc=790 deg. C) was found to be independent of measured frequency. The behavior of ac conductivity as a function of frequency (100 Hz-1 MHz) at low temperatures (33). The observed results indicate the important role of orthorhombic distortion in determining the improved property of multicomponent ferroelectric material.

  17. 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.

  18. High temperature crystallographic and thermodynamic investigations on synthetic calzirtite (Ca2Zr5Ti2O16)

    International Nuclear Information System (INIS)

    Immobilization of actinides in the high level waste (HLW) produced from nuclear reactors in durable host matrix is one of the important concerns in nuclear power technology. Rock analogue (SYNROC) ceramic composites of titanates and zirconates namely zirconolite, calzirtite etc. have been proposed as alternate host matrix for disposal of long lived fission products. These minerals have ability to incorporate or immobilize a wider variety of ions simultaneously without further segregation to any other phases and are stable in geothermal conditions. Knowledge of thermodynamic stability of these minerals is important for their deployment as host matrix for actinide waste disposal. In this work crystal structure and thermodynamic parameters of a mineral analogous titanate termed as calzirtite (Ca2Zr5Ti2O16) has been determined

  19. Validação dos sistemas de alerta Machardy e Colpam 40® para previsão da requeima do tomateiro em Caçador, SC Validation of the warning systems MacHardy and Colpam 40® to forecast late blight in tomato from Caçador municipality, Santa Catarina state (SC Brazil

    Directory of Open Access Journals (Sweden)

    Walter Ferreira Becker

    2010-09-01

    Full Text Available Foram validados dois sistemas de alerta na requeima do tomateiro, no município de Caçador-SC em dois ciclos de cultivo. No primeiro ciclo, os métodos de MacHardy modificado e Colpam 40®, este com valor de severidade acumulado da doença (VS igual a 10, como alerta para a pulverização de fungicidas de contato e comparados ao sistema convencional de calendário no híbrido Carmen e na cultivar Santa Clara. Em relação ao convencional, a indicação de pulverizações pelos sistemas de alerta permitiu uma redução na aplicação de fungicidas de 33,3% e 48,1%, pelos métodos de MacHardy modificado e Colpam 40®, respectivamente. A produtividade foi maior no híbrido Carmen do que na cv. S. Clara, mas em cada um destes materiais não houve diferença entre os sistemas de alerta e o convencional. Na cv. Carmen não houve diferença no controle da requeima na comparação do sistema convencional com o Colpam 40®. No segundo ciclo, usou-se o híbrido Carmen e os sistemas de alerta McHardy e Colpam 40 ® este com VS igual a 8 e 10 comparando-os ao sistema convencional. Não houve diferença na produtividade entre os tratamentos. Em relação ao número de pulverizações houve redução de 42,8% e 60,7% para VS igual a 8 e 10, respectivamente, com o sistema de alerta do Colpam 40® e de 39,2% com o de McHardy. Na avaliação da requeima, não houve diferença entre os tratamentos, exceto para o maior VS de alerta monitorado segundo o Colpam 40® cuja intensidade da doença foi maior. Este trabalho demonstrou que o uso destes dois sistemas de alerta da requeima, MacHardy e Colpam 40, poderiam ser ferramentas úteis para os produtores de tomate na tomada de decisão da pulverização em tomate na região de Caçador, SC.Two warning systems for late blight in tomato were evaluated in two growing seasons in Caçador Municipality, Santa Catarina State (SC, Brazil. In the first growing season, as warming for fungicide spraying in late blight control

  20. Structural, dielectric and electrical properties of CaBa4SmTi3Nb7O30 ferroelectric ceramic

    Indian Academy of Sciences (India)

    Prasun Ganguly; A K Jha

    2011-07-01

    The polycrystalline sample of CaBa4SmTi3Nb7O30, a member of tungsten bronze family, was prepared by solid-state reaction method. X-ray diffraction analysis shows the formation of single-phase compound with an orthorhombic structure at room temperature. Scanning electron micrograph of the material shows uniform distribution of grains. Detailed studies of dielectric properties of the compound as a function of temperature at different frequencies suggest that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 198°C, and exhibits non-relaxor kind of diffuse phase transition. The ferroelectric nature of the compound has been confirmed by recording polarization–electric field hysteresis loop. Piezoelectric and pyroelectric studies of the compound have been discussed in this paper. Electrical properties of the material have been analyzed using complex impedance technique. The Nyquist plots manifest the contribution of grain boundaries (at higher temperature), in addition to granular contribution (at all temperatures) to the overall impedance. The temperature dependence of dc conductivity suggests that the compound has negative temperature coefficient of resistance (NTCR) behaviour. The frequency dependence of ac conductivity is found to obey Jonscher’s universal power law. The observed properties have been compared with calcium free Ba5SmTi3Nb7O30 compound.

  1. Electrical and Pyroelectric Properties of Sol-Gel Derived (Pb, Ca)TiO3 Thin Films with Various Orientations

    Institute of Scientific and Technical Information of China (English)

    唐新桂; 丁爱丽; 王丽华

    2003-01-01

    (Pb0.76Ca0.24)TiO3(PCT)thin films with various orientations were grown on Pt/Ti/SiO2/Si substrates by using a sol-gel process and by controlling the temperature of heat-treatment.The PCT thin films with(100)and random orientation showed well-saturated hysteresis loops at an applied field of 800kV/cm,with remanent polarization and coercive electric field of 23.6 μC/cm2 and 225 k V/cm,17.8 μC/cm2 and 195 k V/cm,respectively.For highly(100)-and random-oriented PCT films,the dielectric constant and dielectric loss values of these films are 121 and 0.016,121 and 0.024 at 1 kHz,respectively.The pyroelectric coefficients p of the PCT thin films are measured by a dynamic technique.At room temperature,the p values and figures of merits of the highly(100)-and random-oriented PCT films are 185μC/m2K and 1.79 × 10-5Pa-0.5,176μC/m2K and 1.39 × 10-5Pa-0.5,respectively.

  2. Radiolabeling of DOTATOC with the long-lived positron emitter {sup 44}Sc

    Energy Technology Data Exchange (ETDEWEB)

    Pruszynski, Marek; Majkowska-Pilip, Agnieszka [Centre of Radiochemistry and Nuclear Chemistry, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warszawa (Poland); Loktionova, Natalia S.; Eppard, Elisabeth [Institute of Nuclear Chemistry, Johannes Gutenberg-University of Mainz, Fritz-Strassmann-Weg 2, D-55128 Mainz (Germany); Roesch, Frank, E-mail: frank.roesch@uni-mainz.de [Institute of Nuclear Chemistry, Johannes Gutenberg-University of Mainz, Fritz-Strassmann-Weg 2, D-55128 Mainz (Germany)

    2012-06-15

    The positron-emitting radionuclide {sup 44}Sc with a half-life of 3.97 h and a {beta}{sup +} branching of 94.3% is of potential interest for clinical PET. As so far it is available from a {sup 44}Ti/{sup 44}Sc generator in Mainz, where long-lived {sup 44}Ti decays to no-carrier-added (nca) {sup 44}Sc. The {sup 44}Sc is a trivalent metal cation and should be suitable for complexation with many well established bifunctional chelators conjugated to peptides or other molecular targeting vectors. Thus, the aim of this work was to investigate the potential of {sup 44}Sc for labeling of DOTA-conjugated peptides. DOTA-D-Phe{sup 1}-Tyr{sup 3}-octreotide (DOTATOC) was used as a model molecule to study and optimize labeling procedure. Reaction parameters such as buffer conditions, concentration of peptide, pH range, reaction temperature and time were optimized. Addition of 21 nmol of DOTATOC to {sup 44}Sc in ammonium acetate buffer pH 4.0 provided labeling yields >98% within 25 min of heating in an oil-bath at 95 Degree-Sign C. This time can be reduced to 3 min only by applying microwave supported heating. {sup 44}Sc-DOTATOC was found to be stable in 0.9% NaCl, PBS pH 7.4, fetal calf and human serums, and also in the presence of competing metal cations (Fe{sup 3+}, Ca{sup 2+}, Cu{sup 2+}, Mg{sup 2+}), as well as other ligand competitors, like EDTA and DTPA, even after almost 25 h incubation at 37 Degree-Sign C. Present study shows that nca {sup 44}Sc forms stable complexes with the macrocyclic ligand DOTA and that {sup 44}Sc-DOTATOC and analog targeting vectors may be synthesized for further preclinical and clinical investigations. - Highlights: Black-Right-Pointing-Pointer Labeling of somatostatin analouges with positron emitter {sup 44}Sc was tested. Black-Right-Pointing-Pointer DOTATOC was labeled with {sup 44}Sc isotope. Black-Right-Pointing-Pointer Optimal conditions for {sup 44}Sc-DOTATOC synthesis were found. Black-Right-Pointing-Pointer Stability of {sup 44}Sc

  3. Dielectric properties of [Ca1-x(Li1/2Nd1/2)x]1-yZnyTiO3 ceramics at microwave frequencies

    International Nuclear Information System (INIS)

    Dielectric properties of Ca1-x(Li1/2Nd1/2)xTiO3 (0.0≤x≤0.6, CLNT) and [Ca0.6(Li1/2Nd1/2)0.4]1-yZnyTiO3 (0.5≤y≤1.0, CLNZT) ceramics were investigated at 4-10 GHz. For the CLNT system, a single perovskite phase was detected in the entire composition range. The dielectric constants (K), and the temperature coefficients of the resonant frequency (TCF) were dependent on the B-site bond valence. Qf value decreases with the increase in (Li1/2Nd1/2)TiO3 content (x) due to a decrease in grain size. For the CLNZT system, Qf value and TCF were improved with Zn content (y) due to the formation of Zn2TiO4. Typically, K of 47, Qf of 13000 GHz, TCF of 14 ppm per deg. C were obtained for [Ca0.6(Li1/2Nd1/2)0.4]0.4Zn0.6TiO3 sintered at 1150 deg. C for 4 h

  4. Effects of Fuel to Synthesis of CaTiO3 by Solution Combustion Synthesis for High-Level Nuclear Waste Ceramics.

    Science.gov (United States)

    Jung, Choong-Hwan; Kim, Yeon-Ku; Han, Young-Min; Lee, Sang-Jin

    2016-02-01

    A solution combustion process for the synthesis of perovskite (CaTiO3) powders is described. Perovskite is one of the crystalline host matrics for the disposal of high-level radioactive wastes (HLW) because it immobilizes Sr and Lns elements by forming solid solutions. Solution combustion synthesis, which is a self-sustaining oxi-reduction reaction between nitrate and organic fuel, the exothermic reaction, and the heat evolved convert the precursors into their corresponding oxide products above 1100 degrees C in air. To investigate the effects of amino acid on the combustion reaction, various types of fuels were used; a glycine, amine and carboxylic ligand mixture. Sr, La and Gd-nitrate with equivalent amounts of up to 20% of CaTiO3 were mixed with Ca and Ti nitrate and amino acid. X-ray diffraction analysis, SEM and TEM were conducted to confirm the formed phases and morphologies. While powders with an uncontrolled shape are obtained through a general oxide-route process, Ca(Sr, Lns)TiO3 powders with micro-sized soft agglomerates consisting of nano-sized primary particles can be prepared using this method. PMID:27433645

  5. Structural and luminescence properties of CaTiO3:Eu3+ phosphor synthesized by chemical co-precipitation method for the application of solid state lighting devices

    Science.gov (United States)

    Singh, Dhananjay Kumar; Manam, J.

    2016-05-01

    The present work report a series of trivalent Europium (Eu3+) doped well crystallized perovskite CaTiO3 phosphors successfully synthesized by chemical co-precipitation method. The crystal structure was confirmed by X-ray diffraction (XRD) which is in good agreement with pure orthorhombic phase with space group Pbnm, and it also indicated that the incorporation of the dopant did not affect the crystal structure. The impact of doping on the photoluminescence performances of the sample has been investigated by emission, excitation, and diffuse reflectance spectra at the room temperature. Photoluminescence spectra of Eu3+ doped CaTiO3 nanophosphor revealed the characteristic emission peak around wavelength 618nm in the visible region upon the excitation of near-UV light at wavelength 397nm due to 5D0 → 7F2 transition in Eu3+. It was further proved that the dipole- dipole interactions results in the concentration quenching of Eu3+ in CaTiO3:Eu3+ nanophosphors. The elemental composition of sample carried out by energy dispersive spectroscopy (EDS). EDS analysis reveals that the Eu3+ doped successfully into host CaTiO3. The experimental result reveals that prepared nanophosphor can be used in the application of solid state lighting devices.

  6. Spectroscopic and photoluminescence characterization of Dy(3+) in Sr0.5Ca0.5TiO3 phosphor.

    Science.gov (United States)

    Vidyadharan, Viji; Sreeja, E; Jose, Saritha K; Joseph, Cyriac; Unnikrishnan, N V; Biju, P R

    2016-02-01

    The spectroscopic and photoluminescence characteristics of trivalent dysprosium (Dy(3+))-doped Sr0.5Ca0.5TiO3 phosphor materials synthesized via solid-state reaction method were studied. The X-ray diffraction profile confirmed the orthorhombic perovskite structure of the prepared samples. Judd-Ofelt analysis was carried out to obtain the intensity parameters and predicted radiative properties of Sr0.5Ca0.5TiO3:2wt%Dy(3+). The photoluminescence spectrum of Dy(3+)-doped Sr0.5Ca0.5TiO3 showed three emission peaks at 481, 574 and 638 nm corresponding to (4)F9/2 →(6)H15/2, (4)F9/2 →(6)H13/2 and (4)F9/2 →(6)H11/2 transitions respectively. The variation of luminescence intensity with different excitation wavelengths and Dy(3+) concentrations is discussed. The decay profiles of (4)F9/2 excited levels of Dy(3+) ions show bi-exponential behaviour and also a decrease in average lifetime with increase in Dy(3+) concentration. Yellow to blue luminescence intensity ratio, CIE chromaticity co-ordinates and correlated color temperature were also calculated for different concentrations of Dy(3+)-doped Sr0.5Ca0.5TiO3 phosphor at different λex. PMID:26032295

  7. X-ray diffraction and Raman spectroscopic investigations on CaZrTi2O7sbnd Y2Ti2O7 system: Delineation of phase fields consisting of potential ceramic host materials

    Science.gov (United States)

    Jafar, M.; Achary, S. N.; Salke, Niliesh P.; Sahu, A. K.; Rao, Rekha; Tyagi, A. K.

    2016-07-01

    Phase evolution from CaZrTi2O7 (zirconolite) to Y2Ti2O7 (pyrochlore) have been delineated by systematic characterization of a series of sample with composition as Ca1-xZr1-xY2xTi2O7 (0.00 ≤ x ≤ 1.00) by powder XRD, Raman spectroscopy, SEM and EDS analyses. Comparative analyses of XRD and Raman spectra revealed sequential evolution of phases with increasing concentration of Y3+ in the compositions. From the XRD studies, three distinct phase fields, namely two layer (2M) and four layer (4M) zirconolite-types and cubic pyrochlore-type are observed in between zirconolite (CaZrTi2O7) and Y2Ti2O7. 4M-zirconolite phase is observed in a narrow range of composition, viz. 0.35 ≤ x ≤ 0.40 while cubic pyrochlore type phase is observed in the compositions with x ≥ 1.20. The unit cell volume of different phases shows a non-linear increasing trend with Y3+ ion concentration which has been attributed to the distribution of cations in different structure and change in their coordination number.

  8. Alguns aspectos epidemiológicos da mancha bacteriana (Xanthomonas spp. do tomateiro na região de Caçador/SC Some epidemiological aspects of bacterial spot (Xanthomonas spp. of tomato in Caçador/SC, Brazil

    Directory of Open Access Journals (Sweden)

    Leandro Luiz Marcuzzo

    2009-06-01

    Full Text Available Objetivando explorar alguns aspectos da epidemiologia da de orvalho e um período médio de 13 horas continuas de umidade mancha bacteriana do tomateiro, incitada por Xanthomonas spp., relativa e"90%. A população bacteriana epifítica oscilou nas 10 em Caçador/SC, um ensaio a campo foi conduzido com plantas semanas após o plantio, conforme as condições climáticas, no inoculadas antes do transplantio. A cada sete dias e durante 19 entanto após o inicio dos sintomas manteve-se estável. O semanas foi monitorada a população bacteriana epifítica, as progresso da doença foi representado pelo modelo logístico y = condições climáticas e a severidade na planta. Constatou-se que o 0.99964/(1+exp(10.35989-0.69762*x e devido a pratica de inicio da epidemia teve concomitância com início da maturação apenas 1 colheita semanal, a severidade em frutos foi alta, fisiológica dos frutos do primeiro cacho, sendo que 77 dias antes atingindo 30,22% com produtividade total de117,88 ton.ha-1. Este do início da colheita não houve sintomas nas folhas. Observou-se, estudo epidemiológico servirá de um indicativo para determinação que mesmo em condição de estiagem, houve acréscimo da doença do inicio da epidemia e será usado na validação de um sistema de devido ao constante molhamento foliar decorrente da formação previsão para a mancha bacteriana do tomateiro.Aiming to explore some epidemiological aspects of bacterial spot of tomato incited by Xanthomonas spp., a field experiment was carried out in Caçador, SC. Tomato plants were inoculated with a bacterial suspension before transplanting. At seven-day intervals the bacterial population on leaf surface and disease severity were monitored during 19 weeks. Daily weather records were registered during the crop season. It was observed that epidemic onset coincided with physiological maturation of the first fruit clusters. Leaves were symptomless until 77 days before harvest. It was

  9. High homogeneity powder of Ti-Ba-Ca-Cu-O (2223) prepared by Freeze-Drying method

    International Nuclear Information System (INIS)

    Full text.Homogeneous high temerature superconductor ceramic powder of TI-Ba-Ca-Cu-O with transition temperature [Tc=123K] have been successfully prepared from the mixture of nitrate salts [TlNO3, Ba(NO3)2, Ca(NO3)2.4H2O and Cu(NO3)2.3H2O] by using freeze-drying method. Freeze-dryer that was used in this work designed locally in our laboratory. This technique consider a better to get a fine powder of ceramic materials by depending on the procedure of frozen droplets with present of liquid nitrogen. SEM pictures showed the size of grains of about [0.8 μm]. We conclude that the high sintering temperature, for the prepared powders in this technique, for long time [120 hrs] will increase the inter diffusion between the grains ahich caused the decreasing in the density of the sample which may be given a better results than the obtained in a previous works

  10. Symmetry-dependent interfacial reconstruction to compensate polar discontinuity at perovskite oxide interfaces (LaAlO3/SrTiO3 and LaAlO3/CaTiO3)

    International Nuclear Information System (INIS)

    We report the crystal symmetry-dependency of the interfacial reconstruction to relieve the polar discontinuity at the complex oxide heterointerfaces. We chose LaAlO3/SrTiO3 and LaAlO3/CaTiO3 interfaces as model systems, where the neutral TiO2 and the positive LaO+ layers form the polar discontinuity at the interface with TiO2-terminated (001) cubic SrTiO3 and orthorhombic CaTiO3. Using scanning transmission electron microscopy, we observed that the interlayer distance abnormally increased at the interface. We performed the first-principles calculations to understand the detailed atomic displacement at the interfaces having no oxygen vacancy and intermixing. Our results show that cations were reconstructed in different ways depending on the crystal symmetry through the octahedral tilts and atomic displacements to compensate the polar discontinuity at the interfaces. Our results imply that the interfacial reconstructions have to be considered along with the ionic compensation (intermixing) and electronic compensation (two dimensional electron gas) to fully understand the interfacial phenomena

  11. Symmetry-dependent interfacial reconstruction to compensate polar discontinuity at perovskite oxide interfaces (LaAlO{sub 3}/SrTiO{sub 3} and LaAlO{sub 3}/CaTiO{sub 3})

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Joohwi; Moon, Seon Young; Kim, Jin-Sang; Choi, Jung-Hae, E-mail: choijh@kist.re.kr, E-mail: almacore@kist.re.kr [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Choi, Jong Kwon [Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Park, Jaehong [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Department of Materials Science and Engineering and Inter-University Semiconductor Research Center, Seoul National University, Seoul 151-744 (Korea, Republic of); Hwang, Cheol Seong [Department of Materials Science and Engineering and Inter-University Semiconductor Research Center, Seoul National University, Seoul 151-744 (Korea, Republic of); Baek, Seung-Hyub [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Department of Nanomaterials Science and Technology, Korea University of Science and Technology, Daejeon 305-333 (Korea, Republic of); Chang, Hye Jung, E-mail: choijh@kist.re.kr, E-mail: almacore@kist.re.kr [Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Department of Nanomaterials Science and Technology, Korea University of Science and Technology, Daejeon 305-333 (Korea, Republic of)

    2015-02-16

    We report the crystal symmetry-dependency of the interfacial reconstruction to relieve the polar discontinuity at the complex oxide heterointerfaces. We chose LaAlO{sub 3}/SrTiO{sub 3} and LaAlO{sub 3}/CaTiO{sub 3} interfaces as model systems, where the neutral TiO{sub 2} and the positive LaO{sup +} layers form the polar discontinuity at the interface with TiO{sub 2}-terminated (001) cubic SrTiO{sub 3} and orthorhombic CaTiO{sub 3}. Using scanning transmission electron microscopy, we observed that the interlayer distance abnormally increased at the interface. We performed the first-principles calculations to understand the detailed atomic displacement at the interfaces having no oxygen vacancy and intermixing. Our results show that cations were reconstructed in different ways depending on the crystal symmetry through the octahedral tilts and atomic displacements to compensate the polar discontinuity at the interfaces. Our results imply that the interfacial reconstructions have to be considered along with the ionic compensation (intermixing) and electronic compensation (two dimensional electron gas) to fully understand the interfacial phenomena.

  12. Synthesis of hierarchically porous structured CaCO3 and TiO2 replicas by sol-gel method using lotus root as template.

    Science.gov (United States)

    Chen, Jui-Yi; Yang, Ching-Yu; Chen, Po-Yu

    2016-10-01

    Intensive attention has been put in mimicking the morphologies in nature owing to their uniqueness, complexity, and diversity. One of the effective approaches to mimic bio-morphologies is through biotemplating - the technique of using biological structures as template to reproduce intricate structure in other forms of materials. This work presents a facile sol-gel technique that can be widely used to convert various carbon-rich bio-structures into different materials. Lotus root, a biomorphic template with high porosity at varying length scales, was selected as the example to demonstrate this approach. The experiment was conducted by infiltrating precursors - titanium (IV) n-butoxide (TnBT) and acetic acid calcium solution - into the lotus root template under vacuum system, followed by calcination. After the treatment, the replicas were calcite CaCO3 and anatase TiO2. In both CaCO3 and TiO2 replicas, the intact structure of the template was preserved. In spite of the overall similarity of the CaCO3 and TiO2 lotus root replicas, some respective differences were found. TiO2 replica was covered with nanowire bundles of 100-200nm in diameter, formed by preferable crystallization of particles, while CaCO3 replica presented the gradient-distributed pores of 10-100μm, which greatly resembled the microstructure of lotus root template. In the BET result, TiO2 replica was mesoporous structure with pores centralizing in 3-4nm. On the other hand, CaCO3 replica had pores in a wider distribution ranging from micro to macro scale. In addition, the surface area was greatly enhanced in both cases. The synthesized materials with hierarchical biomorphic structures may have great potential for purification applications due to their large specific surface area, photocatalytic property, and high adsorption rate. PMID:27287102

  13. The optically stimulated luminescence (OSL) properties of LiF:Mg,Ti, Li2B4O7:Cu, CaSO4:Tm, and CaF2:Mn thermoluminescent (TL) materials

    International Nuclear Information System (INIS)

    This paper reports on an investigation into the optically stimulated luminescence (OSL) properties of several known thermoluminescent materials, namely LiF:Mg,Ti, Li2B4O7:Cu, CaSO4:Tm, and CaF2:Mn. Samples were irradiated to air doses of 15 mGy, 150 mGy and 1.5 Gy and analyzed using a commercially available OSL reader system to determine their luminescence response to continuous blue and infrared light (IR) excitation, centered at 470 nm and 830 nm wavelengths, respectively. CaF2:Mn did not show an OSL response with either IR or blue light stimulation. Li2B4O7:Cu and LiF:Mg,Ti demonstrated relatively weak OSL signals only under blue light excitation. CaSO4:Tm exhibited OSL under both IR and blue light stimulation at sensitivities roughly one order of magnitude less than the OSL response of α-Al2O3:C under the same conditions. - Highlights: • Optically stimulated luminescence (OSL) properties of several known thermoluminescent materials were investigated. • CaF2:Mn did not show an OSL response with either IR or blue light stimulation. • Li2B4O7:Cu and LiF:Mg,Ti demonstrated very weak OSL signals only under blue light excitation. • CaSO4:Tm exhibited OSL under both IR and blue light stimulation. • OSL properties of CaSO4:Tm indicated an optimal OSL readout regime

  14. Hydrothermal growth of TiO2-CaP nano-films on a Ti–Nb-based alloy in concentrated calcium phosphate solutions

    International Nuclear Information System (INIS)

    The Ti–Nb-based TLM alloy (Ti–25Nb–3Zr–2Sn–3Mo) was subjected to hydrothermal treatment in the concentrated Ca3(PO4)2, CaHPO4, and Ca(H2PO4)2 solutions for the purpose of calcification. The treated samples are covered by films consisting of Ca-rich nano-crystallites (100–500 nm) and small nano-grains. XPS and XRD analyses reveal the formation of hydroxyapatite, TiO2, and Nb2O5 at the sample surface. The sample hydrothermally treated in CaHPO4 solution exhibits bioactivity by inducing the formation of apatite layer after soaking test in the simulated body fluid for 15 days. The work would provide a good bioactive surface modification method for Ti–Nb alloy implants with complex shapes and even pores

  15. Dielectric behaviour of CaCu3Ti4O12-epoxy composites

    Directory of Open Access Journals (Sweden)

    Leandro Alfredo Ramajo

    2008-03-01

    Full Text Available The dielectric behavior of composite materials (epoxy resin - barium titanate and epoxy - CCTO was analysed as a function of ceramic amount. Composites were prepared by mixing the components and pouring them into suitable moulds. In some compositions, the matrix was reduced by tetrahydrofuran (THF incorporation. Samples containing various amounts of ceramic filler were examined by TG/DTA and scanning electron microscopy analysis. Dielectric measurements were performed from 20 Hz to 1 MHz and 30 to 120 °C. It was demonstrated that the epoxy - CCTO composites possessed higher permittivity than classic epoxy - BaTiO3 composites. However, the low resin permittivity prevailed in the composite dielectric performance.

  16. A structure energy model for C2/c pyroxenes in the system Na-Mg-Ca-Mn-Fe-Al-Cr-Ti-Si-O

    International Nuclear Information System (INIS)

    The structure of C2/c pyroxenes in the Na-Mg-Ca-Fe-Al-Cr-Ti-Si-O system can be accurately simulated by the calculation of all interionic distances in the asymmetric unit, followed by a DLS treatment that optimizes cell parameters and atomic fractional coordinates. The precise structural simulation allows an accurate treatment of the static bulk lattice energy of the phase through two-body interaction potential calculations extended to all atoms within the asymmetric unit. The parametrization of the repulsive energy is achieved with the Huggins Mayer formulation that assumes the hardness factor of substances to be constant for all salts in the family and the repulsive factors of components to be variable from salt to salt. The linear relationship observed between repulsive factors of components and ionic radii of substituting ions on sites allows a rough estimate of lattice energy (hence of enthalpy, through the Born-Haber treatment) of unknown components. The structure-energy model developed for C2/c pyroxenes in the quadrilateral can be extended to the Na-Mg-Ca-Mn-Fe-Al-Cr-Ti-Si-O system when the molar abundances of minor components CaAl2SiO6, NaAlSi2O6, NaCrSi2O6, CaMnSi2O6, CaTiAl2O6 are limited to X ≤ 0.1 and the molar abundance of CaTiAl2O6 is restricted to X ≤ 0.05. The precision of the results rests on the precision of the enthalpy values selected at Tr, Pr reference conditions, as the uncertainty involved in the static lattice energy calculations is virtually negligible. Once new experimental data are available for the end-member components of interest, the model can be easily recast to obey the new limiting conditions

  17. Effect of structural transition on magnetic and optical properties of Ca and Ti co-substituted BiFeO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pawan; Kar, Manoranjan, E-mail: mano@iitp.ac.in

    2014-01-25

    Highlights: • Secondary phase formation has been controlled for Bi{sub 0.9}Ca{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} • Co-substitution of Ca and Ti at Bi and Fe sites significantly increases M{sub S} and H{sub C} • Compositional driven structural transition from rhombohedral to orthorhombic symmetry. • The leakage current has reduced significantly for Ca{sup 2+} and Ti{sup 4+} co-substituted BiFeO{sub 3}. • Small band gap of co-substituted BiFeO{sub 3} may be useful for optoelectronic devices. -- Abstract: Bi{sub 1−x}Ca{sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} ceramics with x = 0.0, 0.05, 0.075, 0.10, 0.125, 0.15 and 0.2 nanoparticles were prepared by the tartaric acid modified sol–gel technique. The co-substitution of Ca and Ti in certain proportion controls the formation of secondary phases. Structural phase analysis by XRD suggested that pure bismuth ferrite stabilized in rhombohedral crystal symmetry (space group R3c) and orthorhombic (Pbnm) phase fraction was observed in co-substituted samples which increase with the increase in substitution percentage. The changes in the phonon frequencies (A{sub 1}) and line widths in Raman spectra reveal the lattice distortion in co-substituted samples which are in agreement with our XRD analysis. The improved magnetization and coercive field in co-substituted samples occurs due to the suppression of cycloid spin structure which could be explained in terms of field induced spin reorientation and weak ferromagnetism. The Ti{sup 4+} substitution at Fe site in BiFeO{sub 3} significantly reduced the oxygen vacancies and hence the associated leakage current, which leads to the increase of dielectric constant as well as frequency independent region for ∊{sub r} and tan δ (maximum in Bi{sub 0.85}Ca{sub 0.15}Fe{sub 0.85}Ti{sub 0.15}O{sub 3}). The significant decrease in dielectric loss with the increase in substitution percentage leads to the decrease in the room temperature bulk conductivity and thus enhanced

  18. Development of methods for the selective separation of Sc for use in nuclear medicine

    International Nuclear Information System (INIS)

    Full text of publication follows. Scandium radioisotopes are increasingly finding application in PET imaging or targeted therapy [Ref.1]. They can be produced in a no-carrier-added form through various charged particle reactions using Ti or Ca targets [Refs.1,2]. In order to provide Sc of sufficient quantity and quality, fast and reliable methods for its production are needed, including, depending on the production route, the quantitative recovery of the target material. Extraction chromatographic resins allow an easy adjustment of selectivity, show fast kinetics and high capacity and are thus well suited for fast and selective separations [Ref.3]. The aim of the presented project is the development of methods for the separation of Sc radionuclides from irradiated targets. The development of the methods includes the determination of k' values of Sc, Ca, Ti and other potentially interfering elements and impurities for varying Resins, notably TRU and DGA resin, acids and pH values and the influence of macro amounts of Ti and Ca on the extraction of Sc. Elution studies were performed in order to evaluate best suited rinsing/elution conditions and volumes. Based on the obtained results, methods for the separation of Sc and its purification, from irradiated targets were developed and tested on simulated Ti and Ca targets. In order to further improve the separation new extraction chromatographic resins based on the coated nano-tubes were prepared and tested. The recovery of the target materials will also be addressed. References: [1] K. L. Kolsky, V. Joshi, L. F. Mausner and S. C. Srivastava; Radiochemical Purification of No-carrier- added Scandium-47 for Radioimmunotherapy, Appl. Radiat. Isot. Vol. 49, No. 12, pp. 1541-1549, 1998; [2] Sadeghi, Mahdi; Enferadi, Milad; Aref, Morteza; Jafari, Hoda, Nuclear data for the cyclotron production of 66Ga, 86Y, 76Br, 64Cu and 43Sc in PET imaging, Nukleonika, Volume 55, Issue 3, 293-302 (2010); [3] Horwitz, E.P., McAlister, D

  19. Theoretical study of phase stability and elastic properties of T0.75Y0.75B14 (T  =  Sc, Ti, V, Y, Zr, Nb, Si)

    International Nuclear Information System (INIS)

    In this study the phase stability, elastic properties, and plastic behaviour of icosahedral transition metal borides T 0.75Y0.75B14 (T  =  Sc, Ti, V, Y, Zr, Nb, Si) have been investigated using density functional theory. Phase stability critically depends on the charge transferred by T and Y to the B icosahedra. For the metal sublattice occupancy investigated here, the minimum energy of formation is identified at an effective B icosahedra charge of  −1.8  ±  0.1. This charge corridor encompasses the highest phase stability among all the reported icosahedral transition metal boride systems so far. This data provides guidance for future experimental efforts: from a wear-resistance point of view, Sc0.75Y0.75B14, Ti0.75Y0.75B14, and Zr0.75Y0.75B14 exhibit a rather unique and attractive combination of large Young’s modulus values ranging from 488 to 514 GPa with the highest phase stability for icosahedral transition metals borides reported so far. (paper)

  20. The resonance triplet at E_alpha = 4.5 MeV in the 40Ca(alpha,gamma)44Ti reaction

    CERN Document Server

    Schmidt, Konrad; Anders, Michael; Bemmerer, Daniel; Boretzky, Konstanze; Caciolli, Antonio; Degering, Detlev; Dietz, Mirco; Dressler, Rugard; Elekes, Zoltán; Fülöp, Zsolt; Gyürky, György; Hannaske, Roland; Junghans, Arnd R; Marta, Michele; Menzel, Marie-Luise; Munnik, Frans; Schumann, Dorothea; Schwengner, Ronald; Szücs, Tamás; Wagner, Andreas; Yakorev, Dmitry; Zuber, Kai

    2013-01-01

    The 40Ca(alpha,gamma)44Ti reaction is believed to be the main production channel for the radioactive nuclide 44Ti in core-collapse supernovae. Radiation from decaying 44Ti has been observed so far for two supernova remnants, and a precise knowledge of the 44Ti production rate may help improve supernova models. The 40Ca(alpha,gamma)44Ti astrophysical reaction rate is determined by a number of narrow resonances. Here, the resonance triplet at E_alpha = 4497, 4510, and 4523 keV is studied both by activation, using an underground laboratory for the gamma counting, and by in-beam gamma spectrometry. The target properties are determined by elastic recoil detection analysis and by nuclear reactions. The strengths of the three resonances are determined to omega gamma = (0.92+-0.20), (6.2+-0.5), and (1.32+-0.24) eV, respectively, a factor of two more precise than before. The strengths of this resonance triplet may be used in future works as a point of reference. In addition, the present new data directly affect the as...

  1. Non-stoichiometry of Li{sub 2}TiO{sub 3} under hydrogen atmosphere condition

    Energy Technology Data Exchange (ETDEWEB)

    Hoshino, Tsuyoshi [Naka Research Establishment (Oarai site), Japan Atomic Energy Research Institute, 3607, Narita-cho, Oarai-machi, Higashi ibaraki-gun, Ibaraki-ken 311-1394 (Japan)]. E-mail: hoshino@sky.biglobe.ne.jp; Tsuchiya, Kunihiko [Naka Research Establishment (Oarai site), Japan Atomic Energy Research Institute, 3607, Narita-cho, Oarai-machi, Higashi ibaraki-gun, Ibaraki-ken 311-1394 (Japan); Hayashi, Kimio [Naka Research Establishment (Oarai site), Japan Atomic Energy Research Institute, 3607, Narita-cho, Oarai-machi, Higashi ibaraki-gun, Ibaraki-ken 311-1394 (Japan); Terai, Takayuki [Nuclear Engineering Research Laboratory, School of Engineering, The University of Tokyo, 2-22 Shirakata-Shirane, Ibaraki 319-1106 (Japan); Tanaka, Satoru [Department of Quantum Engineering and Systems Science, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Takahashi, Yoichi [Department of Applied Chemistry, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2005-11-15

    Li{sub 2}TiO{sub 3} is one of the most promising candidates for solid breeder materials. In order to control the grain growth at the time of high temperature use, the development of Li{sub 2}TiO{sub 3} which has oxide additive is needed. In the present paper, the structure and the non-stoichiometry of Li{sub 2}TiO{sub 3} added with some different oxides have been extensively investigated by means of thermogravimetry and X-ray diffractometry (XRD). In the case of the Li{sub 2}TiO{sub 3} samples used in this study, Li{sub 2}TiO{sub 3} powder and oxide powder (CaO, ZrO{sub 2}, Sc{sub 2}O{sub 3}) in small quantity were mixed in the following molecular ratio: CaO/Li{sub 2}TiO{sub 3} = 0.20%, ZrO{sub 2}/Li{sub 2}TiO{sub 3} = 0.44% or Sc{sub 2}O{sub 3}/Li{sub 2}TiO{sub 3} 0.40%. These samples are designated as Ca-Li{sub 2}TiO{sub 3}, Zr-Li{sub 2}TiO{sub 3}, and Sc-Li{sub 2}TiO{sub 3}, respectively. Ca-Li{sub 2}TiO{sub 3} and Zr-Li{sub 2}TiO{sub 3} exist as double phases, and Sc-Li{sub 2}TiO{sub 3} exists as a single phase. In thermogravimetry, Ca-Li{sub 2}TiO{sub 3} has fewer oxygen defects than the other kinds of Li{sub 2}TiO{sub 3} in the hydrogen atmosphere. The overall results suggest that the oxide additives are able to control not only the growth of the grain size but also the amount of oxygen defects.

  2. Cubic-tetragonal phase transition in Ca0.04Sr0.96TiO3: a combined specific heat and neutron diffraction study

    International Nuclear Information System (INIS)

    The specific heat corresponding to the tetragonal-to-cubic transition in Ca0.04Sr0.96TiO3 perovskite has been measured by conduction calorimetry. The order parameter of the transition has been obtained by means of neutron diffraction at low temperatures. Comparison of calorimetric data with the evolution of the order parameter indicates that this transition seems to follow a mean field Landau potential as in SrTiO3. The linear behaviour of the excess of entropy versus temperature suggests that a 2-4 Landau potential is sufficient to describe the transition

  3. Interfacial resistive switching properties in Ti/La{sub 0.7}Ca{sub 0.3}MnO{sub 3}/Pt sandwich structures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X.J.; Li, X.M.; Wang, Q.; Yu, W.D.; Chen, L.D. [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding Xi Road, Shanghai 200050 (China); Yang, R.; Cao, X. [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding Xi Road, Shanghai 200050 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China)

    2010-05-15

    La{sub 0.7}Ca{sub 0.3}MnO{sub 3} (LCMO) films with and without in situ oxygen annealing have been prepared by pulsed laser deposition. After depositing Ti top electrodes (TEs) at room temperature, both the Ti/LCMO/Pt structures show a reversible, nonlinear, and hysteretic current-voltage (I-V) characteristics. The switching ratio between high and low resistance state is significantly reduced by in situ oxygen annealing due to the decrease of oxygen vacancies in the surface of LCMO film. Moreover, the switching ratio is also significantly reduced by depositing Ti TEs at a higher temperature such as 200 C. These results suggest that the oxidation/reduction reaction between the TiO{sub x} interlayer and the oxygen-deficient LCMO layer plays a crucial role in the resistive switching of the Ti/LCMO/Pt structures. Furthermore, it is also suggested that the formation/rupture of the conductive filament paths in the TiO{sub x} interlayer by the electrochemical migration of oxygen is responsible for the anomalous changes of current and the large hysteresis in the I-V curves. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

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

    International Nuclear Information System (INIS)

    Highlights: • Faster desorption reaction for doped materials vs. the pure composite system. • Kinetic improvement concerning re-hydrogenation reaction showed by the addition of NbF5. • Full characterization of the de-hydrogenation reaction pathway by means of both SR-PXD and 11B{1H} MAS-NMR. • Study of the evolution of the chemical state of the additives upon both milling and sorption reactions. - Abstract: In the last decade, alkaline and alkaline earth metal tetrahydroborates have been the focuses of the research due to their high gravimetric and volumetric hydrogen densities. Among them, Ca(BH4)2 and the Ca(BH4)2 + MgH2 reactive hydride composites (RHC), were calculated to have the ideal thermodynamic properties which fall within the optimal range for mobile applications. In this study, the addition of NbF5 or TiF4 to the Ca(BH4)2 + MgH2 reactive hydride composite system was attempted aiming to obtain a full reversible system with the simultaneous suppression of CaB12H12. Structural characterization of the specimens was performed by means of in-situ Synchrotron Radiation Powder X-ray diffraction (SR-PXD) and 11B{1H} Solid State Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). The evolution of the chemical state of the Nb- and Ti-based additives was monitored by X-ray Absorption Near Edge Structure (XANES). The addition of NbF5 or TiF4 to the Ca(BH4)2 + MgH2 system have not suppressed completely the formation of CaB12H12 and only a slight improvement concerning the reversible reaction was displayed just in the case of Nb-doped composite material

  5. Sc-47 production from titanium targets using electron linacs.

    Science.gov (United States)

    Mamtimin, Mayir; Harmon, Frank; Starovoitova, Valeriia N

    2015-08-01

    In this work we have studied the feasibility of photonuclear production of (47)Sc from (48)Ti via (48)Ti(γ,p)(47)Sc reaction. Photon flux distribution for electron beams of different energies incident on tungsten converter was calculated using MCNPX radiation transport code. (47)Sc production rate dependence on electron beam energy was found and (47)Sc yields were estimated. It was shown that irradiating a natural Ti target results in numerous scandium isotopes which can reduce the specific activity of (47)Sc. Irradiating enriched (48)Ti targets with a 22MeV 1mA beam will result in hundreds of MBq/g activity of (47)Sc and no other isotopes of scandium. Decreasing the size of the target will result in much higher average photon flux through the target and tens of GBq/g levels of specific activity of (47)Sc. Increasing the beam energy will also result in higher yields, but as soon as the electron energy exceeds the (48)Ti(γ,np)(46)Sc reaction threshold, (46)Sc starts being produced and its fraction in total scandium atoms grows as beam energy increases. The results of the simulations were benchmarked by irradiating natural titanium foil with 22MeV electron beam incident on the tungsten converter. Measured (47)Sc activities were found to be in very good agreement with the predictions. PMID:25931136

  6. Phase developments and dielectric responses of barium substituted four-layer CaBi4Ti4O15 Aurivillius

    Indian Academy of Sciences (India)

    Huiling Du; Xiang Shi; Huilu Li

    2011-10-01

    In this paper, mixed Ca–Ba oxide Ca1−BaBi4Ti4O15 (CBBT) ceramics, fabricated by the improved traditional ceramics process were investigated by doping concentrations of Ba ion up to = 0.9 (in steps of 0.1). At room temperature, an orthorhombic crystal system was confirmed using XRD, and their parameter was obtained using the Rietveld method. Dielectric properties and phase transitions were studied and are explained in terms of lattice response of these ceramics. A shift in ferroelectric–paraelectric phase transition (C) to lower temperatures and a corresponding decrease in permittivity peak with increasing concentration of Ba2+ are also observed. The ferroelectric–paraelectric phase transition of CBBT compounds is of normal type in nature, differing from the relaxor characteristic of BBT. The decrease of orthorhombicity in the lattice structure by the larger Ba2+ ion incorporation, indicating an approach of and , results in lower Curie temperature. Appearance of anomalous loss peaks of Ba-rich compounds at 530°C reveals a phase transition development trend from ferroelectric orthorhombic structure to the paraelectric orthorhombic structure. Relationship of polarization with lattice response is discussed.

  7. Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2013-11-01

    Full Text Available This work reports the excellent dielectric properties of polyimide (PI embedded with CaCu3Ti4O12 (CCTO nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz–1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67 is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

  8. Crystallographic and electronic structure of the Ca{sub 2}TiMnO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    López, J.P. Garzón [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Grupo de Estudios de Materiales – GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Cardona, R. [Grupo de Estudios de Materiales – GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Santos, A. Sarmiento [Grupo de Superficies, Electroquímica y Corrosión, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Téllez, D.A. Landínez [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia)

    2014-12-15

    In this work, we report synthesis and crystalline structure study of the Ca{sub 2}TiMnO{sub 6} complex perovskite, by X-ray diffraction experiments and through the application of the Rietveld refinement using the GSAS code. Results revealed the crystallization of the system in a tetragonal perovskite with the characteristic structure given by I4/m (#87) space group and lattice parameters a=5.339(4) Å and c=7.736(6) Å. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system, by the Density Functional Theory (DFT) and using the Full-potential Linearized Augmented Plane Waves (FP-LAPW) method. The exchange-correlation potential was treated using the Generalized Gradient Approximation (GGA). All calculations were carried-out using spin polarization. For the up spin orientation the compound has a semiconducting behavior and for down spin polarization it behaves like a conductor. The calculated effective magnetic moment in cell was 4.02 μ{sub B}, which is close to the expected value calculated from Hund's rules.

  9. Preparation and Characterization of Nanostructured CaCu2.90Zn0.10Ti4O12 Ceramic

    Directory of Open Access Journals (Sweden)

    Laxman Singh

    2011-12-01

    Full Text Available Nanostructure CaCu2.90Zn0.10Ti4O12 (CCZTO electronic ceramic was synthesized by semi‐wet route. The objective of this route is to enable the calcination and sintering processes to go for completion in shorter time and at lower temperature.The samples were characterized by XRD, TEM, SEM and EDX analyses. The crystallite size of the CCZTO ceramic, obtained by XRD using Debye Scherrer formula, range from 38‐74nm which is in good agreement with the particle size observed by TEM analysis. It was observed clearly that the grain size significantly increased with an increase in sintering duration. Dielectric measurements were carried out by LCR meter in the temperature range, 300‐ 500K, at few selected frequencies. It was also observed that the dielectric constant and dielectric loss of CCZTO are temperature independent in higher frequency whereas temperature dependent in low frequency region. The ceramics exhibit high dielectric constant of 1.35 x 104 at 1 kHz.

  10. Synthesis and microwave dielectric properties of Ca substituted SrLa4Ti4.93Zr0.07O17 ceramics

    Indian Academy of Sciences (India)

    Abdul Manan; Ibrahim Qazi

    2014-05-01

    Microwave dielectric ceramics in Sr1-CaLa4Ti4.93Zr0.07O17 (0 ≤ ≤ 0.5) composition series were processed via a solid-state sintering rout. X-ray diffraction revealed single phase ceramics. Ca substitutions for Sr tuned f towards zero with increased uo values. In the present study, r∼ 55, uo ∼ 11960 GHz and ∼ 5.2 ppm/°C were achieved for the composition with = 0.3.

  11. Observation of coherent phonons in Ca-doped SrTiO{sub 3}: Doping-induced ferroelectric phase transition and ultraviolet-illumination effect

    Energy Technology Data Exchange (ETDEWEB)

    Koyama, Y; Okamura, H; Kohmoto, T [Graduate School of Science, Kobe University, Kobe 657-8501 (Japan); Moriyasu, T [Graduate School of Science and Technology, Kobe University, Kobe 657-8501 (Japan); Yamada, Y [Institute for Chemical Research, Kyoto University, Kyoto 611-0011 (Japan); Tanaka, K, E-mail: kohmoto@kobe-u.ac.j [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

    2009-02-01

    Photo-induced effect in Ca-doped SrTiO{sub 3} was investigated by observing coherent phonons. Coherent phonons of soft modes were studied by using ultrafast polarization spectroscopy. Under an ultraviolet (UV) illumination, a shift of the ferroelectric phase transition point at 28 K toward the lower temperature side was observed, and a decrease of phonon frequencies after the UV illumination was found.

  12. The dimensional effect of dielectric performance in CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics: Role of grain boundary

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jianying, E-mail: lijy@mail.xjtu.edu.cn; Jia, Ran; Hou, Linlin; Gao, Lu; Wu, Kangning; Li, Shengtao

    2015-09-25

    Highlights: • CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics with varied thickness were prepared by grinding and sintering. • The dimensional effect of varistor performance can be observed. • Low-frequency dielectric constant and loss tangent was increased. • IS and SEM analysis showed that the grain boundary play a key role. - Abstract: The relationship between dielectric performance and sample thickness in CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics was investigated. The geometric dimensional effect, observed in gradually grinded CaCu{sub 3}Ti{sub 4}O{sub 12} samples, is referred to as the responsible parameter for the change in breakdown field and nonlinear coefficient with the variation in the thickness. An inflection point behavior of the breakdown electric field, analogous to ZnO based varistor, can be observed with reduced thickness. When the thickness was reduced from 2.2 mm to 0.45 mm, the low-frequency (<100 Hz) dielectric permittivity and dielectric loss was increased while high frequency dielectric relaxation can be barely affected. Impedance spectroscopy results show that the grain resistance remained as ∼40 Ω cm, while grain boundary resistance decrease sharply from 79 MΩ cm to 14 MΩ cm. Scanning electron micrographs illustrate that there exists great difference between microstructure of surface area and interior area along thickness direction, which can be possibly caused by heterogeneous diffusion of oxygen and liquid phase sintering of ceramics. It was proposed that grain boundary play a key role in the dimensional effect, which can also be verified by the results of as-sintered CaCu{sub 3}Ti{sub 4}O{sub 12} samples with varied thickness.

  13. Improvement in the microwave dielectric properties of SrCa4Nb4TiO17 ceramics by Ba substitution

    Indian Academy of Sciences (India)

    Abdul Manan; Yaseen Iqbal

    2014-10-01

    Microwave dielectric ceramics in the Sr1–BaCa4Nb4TiO17 (0 ≤ ≤ 0.75) composition series were fabricated via a solid-state mixed oxide route. All the compositions formed single phase in Sr1–BaCa4Nb4TiO17 (0 ≤ ≤ 0.75) solid solutions within the detection limit of in-house X-ray diffraction (XRD). The sintered microstructure of these ceramics comprised densely packed elongated and plate-like grains. The dielectric properties varied linearly with . Relative permittivity (r) increased from 47.2 to 54.5, unloaded quality factor multiplying the resonant frequency (u o) decreased from 11,984 to 9345 GHz and temperature coefficient of resonant frequency (f) increased from –78.6 to 20 ppm/°C with an increase in x from 0 to 0.75. In the present study, r ≈ 51.6, u o ≈ 10,160 GHz (5.37 GHz) and f ≈ –13.5 ppm/°C were achieved for Sr0.5Ba0.5Ca4Nb4TiO17 ( = 0.5) ceramics.

  14. CaCu3Ti4O12 thin films on conductive oxide electrode: A comparative study between chemical and physical vapor deposition routes

    International Nuclear Information System (INIS)

    Highlights: ► Dielectrics growth and characterization is one of the most hot topics of materials science and microelectronics. ► CaCu3Ti4O12 perovskite, recently, demonstrated to possess peculiar dielectric properties (Science, 2001, 293, 673–676). ► To date no deep discussion on the growth processes, properties and perspective of CCTO thin films has been proposed. ► Our paper is an effective example of interdisciplinarity, since the comparison between PLD and MOCVD has been addressed. ► Great attention has been paid to CaCu3Ti4O12 film/substrate interfaces since dielectric properties are strongly affected. - Abstract: Metal Organic Chemical Vapor Deposition (MOCVD) and Pulsed Laser Deposition (PLD) techniques have been used for the growth of CaCu3Ti4O12 (CCTO) thin films on La0.9Sr1.1NiO4/LaAlO3 (LSNO/LAO) stack. (1 0 0) oriented CCTO films have been formed through both deposition routes and film complete structural and morphological characterizations have been carried out using several techniques (X-ray diffraction, scanning electron microscopy, energy-filtered transmission electron microscopy). The comparative study demonstrated some differences at the CCTO/LSNO interfaces depending on the adopted deposition technique. Chemical/structural modification of the LSNO electrode probably occurred as a function of the different oxygen partial pressure used in the PLD and MOCVD processes.

  15. Antifungal coatings based on Ca(OH)2 mixed with ZnO/TiO2 nanomaterials for protection of limestone monuments.

    Science.gov (United States)

    Gómez-Ortíz, Nikte; De la Rosa-García, Susana; González-Gómez, William; Soria-Castro, Montserrat; Quintana, Patricia; Oskam, Gerko; Ortega-Morales, Benjamin

    2013-03-13

    The presence and deteriorating action of microbial biofilms on historic stone buildings have received considerable attention in the past few years. Among microorganisms, fungi are one of the most damaging groups. In the present work, antimicrobial surfaces were prepared using suspensions of Ca(OH)2 particles, mixed with ZnO or TiO2 nanoparticles. The antimicrobial surfaces were evaluated for their antifungal activity both in the dark and under simulated natural photoperiod cycles, using Penicillium oxalicum and Aspergillus niger as model organisms, and two limestone lithotypes commonly used in construction and as materials for the restoration of historic buildings. Both Ca(OH)2-ZnO and Ca(OH)2-TiO2 materials displayed antifungal activity: ZnO-based systems had the best antifungal properties, being effective both in the dark and under illumination. In contrast, TiO2-based coatings showed antifungal activity only under photoperiod conditions. Controls with coatings consisting of only Ca(OH)2 were readily colonized by both fungi. The antifungal activity was monitored by direct observation with microscope, X-ray diffraction (XRD), and scanning electron microscopy (SEM), and was found to be different for the two lithotypes, suggesting that the mineral grain distribution and porosity played a role in the activity. XRD was used to investigate the formation of biominerals as indicator of the fungal attack of the limestone materials, while SEM illustrated the influence of porosity of both the limestone material and the coatings on the fungal penetration into the limestone. The coated nanosystems based on Ca(OH)2-50%ZnO and pure zincite nanoparticulate films have promising performance on low porosity limestone, showing good antifungal properties against P. oxalicum and A. niger under simulated photoperiod conditions. PMID:23347459

  16. DSC and dielectric investigations in new oxifluoride ceramics Ca(Ti{sub 1-x}Li{sub x})O{sub 3-3x}F{sub 3x}

    Energy Technology Data Exchange (ETDEWEB)

    Cherfouh, H.; Benziada-Taibi, L. [Univ. des Sciences et de la Technologie Houari Boumediene, Algiers (Algeria). Inst. de Chimie; Mezroua, A.; Melouani, B. [Ecole Militaire Polytechnique, Unite d' Enseignement et de Recherche en Chimie Appliquee, Algiers (Algeria)

    2002-07-01

    A new solid solution has been prepared by solid state reaction at 950 C between the calcium titanate CaTiO{sub 3} and the fluoride CaLiF{sub 3}. The oxifluoride solid solution with the generalized formula Ca(Ti{sub 1-x}Li{sub x})O{sub 3-3x}F{sub 3x} occurred in the composition range 0 {<=} x < 0.40. The influence of the double substitution Ti - Li and O - F on the crystallographic properties and the microstructure of CaTiO{sub 3} was determined. The phase transitions in these new compounds were investigated by DSC and dielectric measurements. For each ceramic, three anomalies were observed in the temperature range 300 K - 873 K. (orig.)

  17. Shape Memory Characteristics of Ti(sub 49.5)Ni(sub 25)Pd(sub 25)Sc(sub 0.5) High-Temperature Shape Memory Alloy After Severe Plastic Deformation

    Science.gov (United States)

    Atli, K. C.; Karaman, I.; Noebe, R. D.; Garg, A.; Chumlyakov, Y. I.; Kireeva, I. V.

    2011-01-01

    A Ti(49.5)Ni25Pd25Sc(0.5) high-temperature shape memory alloy is thermomechanically processed to obtain enhanced shape-memory characteristics: in particular, dimensional stability upon repeated thermal cycles under constant loads. This is accomplished using severe plastic deformation via equal channel angular extrusion (ECAE) and post-processing annealing heat treatments. The results of the thermomechanical experiments reveal that the processed materials display enhanced shape memory response, exhibiting higher recoverable transformation and reduced irrecoverable strain levels upon thermal cycling compared with the unprocessed material. This improvement is attributed to the increased strength and resistance of the material against defect generation upon phase transformation as a result of the microstructural refinement due to the ECAE process, as supported by the electron microscopy observations.

  18. Morphotropic phase boundaries in (BiScO3)1-x(PbTiO3)x (0.60

    International Nuclear Information System (INIS)

    We have performed a structural study of the morphotropic phase boundary system (1-x)BiScO3-xPbTiO3 in which both A and B sites of the perovskite are randomly occupied. A MA monoclinic phase coexisting with a tetragonal phase has been evidenced for concentration 0.60< x<0.70. No evidence of local cations ordering nor chemical inhomogeneity has been found. Taking into account data of Eitel et al. [Jpn. J. Appl. Phys., Part 1 40, 5999 (2001); Jpn. J. Appl. Phys. 41, 2099 (2002)] and our results, a global phase diagram has been drawn. This phase diagram reveals some similarities with that of lead zirconate titanate. The results are discussed in relation with previous works in morphotropic phase boundary systems

  19. Morphotropic phase boundary of heterovalent perovskite solid solutions: Experimental and theoretical investigation of PbSc1/2Nb1/2O3-PbTiO3

    International Nuclear Information System (INIS)

    X-ray and neutron diffraction techniques are combined with first-principles-based simulations to derive and understand the structural properties of Pb(Sc,Nb,Ti)O3 (PSN-PT) near its morphotropic phase boundary (MPB). An analysis of our measurements yields, at room and low temperatures, an overall tetragonal T--monoclinic MC--monoclinic MB--rhombohedral R path (when adopting the notations of Vanderbilt and Cohen, Phys. Rev. B 63, 94108 (2001) for the monoclinic phases) as the Ti composition decreases across the MPB. A composition- and temperature-dependent significant mixing between some of these phases is also measured and reported here. The overall T-MC-MB-R path, which has also been proposed for Pb(Mg,Nb,Ti)O3 [A. K. Singh and D. Pandey, Phys. Rev. B 67, 64102 (2003)] is rather complex since it involves a change in the polarization path: this polarization first rotates in a (100) plane for the T-MC part of the path and then in a (1-10) plane for the MB-R part of the path. Moreover, a comparison between these measurements and first-principles-based calculations raises the possibility that this complex path, and the associated MC and MB phases, can only occur if the samples exhibit a deviation from a perfectly homogeneous and disordered situation, e.g. possess nanoscale chemically-ordered regions. If not, homogeneously disordered PSN-PT is predicted to exhibit at low temperature the same polarization path as Pb(Zr,Ti)O3, that is T-monoclinic MA-R which involves a 'single' polarization rotation in a (1-10) plane. Nanoscale inhomogeneity may thus play a key role on the macroscopic properties of PSN-PT, in particular, and of other heterovalent complex solid solutions, in general, near their MPB

  20. Chemical bonding in RFe6Ge4 (R = Li, Sc, Zr) and LuTi6Sn4 with rhombohedral LiFe6Ge4 type structure

    OpenAIRE

    Matar, Samir F.; Fickenscher, Thomas; Gerke, Birgit; Niehaus, Oliver; Rodewald, Ute Ch.; Al Alam, Adel F.; Ouaini, Naïm; Pöttgen, Rainer

    2015-01-01

    The germanide ScFe6Ge4 was synthesized from the elements by arc-melting. Its crystal structure was refined from single crystal X-ray diffractometer data: LiFe6Ge4 type, R View the MathML source3¯m, a = 507.9(3), c = 2000.9(1) pm, wR2 = 0.0737, 242 F2 values, 16 variables. The structure has two main building units. The iron atoms form double-layers of Kagomé networks (248–297 pm Fe–Fe) which are separated by layers of edge-sharing Sc@Ge8 hexagonal bipyramids (265–293 pm Sc–Ge). Chemical bondin...

  1. Stability, elastic properties and fracture toughness of Al0.75X0.75B14 (X=Sc, Ti, V, Cr, Y, Zr, Nb, Mo) investigated using ab initio calculations.

    Science.gov (United States)

    Emmerlich, Jens; Thieme, Niklas; to Baben, Moritz; Music, Denis; Schneider, Jochen M

    2013-08-21

    The effect of the transition metal valence electron concentration on the energy of formation, effective charge of B icosahedra, elastic properties, surface energy and fracture toughness was calculated using density functional theory for icosahedral transition metal borides of AlXB14 (X=Sc, Ti, V, Cr, Y, Zr, Nb, Mo). Consistent with previous work on AlYB14 (Kölpin et al 2009 J. Phys.: Condens. Matter 21 355006) it is shown that phase stability is generally dependent on the effective charge of the icosahedral transition metal borides. Also, ionization potential and electronegativity are identified as parameters affecting the effective charge of B icosahedra suitable for use in predicting the phase stability. Al0.75Y0.75B14, Al0.75Sc0.75B14 and Al0.75Zr0.75B14 have been identified as promising phases for application as protective coatings as they exhibit high phase stability and stiffness combined with a comparatively high fracture toughness. PMID:23877961

  2. Observation of rotation of polarization in thin films of Pb(Sc1/2Nb1/2)O3-PbTiO3 via a monoclinic phase

    International Nuclear Information System (INIS)

    Using a simple methodology based on the classical Bragg-Brentano X-ray geometry we have evidenced at room temperature a pseudo-cubic phase and a monoclinic (Pm) phase in thin films of PbSc1/2Nb1/2O3 (PSN) and (PbSc1/2Nb1/2O3)0.57-(PbTiO3)0.43 (PSN-PT) respectively, the latter compound corresponding to a morphotropic phase boundary (MPB) composition. Depending on the substrate and the thickness, different domains configuration are obtained. Competition between epitaxial and thermal stress induces a complex structural evolution with temperature which is different from that of ceramic samples. Indeed PSN films transform from a pseudo-cubic (triclinic) phase towards a cubic phase whereas in PSN-PT, a succession of transformations from a pure Pm phase toward a tetragonal (possibly non polar) phase is observed, a cubic phase never being reached up to 950 K. (author)

  3. Transport and photoresponse properties in Pr0.5Ca0.5CoO3/Nb-SrTiO3 heterostructure

    Science.gov (United States)

    Zhao, S. G.; Gu, A.; Yan, X. L.; Hao, L. M.; Xie, Y.; Zhang, T.; Jin, K. X.

    2015-01-01

    Transport and photoresponse properties of the heterostructure consisting of a Pr0.5Ca0.5CoO3 film and a Nb-SrTiO3 substrate were investigated. The Pr0.5Ca0.5CoO3 film exhibits semiconducting behavior and the resistances are decreased when irradiated by a 532 nm laser. The rectifying behaviors are observed in the heterostructure. The ideality factors and the diffusion voltages monotonically decrease with increasing the temperature. The photovoltatges of the heterostructure under the irradiation approach the saturation at about 8.5 \\text{mW/mm}2 . The minority carrier lifetime of τp=0.281 \\text{s} is estimated from the time response properties in the falling process of photovoltages. These results reveal that the Pr0.5Ca0.5CoO3 heterostructures have great potentials in photoresponse and photoelectric conversion applications.

  4. In vivo behavior of bioactive phosphate glass-ceramics from the system P2O5-Na2O-CaO containing TiO2.

    Science.gov (United States)

    Monem, Ahmed Soltan; ElBatal, Hatem A; Khalil, Elsayed M A; Azooz, Moenis A; Hamdy, Yousry M

    2008-03-01

    Soda lime phosphate bioglass-ceramics with incorporation of small additions of TiO2 were prepared in the metaphosphate and pyrophosphate region, using an appropriate two-step heat treatment of controlled crystallization defined by differential thermal analysis results. Identification and quantification of crystalline phases precipitated from the soda lime phosphate glasses were performed using X-ray diffraction analysis. Calcium pyrophosphate (beta-Ca2P2O7), sodium metaphosphate (NaPO3), calcium metaphosphate (beta-Ca(PO3)2), sodium pyrophosphate (Na4P2O7), sodium calcium phosphate (Na4Ca(PO3)6) and sodium titanium phosphate (Na5Ti(PO4)3) phases were detected in the prepared glass-ceramics. The degradation of the prepared glass-ceramics were carried out for different periods of time in simulated body fluid at 37 degrees C using granules in the range of (0.300-0.600 mm). The released ions were estimated by atomic absorption spectroscopy and the surface textures were measured by scanning electron microscopy. Evaluation of in vivo bioactivity of the prepared glass-ceramics was carried through implanting the samples in the rabbit femurs. The results showed that the addition of 0.5 TiO2 mol% enhanced the bioactivity while further increase of the TiO2 content decreased the bioactivity. The effect of titanium dioxide on the bioactivity was interpreted on the basis of its action on the crystallization process of the glass-ceramics. PMID:17701314

  5. Improved tribo-mechanical behavior of CaP-containing TiO2 layers produced on titanium by shot blasting and micro-arc oxidation.

    Science.gov (United States)

    Szesz, Eduardo M; de Souza, Gelson B; de Lima, Gabriel G; da Silva, Bruno A; Kuromoto, Neide K; Lepienski, Carlos M

    2014-10-01

    The combination of shot blasting (SB) and micro-arc oxidation (or anodic oxidation--AO) in titanium surfaces was shown to provide enhanced conditions for cell differentiation and osseointegration than those provided by SB or AO alone. This study associated both methods aiming to attain titania layers on Ti with adequate tribo-mechanical features for bone implants. SB was performed using alumina particles, and titania layers were grown by AO using a CaP-based electrolyte. Mechanical properties and scratch resistance were characterized at nanoscale by instrumented indentation and nanoscratch, and correlated with morphological and microstructural changes (XRD, SEM, EDS, AFM, and profilometry). Analytical methods were employed to correct roughness and substrate effects on the indentation results. CaP-containing TiO2 layers were produced on AO and SB + AO. The latter presented small pore size and inhomogeneous layer thickness and Ca/P ratios, caused by the non-uniform surface straining by SB that affects the oxide growth kinetics in the electrochemical process. Elastic modulus of SB + AO layer (37 GPa) were lower than the AO one (45 GPa); both of them were smaller than bulk Ti (130 GPa) and close to bone values. The hardness profiles of AO and SB + AO were similar to the substrate ones. Because of the improved load bearing capacity and unique layer features, the critical load to remove the SB + AO titania coating in scratch tests was three times as much or higher than in AO. Results indicate improved mechanical biocompatibility and tribological strength of anodic titania layers grown on sand blasted Ti surfaces. PMID:24845307

  6. Energy dependence of thermoluminescent response of CaSO{sub 4}:Dy, LiF:Mg and micro LiF:Mg,Ti in clinical beams of electrons by using different simulator objects; Dependencia energetica da resposta TL de dosimetros de CaSO{sub 4}:Dy, LiF:Mg e microLiF:Mg,Ti em feixes clinicos de eletrons utilizando diferentes objetos simuladores

    Energy Technology Data Exchange (ETDEWEB)

    Bravim, Amanda; Campos, Leticia Lucente, E-mail: abravin@ipen.b, E-mail: rsakuraba@einstein.b, E-mail: lcrodri@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Sakuraba, Roberto K.; Cruz, Jose Carlos da, E-mail: rsakuraba@einstein.b, E-mail: josecarlosc@einstein.b [Hospital Israelita Albert Einstein (HIAE), Sao Paulo, SP (Brazil)

    2011-10-26

    Yet not so widely applied in radiotherapy, the calcium sulfate doped with dysprosium (CaSO{sub 4}:Dy) is used in radioprotection and studies has been demonstrated its great potential for the dosimetry in radiotherapy. This work evaluates the energy dependence of the thermoluminescent answer of the CaSO{sub 4}:D, LiF:Mg,Ti (TLD-100) and micro LiF:Mg,Ti in clinical beams of electrons by using water simulators, PMMA and solid water

  7. Sc-47 production from titanium targets using electron linacs

    International Nuclear Information System (INIS)

    In this work we have studied the feasibility of photonuclear production of 47Sc from 48Ti via 48Ti(γ,p)47Sc reaction. Photon flux distribution for electron beams of different energies incident on tungsten converter was calculated using MCNPX radiation transport code. 47Sc production rate dependence on electron beam energy was found and 47Sc yields were estimated. It was shown that irradiating a natural Ti target results in numerous scandium isotopes which can reduce the specific activity of 47Sc. Irradiating enriched 48Ti targets with a 22 MeV 1 mA beam will result in hundreds of MBq/g activity of 47Sc and no other isotopes of scandium. Decreasing the size of the target will result in much higher average photon flux through the target and tens of GBq/g levels of specific activity of 47Sc. Increasing the beam energy will also result in higher yields, but as soon as the electron energy exceeds the 48Ti(γ,np)46Sc reaction threshold, 46Sc starts being produced and its fraction in total scandium atoms grows as beam energy increases. The results of the simulations were benchmarked by irradiating natural titanium foil with 22 MeV electron beam incident on the tungsten converter. Measured 47Sc activities were found to be in very good agreement with the predictions. - Highlights: • Optimum irradiation conditions of titanium targets were found. • MCNPX simulation and experimental results of Sc-47 yield are presented. • We demonstrated the feasibility of photonuclear production of Sc-47 from Ti-48

  8. Morphotropy, isomorphism, and polymorphism of Ln2M2O7-based (Ln = La-Lu, Y, Sc; M = Ti, Zr, Hf, Sn) oxides

    International Nuclear Information System (INIS)

    Structural studies of compounds of variable composition and measurements of their conductivity have made it possible to identify new oxygen-ion-conducting rare-earth pyrochlores, Ln2Ti2O7 (Ln = Dy-Lu) and Ln2Hf2O7 (Ln = Eu, Gd), with intrinsic high-temperature oxygen ion conductivity (up to 1.4 × 10−2 S/cm at 800°C). Twenty six systems have been studied, and more than 50 phases based on the Ln2M2O7 (Ln= La-Lu; M = Ti, Zr, Hf) oxides have been synthesized and shown to be potential oxygen ion conductors. The morphotropy and polymorphism of the Ln2M2O7 (Ln = La-Lu; M = Ti, Zr, Hf) rare-earth pyrochlores have been analyzed in detail for the first time. Thermodynamic and kinetic (growth-related) phase transitions have been classified with application to the pyrochlore family

  9. Influences of xTi/xAl on atomic states, lattice constants and potential-energy planes of ordered FCC TiAl-type alloys

    International Nuclear Information System (INIS)

    Based on the framework of systematic science of alloys, the basic information about states, volumes and potential energies of characteristic atoms in FCC Ti-Al system has been determined. For ordered FCC TiAl type alloys, the functions of the atomic states, atomic potential energies, cohesive energies, atomic volumes, the lattice constants and axis ratio c/a' varying with concentrations have also been established. The extreme points of curves v∼xAl,a∼xAl and c/a'∼xAl are all at the xAl=70%. When xTi/xAl=1, ψ(FCC TiAl)=ψ8Ti+ψ4Al=[Ar](3dn)0.125(3dc)2.7125(4sc)0.55(4sf)0.6125+[Ne] (3sc)1.789(3pc)0.75(3sf+3pf)0.454, calculated lattice constants a'=0.39954 nm, c=0.40777 nm, c/a'=1.0206, which are in good agreement with experimental values. When xTi/xAl>1, ψ8Ti atoms decrease and ψ7Ti, ψ6Ti ... atoms appear in succession with the increase of xTi; ψ4Al atoms decrease and ψ3Al, ψ2Al ... atoms appear one after another. Because the influence of the change of Ti atomic states exceeds that of the change of Al atomic states, rich Ti-FCC TiAl alloys have larger atomic volumes, larger lattice constants, c/a' much closer to unity and comparatively good ductility, though the stability of FCC lattice is reduced. When xTi/xAlAl, the atomic states ψ8Ti and ψ4Al changes in the direction opposite to the case with xTi/xAl>1. Thus, ordered rich Al-FCC TiAl alloys have smaller atomic volumes, smaller lattice constants, larger c/a' which depart further from unity and poorer ductility, and there is an increase of stability for the FCC lattice.

  10. Static and reversible elastic strain effects on magnetic order of La0.7Ca0.3MnO3/SrTiO3 superlattices

    Science.gov (United States)

    Das, Sujit; Herklotz, Andreas; Jia Guo, Er; Dörr, Kathrin

    2014-04-01

    [La0.7Ca0.3MnO3(2.6 nm)/SrTiO3(6.3 nm)]15 superlattices (SLs) have been simultaneously grown by Pulsed Laser Deposition (PLD) on different oxide substrates in an attempt to obtain different residual strain states. The substrates are (100)-oriented SrTiO3 (STO), LaAlO3 (LAO), and piezoelectric 0.72Pb (Mg1.3 Nb2.3)3-0.28PbTiO3 (PMN-PT). The La0.7Ca0.3MnO3 layers show tensile strain of ɛ = 1% on LAO and stronger strain on STO and PMN-PT (ɛ = 1.7%). The magnetization has been measured and is found to be quite different for the three SLs. Reversible biaxial compression of Δɛ=-0.1% using the PMN-PT substrate helps one to estimate which part of the differences in magnetic order among the samples is induced by elastic strain. The influence of elastic strain is found to be substantial, but does not completely account for the different behavior of the samples.

  11. Preparation and Characterization of Red Luminescent Ca0.8Zn0.2TiO3: Pr3+, Na+ Nanophosphor

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nanophosphor with the nominal composition of Ca0.8Zn0.2TiO3∶Pr3+, Na+ (CZTOPN) was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti(OC4H9)4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis (TG-DSC), powder X-ray diffraction (XRD), and scan election microscopy (SEM). Results of TG-DSC and XRD reveal that the composition of Ca0.8Zn0.2TiO3∶Pr3+, Na+ changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 ℃. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly.

  12. Characterization of Ti6Al7Nb alloy foams surface treated in aqueous NaOH and CaCl2 solutions.

    Science.gov (United States)

    Bütev, Ezgi; Esen, Ziya; Bor, Şakir

    2016-07-01

    Ti6Al7Nb alloy foams having 53-73% porosity were manufactured via evaporation of magnesium space holders. A bioactive 1µm thick sodium hydrogel titanate layer, NaxH2-xTiyO2y+1, formed after 5M NaOH treatment, was converted to crystalline sodium titanate, Na2TiyO2y+1, as a result of post-heat treatment. On the other hand, subsequent CaCl2 treatment of NaOH treated specimens induced calcium titanate formation. However, heat treatment of NaOH-CaCl2 treated specimens led to the loss of calcium and disappearance of the titanate phase. All of the aforementioned surface treatments reduced yield strengths due to the oxidation of the cell walls of the foams, while elastic moduli remained mostly unchanged. Accordingly, equiaxed dimples seen on the fracture surfaces of as-manufactured foams turned into relatively flat and featureless fracture surfaces after surface treatments. On the other hand, Ca- and Na-rich coating preserved their mechanical stabilities and did not spall during fracture. The relation between mechanical properties of foams and macro-porosity fraction were found to obey a power law. The foams with 63 and 73% porosity met the desired biocompatibility requirements with fully open pore structures and elastic moduli similar to that of bone. In vitro tests conducted in simulated body fluid (SBF) showed that NaOH-heat treated surfaces exhibit the highest bioactivity and allow the formation of Ca-P rich phases having Ca/P ratio of 1.3 to form within 5 days. Although Ca-P rich phases formed only after 15 days on NaOH-CaCl2 treated specimens, the Ca/P ratio was closer to that of apatite found in bone. PMID:26807769

  13. Structural defects as a factor controlling the magnetic properties of pure and Ti-doped Bi(1-x)Ca(x)FeO(3-x/2) multiferroics.

    Science.gov (United States)

    Khomchenko, V A; Paixão, J A

    2015-11-01

    Recognition of the factors that may significantly affect the multiferroic properties of BiFeO3-based perovskites remains one of the most challenging tasks in condensed matter physics. To reveal the reasons behind the doping-driven instability of the cycloidal antiferromagnetic order in the polar phase of Bi(1-x)Ca(x)FeO(3-x/2), synthesis and investigation of the crystal structure, microstructure, local ferroelectric and magnetic properties of the ceramic samples of Bi0.9Ca0.1Fe(1-x)Ti(x)O(3-δ) (x  =  0.05, 0.1, 0.15) have been carried out. The compounds possess a rhombohedral structure (space group R3c). The compositional dependence of unit cell volume in this series can be interpreted as suggesting the doping-induced elimination of anion vacancies at x  ⩽  0.1 and the formation of cation vacancies at x  >  0.1. The filling of oxygen vacancies suppresses a weak ferromagnetic contribution characteristic of the parent Bi0.9Ca0.1FeO2.95. The appearance of cation vacancies restores the weak ferromagnetic phase. The key role of lattice defects in the magnetic behavior of Ca-doped BiFeO3 has been confirmed by the observation of a correlation between the magnetic properties and the morphology/ferroelectric domain structure of the Bi0.9Ca0.1Fe(1-x)Ti(x)O(3-δ) ceramics. PMID:26447603

  14. Hall measurements of La0.8A0.2TiO3-δ (A= Ba, Sr, Ca, Li, Mg) perovskites

    International Nuclear Information System (INIS)

    Metal-insulator transitions have been extensively studied in an effort to understand the mechanism essential for the localization of carriers in a wide range of materials. Electron correlation plays an important role in complex oxides, including colossal magnetoresistive materials and high-Tc superconductors. The Mott insulator LaTiO3 has received renewed interest because of its metallicity in (001) superlattices. The effects of chemical doping have been investigated extensively in bulk LaTiO3 in order to study the roles of electronic bandwidth and band filling. Metallicity in LaTiO3 can be induced by cation vacancies, excess oxygen, or alkaline-earth doping of the rare-earth site. In a search to observe the effect of nanosize on its electrical and magnetic properties, A-site doped LaTiO3 (with Ba, Sr, Ca, Li. Mg) were prepared by sol-gel method followed by calcinations. After calcinations these perovskites were deposited as thin films in a glass substrates using chemical deposition method. The structural characteristics of the perovskites were analysed through X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). To know the electrical nature and the majority charge carriers Hall measurements were carried out at room temperature. The normal state resistivity, upper critical field and hall coefficient in the perovskite materials were reported. (author)

  15. CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system

    International Nuclear Information System (INIS)

    Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. The electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt% dissolved Ca was measured as a function of time at temperatures between 250 and 600 C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420 C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was ∼106 Ω at 400 C. Thermal cycling between 300 and 700 C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at ≥360 C. (orig.)

  16. Hydrothermal growth of TiO{sub 2}-CaP nano-films on a Ti–Nb-based alloy in concentrated calcium phosphate solutions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongwei, E-mail: lihw74@foxmail.com [Chang’an University, School of Materials Science and Engineering (China); Fu, Tao, E-mail: taofu@mail.xjtu.edu.cn [Xi’an Jiaotong University, Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology (China); Li, Wen [Chang’an University, School of Materials Science and Engineering (China); Alajmi, Zafer; Sun, Jiamao [Xi’an Jiaotong University, Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology (China)

    2016-01-15

    The Ti–Nb-based TLM alloy (Ti–25Nb–3Zr–2Sn–3Mo) was subjected to hydrothermal treatment in the concentrated Ca{sub 3}(PO{sub 4}){sub 2}, CaHPO{sub 4}, and Ca(H{sub 2}PO{sub 4}){sub 2} solutions for the purpose of calcification. The treated samples are covered by films consisting of Ca-rich nano-crystallites (100–500 nm) and small nano-grains. XPS and XRD analyses reveal the formation of hydroxyapatite, TiO{sub 2}, and Nb{sub 2}O{sub 5} at the sample surface. The sample hydrothermally treated in CaHPO{sub 4} solution exhibits bioactivity by inducing the formation of apatite layer after soaking test in the simulated body fluid for 15 days. The work would provide a good bioactive surface modification method for Ti–Nb alloy implants with complex shapes and even pores.

  17. CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system

    International Nuclear Information System (INIS)

    Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. Electrical resistance of CaO coatings that were produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li containing 0.5-85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600 degrees C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420 degrees C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was ∼106 Ω at 400 degrees C. Thermal cycling between 300 and 700 degrees C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at ≥360 degrees C

  18. Excellent stability of plasma-sprayed bioactive Ca3ZrSi2O9 ceramic coating on Ti-6Al-4V

    International Nuclear Information System (INIS)

    In this work, novel zirconium incorporated Ca-Si based ceramic powder Ca3ZrSi2O9 was synthesized. The aim of this study was to fabricate Ca3ZrSi2O9 coating onto Ti-6Al-4V substrate using atmospheric plasma-spraying technology and to evaluate its potential applications in the fields of orthopedics and dentistry. The phase composition, surface morphologies of the coating were examined by XRD and SEM, which revealed that the Ca3ZrSi2O9 coating was composed of grains around 100 nm and amorphous phases. The bonding strength between the coating and the substrate was 28 ± 4 MPa, which is higher than that of traditional HA coating. The dissolution rate of the coating was assessed by monitoring the ions release and mass loss after immersion in the Tris-HCl buffer solution. The in vitro bioactivity of the coating was determined by observing the formation of apatite on its surface in simulated body fluids. It was found that the Ca3ZrSi2O9 coating possessed both excellent chemical stability and good apatite-formation ability, suggesting its potential use as bone implants.

  19. Sorption properties and reversibility of Ti(IV) and Nb(V)-fluoride doped-Ca(BH{sub 4}){sub 2}-MgH{sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Bonatto Minella, Christian, E-mail: christian.minella@kit.edu [Institute for Metallic Materials, IFW Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany); Technische Universität Dresden, D-01062 Dresden (Germany); Garroni, Sebastiano [Dipartimento di Chimica e Farmacia, Universitá di Sassari and INSTM, Via Vienna 2, I-07100 Sassari (Italy); Pistidda, Claudio [Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH, Max Planck Str. 1, D-21502 Geesthacht (Germany); Baró, Maria Dolors [Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Gutfleisch, Oliver [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt (Germany); Klassen, Thomas; Dornheim, Martin [Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH, Max Planck Str. 1, D-21502 Geesthacht (Germany)

    2015-02-15

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

  20. Dependence of annealing time on structural and morphological properties of Ca(Zr0.05Ti0.95)O3 thin films

    International Nuclear Information System (INIS)

    Ca(Zr0.05Ti0.95)O3 (CZT) thin films were prepared by the polymeric precursor method by spin-coating process. The films were deposited on Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates and annealed at 650 deg. C for 2, 4, and 6 h in oxygen atmosphere. Structure and morphology of the CZT thin films were characterized by the X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and field-emission scanning electron microscopy (FEG-SEM). XRD revealed that the film is free of secondary phases and crystallizes in the orthorhombic structure. The annealing time influences the grain size, lattices parameter and in the film thickness

  1. Giant dielectric response and low dielectric loss in Al{sub 2}O{sub 3} grafted CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rajabtabar-Darvishi, A. [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Center for Surface and Nanoanalytics (ZONA), Johannes Kepler University, Altenberger Straße 69, 4040 Linz (Austria); Bayati, R., E-mail: reza.bayati@intel.com, E-mail: mbayati@ncsu.edu, E-mail: wdfei@hit.edu.cn [Intel Corporation, IMO-RA, RA2, Hillsboro, Oregon 97124 (United States); Sheikhnejad-Bishe, O. [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Wang, L. D.; Li, W. L.; Sheng, J.; Fei, W. D., E-mail: reza.bayati@intel.com, E-mail: mbayati@ncsu.edu, E-mail: wdfei@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-03-07

    This study sheds light on the effect of alumina on dielectric constant and dielectric loss of novel CaCu{sub 3}Ti{sub 4}O{sub 12} composite ceramics. Alumina, at several concentrations, was deposited on the surface of CaCu{sub 3}Ti{sub 4}O{sub 12} particles via sol-gel technique. The dielectric constant significantly increased for all frequencies and the dielectric loss substantially decreased for low and intermediate frequencies. These observations were attributed to the change in characteristics of grains and grain boundaries. It was found that the insulating properties of the grain boundaries are improved following the addition of Al{sub 2}O{sub 3}. The relative density of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics decreased compared to the pure CaCu{sub 3}Ti{sub 4}O{sub 12} and the grain size was greatly changed with the alumina content affecting the dielectric properties. With the addition of alumina into CaCu{sub 3}Ti{sub 4}O{sub 12}, tighter interfaces formed. The 6%- and 10%-alumina ceramics showed the minimum dielectric loss and the maximum dielectric constant, respectively. Both the dielectric constant and loss tangent decreased in the 20%-alumina ceramic due to the formation of CuO secondary phase. It was revealed that Al serves as an electron acceptor decreasing the electron concentration, if Al{sup 3+} ions substitute for Ti{sup 4+} ions, and as an electron donor increasing the electron concentration, if Al{sup 3+} ions substitute for Ca{sup 2+} ions. We established a processing-microstructure-properties paradigm which opens new avenues for novel applications of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics.

  2. Sol-gel synthesis of mesoporous CaCu3Ti4O12 thin films and their gas sensing response

    International Nuclear Information System (INIS)

    A new sol-gel synthesis procedure of stable calcium copper titanate (CaCu3Ti4O12-CCTO) precursor sols for the fabrication of porous films was developed. The composition of the sol was selected in order to avoid the precipitation of undesired phases; ethanol was used as solvent, acetic acid as modifier and poly(ethyleneglycol) as a linker agent. Films deposited by spin-coating onto oxidized silicon substrates were annealed at 700 oC. The main phase present in the samples, as detected by X-ray diffraction and Raman spectroscopy, was CaCu3Ti4O12. Scanning electron microscopy analysis showed that mesoporous structures, with thicknesses between 200 and 400 nm, were developed as a result of the processing conditions. The films were tested regarding their sensibility towards oxygen and nitrogen at atmospheric pressure using working temperatures from 200 to 290 oC. The samples exhibited n-type conductivity, high sensitivity and short response times. These characteristics indicate that CCTO mesoporous structures obtained by sol-gel are suitable for application in gas sensing. - Graphical abstract: A sol-gel synthesis procedure toward stable CaCu3Ti4O12-precursor sols avoiding the precipitation of undesired compounds is proposed. Films deposited by spin-coating onto oxidized silicon substrates were annealed at 700 oC. The thickness varied between 200 and 400 nm depending on sol composition. The films, tested as gas sensors for O2, showed n-type conductivity, good sensitivity and short response times.

  3. Fusion and quasifission dynamics in the reactions 48Ca+249Bk and 50Ti+249Bk using a time-dependent Hartree-Fock approach

    Science.gov (United States)

    Umar, A. S.; Oberacker, V. E.; Simenel, C.

    2016-08-01

    Background: Synthesis of superheavy elements (SHEs) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHEs have been recently produced with doubly-magic 48Ca beams. However, SHE synthesis experiments with single-magic 50Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for Z =117 ,119 superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in 48Ca,50Ti+249Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles. Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment. Results: Nucleus-nucleus potentials, nuclear contact times, masses and charges of the fragments, as well as their kinetic and excitation energies strongly depend on the orientation of the prolate 249Bk nucleus. Long contact times associated with fusion are observed in collisions of both projectiles with the side of the 249Bk nucleus, but not on collisions with its tip. The energy and impact parameter dependencies of the fragment properties, as well as their mass-angle and mass-total kinetic energy correlations are investigated. Conclusions: Entrance channel reaction dynamics are similar with both 48Ca and 50Ti projectiles. Both are expected to lead to the formation of a compound nucleus by fusion if they have enough energy to get in contact with the side of the 249Bk target.

  4. Dielectric and infrared response of Ba.sub.0.77./sub.Ca.sub.0.23./sub.TiO.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Savinov, Maxim; Trepakov, Vladimír; Kamba, Stanislav; Kapphan, S. E.; Petzelt, Jan; Pankrath, R.; Kislova, I. L.; Kutshenko, A. B.; Jastrabík, Lubomír

    2003-01-01

    Roč. 295, - (2003), s. 31-38. ISSN 0015-0193 R&D Projects: GA MŠk LN00A015; GA AV ČR IAA1010213; GA ČR GA202/01/0612 Grant ostatní: NATO(XX) PST .CLG.977348; NATO(XX) LGPST.CLG.977561 Institutional research plan: CEZ:AV0Z1010914 Keywords : dielectric permittivity * infrared spectroscopy * Ba 1-x Ca x TiO 3 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.406, year: 2003

  5. Effect of hafnium substitution on the dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Late, Ravikiran, E-mail: ravikiranlate5887@gmail.com; Rai, Hari Mohan; Saxena, Shailendra K.; Kumar, Rajesh; Sagdeo, P. R. [Material Research Laboratory, Discipline of Physics & MSE, Indian Institute of Technology, Indore-452017 (India)

    2015-06-24

    CaCu{sub 3}Ti{sub 4-x}Hf{sub x}O{sub 12} (x = 0, 0.04, 0.08 and 0.12 i.e. 0, 1, 2 and 3 atomic %) has been prepared by conventional solid state reaction method. The structural, dielectric and optical properties of the prepared samples were studied using x-ray diffraction, impedance analyzer and diffuse reflectance spectroscopy. With increasing Hf concentration dielectric permittivity decreases whereas the dielectric loss slightly increases and optical band gap almost remain constant. The results are explained on the basis of increase in the structural disorder and porosity of the sample with Hf doping.

  6. Dielectric behaviour of Hf-doped CaCu3Ti4O12 ceramics obtained by conventional synthesis and reactive sintering

    OpenAIRE

    Rubia López, Miguel Ángel de la; Leret Molto, Pilar; Campo García, Ángel Adolfo del; Alonso, Roberto Emilio; López García, Alberto Raúl; Fernández Lozano, José Francisco; Frutos Vaquerizo, José de

    2012-01-01

    CaCu3(Ti4xHfx)O12 ceramics (JC = 0.04, 0.1 and 0.2) were prepared by conventional synthesis (CS) and through reactive sintering (RS), in which synthesis and sintering of the material take place in one single step. The microstructure and the dielectric properties of Hf-doped CCTO (CCTOHf) have been studied by XRD, FE-SEM, AFM, Raman and impedance spectroscopy (IS) in order to correlate the structure, microstructure and the electrical properties. Samples prepared by reactive sintering show s...

  7. Spark Plasma Sintering of Multilayer Ceramics – Case Study of Al2O3 - Mg(Ca)TiO3 Sandwich

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Kubatík, Tomáš František; Chráska, Pavel

    Vol. 606. Zurich: Trans Tech Publications Ltd, 2014 - (Haušíld, P.; Materna, A.; Vilémová, M.), s. 205-208 ISSN 1662-9795. [International Conference on Local Mechanical Properties, LMP 2013/10./. Kutná Hora (CZ), 06.11.2013-08.11.2013] Institutional support: RVO:61389021 Keywords : Al2O3 - Mg(Ca)TiO3 * Sandwich ceramics * Spark Plasma Sintering Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass http://www.scientific.net/KEM.606.205

  8. Detector de IR de lámina ferroeléctrica de (Pb,Ca)TiO3

    OpenAIRE

    González, A; Calzada, M. L.; Jiménez, R.; Mendiola, J.; Ramos, P.; Tejedor, P.

    2002-01-01

    A sol-gel (Pb0.76Ca0.24)TiO3 solution was deposited onto Pt/MgO(100) substrates. Previous thermal treatment of the substrate and the high rate of crystallization heating promote an important preferred orientation along the polar axis, and therefore selfpolarization , very convenient for the use of IR pyroelectric detectors. By depositing circular electrodes, 7.10-3 cm2 of area, an array of small capacitors are developed which are characterized as detectors in standard conditions: radiation f...

  9. P-type semiconducting gas sensing behavior of nanoporous rf sputtered CaCu3Ti4O12 thin films

    International Nuclear Information System (INIS)

    The fabrication of nanoporous sputtered CaCu3Ti4O12 thin films with high gas sensitivity is reported in this work. The porous microstructure and the nanocrystalline nature of the material promoted the diffusion of the atmosphere into the film, shortening the response time of the samples. Behaving as p-type semiconductor, the material presents enhanced sensitivity even at low working temperatures. Impedance spectroscopy measurements were performed in order to investigate the mechanisms responsible for the performance of the devices

  10. CaCu3Ti4O12 ceramics from co-precipitation method: Dielectric properties of pellets and thick films

    OpenAIRE

    Barbier, B.; Combettes, Céline; Guillemet-Fritsch, Sophie; Chartier, Thierry; Rossignol, Fabrice; RUMEAU A.; Lebey, Thierry; Dutarde, E.

    2009-01-01

    Dielectric properties of CaCu3Ti4O12 (CCTO)-based ceramics and thick films (e ∼50m) prepared from powders synthesized by a soft chemistry method (co-precipitation) are presented and discussed. The characteristics of pellets and thick films are compared. The pellets exhibit high values of the dielectric permittivity (εr ∼1.4×105) and relatively small dielectric losses (tan δ ∼0.16) at 1 kHz and room temperature. These properties are independent of the nature of the metallization of th...

  11. Relativistic fine structure oscillator strengths for Li-like ions: C IV - Si XII, S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, and Ni XXVI

    OpenAIRE

    Nahar, Sultana N.

    2002-01-01

    Ab initio calculations including relativistic effects employing the Breit-Pauli R-matrix (BPRM) method are reported for fine structure energy levels and oscillator strengths upto n = 10 and 0.leq. l .leq.9 for 15 Li-like ions: C IV, N V, O VI, F VII, Ne VIII, Na IX, Mg X, Al XI, Si XII, S XIV, Ar XVI, Ca XIII, Ti XX, Cr XXII, and Ni XXVI. About one hundred bound fine structure energy levels of total angular momenta, 1/2 .leq. J .leq. 17/2 of even and odd parities, total orbital angular moment...

  12. Electronic Properties of Lead-Free (Ba0.95Ca0.05)(Ti0.92Sn0.08)O3 Piezoceramic Nanofibers by Electrospinning

    Science.gov (United States)

    Sahoo, Benudhar; Panda, Prasanta Kumar

    2015-11-01

    Lead-free (Ba0.95Ca0.05)(Ti0.92Sn0.08)O3, (BCTS) piezoceramic nanofibers were prepared by electrospinning acetate precursor solutions in polyvinyl pyrrolidone, followed by calcining at 1150ºC for 2 h. X-ray diffraction of calcined nanofibers confirmed the formation of the BCTS phase and energy dispersive x-ray analysis confirmed the presence of Ca and Sn ions. The scanning electron microscope studies showed cylindrical fibers with a diameter in the range 80-275 nm. The dielectric constant and piezoelectric charge constant ( d 33) were 3485 at 100 Hz, RT and 398 pC/N, respectively.

  13. A sol-gel route to prepare Ti-Ca-Ba-Cu-O superconductor with Tc above 120

    International Nuclear Information System (INIS)

    This paper reports on the preparation of Tl-Ca-Ba-Cu-O superconductor with Tc above 120 K from Ca-Ba-Cu-O precursor mixed with thallium oxide. The Ca-Ba-Cu-O precursor was prepared by sol-gel method from the proper complexation and polymerization of the metal nitrates by citric acid and ethylene diamine. The homogeneity and small particle size make the sol-gel precursor a potential candidate for Tl-Ca-Ba-Cu-P film preparation by screen-printing or spin-coating and thallium vapor diffusion

  14. Fe4+ content and ordering of anion vacancies in partially reduced AFexTi1-xO3-y (A = Ca, Sr; x≤0.6) perovskites. An 57Fe Moessbauer spectroscopy study

    International Nuclear Information System (INIS)

    CaFexTi1-xO3-y (0.05≤x≤0.60) and SrFexTi1-xO3-y (0.20≤x≤0.60) perovskites were prepared by solid state reaction and subjected to different heat treatments in different atmospheres. Moessbauer spectroscopy of the CaFexTi1-xO3-y could detect Fe4+ in all the samples, even in those heated at 1000 deg. C in Ar atmosphere for 10 hours. Fe3+ coordinated by six, five and four anions were also identified and the estimated hyperfine parameters were consistent with those previously reported for the CaFexTi1-xO3-x/2 oxides where all the Fe cations were present as Fe3+. The Fe4+/Fe3+ ratios estimated from Moessbauer data are in agreement with coulometric titration data. The absence of tetracoordinated Fe3+ in SrFexTi1-xO3-y suggests that in contrast to CaFexTi1-xO3-y no ordering of anion vacancies takes place even for x=0.60 and explains the differences in the Fe concentration dependence of the electric transport properties of these materials. (author)

  15. Enhanced electrical and magnetic properties in La{sub 0.7}Sr{sub 0.3}MnO{sub 3} thin films deposited on CaTiO{sub 3}-buffered silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Adamo, C. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Méchin, L.; Guillet, B.; Wu, S.; Routoure, J.-M. [Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen, (GREYC-UMR 6072), CNRS-ENSICAEN—Université de Caen Basse-Normandie, 6 Boulevard Maréchal Juin, 14050 Caen Cedex (France); Heeg, T. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501 (United States); Katz, M.; Pan, X. Q. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Mercone, S. [Laboratoire de Sciences des Procédés et des Matériaux, UPR3407, CNRS, Institut Galilee, Universite Paris-Nord, Villetaneuse (France); Schubert, J.; Zander, W. [Peter Grünberg Institute (PGI9-IT), JARA-Fundamentals of Future Information Technology, Research Centre Jülich, Jülich D-52425 (Germany); Misra, R. [Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Schiffer, P. [Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); and others

    2015-06-01

    We investigate the suitability of an epitaxial CaTiO{sub 3} buffer layer deposited onto (100) Si by reactive molecular-beam epitaxy (MBE) for the epitaxial integration of the colossal magnetoresistive material La{sub 0.7}Sr{sub 0.3}MnO{sub 3} with silicon. The magnetic and electrical properties of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} films deposited by MBE on CaTiO{sub 3}-buffered silicon (CaTiO{sub 3}/Si) are compared with those deposited on SrTiO{sub 3}-buffered silicon (SrTiO{sub 3}/Si). In addition to possessing a higher Curie temperature and a higher metal-to-insulator transition temperature, the electrical resistivity and 1/f noise level at 300 K are reduced by a factor of two in the heterostructure with the CaTiO{sub 3} buffer layer. These results are relevant to device applications of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} thin films on silicon substrates.

  16. Enhanced electrical and magnetic properties in La0.7Sr0.3MnO3 thin films deposited on CaTiO3-buffered silicon substrates

    Directory of Open Access Journals (Sweden)

    C. Adamo

    2015-06-01

    Full Text Available We investigate the suitability of an epitaxial CaTiO3 buffer layer deposited onto (100 Si by reactive molecular-beam epitaxy (MBE for the epitaxial integration of the colossal magnetoresistive material La0.7Sr0.3MnO3 with silicon. The magnetic and electrical properties of La0.7Sr0.3MnO3 films deposited by MBE on CaTiO3-buffered silicon (CaTiO3/Si are compared with those deposited on SrTiO3-buffered silicon (SrTiO3/Si. In addition to possessing a higher Curie temperature and a higher metal-to-insulator transition temperature, the electrical resistivity and 1/f noise level at 300 K are reduced by a factor of two in the heterostructure with the CaTiO3 buffer layer. These results are relevant to device applications of La0.7Sr0.3MnO3 thin films on silicon substrates.

  17. Giant dielectric behavior and electrical properties of Ca{sub 1-3x/2}Lu{sub x}Cu{sub 3}Ti{sub 4}O{sub 12} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Boonlakhorn, Jakkree [Khon Kaen University, Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen (Thailand); Kidkhunthod, Pinit [Synchrotron Light Research Institute (Public Organization), Nakhon Ratchasima (Thailand); Putasaeng, Bundit; Yamwong, Teerapon [Thailand Science Park, National Metal and Materials Technology Center (MTEC), Pathumthani (Thailand); Thongbai, Prasit [Khon Kaen University, Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen (Thailand); Khon Kaen University, Department of Physics, Faculty of Science, Khon Kaen (Thailand); Maensiri, Santi [Suranaree University of Technology, Institute of Science, School of Physics, Nakhon Ratchasima (Thailand)

    2015-07-15

    Giant dielectric behavior and electrical properties of Ca{sub 1-3x/2}Lu{sub x}Cu{sub 3}Ti{sub 4}O{sub 12} ceramics were studied by focusing on the influences of Lu{sup 3+} doping on their microstructure and electrical properties. The mean grain size of CaCu{sub 3}Ti{sub 4}O{sub 12} was greatly reduced as the dopant content was increased to 15 at.% (x = 0.15), which was ascribed to the effect of solute drag. X-ray absorption near-edge structure confirmed the presence of Ti{sup 3+} ions in Ca{sub 1-3x/2}Lu{sub x} Cu{sub 3}Ti{sub 4}O{sub 12} ceramics. The ratio of Ti{sup 3+}/Ti{sup 4+} in CaCu{sub 3}Ti{sub 4}O{sub 12} was reduced by Lu{sup 3+} doping. Dielectric permittivity (ε') decreased with increasing Lu{sup 3+} content, which was ascribed to reduce grain boundary capacitance caused by the presence of Lu{sup 3+}. Activation energies for conduction in the grain interiors and at the grain boundaries were slightly changed with Lu{sup 3+} content. Interestingly, improved dielectric properties with ε' ∝3.56 x 10{sup 4} and tan δ ∝0.059 at 1 kHz in the Ca{sub 0.925}Lu{sub 0.05}Cu{sub 3}Ti{sub 4}O{sub 12} ceramic were achieved. (orig.)

  18. Influence of Yb2O3 on electrical and microstructural characteristics of CaCu3Ti4O12 ceramics

    International Nuclear Information System (INIS)

    Graphical abstract: Some Yb atoms entered in the lattice of CCTO substituted the Ca sites, the rest of Yb atoms concentrated at grain boundaries decreased the grain size. The dielectric constant was decreased by Yb doping. The dielectric loss of the CCTO could be greatly reduced at low frequency. - Highlights: • Yb atoms may take the place of Ca sites and concentrate at grain boundaries. • Tiny second phase corresponding to Yb may decrease the grain size. • Decrease of the grain size leads to the decrease of dielectric constant. • Yb doping could decrease the dielectric loss of CCTO. - Abstract: This paper focuses on the remarkable effects of Yb2O3 doping on the microstructure and dielectric characteristics of CaCu3Ti4O12 (CCTO). Samples were prepared by the solid phase reaction method and sintered in air at 1030 °C for 12 h. X-ray diffraction and X-ray photoelectron spectroscopy studies confirm that the primary phase is CCTO. Some Yb3+ ions may substitute into the Ca site at the center or zenith sites of the CCTO lattice hexahedron, while the rest of the Yb atoms may concentrate at grain boundaries. The grain size of Yb2O3-doped CCTO ceramics were examined by scanning electron microscopy and demonstrate sharp grain size reduction with Yb2O3 doping. From dielectric property measurements, the Yb2O3 doping reduces the dielectric constant of CCTO, and the dielectric loss is also reduced

  19. Assessment of CaSO4:Dy and LiF:Mg,Ti thermoluminescent dosimeters performance in the dosimetry of clinical electron beams

    International Nuclear Information System (INIS)

    The assessment of the performance of CaS04:Dy thermoluminescent detectors produced by IPEN in the dosimetry of clinical electron beams aims to propose an alternative to the LiF:Mg,Ti commercial dosimeters (TLD-100) largely applied in radiation therapy. The two types of thermoluminescent dosimeters were characterised with the use of PMMA, RMI-457 type solid water and water phantoms in radiation fields of 4, 6, 9, 12 and 16 MeV electrons of nominal energies in which the dose-response curves were obtained and the surface and depth doses were determined. The thermoluminescent response dependency with the electron nominal energies and the applied phantom were studied. The CaS04:Dy presented the same behaviour than the LiF:Mg,Ti in such a way that its application as an alternative to the TLD-100 pellets in the radiation therapy dosimetry of electron beams is viable and presents the significantly higher sensitivity to the electron radiation as its main advantage. (author)

  20. Extremely large electronic anisotropy caused by electronic phase separation in Ca3(Ru0.97Ti0.03)2O7 single crystal

    Science.gov (United States)

    Peng, Jing; Wu, Xiaoshan; Mao, Zhiqiang

    2015-03-01

    Bilayered ruthenate Ca3 Ru2O7 exhibits rich electronic and magnetic properties. It orders at 56K, with FM bilayers antiferromagnetically coupled along c-axis (AFM-a). The AFM transition is closely followed by a first-order metal-insulator (MI) transition at 48K where spin directions switch to the b-axis (AFM-b). While this MI transition is accompanied by the opening of anisotropic charge gap; small Fermi pockets survive from the MI transition, thus resulting in quasi-2D metallic transport behavior for Tinsulating state with a nearest-neighbor AFM order via Ti doping. Ca3(Ru0 . 97 Ti0 . 03) 2O7 is close to the critical composition for the AFM-b-to-G-AFM phase transition. Our recent studies show the sample with this composition is characterized by an electronic phase separation between the insulating G-AFM phase (major) and the localized AFM-b phase (minor). The minor AFM-b phase forms a conducting path through electronic percolation within the ab-plane, but not along the c-axis, thus resulting in extremely large electronic anisotropy with ρab /ρc ~109 , which may be the largest among bulk materials.

  1. Analysis of Fe, Ca, Ti, Ba, Ce, Zr and La element in the Sea sediment at Muria peninsula by X RF method

    International Nuclear Information System (INIS)

    he analysis of metals (Fe, Ca, Ti, Ba, Ce, Zr and La) in the sea sediment environmental samples at Muria peninsula has been carried out with X-Ray Fluorescence (XRF) method. The aim of this analysis is to know the distribution metals which accommodate the recent environmental data in supporting the license of site and Environmental Impact Assessment (EIA) for the Nuclear Power Plants (NPP). Samples taken preparation and analysis based on the procedures of environmental analysis. The result analysis that contents of mayor elements in 7 sea sediment location of sampling were Ca, Ti and Fe with concentration are (6.74 – 11.69 ) %; (0.74 – 6.89 ) % and (0.45 -1.94 ) % successively; while minor elements were Ba, Ce, Zr and La with concentration are 451.4 – 1331.6 ) mg/kg; (201.8 – 427.3) mg/kg; (192.3 – 338.5) mg/kg dan (171.7 – 298.4) mg/kg. The statistic test result shows that sampling location there is a significant difference all of element with the level significant of 95 %. (author)

  2. Structural phase transition and spontaneous interface reconstruction in La2/3Ca1/3MnO3/BaTiO3 superlattices

    Science.gov (United States)

    Turner, S.; Lebedev, O. I.; Verbeeck, J.; Gehrke, K.; Moshnyaga, V.; Van Tendeloo, G.

    2013-01-01

    (La2/3Ca1/3MnO3)n/(BaTiO3)m (LCMOn/BTOm) superlattices on MgO and SrTiO3 substrates with different layer thicknesses (n = 10, 38, 40 and m = 5, 18, 20) have been grown by metal organic aerosol deposition (MAD) and have been fully characterized down to the atomic scale to study the interface characteristics. Scanning transmission electron microscopy combined with spatially resolved electron energy-loss spectroscopy provides clear evidence for the existence of atomically sharp interfaces in MAD grown films, which exhibit epitaxial growth conditions, a uniform normal strain, and a fully oxidized state. Below a critical layer thickness the LCMO structure is found to change from the bulk Pnma symmetry to a pseudocubic R3¯c symmetry. An atomically flat interface reconstruction consisting of a single Ca-rich atomic layer is observed on the compressively strained BTO on LCMO interface, which is thought to partially neutralize the total charge from the alternating polar atomic layers in LCMO as well as relieving strain at the interface. No interface reconstruction is observed at the tensile strained LCMO on BTO interface.

  3. Influence of CaCO3, Al2O3, and TiO2 microfillers on physico-mechanical properties of Luffa cylindrica/polyester composites

    Directory of Open Access Journals (Sweden)

    Vinay Kumar Patel

    2016-06-01

    Full Text Available The development of natural fibre reinforced polymer composites has gained popularity in many applications due to their environment friendly characteristics over the synthetic fibre based polymer composites. This paper describes the fabrication and physical, mechanical, three-body abrasive wear and water absorption behaviour of Luffa fibre reinforced polyester composites with and without addition of micro-fillers of Al2O3, CaCO3 and TiO2. The ranking of the composite materials has been made by using Technique for order preference by similarity to ideal solution (TOPSIS method with output parameters of their physical, mechanical and abrasive wear and water absorption attributes. The addition of microfillers has enhanced greatly the physical and mechanical properties of Luffa-fibre based composites. The addition of microfillers has influenced the physico-mechanical properties of Luffa-fibre based polyester composites in descending order of CaCO3, Al2O3, and TiO2.

  4. 稀土发光材料Mg0.2Ca0.8TiO3:Pr的合成与表征%Synthesis and characterization of rare earth luminescent materials Mg0.2Ca0.8TiO3:Pr

    Institute of Scientific and Technical Information of China (English)

    王晓楠; 左斌

    2012-01-01

    应用溶胶凝胶法制备了不同Pr^3+摩尔浓度下的Mg0.2Ca0.8TiO3:Pr纳米粉体,并通过XRD,TG,TEM,发射光谱和激发光谱等测试手段来表征Mg0.2Ca0.8TiO3:Pr的结构、形貌和荧光性质.X射线衍射结果表明:样品为正方晶格结构,其晶粒尺寸随着热处理温度的提高而逐渐增大,Pr离子浓度的提高不会影响晶体结构.发射光谱与激发光谱的强度都随着温度的升高而增强,而Pr^3+摩尔浓度的提高对发射光谱和激发光谱的影响不大.余辉性能测试表明Mg0.2Ca0.8TiO3:Pr的余辉时间可达30ms.%Mg0.2Ca0.8TiO3:Pr Pr nano powder with different Pr^3+ concentration and its structure, morphology and fluorescence property were characterized were prepared by sol-gel method, through the XRD, TG, TEM, emission and excitation spectra and other means. X ray diffraction results show that the sample is affirmative,lattice structure, its grain size increases with the heat treatment temperature increasing, and the increase of Pr ion concentration will not affect the crystal structure. The intensity of emission and excitation spectra grows with the temperature increasing, and Pr^3 + molar concentration increasing has little effect on the emission and excitation spectra. Afterglow performance test shows that the afterglow time of Mg0.2Ca0.8TiO3:Pr can reach to 30ms.

  5. Magnetic behavior of La2/3Ca1/3MnO3 / BaTiO3 bilayers

    Science.gov (United States)

    Ordonez, John E.; Gomez, Maria E.; Lopera, Wilson; Marin, Lorena; Pardo, Jose A.; Morellon, Luis; Algarabel, Pedro; Prieto, Pedro

    2013-03-01

    We have grown ferroelectric BaTiO3(BTO) and ferromagnetic La2/3Ca1/3MnO3 (LCMO) onto (001) SrTiO3 and Nb:SrTiO3 by pulsed laser deposition (PLD) at pure oxygen atmosphere, and a substrate temperature of 820° C, seeking for a multiferroic behavior in this structure. From x-ray diffraction (XRD) we found lattice parameter aBTO=4.068 Å, and aLCMO=3.804 Å, for each individual layer. In the BTO/LCMO bilayer, (002)-Bragg peak for BTO maintain its position whereas (002) LCMO peak shift to lower Bragg angle indicating a strained LCMO film. Magnetization measurements reveal an increase in the Curie temperature from 170 K to 220 K for the bilayer when LCMO (t = 47 nm) is deposited on BTO (t=52 nm) film, while depositing the BTO (50 nm) above LCMO (48 nm) the Curie temperature remains at values close to that obtained for a LCMO single layer (~175 K), deposited under identical growth parameters This work has been supported by Instituto de Nanociencias de Aragón, Zaragoza, Spain, ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' COLCIENCIAS-CENM Contract RC 275-2011 and Research Project COLCIENCIAS-UNIVALLE.

  6. Texture design for microwave dielectric (Ca0.7Nd0.3)0.87TiO3 ceramics through reactive-templated grain growth

    Science.gov (United States)

    Tani, Toshihiko; Takeuchi, Tsuguto

    2015-06-01

    Plate-like Ca3Ti2O7 (CT) and Nd2Ti2O7 (NT) particles were synthesized in molten salts and used as reactive templates for the preparation of highly textured (Ca0.7Nd0.3)0.87TiO3 bulk ceramics (CNT) with preferred pseudocubic and orientations, respectively. During flux growth CT and NT particles developed facets parallel to the pseudocubic {100} and {110} planes, respectively, in a perovskite unit cell, since those planes correspond to the interlayers of the layered perovskite-type crystal structures. Complementary reactants for the CNT stoichiometry were wet-mixed with the reactive templates and the slurries were tape-cast. Then stacked tapes were heat-treated for dense single-phase CNT ceramics with a distorted and A-site deficient regular perovskite-type structure. The CNT ceramics prepared with CT and NT reactive templates exhibited strong pseudocubic 100- and 110-family x-ray diffraction peaks, respectively, with other peaks drastically suppressed when non-perovskite sources were used as complementary reactants. The textured ceramics possess unique microstructures; as either parallel or obliquely stacked block structures with a pseudocubic {100} plane faceted. The pseudocubic {100}-and {110}-textured CNT ceramics exhibited ∼10 and ∼20% higher products of the dielectric quality factor and frequency, Q · f, respectively, than conventional ceramic sintered at the same temperature. When Q · f is compared based on the same grain size, the {100}-textured CNT exhibited 27% higher values than non-textured while relative permittivity and temperature coefficient of resonant frequency were of similar values. Simple geometrical relationships between electric field and penetrated pseudocubic {hk0}-type grain boundaries must lead to the reduced scattering and dielectric loss.

  7. Low sintering temperature and high piezoelectric properties of Li-doped (Ba,Ca)(Ti,Zr)O3 lead-free ceramics

    International Nuclear Information System (INIS)

    Highlights: • Li-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) lead-free piezoceramics were prepared by the two-step synthesis and solid-state reaction method. • Their sintering temperature decreases from about 1540 °C down to about 1400 °C. • With the proper addition of Li, the densities and grain sizes of ceramics increase. • The ceramics not only have the characteristics of hard piezoceramics but also possesses the features of soft piezoceramics at low sintering temperature. - Abstract: Li-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) lead-free piezoelectric ceramics were prepared by the two-step synthesis and the solid-state reaction method. The density and grain size of ceramics sufficiently increases by Li-doped sintering aid, and their sintering temperature decreases from about 1540 °C down to about 1400 °C. X-ray diffraction reveals that the phase structure of Li-doped BCTZ ceramics is changed with the sintering temperature, which is consistent with their phase transition observed by the temperature-dependent dielectric curves. The well-poled Li-doped BCZT ceramics show a high piezoelectric constant d33 (512 pC/N) and a planar electromechanical coupling factor kp (0.49), which have the characteristics of soft Pb(Zr,Ti)O3 (PZT) piezoceramic, on the other hand, the mechanical quality factor Qm is about 190, which possesses the features of hard PZT piezoceramics. The enhanced properties of the Li-doped BCZT are explained by the combination of Li-doped effect and sintering effect on the microstructure and the phase transition around room temperature

  8. {sup 48}Ti(n,xnpa{gamma}) reaction cross sections using spallation neutrons for E{sub n} = 1 to 20 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D; Mitchell, G E; Garrett, P E; Agvaanluvsan, U; Becker, J A; Bernstein, L A; Cooper, J R; Hoffman, R D; Younes, W; Devlin, N; Fotiades, N; Nelson, R O

    2005-01-06

    {gamma}-ray excitation functions have been measured for the interaction of fast neutrons with {sup 48}Ti (neutron energy from 1 MeV to 250 MeV). The Los Alamos National Laboratory spallation neutron source, at the LANSCE/WNR facility, provided a ''white'' neutron beam which is produced by bombarding a natural W target with a pulsed proton beam. The prompt-reaction {gamma} rays were measured with the large-scale Compton-suppressed Ge spectrometer, GEANIE. Neutron energies were determined by the time-of-flight technique. Excitation functions were converted to partial {gamma}-ray cross sections, taking into account the dead-time correction, the target thickness, the detector efficiency, and neutron flux (monitored with an in-line fission chamber). The data analysis is presented here for neutron energies between 1 to 20 MeV. Partial {gamma}-ray cross sections for transitions in {sup 47,48}Ti, {sup 48}Sc, and {sup 45}Ca have been determined. These results are compared to Hauser-Feshbach predictions calculated using the STAPRE code, which includes compound nuclear and pre-equilibrium emission. The partial cross sections for {gamma} rays, whose discrete {gamma}-ray cascade path leads to the ground state in {sup 48}Ti, {sup 47}Ti, {sup 48}Sc, and {sup 45}Ca have been summed to obtain estimates of the lower limits for reaction cross sections. Partial cross sections for unobserved {gamma}-rays are predicted from the STAPRE code. These lower limits are combined with Hauser-Feshbach calculations to deduce {sup 48}Ti(n,n'){sup 48}Ti, {sup 48}Ti(n,2n){sup 47}Ti, {sup 48}Ti(n,p){sup 48}Sc, and {sup 48}Ti(n,{alpha}){sup 45}Ca reaction channel cross sections.

  9. Enhancement of luminescence intensity and spectroscopic analysis of Eu3+-activated and Li+ charge-compensated CaTiO3 color tunable phosphors for solid-state lighting

    Science.gov (United States)

    Singh, Dhananjay Kr.; Baitha, Pankaj Kr.; Manam, J.

    2016-07-01

    The present work explores a well-crystallized perovskite calcium titanate (CaTiO3) doped with trivalent europium (Eu3+) and co-doped with lithium ion (Li+) successfully synthesized by a conventional solid-state reaction method, and the impact of single dopant and co-dopant on the photoluminescence performances of the sample has been investigated by emission, excitation and diffuse reflectance spectra at the room temperature. Photoluminescence spectra of Li+-doped CaTiO3:Eu3+ nanophosphor revealed at intense pink emission peak for Ca(0.85- y)Li y TiO3:0.15Eu3+ nanophosphor around wavelength 619 nm in the visible region upon the excitation of near-UV light at wavelength 397 nm due to 5 D 0 → 7 F 2 transition in Eu3+. The incorporation of Li+ ion on CaTiO3:Eu3+ nanophosphors enhanced the emission probability from higher 5 D 0 state to lower 7 F j state, and its PL intensity is found to be three times greater than the intensity of CaTiO3:Eu3+ nanophosphor. The spectral characteristics and the Eu-O ligand behavior were confirmed in light of Judd-Ofelt theory from the Emission spectra rather than absorption spectra. Their crystal structure was confirmed by X-ray diffraction (XRD) which is in good agreement with pure orthorhombic phase with space group Pbnm, and it also indicated that the incorporation of the dopant/co-dopant did not affect the crystal structure. The experimental observation reveals that the developed phosphor material Li+-co-doped CaTiO3:Eu3+ can be used in solid-state lighting devices.

  10. Induction of Chronic Inflammation and Altered Levels of DNA Hydroxymethylation in Somatic and Germinal Tissues of CBA/CaJ Mice Exposed to (48)Ti Ions.

    Science.gov (United States)

    Rithidech, Kanokporn Noy; Jangiam, Witawat; Tungjai, Montree; Gordon, Chris; Honikel, Louise; Whorton, Elbert B

    2016-01-01

    Although the lung is one of the target organs at risk for cancer induction from exposure to heavy ions found in space, information is insufficient on cellular/molecular responses linked to increased cancer risk. Knowledge of such events may aid in the development of new preventive measures. Furthermore, although it is known that germinal cells are sensitive to X- or γ-rays, there is little information on the effects of heavy ions on germinal cells. Our goal was to investigate in vivo effects of 1 GeV/n (48)Ti ions (one of the important heavy ions found in the space environment) on somatic (lung) and germinal (testis) tissues collected at various times after a whole body irradiation of CBA/CaJ mice (0, 0.1, 0.25, or 0.5 Gy, delivered at 1 cGy/min). We hypothesized that (48)Ti-ion-exposure induced damage in both tissues. Lung tissue was collected from each mouse from each treatment group at 1 week, 1 month, and 6 months postirradiation. For the testis, we collected samples at 6 months postirradiation. Hence, only late-occurring effects of (48)Ti ions in the testis were studied. There were five mice per treatment group at each harvest time. We investigated inflammatory responses after exposure to (48)Ti ions by measuring the levels of activated nuclear factor kappa B and selected pro-inflammatory cytokines in both tissues of the same mouse. These measurements were coupled with the quantitation of the levels of global 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC). Our data clearly showed the induction of chronic inflammation in both tissues of exposed mice. A dose-dependent reduction in global 5hmC was found in the lung at all time-points and in testes collected at 6 months postirradiation. In contrast, significant increases in global 5mC were found only in lung and testes collected at 6 months postirradiation from mice exposed to 0.5 Gy of 1 GeV/n (48)Ti ions. Overall, our data showed that (48)Ti ions may create health risks in both

  11. Bioactivity studies on TiO₂-bearing Na₂O-CaO-SiO₂-B₂O₃ glasses.

    Science.gov (United States)

    Jagan Mohini, G; Sahaya Baskaran, G; Ravi Kumar, V; Piasecki, M; Veeraiah, N

    2015-12-01

    Soda lime silica borate glasses mixed with different concentrations of TiO2 are synthesized by the melt-quenching technique. As a part of study on bioactivity of these glasses, the samples were immersed in simulated body fluid (SBF) solution for prolonged times (~21 days) during which weight loss along with pH measurements is carried out at specific intervals of time. The XRD and SEM analyses of post-immersed samples confirm the formation of crystalline hydroxyapatite layer (HA) on the surface of the samples. To assess the role of TiO2 on the formation of HA layer and degradability of the samples the spectroscopic studies viz. optical absorption and IR spectral studies on post- and pre-immersed samples have been carried out. The analysis of the results of degradability together with spectroscopic studies as a function of TiO2 concentration indicated that about 6.0 mol% of TiO2 is the optimal concentration for achieving better bioactivity of these glasses. The presence of the maximal concentration octahedral titanium ions in this glass that facilitates the formation of HA layer is found to be the reason for such a higher bioactivity. PMID:26354260

  12. The 'Porky' Inclusion from the Axtell Carbonaceous Chondrite: A Hercynite-bearing Condensate with Large 48Ca and 50Ti Excesses

    Science.gov (United States)

    Caillet, C.; Zinner, E.

    1995-09-01

    Only a few hercynite-rich refractory inclusions have been identified to date [1,2]. Porky (450 micrometers long) is an unusual CAI with texturally distinct regions and dominant intergrown oxide mineral phases [3]. The core is a symplectitic vermicular intergrowth of ubiquitous ferroan spinel and ilmenite. Inwards branching of ilmenite crystals and projecting fan-shaped hibonite from the borders suggest crystallization from a fast cooling melt. Three marginal regions are mineralogically identical to the core: two fine-grained areas with acicular corroded crystals contrast with an altered spinel area. The inclusion is entirely rimmed by yellow luminescing Al-diopside. Hibonite exhibits pale orange luminescence. Broad beam analyses reveal high FeO (22.5 wt %) and low CaO/Al2O3 (0.024) for the whole CAI [3]. Si, Al and Ti concentrations are very similar to those of CM inclusions. There are no significant chemical differences between the coarse-grained core and the fine-grained regions. Hibonite shows widely varying concentrations (in wt %) of TiO2 (1.5-6.8), MgO (1.2-3.6) and FeO (0.7-4.7). Spinel contains much FeO (20.5-27). Hercynite close to the border of the inclusion next to hibonite has high MgO (11 wt%) and small amounts of Cr2O3 (0.15-1.55) and V2O3 (0.1-0.3), implying a melt origin. The Al-rich, Si-poor composition indicates that Porky experienced higher temperatures than CV3 inclusions. The presence of Fe-rich mineral phases, the lack of metal grains, the relatively high NiO concentration (average = 0.25), and the orange luminescence of hibonite indicate formation or re-equilibration in an oxidizing environment. Trace element patterns are basically volatility-fractionated and mostly ultrarefractory-depleted but vary from a Group II pattern in hercynite (to a lesser extent in hibonite and diopside) to extreme excesses of the less refractory elements Nb, Eu, Tm and Yb in a fine-grained region (Fig. 1). These patterns indicate condensation from a UR-depleted gas

  13. Photo-electronic properties and persistent luminescence in Pr{sup 3+} doped (Ca,Sr)TiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Yumiko, E-mail: katayama.yumiko.48a@st.kyoto-u.ac.jp [Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu, Sakyo, Kyoto 606-8501 (Japan); Ueda, Jumpei [Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu, Sakyo, Kyoto 606-8501 (Japan); Tanabe, Setsuhisa [Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu, Sakyo, Kyoto 606-8501 (Japan); Japan Science and Technology Agency Precursory Research for Embryonic Science and Technology (JST-PRESTO), Chiyoda, Tokyo 102-0075 (Japan)

    2014-04-15

    We obtained direct evidence of intervalence charge transfer (IVCT) in Ca{sub 1−x}Sr{sub x}TiO{sub 3}:Pr{sup 3+} (x=0, 0.3, 0.5, 0.8, and 1) by a photocurrent excitation (PCE) measurement, and proposed a mechanism of the persistent luminescence based on the results of the PCE and persistent luminescence measurements. The PCE spectra in all samples showed two bands in the UV range due to the band-to-band and IVCT transitions. With increasing Sr content, x, the host bandgap energy decreased monotonically from 3.59 to 3.23 eV, and the IVCT energy increased from 3.20 to 3.38 eV. PCE bands of the Pr{sup 3+}:{sup 3}H{sub 4}→{sup 3}P{sub J} transitions in the blue region were observed only in the samples with x=0, 0.3, and 0.5 and the relative intensity decreased with increasing Sr content, x. Based on temperature dependence of the PCE results in the sample with x=0, a thermally assisted photoionization process was indicated under the {sup 3}H{sub 4}→{sup 3}P{sub J} excitation. Red persistent luminescence was observed in the samples with x=0, 0.3 and 0.5, showing trap depth in the range of 0.48–0.35 eV, which was estimated from the thermoluminescence measurement. The afterglow process by the electron moving through the conduction band was evidenced by the similar quenching behavior of the {sup 3}H{sub 4}→{sup 3}P{sub J} band both in the PCE and afterglow excitation spectra. The difference in the processes of persistent luminescence among the band-to-band, IVCT and {sup 3}H{sub 4}→{sup 3}P{sub J} excitations was discussed. -- Highlights: • We obtained direct evidence of intervalence charge transfer (IVCT) in (Ca,Sr)TiO{sub 3}:Pr{sup 3+} by a photocurrent excitation measurement. • We proposed a mechanism of the persistent luminescence in (Ca,Sr)TiO{sub 3}:Pr{sup 3+}. • Two mechanisms including electron or hole trapping processes were proposed under different excitations.

  14. Experimental and numerical investigation of a ceramic dielectric resonator (DRA): CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO)

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, A.F.L. [Departamento de Fisica, Universidade do Aveiro, 3800-193 Aveiro (Portugal); Mestrado em Ciencias Fisicas Aplicadas, Universidade Estadual do Ceara, Campus do Itaperi 1700, CEP 60740-903 Fortaleza, Ceara (Brazil); Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil); Silva, R.R. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil); Rocha, H.H.B. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil); Departamento de Engenharia de Teleinformatica (DETI), Universidade Federal do Ceara, Caixa Postal 6007, CEP 60.755-640 Fortaleza, Ceara (Brazil); Fechine, P.B.A. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil); Departamento de Quimica Analitica e Fisico-Quimica, Universidade Federal do Ceara - UFC, Campus do Pici, CP 12100, CEP 60451-970 Fortaleza - CE (Brazil); Cavalcanti, F.S.A. [Mestrado em Ciencias Fisicas Aplicadas, Universidade Estadual do Ceara, Campus do Itaperi 1700, CEP 60740-903 Fortaleza, Ceara (Brazil); Valente, M.A. [Departamento de Fisica, Universidade do Aveiro, 3800-193 Aveiro (Portugal); Freire, F.N.A.; Sohn, R.S.T.M. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil)] (and others)

    2008-03-01

    In this study, the CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramic phase was synthesized by microwave heating in a much shorter time compared to the conventional heating methods. The results indicate that microwave processing is a promising method for preparing CCTO ceramics. CCTO was prepared using a domestic microwave oven operated at 2.45 GHz with 800 W. After a few minutes of microwave irradiation the formation of CCTO was confirmed by X-ray powder diffraction. The CCTO ceramic was studied in the medium-frequency (MF) range (100 Hz-1 MHz) and in the microwave range of frequencies. The experimental and theoretical characteristics of the dielectric resonator antenna are investigated.

  15. CaCu3Ti4O12 particles and MWCNT-filled microwave absorber with improved microwave absorption by FSS incorporation

    Science.gov (United States)

    Qing, Yuchang; Yang, Zhaoning; Wen, Qinlong; Luo, Fa

    2016-07-01

    Multi-walled carbon nanotube (MWCNTs)- and CaCu3Ti4O12 (CCTO) particle-filled epoxy microwave absorbing coatings were prepared, and their electromagnetic properties and reflection loss (RL) were investigated in the frequency range 8.2-12.4 GHz. The microstructures of these coatings exhibit a uniform dispersion of MWCNTs and CCTO particles in the matrix. The value and frequency dependency of complex permittivity of such coatings enhanced with increasing MWCNT content. Frequency-selective surface was used to improve their microwave absorption (both the operating bandwidth and minimum RL) without increasing the absorber thickness. Such absorber showed high microwave absorbing performance, and the bandwidth of the RL below -8 dB (more than 84.1 % absorption) can be obtained in the whole X-band with a thickness of 1.5 mm.

  16. Large photoconductivity of La0.7Ca0.3MnO3-δ/SrTiO3 heterostructures

    International Nuclear Information System (INIS)

    The electric resistivity of stoichiometric and oxygen-deficient epitaxial 10-nm-thick La0.7Ca0.3MnO3 thin films on SrTiO3 under photoexcitation has been investigated systematically. In contrast to the as-prepared film, the oxygen-deficient one exhibits a pronounced photoinduced decrease of the resistivity of up to five orders of magnitude at low temperatures. A detailed analysis of the resistivity as a function of illumination intensity and wavelength (visible to ultraviolet range) is presented for the bare substrate as well as for the film/substrate heterostructure. The roles of carrier generation in the film and carrier injection from the substrate, which both contribute to the observed effects, are discussed.

  17. Pyrochlore type semiconducting ceramic oxides in Ca-Ce-Ti-M-O system (M = Nb or Ta)-Structure, microstructure and electrical properties

    International Nuclear Information System (INIS)

    A new series of pyrochlore type ceramic semiconducting oxides in Ca-Ce-Ti-M-O (M = Nb or Ta) system has been synthesized by the conventional ceramic route. The electrical conductivity measurements show that these oxides exhibit semiconducting behavior and the conductivity increases with the Ce content in the compound. Activation energy of the current carriers is in the range of 0.5-1.6 eV. The electrical conductivity in these oxides is due to the presence of Ce3+, which remains in the reduced state without being oxidized to Ce4+ by structural stabilization. The photoluminescence and X-ray photoelectron spectroscopy analysis corroborate the presence of Ce in the 3+ state. Impedance spectral analysis is carried out to evaluate the transport properties and indicates that the conduction in these compounds is mainly due to electronic contribution. The X-ray powder diffraction and Raman spectroscopy analysis establishes that these oxides belong to a cubic pyrochlore type structure.

  18. Optical potentials and isoscalar transition rates from 104 MeV alpha-particle scattering by the N=28 isotopes 48Ca, 50Ti and 52Cr

    International Nuclear Information System (INIS)

    Precisely measured differential cross sections for elastic and inelastic scattering from 104 MeV alpha-particles by 48Ca, 50Ti and 52Cr are reported. The analyses aim primarily at the determination of strength, radial shapes and deformation of the scattering potentials, looking for isotonic differences of N = 28 isotones. The mean square radii of the (real) potentials are discussed in terms of mean square radius differences of the matter distributions. The isoscalar transition rates derived by coupled channel analyses of the measured cross sections are compared with electromagnetic rates. In addition to the analyses on the basis of a slightly generalized extended optical model a semi-microscopic deformed folding model has been applied, using a density-dependent effective alpha-bound nucleon interaction. Though an excellent description of the data over the full angular range is obtained the resulting values of the deformation parameters appear to be not consistent with results from various different methods. (orig.)

  19. Observation of indium ion migration-induced resistive switching in Al/Mg0.5Ca0.5TiO3/ITO

    Science.gov (United States)

    Lin, Zong-Han; Wang, Yeong-Her

    2016-08-01

    Understanding switching mechanisms is very important for resistive random access memory (RRAM) applications. This letter reports an investigation of Al/Mg0.5Ca0.5TiO3 (MCTO)/ITO RRAM, which exhibits bipolar resistive switching behavior. The filaments that connect Al electrodes with indium tin oxide electrodes across the MCTO layer at a low-resistance state are identified. The filaments composed of In2O3 crystals are observed through energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, nanobeam diffraction, and comparisons of Joint Committee on Powder Diffraction Standards (JCPDS) cards. Finally, a switching mechanism resulting from an electrical field induced by In3+ ion migration is proposed. In3+ ion migration forms/ruptures the conductive filaments and sets/resets the RRAM device.

  20. Study of the nuclear matter distribution and isoscalar transition rates of 48Ca, 50Ti and 52Cr by scattering of 104 MeV alpha-particles

    International Nuclear Information System (INIS)

    The differential cross-sections for elastic and inelastic scattering of 104 MeV α-particles on 50Ti and 52Cr have been measured for scattering angles in the range 20 0. Additionally using previously measured data for 48Ca, the cross-sections of the N = 28 isotopic sequence 48Ca-50Ti-52Cr were analyzed on the basis of the generalized optical model. Study of the angular distribution of the elastic scattering, using modified phenomenological and microscopic methods, leads to well defined and consistent values for moments of the potentials and of the matter distributions. In particular, the Fourier-Bessel method leads to a nearly model-independent determination of the differences in isotonic radii and also to a realistic determination of error bars. For the analysis of the inelastic scattering a new method is introduced, which strongly reduces the model dependence which arises when simple analytic expressions are used for the form factors (the form of the coupling potentials). For this purpose the Fourier-Bessel method has been extended to the analysis of inelastic scattering using the collective vibrational model. Using the identities between the integral moments of a folded potential and of the underlying nuclear matter distribution, isoscalar transition rates have been derived. The extracted values are confirmed by an explicit folding model analysis. Furthermore, the folding model calculations show that the density dependence of the effective interaction between α-particle and target nucleons must be taken into account also in the analysis of inelastic scattering. (orig.)

  1. Effects of rare earth ionic doping on microstructures and electrical properties of CaCu3Ti4O12 ceramics

    International Nuclear Information System (INIS)

    Graphical abstract: The dielectric constant decreases monotonically with reduced RE doping ion radius and is more frequency independent compared with that of pure CCTO sample. - Highlights: • The mean grain sizes decrease monotonically with reduced RE doping ionic radius. • Doping gives rise to the monotonic decrease of ϵr with reduced RE ionic radius. • The nonlinear coefficient and breakdown field increase with RE ionic doping. • α of all the samples is associated with the potential barrier width rather than Φb. - Abstract: Ca1–xRxCu3Ti4O12(R = La, Nd, Eu, Gd, Er; x = 0 and 0.005) ceramics were prepared by the conventional solid-state method. The influences of rare earth (RE) ion doping on the microstructure, dielectric and electrical properties of CaCu3Ti4O12 (CCTO) ceramics were investigated systematically. Single-phase formation is confirmed by XRD analyses. The mean grain size decreases monotonically with reduced RE ion radius. The EDS results reveal that RE ionic doping reduces Cu-rich phase segregation at the grain boundaries (GBs). Doping gives rise to the monotonic decrease of dielectric constant with reduced RE ionic radius but significantly improves stability with frequency. The lower dielectric loss of doped samples is obtained due to the increase of GB resistance. In addition, the nonlinear coefficient and breakdown field increase with RE ionic doping. Both the fine grains and the enhancement of potential barrier at GBs are responsible for the improvement of the nonlinear current–voltage properties in doped CCTO samples

  2. Calcium titanate (CaTiO3) dielectrics prepared by plasma spray and post-deposition thermal treatment

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Kotlan, Jiří; Pala, Zdeněk; Sedláček, J.; Hájková, Zuzana; Matys Grygar, Tomáš

    2015-01-01

    Roč. 72, December (2015), s. 123-132. ISSN 0025-5408 Institutional support: RVO:61389021 ; RVO:61388980 Keywords : Ceramics * Plasma deposition * Impedance spectroscopy * Raman spectroscopy * Dielectrics Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass; CA - Inorganic Chemistry (UACH-T) Impact factor: 2.288, year: 2014 http://www.sciencedirect.com/science/article/pii/S0025540815300623

  3. High efficiency angular non-critical phase matching for Ti:sapphire laser realized on LaCa4O(BO3)3 single crystals

    International Nuclear Information System (INIS)

    Angular non-critical phase-matching (A-NCPM) second harmonic generation (SHG) for a Ti:sapphire laser was realized on LaCa4O(BO3)3 (LaCOB) single crystals, grown by the Czochralski pulling method. Properties including the wavelength, bandwidth, effective nonlinear optical (NLO) coefficient (deff), and acceptance angle were evaluated. At ambient temperature of 20 °C, the type-I NCPM (808 nm wavelength) was obtained along the y axis of LaCOB crystals, where the effective nonlinear optical coefficient (deff), PM waveband, and angular acceptance were found to be of the order of 0.59 pm/V, 803∼818 nm and 50.6 mrad cm1/2 (ΔϕL), respectively. Moreover, high single-pass SHG conversion efficiency (44.6%) was achieved for 24.8 mm long Y-cut samples at 808 nm, using a mode-locked Ti:sapphire fundamental laser. (letter)

  4. Recent progress in oxide thermoelectric materials: p-type Ca3Co4O9 and n-type SrTiO3(-).

    Science.gov (United States)

    Ohta, Hiromichi; Sugiura, Kenji; Koumoto, Kunihito

    2008-10-01

    Thermoelectric energy conversion technology to convert waste heat into electricity has received much attention. In addition, metal oxides have recently been considered as thermoelectric power generation materials that can operate at high temperatures on the basis of their potential advantages over heavy metallic alloys in chemical and thermal robustness. We have fabricated high-quality epitaxial films composed of oxide thermoelectric materials that are suitable for clarifying the intrinsic "real" properties. This review focuses on the thermoelectric properties of two representative oxide epitaxial films, p-type Ca 3Co 4O 9 and n-type SrTiO 3, which exhibit the best thermoelectric figures of merit, ZT (= S (2)sigma Tkappa (-1), S = Seebeck coefficient, sigma = electrical conductivity, kappa = thermal conductivity, and T = absolute temperature) among oxide thermoelectric materials reported to date. In addition, we introduce the recently discovered giant S of two-dimensional electrons confined within a unit cell layer thickness ( approximately 0.4 nm) of SrTiO 3. PMID:18821809

  5. A miniaturized Microwave Bandpass Filter Based on Modified (Mg0.95Ca0.05TiO3 Substrate

    Directory of Open Access Journals (Sweden)

    Hu Mingzhe

    2016-01-01

    Full Text Available A microwave miniaturized bandpass filter using (Mg0.95Ca0.05TiO3 (abbreviated as 95MCT hereafter ceramic substrate is investigated in the present paper. The paper studies the sintering and microwave dielectric properties of Al2O3, La2O3 and SiO2 co-doped 95MCT. The XRD pattern shows that a secondary phase MgTi2O5 is easily segregated in 95MCT ceramic, however, through co-doping it can be effectively suppressed, and the microwave dielectric properties, especially, the Qf value can be significantly improved. Through optimizing the co-doping ratio of Al2O3, La2O3 and SiO2, the sintering temperature of 95MCT ceramic can be lowered by 80°C, and the microwave dielectric properties can reach Qf=61856GHz and εr=19.84, which indicates the modified 95MCT ceramic have a great potential application in microwave communication devices. Based on this, we also designed a miniaturized microwave bandpass filter (BPF on modified 95MCT substrate. Through a full wave electromagnetic structure simulation, the results show that the center frequency of the BPF is 2.45GHz and the relative bandwidth is 4.09% with the insertion loss of less than 0.2dB in the whole bandpass.

  6. Dielectric properties of Ca(Zr0.05Ti0.95)O3 thin films prepared by chemical solution deposition

    International Nuclear Information System (INIS)

    Ca(Zr0.05Ti0.95)O3 (CZT) thin films were grown on Pt(111)/Ti/SiO2/Si(100) substrates by the soft chemical method. The films were deposited from spin-coating technique and annealed at 928K for 4h under oxygen atmosphere. CZT films present orthorhombic structure with a crack free and granular microstructure. Atomic force microscopy and field-emission scanning electron microscopy showed that CZT present grains with about 47nm and thickness about 450nm. Dielectric constant and dielectric loss of the films was approximately 210 at 100kHz and 0.032 at 1MHz. The Au/CZT/Pt capacitor shows a hysteresis loop with remnant polarization of 2.5μC/cm2, and coercive field of 18kV/cm, at an applied voltage of 6V. The leakage current density was about 4.6x10-8A/cm2 at 3V. Dielectric constant-voltage curve is located at zero bias field suggesting the absence of internal electric fields

  7. Raman spectra of the solid-solution between Rb sub 2 La sub 2 Ti sub 3 O sub 1 sub 0 and RbCa sub 2 Nb sub 3 O sub 1 sub 0

    CERN Document Server

    Kim, H J; Yun, H S

    2001-01-01

    A site preference of niobium atom in Rb sub 2 sub - sub x La sub 2 Ti sub 3 sub - sub x Nb sub x O sub 1 sub 0 (0.0<=x<=1.0) and RbLa sub 2 sub - sub x Ca sub x Ti sub 2 sub - sub x Nb sub 1 sub + sub x O sub 1 sub 0 (0.0<=x<= 2.0), which are the solid-solutions between Rb sub 2 La sub 2 Ti sub 3 O sub 1 sub 0 are RbCa sub 2 Nb sub 3 O sub 1 sub 0 , has been investigated by Raman spectroscopy. The Raman spectra of Rb sub 2 sub - sub x La sub 2 Ti sub 3 sub - sub x Nb sub x O sub 1 sub 0 (0.0<=x<=1.0) gave an evidence that niobium atoms substituted for titanium atoms preferably occupy the highly distorted outer octahedral sites rather than the central ones in triple-octahedral perovskite layers. In contrast, the Raman spectra of RbLa sub 2 sub - sub x Ca sub x Ti sub 2 sub - sub x Nb sub 1 sub + sub x O sub 1 sub 0 (0.0<=x<= 2.0) showed no clear information for the cationic arrangement in perovskite slabs. This difference indicated that a site preference of niobium atoms is observed onl...

  8. Crystal micromorphologies and forming voltage effect on resistance switching behaviors in Ti/Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7}/Pt devices

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yuchen; Song, Liwei; Hua, Lifang; Cai, Wenhui; Chen, Wei [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China); Zhao, Xu, E-mail: xzhao@hebtu.edu.cn [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China)

    2015-10-15

    Two Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7} (PSCMO)-based devices (Ti/PSCMO-1/Pt and Ti/PSCMO-2/Pt) have been prepared by pulsed laser deposition, and the micromorphology of the films can be controlled through the different deposition condition. PSCMO-1 film with a smaller grain size grows with a near-random arrangement, whereas columnar grains with a larger grain size appear in the Ti/PSCMO-2/Pt device. The I–V curves in Ti/PSCMO-2/Pt device show the higher resistance ratio and larger hysteresis than that in the Ti/PSCMO-1/Pt device without forming process. The electron transport property in the PSCMO-2 film shows the higher resistance and metal behavior in room temperature. By fitting the I–V curves, we found that the conduction process in Ti/PSCMO-1/Pt device is dominated by Schottky barrier mechanism, but the conduction behavior in Ti/PSCMO-2/Pt device are dominated by trap-charged space-charge-limited current (SCLC) mechanism. Interesting, after a forming process, the Ti/PSCMO-1/Pt device also displays the higher resistance ratio and larger hysteresis, which can be explained by SCLC mechanism. Our results suggest that the crystal micromorphology and grain size may play a critical role in oxygen vacancy movement, and result in the transformation of resistance switching along with a higher resistance ratio and larger hysteresis in the Ti/PSCMO-2/Pt device. - Highlights: • Two different Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7}-based devices have been prepared. • The device with larger grain and columnar arrangement shows higher resistance ratio. • Crystal morphologies and grain size play critical role in oxygen vacancy movement.

  9. Lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 nanowires for energy harvesting

    Science.gov (United States)

    Zhou, Zhi; Bowland, Christopher C.; Malakooti, Mohammad H.; Tang, Haixiong; Sodano, Henry A.

    2016-02-01

    Lead-free piezoelectric nanowires (NWs) show strong potential in sensing and energy harvesting applications due to their flexibility and ability to convert mechanical energy to electric energy. Currently, most lead-free piezoelectric NWs are produced through low yield synthesis methods and result in low electromechanical coupling, which limit their efficiency as energy harvesters. In order to alleviate these issues, a scalable method is developed to synthesize perovskite type 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) NWs with high piezoelectric coupling coefficient. The piezoelectric coupling coefficient of the BZT-BCT NWs is measured by a refined piezoresponse force microscopy (PFM) testing method and shows the highest reported coupling coefficient for lead-free piezoelectric nanowires of 90 +/- 5 pm V-1. Flexible nanocomposites utilizing dispersed BZT-BCT NWs are fabricated to demonstrate an energy harvesting application with an open circuit voltage of up to 6.25 V and a power density of up to 2.25 μW cm-3. The high electromechanical coupling coefficient and high power density demonstrated with these lead-free NWs produced via a scalable synthesis method shows the potential for high performance NW-based devices.

  10. High pyroelectricity in lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramics

    International Nuclear Information System (INIS)

    We report high pyroelectricity in lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-50BCT) ceramics which were previously reported to exhibit high piezoelectricity. The pyroelectric coefficient measured by the Byer-Roundy method upon heating for dc-poled samples shows a high value of 5.84 × 10-4 C m-2 K-1 at 300 K, comparable to those of PZT-based ceramics and significantly higher than many other lead-free pyroelectric materials. The pyroelectric coefficient calculated from the remanent polarization versus temperature relationship obtained during a cooling process is 17.17 × 10-4 C m-2 K-1 at 300 K, which is considerably larger than the value obtained by the Byer-Roundy method. This difference is attributed to the thermal hysteresis of the rhombohedral-tetragonal phase transition between the heating and cooling processes. (paper)

  11. Atomic site preferences and its effect on magnetic structure in the intermetallic borides M2Fe(Ru0.8T0.2)5B2 (M=Sc, Ti, Zr; T=Ru, Rh, Ir)

    International Nuclear Information System (INIS)

    The site preference for a class of intermetallic borides following the general formula M2Fe(Ru0.8T0.2)5B2 (M=Sc, Ti, Zr; T=Ru, Rh, Ir), has been explored using ab initio and semi-empirical electronic structure calculations. This intermetallic boride series contains two potential sites, the Wyckoff 2c and 8j sites, for Rh or Ir to replace Ru atoms. Since the 8j site is a nearest neighbor to the magnetically active Fe atom, whereas the 2c site is a next nearest neighbor, the substitution pattern should play an important role in the magnetic structure of these compounds. The substitution preference is analyzed based on the site energy and bond energy terms, both of which arise from a tight-binding evaluation of the electronic band energy, and are known to influence the locations of atoms in extended solids. According to these calculations, the valence electron-rich Rh and Ir atoms prefer to occupy the 8j site, a result also corroborated by experimental evidence. Additionally, substitution of Rh or Ir at the 8j site results in a modification of the magnetic structure that ultimately results in larger local magnetic moment on the Fe atoms. - Graphical abstract: The site preference for electron rich atoms to occupy the 8j (gray) site is identified in these intermetallic borides, while the magnetic structure is modified as a function of the substituted atoms band center. Highlights: ► We identify the energetics dictating the site preference in a series of intermetallic borides. ► Establish substitution rules for use in future directed synthetic preparations. ► Identified changes in magnetic structure that accompany the site preference.

  12. Proteomic Profiling of Hematopoietic Stem/Progenitor Cells after a Whole Body Exposure of CBA/CaJ Mice to Titanium (48Ti Ions

    Directory of Open Access Journals (Sweden)

    Kanokporn Noy Rithidech

    2015-07-01

    Full Text Available Myeloid leukemia (ML is one of the major health concerns from exposure to radiation. However, the risk assessment for developing ML after exposure to space radiation remains uncertain. To reduce the uncertainty in risk prediction for ML, a much increased understanding of space radiation-induced changes in the target cells, i.e., hematopoietic stem/progenitor cells (HSPCs, is critically important. We used the label-free quantitative mass spectrometry (LFQMS proteomic approach to determine the expression of protein in HSPC-derived myeloid colonies obtained at an early time-point (one week and a late time-point (six months after an acute whole body exposure of CBA/CaJ mice to a total dose of 0, 0.1, 0.25, or 0.5 Gy of heavy-ion titanium (48Ti ions, which are the important component of radiation found in the space environment. Mice exposed to 0 Gy of 48Ti ions served as non-irradiated sham controls. There were five mice per treatment groups at each harvest time. The Trans-Proteomic Pipeline (TPP was used to assign a probability of a particular protein being in the sample. A proof-of-concept based Ingenuity Pathway Analysis (IPA was used to characterize the functions, pathways, and networks of the identified proteins. Alterations of expression levels of proteins detected in samples collected at one week (wk post-irradiation reflects acute effects of exposure to 48Ti ions, while those detected in samples collected at six months (mos post-irradiation represent protein expression profiles involved in the induction of late-occurring damage (normally referred to as genomic instability. Our results obtained by using the IPA analyses indicate a wide array of signaling pathways involved in response to 1 GeV/n 48Ti ions at both harvest times. Our data also demonstrate that the patterns of protein expression profiles are dose and time dependent. The majority of proteins with altered expression levels are involved in cell cycle control, cellular growth and

  13. Effect of nanoporous TiO2 coating and anodized Ca2+ modification of titanium surfaces on early microbial biofilm formation

    Directory of Open Access Journals (Sweden)

    Wennerberg Ann

    2011-03-01

    Full Text Available Abstract Background The soft tissue around dental implants forms a barrier between the oral environment and the peri-implant bone and a crucial factor for long-term success of therapy is development of a good abutment/soft-tissue seal. Sol-gel derived nanoporous TiO2 coatings have been shown to enhance soft-tissue attachment but their effect on adhesion and biofilm formation by oral bacteria is unknown. Methods We have investigated how the properties of surfaces that may be used on abutments: turned titanium, sol-gel nanoporous TiO2 coated surfaces and anodized Ca2+ modified surfaces, affect biofilm formation by two early colonizers of the oral cavity: Streptococcus sanguinis and Actinomyces naeslundii. The bacteria were detected using 16S rRNA fluorescence in situ hybridization together with confocal laser scanning microscopy. Results Interferometry and atomic force microscopy revealed all the surfaces to be smooth (Sa ≤ 0.22 μm. Incubation with a consortium of S. sanguinis and A. naeslundii showed no differences in adhesion between the surfaces over 2 hours. After 14 hours, the level of biofilm growth was low and again, no differences between the surfaces were seen. The presence of saliva increased the biofilm biovolume of S. sanguinis and A. naeslundii ten-fold compared to when saliva was absent and this was due to increased adhesion rather than biofilm growth. Conclusions Nano-topographical modification of smooth titanium surfaces had no effect on adhesion or early biofilm formation by S. sanguinis and A. naeslundii as compared to turned surfaces or those treated with anodic oxidation in the presence of Ca2+. The presence of saliva led to a significantly greater biofilm biovolume but no significant differences were seen between the test surfaces. These data thus suggest that modification with sol-gel derived nanoporous TiO2, which has been shown to improve osseointegration and soft-tissue healing in vivo, does not cause greater biofilm

  14. Low sintering temperature and high piezoelectric properties of Li-doped (Ba,Ca)(Ti,Zr)O{sub 3} lead-free ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiaoming [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Ruan, Xuezheng; Zhao, Kunyun [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); He, Xueqing [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Zeng, Jiangtao, E-mail: zjt@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Li, Yongsheng [School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zheng, Liaoying [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Park, Chul Hong [Department of Physics Education, Pusan National University, Pusan 609735 (Korea, Republic of); Li, Guorong [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2015-05-25

    Highlights: • Li-doped Ba{sub 0.85}Ca{sub 0.15}Ti{sub 0.9}Zr{sub 0.1}O{sub 3} (BCZT) lead-free piezoceramics were prepared by the two-step synthesis and solid-state reaction method. • Their sintering temperature decreases from about 1540 °C down to about 1400 °C. • With the proper addition of Li, the densities and grain sizes of ceramics increase. • The ceramics not only have the characteristics of hard piezoceramics but also possesses the features of soft piezoceramics at low sintering temperature. - Abstract: Li-doped Ba{sub 0.85}Ca{sub 0.15}Ti{sub 0.9}Zr{sub 0.1}O{sub 3} (BCZT) lead-free piezoelectric ceramics were prepared by the two-step synthesis and the solid-state reaction method. The density and grain size of ceramics sufficiently increases by Li-doped sintering aid, and their sintering temperature decreases from about 1540 °C down to about 1400 °C. X-ray diffraction reveals that the phase structure of Li-doped BCTZ ceramics is changed with the sintering temperature, which is consistent with their phase transition observed by the temperature-dependent dielectric curves. The well-poled Li-doped BCZT ceramics show a high piezoelectric constant d{sub 33} (512 pC/N) and a planar electromechanical coupling factor k{sub p} (0.49), which have the characteristics of soft Pb(Zr,Ti)O{sub 3} (PZT) piezoceramic, on the other hand, the mechanical quality factor Q{sub m} is about 190, which possesses the features of hard PZT piezoceramics. The enhanced properties of the Li-doped BCZT are explained by the combination of Li-doped effect and sintering effect on the microstructure and the phase transition around room temperature.

  15. Effects of LiF on microwave dielectric properties of 0.25Ca0.8Sr0.2TiO3–0.75Li0.5Nd0.5TiO3 ceramics

    Indian Academy of Sciences (India)

    Fei Liu; Changlai Yuan; Xinyu Liu; Jing Jing Qu

    2015-09-01

    The effects of LiF addition on sinterability, microstructure and microwave dielectric properties of 0.25Ca0.8Sr0.2TiO3–0.75Li0.5Nd0.5TiO3 ceramics were investigated. The LiF addition enhanced the sintering temperature of 0.25Ca0.8Sr0.2TiO3–0.75Li0.5Nd0.5TiO3 ceramics from 1200 to 1300°C, because the LiF addition could compensate the evaporation of Li during the sintering process. It was found that the bulk density and dielectric constant (r) gradually decreased, the quality factor (f) greatly increased and the temperature coefficient of resonant frequency (f) shifted to a near-zero value with the increase in LiF addition. Obviously, excess Li addition could efficiently improve the microwave dielectric properties. In addition, 0.25Ca0.8Sr0.2 TiO3–0.75Li0.5Nd0.5TiO3 + 4.0 wt% LiF ceramics sintered at 1350°C for 4 h exhibited good microwave dielectric properties of r ∼ 123.4, f ∼ 2209 GHz (at 2.43 GHz) and f ∼ 12.3 ppm °C–1.

  16. Investigating the addition of SiO₂-CaO-ZnO-Na₂O-TiO₂ bioactive glass to hydroxyapatite: Characterization, mechanical properties and bioactivity.

    Science.gov (United States)

    Yatongchai, Chokchai; Placek, Lana M; Curran, Declan J; Towler, Mark R; Wren, Anthony W

    2015-11-01

    Hydroxyapatite (Ca10(PO4)6(OH)2) is widely investigated as an implantable material for hard tissue restoration due to its osteoconductive properties. However, hydroxyapatite in bulk form is limited as its mechanical properties are insufficient for load-bearing orthopedic applications. Attempts have been made to improve the mechanical properties of hydroxyapatite, by incorporating ceramic fillers, but the resultant composite materials require high sintering temperatures to facilitate densification, leading to the decomposition of hydroxyapatite into tricalcium phosphate, tetra-calcium phosphate and CaO phases. One method of improving the properties of hydroxyapatite is to incorporate bioactive glass particles as a second phase. These typically have lower softening points which could possibly facilitate sintering at lower temperatures. In this work, a bioactive glass (SiO2-CaO-ZnO-Na2O-TiO2) is incorporated (10, 20 and 30 wt%) into hydroxyapatite as a reinforcing phase. X-ray diffraction confirmed that no additional phases (other than hydroxyapatite) were formed at a sintering temperature of 560 ℃ with up to 30 wt% glass addition. The addition of the glass phase increased the % crystallinity and the relative density of the composites. The biaxial flexural strength increased to 36 MPa with glass addition, and there was no significant change in hardness as a function of maturation. The pH of the incubation media increased to pH 10 or 11 through glass addition, and ion release profiles determined that Si, Na and P were released from the composites. Calcium phosphate precipitation was encouraged in simulated body fluid with the incorporation of the bioactive glass phase, and cell culture testing in MC-3T3 osteoblasts determined that the composite materials did not significantly reduce cell viability. PMID:26116020

  17. Assessment of CaSO{sub 4}:Dy and LiF:Mg,Ti thermoluminescent dosimeters performance in the dosimetry of clinical electron beams; Avaliacao do desempenho dos detectores termoluminesncetes de CaSO{sub 4}:Dy e LiF:Mg,Ti na dosimetria de feixes clinicos de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, Maira Goes

    2008-07-01

    The assessment of the performance of CaS0{sub 4}:Dy thermoluminescent detectors produced by IPEN in the dosimetry of clinical electron beams aims to propose an alternative to the LiF:Mg,Ti commercial dosimeters (TLD-100) largely applied in radiation therapy. The two types of thermoluminescent dosimeters were characterised with the use of PMMA, RMI-457 type solid water and water phantoms in radiation fields of 4, 6, 9, 12 and 16 MeV electrons of nominal energies in which the dose-response curves were obtained and the surface and depth doses were determined. The thermoluminescent response dependency with the electron nominal energies and the applied phantom were studied. The CaS0{sub 4}:Dy presented the same behaviour than the LiF:Mg,Ti in such a way that its application as an alternative to the TLD-100 pellets in the radiation therapy dosimetry of electron beams is viable and presents the significantly higher sensitivity to the electron radiation as its main advantage. (author)

  18. Chemical stability of Ca0.86Nd0.14Ti0.86Al0.14SiO5 solid solution by coupling effect of THMC

    International Nuclear Information System (INIS)

    Sphene solid solution doped neodymium (Ca0.86Nd0.14Ti0.86Al0.14SiO5) was prepared using CaCO3, Nd2O3, TiO2, SiO2 and Al2O3 as raw materials by solid-reaction. The chemical stability of sphene solid solution doped Nd by the coupling effect of thermodynamics-hydrodynamics-mechanics-chemistry (THMC) was investigated by the means of product consistency test (PCT), X-ray diffraction (XRD), scanning electron microscope (SEM), inductively coupled plasma atomic emission spectrometry (ICP-OES) and so on. The results indicate that Ca0.86Nd0.14Ti0.86Al0.14SiO5 solid solution has good chemical stability by the coupling effect of the pH=5-9, 150-200 ℃ and 0.476- 1.554 MPa: the pH value and temperature (pressure) have no significant impact on the normalized leach rate of Si4+, Al3+ and Nd3+: the anti-leaching property of Ca2+ at 200 ℃ (1.554 MPa) is better than that at 150 ℃: early in the immersion, the anti-leaching property of Ca2+ in pH=9 is better than that in pH=5 and 7, late in the immersion, the anti-leaching property of Ca2+ in solid solution is converge in the three solution: the anti-leaching property of Ti4+ in pH=9 is better than that in pH=5 and 7. (authors)

  19. Pulsed SC Proton Linac

    OpenAIRE

    Ouchi, N.; Chishiro, E.; Tsukishima, C.; Mukugi, K.

    2000-01-01

    The superconducting (SC) proton linac is proposed in the JAERI/KEK Joint Project for a high-intensity proton accelerator in the energy region from 400 to 600 MeV. Highly stable fields in the SC cavities are required under the dynamic Lorentz force detuning. A new model describing the dynamic Lorentz detuning has been developed and the validity has been confirmed experimentally. The model has been applied successfully to the rf control simulation of the SC proton linac.

  20. Microwave dielectric properties of (1 − x)Mg0.95Zn0.05TiO3–(x)Ca0.6La0.8/3TiO3 ceramic composites

    International Nuclear Information System (INIS)

    Highlights: ► This report presents the microwave dielectric properties of (1 − x)MZT–(x)CLT samples. ► The 0.79MZT-0.21CLT composite sample shows a nearly zero τf ∼ −0.8 ppm/°C. ► A dielectric resonator antenna has been fabricated using 0.79MZT-0.21CLT sample. ► The probe fed DRA provides higher gain as compared to the microstrip line fed DRA. -- Abstract: In this paper the structural and microwave dielectric properties of the (1 − x)(Mg0.95Zn0.05)TiO3–(x)(Ca0.6La0.8/3)TiO3 ceramic composites have been investigated with the variation of x as well as sintering temperature. The grown samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy analysis. The Rietveld analysis of the XRD data has been carried out for structure refinement of the phases. The relative permittivity (∊r), quality factor (Q) and temperature coefficient of resonant frequency τf of the grown samples have been thoroughly studied. Out of all samples of this series, the sample with x = 0.21 shows excellent dielectric properties with ∊r∼26.26, Q × f ∼ 60,738 GHz (at 6.44 GHz) and a nearly zero τf ∼ −0.8 ppm/°C. Two types of dielectric resonator antennas with different feeding mechanisms have been fabricated using this sample to study their performance. The experimental results have been compared with the simulated results obtained using Ansoft High Frequency Structure Simulator software

  1. Finding the lowest-energy crystal structure starting from randomly selected lattice vectors and atomic positions: first-principles evolutionary study of the Au-Pd, Cd-Pt, Al-Sc, Cu-Pd, Pd-Ti, and Ir-N binary systems

    International Nuclear Information System (INIS)

    Two types of global space-group optimization (GSGO) problems can be recognized in binary metallic alloys AqB1-q: (i) configuration search problems, where the underlying crystal lattice is known and the aim is finding the most favorable decoration of the lattice by A and B atoms and (ii) lattice-type search problems, where neither the lattice type nor the decorations are given and the aim is finding energetically favorable lattice vectors and atomic occupations. Here, we address the second, lattice-type search problem in binary AqB1-q metallic alloys, where the constituent solids A and B have different lattice types. We tackle this GSGO problem using an evolutionary algorithm, where a set of crystal structures with randomly selected lattice vectors and site occupations is evolved through a sequence of generations in which a given number of structures of highest LDA energy are replaced by new ones obtained by the generational operations of mutation or mating. Each new structure is locally relaxed to the nearest total-energy minimum by using the ab initio atomic forces and stresses. We applied this first-principles evolutionary GSGO scheme to metallic alloy systems where the nature of the intermediate A-B compounds is difficult to guess either because pure A and pure B have different lattice types and the (i) intermediate compound has the structure of one end-point (Al3Sc, AlSc3, CdPt3), or (ii) none of them (CuPd, AlSc), or (iii) when the intermediate compound has lattice sites belonging simultaneously to a few types (fcc, bcc) (PdTi3). The method found the correct structures, L12 type for Al3Sc, D019 type for AlSc3, 'CdPt3' type for CdPt3, B2 type for CuPd and AlSc, and A15 type for PdTi3. However, in such stochastic methods, success is not guaranteed, since many independently started evolutionary sequences produce at the end different final structures: one has to select the lowest-energy result from a set of such independently started sequences. Interestingly, we

  2. Creating Two-Dimensional Electron Gas in Nonpolar/Nonpolar Oxide Interface via Polarization Discontinuity: First-Principles Analysis of CaZrO3/SrTiO3 Heterostructure.

    Science.gov (United States)

    Nazir, Safdar; Cheng, Jianli; Yang, Kesong

    2016-01-13

    We studied strain-induced polarization and resulting conductivity in the nonpolar/nonpolar CaZrO3/SrTiO3 (CZO/STO) heterostructure (HS) system by means of first-principles electronic structure calculations. By modeling four types of CZO/STO HS-based slab systems, i.e., TiO2/CaO and SrO/ZrO2 interface models with CaO and ZrO2 surface terminations in each model separately, we found that the lattice-mismatch-induced compressive strain leads to a strong polarization in the CZO film and that as the CZO film thickness increases there exists an insulator-to-metal transition. The polarization direction and critical thickness of the CZO film for forming interfacial metallic states depend on the surface termination of CZO film in both types of interface models. In the TiO2/CaO and SrO/ZrO2 interface models with CaO surface termination, the strong polarization drives the charge transfer from the CZO film to the first few TiO2 layers in the STO substrate, leading to the formation of two-dimensional electron gas (2DEG) at the interface. In the HS models with ZrO2 surface termination, two polarization domains with opposite directions are in the CZO film, which results in the charge transfer from the middle CZO layer to the interface and surface, respectively, leading to the coexistence of the 2DEG on the interface and the two-dimensional hole gas (2DHG) at the middle CZO layer. These findings open a new avenue to achieve 2DEG (2DHG) in perovskite-based HS systems via polarization discontinuity. PMID:26649746

  3. Effect of (Ca0.8Sr0.2)0.6La0.267TiO3 on Phase, Microstructure, and Microwave Dielectric Properties of Mg0.95Zn0.05TiO3 Synthesized by Polymeric Precursor Method

    Science.gov (United States)

    Naeem, Abdul; Ullah, Asad; Mahmood, Tahira; Iqbal, Yaseen; Mahmood, Asad; Hamayun, Muhammad

    2016-08-01

    A number of compounds in the (1 - x)Mg0.95Zn0.05TiO3- x(Ca0.8Sr0.2)0.6 La0.267TiO3 ( x = 0 to 0.25) composition series have been obtained via a polymeric precursor route to investigate the effect of increasing (Ca0.8Sr0.2)0.6La0.267TiO3 proportion on the phase, microstructure, and microwave dielectric properties of the sintered ceramics. Composite powders having nanometric particles were obtained by calcining the precursors at 700°C. Refinement results revealed that these samples comprised a mixture of Mg0.95Zn0.05TiO3 and (Ca0.8Sr0.2)0.6La0.267TiO3 ceramics. A combination of optimum microwave dielectric properties, i.e., dielectric constant of 25.17, quality factor of 58,754 GHz, and temperature coefficient of resonant frequency of -5.8 ppm/°C, was achieved for the x = 0.2 composition sintered at 1200°C.

  4. Investigation on microwave dielectric properties and microstructures of (1−x) LaAlO{sub 3}-xCa{sub 0.2}Sr{sub 0.8}TiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liangzhu, E-mail: huixinglin@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Lin, Huixing; Zhao, XiangYu; Yao, Xiaogang; Jiang, Shaohu; He, Fei; Li, Botao; Luo, Lan [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800 (China)

    2015-11-15

    The structural, microstructural and microwave dielectric properties of (1−x) LaAlO{sub 3}-xCa{sub 0.2}Sr{sub 0.8}TiO{sub 3} ceramics prepared by the conventional solid state ceramic route have been investigated. The formation of solid solutions (1−x) LaAlO{sub 3}-xCa{sub 0.2}Sr{sub 0.8}TiO{sub 3} was confirmed by the X-ray diffraction patterns and the EDS analysis. The lattice parameter, average grain size and dielectric constant (ε{sub r}) increase with increasing amount of Ca{sub 0.2}Sr{sub 0.8}TiO{sub 3} whereas the quality factor (Q × f) decreases. The increasing temperature coefficient of resonant frequency (τ{sub f}) caused by the decreasing tolerance factor with x ranging from 0.3 to 0.7. The τ{sub f} can be tuned near zero at x = 0.5. Specimen with the composition of 0.5LaAlO{sub 3}–0.5Ca{sub 0.2}Sr{sub 0.8}TiO{sub 3} possesses an excellent combination of microwave dielectric properties: ε{sub r} ∼ 32.7, Q × f ∼ 33400 GHz, τ{sub f} ∼ −2.5 ppm/°C. - Highlights: • A novel (1−x) LaAlO{sub 3}-xCa{sub 0.2}Sr{sub 0.8}TiO{sub 3} microwave ceramics were investigated. • The ceramics formed a solid solution confirmed by XRD and EDS. • When x increases, the ceramics Q × f·τ{sub f} decrease, while ε{sub r} increased nonlinearly. • 0.5LaAlO{sub 3}–0.5Ca{sub 0.2}Sr{sub 0.8}TiO{sub 3}ε{sub r} ∼ 32.7, Q × f ∼ 33400 GHz, τ{sub f} ∼ −2.5 ppm/°C.

  5. Investigation of the structural, optical and dielectric properties of highly (1 0 0)-oriented (Pb0.60Ca0.20Sr0.20)TiO3 thin films on LaNiO3 bottom electrode

    International Nuclear Information System (INIS)

    Highlights: • Highly (h 0 0) oriented LNO and PCST thin films were grown on LAO(1 0 0) substrate. • PCST/LNO/LAO structure shown classic ferroelectric–paraelectric phase transition. • PCST/LNO/LAO structure shows superior dielectric properties. • PCST/LAO films showed a direct allowed optical transition. - Abstract: Highly (1 0 0)-oriented Pb0.60Ca0.20Sr0.20TiO3/LNO/LAO structure was fabricated using a chemical deposition process via spin-coating technique. XRD revealed that both LNO and Pb0.60Ca0.20Sr0.20TiO3 films grown on LAO(1 0 0) substrate and LNO/LAO(1 0 0) structure were crystallized to be highly (h 0 0)-oriented, respectively. AFM images revealed smooth surfaces, spherical-shaped grains and a crack-free surface with a roughness of about 3–7 nm. The tetragonal perovskite phase was confirmed by Raman spectroscopy for Pb0.60Ca0.20Sr0.20TiO3/LNO/LAO and Pb0.60Ca0.20Sr0.20TiO3/LAO structures. The optical transmittance of 340 nm thick Pb0.60Ca0.20Sr0.20TiO3 films on a LAO(1 0 0) substrate exhibited an average transmittance above 80% in the wavelength range of 500–1000 nm and an optical band gap Eg of 3.56 and 2.87 eV for the direct and indirect transition processes, respectively. The Au/Pb0.60Ca0.20Sr0.20TiO3/LNO/LAO structure has a hysteresis loop with remnant polarization, Pr, of 12 μC/cm2, and a coercive field, Ec, of 46 kV/cm for an electric field at 370 kV/cm along with a dielectric constant over 1200

  6. High-Temperature Monoclinic Cc Phase with Reduced c/a Ratio in Bi-based Perovskite Compound Bi2ZnTi1-xMnxO6.

    Science.gov (United States)

    Yu, Runze; Matsuda, Narumi; Tominaga, Ken; Shimizu, Keisuke; Hojo, Hajime; Sakai, Yuki; Yamamoto, Hajime; Oka, Kengo; Azuma, Masaki

    2016-06-20

    Monoclinic phases with Cm, Pm, and Cc space groups are indispensable to understand the high performance of electromechanical properties at the morphotropic phase boundary (MPB) of lead-based perovskite oxides Pb(ZrxTi1-x)O3 (PZT), [Pb(Mg1/3Nb2/3)O3]1-x-(PbTiO3)x (PMN-PT), and [Pb(Zn1/3Nb2/3)O3]1-x-(PbTiO3)x (PZN-PT). Here, a nearly single monoclinic phase with space group Cc was observed in the Bi-based lead-free perovskite compound Bi2ZnTi1-xMnxO6 at x = 0.4. This phase was the same as the low-temperature phase of the MPB composition of PZT but existed at a much higher temperature. Despite the reduced pseudo c/a ratio of 1.065, which is the same as that of PbTiO3 at room temperature, ionic model calculation based on the Rietveld refinement data indicated the polarization of Bi2ZnTi0.6Mn0.4O6 is 95.8 μC/cm(2). The tilting and significant anisotropic distortion of the octahedron were found to cause the c/a ratio to reduce. Accordingly, the effective piezoelectric constant d33 of Bi2ZnTi0.6Mn0.4O6 thin film was found to be 12 pm/V. PMID:27254112

  7. Tailoring the sealing properties of TiO2-CaO-SrO-B2O3-SiO2 glass-ceramic seals: Thermal properties, chemical compatibility and electrical property

    Science.gov (United States)

    Chen, Jialin; Zou, Qi; Zeng, Fanrong; Wang, Shaorong; Tang, Dian; Yang, Hsiwen; Zhang, Teng

    2013-11-01

    In this paper, TiO2 is added to CaO-SrO-B2O3-SiO2 sealing system to tailor the sealing properties of glass-ceramic seals. The coefficient of thermal expansion (CTE) of quenched glasses and glass-ceramics (held at 750 °C for 100 h) does not change significantly with the addition of TiO2; whereas, the glass stability (ΔTxg = Tx - Tg) decreases systematically with increasing TiO2. The addition of TiO2 accelerates the crystallization of sealing glasses. The formation of Sr-containing phase, e.g., Sr(TiO3), contributes to the improved chemical compatibility as well as the increase in conductivity of sealing glasses (e.g., from 7.9 × 10-8 S cm-1 to 6.9 × 10-5 S cm-1 at 800 °C). In addition, the good bonding is observed at the interface between Cr-containing interconnect (430SS) and glasses containing 4-8 mole % TiO2, held at 750 °C for 100 h.

  8. Large pyroelectric figure of merits for Sr-modified Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics

    Science.gov (United States)

    Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

    2016-02-01

    In the present work ferroelectric, dielectric and pyroelectric properties of Sr-modified Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics were investigated. A significant increase in polarization has been observed, from 16 μC/cm2 to 25 μC/cm2 for 15% Sr added BCZT compositions. Correspondingly an improvement in dielectric constant, from 2743 to 4040, was observed at room temperature (1 MHz). It was found that Curie-Weiss temperature (TCW) decreases from 357 K to 308 K for 15% Sr containing BCZT ceramics. Simultaneously, it also enhances the order-disorder to displacing phase transition as γ varies from 1.91 to 1.31. Pyroelectric coefficient was found to be 25 μC/cm2K at 308 K. Finally, pyroelectric figures of merit (FOMs) for voltage responsivity (Fv), current responsivity (Fi), detectivity (Fd), energy harvesting (Fe) and new energy harvesting (Fe∗) are calculated. A large improvement in pyroelectric FOMs indicates that it might be a potential material for pyroelectric applications.

  9. Studies on La0.67Ca0.33MnO3-SrTiO3 composites using two-phase model

    International Nuclear Information System (INIS)

    Highlights: → In this report, we have presented detailed studies on structural, electrical and magnetic behaviours of (1 - x)LCMO-(x)STO composite series. The samples of the present series show TMI C, along with the occurrence of percolation threshold for x = 0.30 sample. Very low temperature (0.67Ca0.33MnO3 (LCMO)-(x)SrTiO3(STO) composites. For this series we have observed a minute change in ferromagnetic (FM)-paramagnetic (PM) transition temperature with STO addition in LCMO matrix; however a reasonable change is observed in metal-insulator transition temperature, along with the occurrence of percolation threshold for x = 0.30 sample. Overall pattern for temperature dependence of resistivity for this series has been best-fitted using the formula 1/ρ = (1 - f)/ρPM + (f/ρFM), whereρPM and ρFM are the resistivities of the PM and FM contents in the sample and f is the volume fraction of FM phase in the sample. Investigations on magnetoresistance (MR) using magnetic field up to 3 T show enhancement of extrinsic MR in the composite samples which can be viewed in the light of spin polarized tunneling.

  10. Structural, dielectric and electrocaloric properties in lead-free Zr-doped Ba0.8Ca0.2TiO3 solid solution

    Science.gov (United States)

    Asbani, B.; Gagou, Y.; Dellis, J.-L.; Lahmar, A.; Amjoud, M.; Mezzane, D.; Kutnjak, Z.; El Marssi, M.

    2016-07-01

    We investigate in the present work the additional data points (x=0.02, 0.06 and 0.08) to the previous reported paper (Asbani et al., 2015) [21] that sufficiently enrich to understand the EC properties and underlying phase diagram of the lead-free Ba0.8Ca0.2Ti(1-x)ZrxO3 (xBCTZ) system. X-ray diffraction analysis performed at room temperature, confirms a continuous tetragonal solid solution with P4mm (No. 99) space group that evolved to pseudo-cubic symmetry for the high Zr-content compounds. Ferroelectric and paraelectric behaviors were highlighted using P-E hysteresis data versus temperature. Phase transition was confirmed by dielectric permittivity measurements versus temperature showing a decrease of the Curie temperature when Zr-content increases. From P-E hysteresis recording the electrocaloric temperature change (ΔT) was calculated that ranged in between 0.12 and 0.27 K and the electrocaloric responsivity (ξ) in 0.15 to 0.34×10-6 K·m/V under 7.95 kV/cm applied electric field. The zero-field entropy is compared to electrocaloric isothermal entropy to estimate the extent the EC is being under-driven.

  11. Novel magnetic–dielectric composite ceramic obtained from Y{sub 3}Fe{sub 5}O{sub 12} and CaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Paiva, D.V.M. [Grupo de Química de Materiais Avançados (GQMAT), Departamento de Química Analítica e Físico-Química, Universidade Federal do Ceará – UFC, Campus do Pici, CP 12100, CEP 60451-970 Fortaleza, CE (Brazil); Silva, M.A.S. [Laboratório de Telecomunicações e Ciência e Engenharia de Materiais (LOCEM), Departamento de Física, Universidade Federal do Ceará (Brazil); Ribeiro, T.S.; Vasconcelos, I.F. [Laboratório de Magnetismo e Materiais Magnéticos, Departamento de Engenharia Metalúrgica e de Materiais, UFC (Brazil); Sombra, A.S.B.; Góes, J.C. [Laboratório de Telecomunicações e Ciência e Engenharia de Materiais (LOCEM), Departamento de Física, Universidade Federal do Ceará (Brazil); Fechine, P.B.A., E-mail: fechine@ufc.br [Grupo de Química de Materiais Avançados (GQMAT), Departamento de Química Analítica e Físico-Química, Universidade Federal do Ceará – UFC, Campus do Pici, CP 12100, CEP 60451-970 Fortaleza, CE (Brazil)

    2015-09-25

    Highlights: • The density of composites was improved with addition of CTO. • Dielectric permittivity of the composites presented values above the expected. • The composites presented magnetic permeability higher than YIG after 500 MHz. - Abstract: This work investigates the microstructure and magnetic–dielectric properties of the CaTiO{sub 3} (CTO) and Y{sub 3}Fe{sub 5}O{sub 12} (YIG) composite ceramic. CTO is a paramagnetic ceramic, presents a positive value of Resonant Frequency Temperature Coefficients (τ{sub f}) and has high dielectric permittivity (ε{sub r}) while YIG is ferromagnetic, has low ε{sub r} and negative τ{sub f} values. Therefore, it is expected that the composite from these individual phase shows new properties, or a mix of them derived from each component. X-ray powder diffraction (XRPD), Scanning Electron Microscope (SEM), Raman and {sup 57}Fe Mössbauer spectroscopy were performed to confirm the phases of the composites. The dielectric and magnetic properties in Radio-Microwave frequencies were studied by impedance spectroscopy using different geometries. It was observed a densification improvement resulting from the insertion of the CTO in composites and a chemical reaction between YIG and CTO phases. This new composite has potential applications in bulk and thick/thin films devices.

  12. Multiferroic behavior on nanometric La2/3Ca1/3MnO3 / BaTiO3 bilayers

    Science.gov (United States)

    Prieto, Pedro; Ordoñez, John Edward; Gomez, Maria Elena; Lopera, Wilson

    2014-03-01

    We have deposited bilayers of the FM La2/3Ca1/3MnO3 and FE BaTiO3 as a route to design systems with artificial magnetoelectric coupling on LCMO/BTO/Nb:STO system. We maintain a fixed magnetic layer thickness (tLCMO = 48 nm) and varying the thickness of the ferroelectric layer (tBTO = 20, 50, 100 nm). We analyze the influence of the thickness ratio (tBTO/ tLCMO) in electrical and magnetic properties of manganite. From X-ray diffraction analysis we observed that the samples grew textured. Magnetization and transport measurements indicate a possible multiferroic behavior in the bilayer. We found an increase in the Curie and metal-insulator transition temperature in the bilayer in comparison with those for LCMO (48nm)/STO. Hysteresis loops on bilayers show ferromagnetic behavior. This work has been supported by the ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' Colciencias-CENM Research Projects: No. 1106-48-925531 and CI7917-CC 10510 contract 0002-2013 COLCIENCIAS-UNIVALLE.

  13. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption.

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%-95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

  14. Effects of adding HfO2 on the microstructure and dielectric properties of giant dielectric constant ceramic CaCu3Ti4O12

    Science.gov (United States)

    Yuan, W. X.; Hark, S. K.

    2010-03-01

    CaCu3Ti4O12 (CCTO), an unusual perovskite-like ceramic, is known for its extraordinarily high (˜10^4) and relatively frequency independent dielectric constant. It has drawn a lot of attention recently because of its potential applications in microelectronics and microwave devices. In this investigation, HfO2 powder was added to a pre-reacted CCTO powder, which was synthesized by a conventional solid-state reaction, at different concentrations from 1 to 70 wt% and the mixture was sintered into disc-shaped ceramic samples. The effects of adding HfO2 on the microstructure and dielectric properties of CCTO ceramics were investigated. In general, we found that the dielectric constant tends to increase with HfO2 addition up to 8 wt% and then decrease with further addition. Moreover, the dielectric loss was also influenced by the addition of HfO2, and a low loss tangent of ˜0.035 was obtained. The ac conductivity, impedance, complex dielectric permittivity and electric modulus graphs were used to analyze the data. These observations were explained on the basis of the internal-barrier-layer capacitor model with Maxwell-Wagner relaxations.

  15. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors.

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Azrin Shah, Nabila Farhana; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E″/E': 0.225) and glass transition temperature (Tg: -58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials. PMID:26927116

  16. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors

    Directory of Open Access Journals (Sweden)

    Ashis Tripathy

    2016-02-01

    Full Text Available Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx, their chemical reactions and bonding with polydimethylsiloxane (PDMS were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz was obtained for the ceramic sintered at 1050 °C (S1050 and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%, viscoelastic property (tanδ = E″/E′: 0.225 and glass transition temperature (Tg: −58.5 °C were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000% and its flexible S1050/PDMS composite film (306% based humidity sensors was found to be at 100 Hz, better than conventional materials.

  17. Structure, tribocorrosion and biocide characterization of Ca, P and I containing TiO2 coatings developed by plasma electrolytic oxidation

    Science.gov (United States)

    de Viteri, V. Sáenz; Bayón, R.; Igartua, A.; Barandika, G.; Moreno, J. Esteban; Peremarch, C. Pérez-Jorge; Pérez, M. Martínez

    2016-03-01

    In hip joint implants, in particular in the stems, wear-corrosion effects can accelerate the degradation of the biomaterial. The lack of osseointegration and the risk of contracting implant-associated infections may be other reasons for a premature failure of the implant. In this work, TiO2 coatings have been developed by means of plasma electrolytic oxidation (PEO) technique in order to achieve wear-resistant hard coatings with osseointegration ability and biocide characteristics. During the PEO process, elements that favor cell growth, like Ca and P, were introduced into the coating. With the purpose of providing the coating with antibacterial properties iodine was added like biocide agent. The microstructure and chemical composition of the developed coatings were analyzed in order to see if the surface of the films was suitable for the cell attachment. The effect of wear-corrosion synergy was studied by means of tribocorrosion tests. Finally, the biocide capacity of iodine against Staphylococcus aureus and Staphylococcus epidermidis was analyzed through bacterial adhesion tests. High wear and corrosion resistance was shown in one of the developed coatings. The achieved surface microstructures seem to be appropriate to improve the osseointegration with proper pore size and porosity index. The antibacterial capacity of iodine was confirmed for S. epidermidis.

  18. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

  19. Relativistic fine structure oscillator strengths for Li-like ions C IV - Si XII, S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, and Ni XXVI

    CERN Document Server

    Nahar, S N

    2002-01-01

    Ab initio calculations including relativistic effects employing the Breit-Pauli R-matrix (BPRM) method are reported for fine structure energy levels and oscillator strengths upto n = 10 and 0.leq. l .leq.9 for 15 Li-like ions: C IV, N V, O VI, F VII, Ne VIII, Na IX, Mg X, Al XI, Si XII, S XIV, Ar XVI, Ca XIII, Ti XX, Cr XXII, and Ni XXVI. About one hundred bound fine structure energy levels of total angular momenta, 1/2 .leq. J .leq. 17/2 of even and odd parities, total orbital angular momentum, 0 .leq L .leq. 9 and spin multiplicity (2S+1) = 2, 4 are considered for each ion. The levels provide almost 900 dipole allowed and intercombination bound-bound transitions. The BPRM method enables consideration of large set of transitions with uniform accuracy compared to the best available theoretical methods. The CC eigenfunction expansion for each ion includes the lowest 17 fine structure energy levels of the core configurations 1s^2, 1s2s, 1s2p, 1s3s, 1s3p, and 1s3d. The calculated energies of the ions agree with ...

  20. Fabrication of TiO2-strontium loaded CaSiO3/biopolymer coatings with enhanced biocompatibility and corrosion resistance by controlled release of minerals for improved orthopedic applications.

    Science.gov (United States)

    Raj, V; Raj, R Mohan; Sasireka, A; Priya, P

    2016-07-01

    Titanium dioxide (TiO2) arrays were fabricated on Ti alloy by anodization method. Synthesis of CaSiO3 (CS) and various concentrations (1X-5X) of Sr(2+) substitutions in CS coatings on TiO2 substrate was achieved through an electrophoretic deposition technique. Fast release of mineral ions from implant surface produce over dosage effect and it is a potential hazardous factor for osteoblasts. So, in order to prevent the fast release of minerals, biopolymer coating was applied above the composite coatings. The coatings were characterized by FTIR, XRD, FE-SEM and EDX techniques. The mechanical, anticorrosion, antimicrobial properties and biocompatibility of the coatings were evaluated. Studies on the mechanical properties indicate that the addition of Sr(2+) and biopolymer increase the hardness strength of the coatings. The metal ion release from the coatings was studied by ICP-AES. The electrochemical properties of the coatings were studied in Ringer's solution, in which CS-3X/Chi-PVP coating on TiO2 exhibits good anticorrosion property and high resistivity against Escherichia coli and Staphylococcus aureus compared to CS-3X coating on TiO2. In vitro cell experiments indicate that osteoblasts show good adhesion and high growth rates for CS-3X/Chi-PVP coated TiO2 substrate, indicating that the surface cytocompatibility of CS-3X/Chi-PVP coated TiO2 substrate is significantly improved by the controlled release of mineral ions. In conclusion, the surface modification of TiO2/CS-3X/Chi-PVP coated titanium is a potential candidate for implant coating. PMID:27018944

  1. Burovaite-Ca, (Na,K)4Ca2(Ti,Nb)8[Si4O12]4(OH,O)8·12H2O, a new labuntsovite-group mineral species and its place in low-temperature mineral formation in pegmatites of the Khibiny pluton, Kola Peninsula, Russia

    Science.gov (United States)

    Azarova, Yu. V.; Shlyukova, Z. V.; Zolotarev, A. A.; Organova, N. I.

    2009-12-01

    This paper presents data on burovaite-Ca, the first Ti-dominant member of the labuntsovite group with a calcium D-octahedron. The idealized formula of burovaite-Ca is (K,Na)4Ca2(Ti,Nb)8[Si4O12]4(OH,O)8 · 12H2O. The mineral has been found in the hydrothermal zone of aegirine-microcline pegmatite located in khibinite at Mt. Khibinpakhkchorr, the Khibiny pluton, Kola Peninsula, Russia. Radiaxial intergrowths of burovaite-Ca and labuntsovite-Mn associated with lemmleynite-Ba, analcime, and apophyllite have been identified in caverns within microcline. The mean composition of the mineral is as follows, wt %: 3.72 Na2O, 2.76 K2O, 4.22 CaO, 0.47 SrO, 0.23 BaO, 0.01 MnO, 0.30 Fe2O3, 0.14 Al2O3, 42.02 SiO2, 17.30 TiO2, 15.21 Nb2O5, 12.60 H2O (measured); the total is 98.98. Its empirical formula has been calculated on the basis of [(Si,Al)16O48]: {(Na3.10K1.07Ca0.37Sr0.04Ba0.04)4.62}(Ca1.28Zn0.01)1.29(Ti4.97Nb2.56Fe0.08Ta0.02)7.63(Si15.93Al0.07)16O48(OH6.70O0.93)7.63 · 12H2O. The strongest lines in the X-ray powder diffraction pattern of burovaite-Ca ( I-d Å] are as follows: 70-7.08, 40-6.39, 40-4.97, 30-3.92, 40-3.57, 100-3.25, 70-3.11, 50-2.61, 70-2.49, 40-2.15, 50-2.05, 70-1.712, 70-1.577, and 70-1.444. The structure of burovaite-Ca was solved by A.A. Zolotarev, Jr. The mineral is monoclinic, space group C2/ m. The unit-cell dimensions are a = 14.529(3), b = 14.203(3), c = 7.899(1), β = 117.37(1)°, V = 1447.57 Å3. Burovaite-Ca is an isostructural Ti-dominant analogue of karupmøllerite-Ca and gjerdingenite-Ca. Two stages of mineral formation—pegmatite proper and hydrothermal—have been recognized in the host pegmatite. The hydrothermal stage included K-Ba-Na, Na-K-Ca, and Na-Sr substages. Burovaite-Ca is related to the intermediate Na-K-Ca substage. At the first substage, labuntsovite-Mn and lemmleynite-Ba were formed, and tsepinite-Na, paratsepinite-Nd, and tsepinite-Sr were formed at the final substage. Thus, the sequence of crystallization of labuntsovite

  2. A percepção dos gestores operacionais sobre os impactos gerados nos processos de trabalho após a implementação das melhores práticas de governança de TI no TRE/SC

    Directory of Open Access Journals (Sweden)

    Rosangela Klumb

    2014-08-01

    Full Text Available Este estudo objetivou compreender a percepção dos gestores operacionais da Secretaria de Tecnologia da Informação (STI do TRE/SC acerca dos impactos gerados nos processos de trabalho internos do órgão após a implementação das melhores práticas de governança de TI. Em termos metodológicos, trata-se de um estudo de caso descritivo-avaliativo, de abordagem qualitativa no que concerne às características e ao modo de investigação. Como resultados, verificou-se que até março de 2013 foram implementados oito dos 24 processos de governança de TI baseados no modelo Cobit, versão 4.1, definidos como meta do Planejamento Estratégico de TI para 2013. Concluiu-se que a percepção dos gestores é positiva em relação à governança de TI, embora existam algumas falhas, como na comunicação intra e interáreas e na centralização de informações por alguns setores.

  3. Study of LiF:Mg,Ti and CaSO4:Dy dosimeters TL response to electron beams of 6 MeV applied to radiotherapy using PMMA and solid water phantoms

    International Nuclear Information System (INIS)

    The performance of CaSO4:Dy and LiF:Mg,Ti dosimeters to electron beams applied to radiotherapy was investigated. The TL response of these dosimeters was studied for 6 MeV electron beams using PMMA and Solid Water (SW) phantoms. The dosimeters were previously separated in groups according to their TL individual sensitivities to 60Co gamma-radiation in air under electronic equilibrium conditions. After that, they were irradiated with 6 MeV electron doses of 0.1, 0.5, 1, 5 and 10 Gy using a linear accelerator Clinac 2100C Varian of Hospital Israelita Albert Einstein – HIAE. The electron beam irradiations were performed using a 10 × 10 cm2 field size, 100 cm source-phantom surface distance and the dosimeters were positioned at the depth of maximum dose (1.2 cm). The TL readings were carried out between 24 and 32 h after irradiation using a Harshaw 3500 TL reader. The TL dose–response of both type of dosimeters and phantoms presented linear behavior on the electron dose range from 0.1 to 5 Gy CaSO4:Dy dosimeter is 21 times more sensitive than LiF:Mg,Ti, dosimeter commonly used in clinical dosimetry. The obtained results indicate that the performance of CaSO4:Dy dosimeters is similar to LiF:Mg,Ti dosimeters and this material can be an alternative dosimetric material to be used to clinical electron beams dosimetry.

  4. Influence of secondary phases on phase and microwave dielectric properties of new Ca{sub 2}Ce{sub 2}Ti{sub 5}O{sub 16} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Manan, Abdul, E-mail: drmanan82@yahoo.com, E-mail: samiullah685@yahoo.com; Khan, Sami Ullah, E-mail: drmanan82@yahoo.com, E-mail: samiullah685@yahoo.com [Department of Physics, University of Science and Technology Bannu, 28100 KPK (Pakistan); Qazi, Ibrahim, E-mail: dr.ibrahim.qazi@gmail.com [Departments of Materials Science and Engineering, Institute of Space Technology, Islamabad 44000 (Pakistan)

    2014-11-05

    Ca{sub 2}Ce{sub 2}Ti{sub 5}O{sub 16} ceramics processed via mix oxide route was investigated. Phase composition and microwave dielectric properties were measured using X-ray diffraction and a cavity method, respectively. CeO{sub 2} and another unidentified phase (that vanishes at ≥1400°C) existed as secondary phases along with the parent Ca{sub 2}Ce{sub 2}Ti{sub 5}O{sub 16} phase. The amount of the parent Ca{sub 2}Ce{sub 2}Ti{sub 5}O{sub 16} phase increased with increasing sintering temperature from 1350°C to 1450 °C accompanied by a decrease in the apparent density. The density decreased but ε{sub r} and Qufo increased with sintering temperature. An ε{sub r} ∼87.2, Qufo ∼5915 GHz and τ{sub f} ∼219 GHz was achieved for the sample sintered at 1450°C.

  5. (La2/5Ba2/5Ca1/5)(Mn(2/5)–NiTi3/5)O3: Rietveld studies, dielectric and magnetic properties of new perovskite-related oxides

    Indian Academy of Sciences (India)

    Pika Jha; Saroj L Samal; Kandalam V Ramanujachary; Samuel E Lofland; Ashok K Ganguli

    2005-10-01

    Oxides of the type (La2/5Ba2/5Ca1/5)(Mn(2/5)–NiTi3/5)O3 (0 ≤ ≤ 0.4) have been synthesized by the ceramic route. All the above oxides have been found to crystallize in the cubic perovskite structure. Rietveld refinement of the Ni-based oxide, (La2/5Ba2/5Ca1/5)(Ni2/5Ti3/5)O3 gave rise to a composition (La0.44Ba0.38Ca0.18) (Ni0.42Ti0.58)O2.85(6) and the refined lattice parameter obtained was 3.9411(2) Å (space group $\\bar{3}$; (2) = 0.026, p = 0.074, p = 0.087). A shift from antiferromagnetic to paramagnetic behaviour is observed with increase in nickel concentration, the Mn-rich phases showing antiferromagnetism around 5 K. There is a systematic decrease in the dielectric constant, and loss tangent with increase in Ni concentration (from = 592 for = 0 to = 78 for = 0.4).

  6. Microstructure and Microwave Dielectric Properties of (1-x)MgAl2O4-x(Ca0.8Sr0.2)TiO3 Ceramics

    Science.gov (United States)

    Huang, Yafei; Yu, Jun; Shen, Chunying; Tang, Mingliang

    2016-06-01

    The microwave dielectric properties of the (1-x)MgAl2O4-x(Ca0.8Sr0.2)TiO3 (x = 0.02 to 0.10) ceramic system synthesized by the traditional solid-state reaction method have been investigated. Spinel-structured MgAl2O4 was present together with perovskite-structured (Ca0.8Sr0.2)TiO3, and this multiphase system was verified by x-ray diffraction (XRD) and energy spectrum analyses throughout the whole compositional range. With increasing x, the temperature coefficient of resonant frequency (τ f) and permittivity (ɛ r) gradually increased. Consequently, near-zero τ f could be obtained for samples with x = 0.08. Excellent microwave dielectric properties with relative permittivity (ɛ r) of 10.92, quality factor (Q × f) of 52,563 GHz (at 12.9 GHz), and temperature coefficient of resonant frequency (τ f) of -5.6 ppm/°C were obtained for 0.92MgAl2O4-0.08(Ca0.8Sr0.2)TiO3 composite sintered at 1440°C for 3 h, making this material a promising candidate for use in global communication satellites and radar detectors.

  7. Piezoelectric properties of new ternary Bi1/2(Na, Li)1/2TiO3-(Bi1/2K1/2)TiO3-Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramics

    International Nuclear Information System (INIS)

    0.852[Bi1/2(Na1-x Lix)1/2]TiO3-0.110(Bi1/2K1/2)TiO3-0.038Ba0.85Ca0.15Ti0.90Zr0.10O3 (BNLT-BKT-BCTZ-x) new ternary piezoelectric ceramics were fabricated by the conventional solid-state method, and their piezoelectric properties as a function of the Li content were mainly investigated. A stable solid solution with a single perovskite structure has been formed, and the depolarization temperature (Td) of these ceramics was identified by using the temperature dependence of the dielectric loss. The Td value of these ceramics gradually decreases, while the Tm value increases with increasing the Li content. The dielectric constant increases and the dielectric loss decreases with increasing the Li content, and an enhanced piezoelectric behavior of d33∝223 pC/N and kp∝35.2 % has been demonstrated in these ceramics with x=0.06. (orig.)

  8. Crystal-field study for the orthorhombic Yb{sup 3+} centers in Ca{sub 3}Sc{sub 2}Ge{sub 3}O{sub 12} and Lu{sub 3}Ga{sub 5}O{sub 12} garnets

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hong-Gang, E-mail: kezhouliu@163.com; Zheng, Wen-Chen

    2015-03-25

    Highlights: • Optical and EPR spectra for CaSGG:Yb{sup 3+} and LuGG:Yb{sup 3+} garnets were explained. • The reliability and standardization of fitted CFPs were performed and discussed. • The unavailability of SPM for LuGG:Yb{sup 3+} garnet was found and analyzed briefly. - Abstract: The crystal-field modeling based on superposition model (SPM) for the orthorhombic Yb{sup 3+} centers in Ca{sub 3}Sc{sub 2}Ge{sub 3}O{sub 12} (CaSGG) and Lu{sub 3}Ga{sub 5}O{sub 12} (LuGG) garnets has been employed to explain their recent experimental optical spectroscopy. Furthermore, the electron paramagnetic resonance (EPR) principal g values for orthorhombic Yb{sup 3+} centers in LuGG garnet have been interpreted and the predicted g factors for CaSGG:Yb{sup 3+} garnet are also given. Both calculated optical spectra and EPR g factors for the two Yb{sup 3+}-doped garnets could be regarded as in reasonable agreement with the experimental ones. Two important facts about reliability and standardization of the fitted phenomenological crystal-field parameters (CFPs) have been discussed and the unexpected unavailability of direct parametric modeling by SPM for LuGG:Yb{sup 3+} garnet is also found and analyzed briefly.

  9. Formation of phases with the structure of Ca3Ga2Ge4O14 in the AO-BO2-M2O3-SiO2 systems (A = Ca, Sr, Ba; B = Ge, Ti, Sn, Zr; M = Ga, Fe, Al)

    International Nuclear Information System (INIS)

    A search was arranged for phases of the structure Ca3Ga2Ge4O14 (I), featuring promising piezoelectric properties, in the systems AO-BO2-M2O3-SiO2 (A = Ca, Sr, Ba; B = Ge, Ti, Sn, Zr; M = Ga, Fe, Al), using the method of X-ray phase analysis. In 17 systems studied phases of variable composition A3BxM2Si4-xO14 with disordered structure of I have been detected. In joins A3M2B4O14 - A3M2Si4O14 homogeneity regions have been defined, which are localized inside tetrahedron of the compositions in 14 systems with B = Ti, Sn, Zr and emerging on one of the tetrahedron faces in three Ge-systems. Thermal stability is studied and cations distribution over synthesized phases is discussed

  10. Optimization of reaction conditions for the radiolabeling of DOTA and DOTA-peptide with 44m/44Sc and experimental evidence of the feasibility of an in vivo PET generator

    International Nuclear Information System (INIS)

    Introduction: Among the number of generator systems providing radionuclides with decay parameters promising for imaging and treatment applications, there is the 44Ti (T1/2 = 60 years)/44Sc (T1/2 = 3.97 h) generator. This generator provides a longer-lived daughter for extended PET/CT measurements compared to the chemically similar system 68Ge/68Ga. Scandium also exists as 47Sc, a potential therapeutic radionuclide. It is possible to produce 44Sc in a cyclotron using, for example, the 44Ca (d, n) 44Sc nuclear reaction. In that case, the isomeric state 44mSc (T1/2 = 58.6 h) is co-produced and may be used as an in vivo44mSc/44Sc generator. The aim of this study is to evaluate the feasibility of this in vivo44mSc/44Sc generator and to demonstrate that the daughter radionuclide stays inside the chelator after decay of the parent radionuclide. Indeed, the physico-chemical process occurring after the primary radioactive decay (EC, IT, Auger electron …) has prevented in many cases the use of in-vivo generator, because of the post-effect as described in the literature. Methods: The DOTA macrocyclic ligand forms stable complexes with many cations and has been shown to be the most suitable chelating moiety for scandium. Initially, the radiolabeling of DOTA and a DOTA-peptide (DOTATATE) with Sc was performed and optimized as a function of time, pH, metal-to-ligand ratio and temperature. Next, the physico-chemical processes that could occur after the decay (post-effect) were studied. 44mSc(III)-labeled DOTA-peptide was quantitatively adsorbed on a solid phase matrix through a hydrophobic interaction. Elutions were then performed at regular time intervals using a DTPA solution at various concentrations. Finally, the radiolabelled complex stability was studied in serum. Results: Radiolabeling yields ranged from 90% to 99% for metal-to-ligand ratio ranging from 1:10 to 1:500 for DOTA or DOTATATE respectively. The optimum physico-chemical parameters were pH = 4–6, t = 20 min, T

  11. An orange emitting phosphor Lu2−xCaMg2Si2.9Ti0.1O12:xCe with pure garnet phase for warm white LEDs

    International Nuclear Information System (INIS)

    A new silicate garnet phosphor, Lu2−xCaMg2Si2.9Ti0.1O12:xCe was synthesized by a high temperature solid-state reaction under reductive atmosphere. X-ray diffraction (XRD) showed that the powder was pure garnet phase. The emission and excitation spectrum indicated that the Lu2−xCaMg2Si2.9Ti0.1O12:xCe phosphors could absorb blue light in the spectral range of 400–550 nm efficiently and exhibit bright yellow–orange emission in the range of 520–750 nm. With the increase of Ce3+ concentration, the emission band of Ce3+ showed a red shift. Interestingly, the concentration quenching occurred when the Ce3+ concentration exceeded 4 mol%. The temperature-dependent luminescent properties of the phosphors were discussed and the Lu1.96CaMg2Si2.9Ti0.1O12:0.04Ce phosphors showed good performances in color temperature (2430 K) and potential applications for warm white LEDs. - Graphical Abstract: This image shows that the phosphor of Lu1.96CaMg2Si2.9Ti0.1O12:0.04Ce can generate a uniform yellow tint under natural light illumination and emit orange–red light when excited by blue light. With a fixed 467 nm emission light, warm white light can be produced by this phosphor, which indicates that the phosphor is potentially applicable in warm white light emitting diodes based on GaN chips. - Highlights: • A new silicate garnet phosphor was synthesized by solid-state method. • Secondary phases can be avoided when a small amount of Si4+ were replaced by Ti4+. • A broad emission band of Ce3+ in the phosphors was described. • The phosphors are potentially applicable in warm white light emitting diodes

  12. Influence of the sintering temperature on the Sr content in a Ca(1-x-y)CexSryAlzTi(1-z)O3 perovskite (x = 0.04-0.16) co-doped with Ce

    Science.gov (United States)

    Kamel, Nour-el-hayet; Mouheb, Yasmina; Kamel, Ziane; Moudir, Dalila; Aouchiche, Fairouz; Arabi, Azeddine

    2016-08-01

    A Sr-Ce co-doped perovskite, with the chemical formula: Ca(1-x-y)CexSryAlzTi(1-z)O3 (y = 0.04, 0.08, 0.12 and 0.16, x = 0.05) is synthesized by sol-gel process. The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. The Sr amount sequestered in the perovskite reaches 85% (y = 0.16, 9.50 wt%) for Ts = 1373 K, giving sintering densities between 3.520 and 4.400. XRD analysis reveals an orthorhombic CaTiO3 structure. The lattice parameters obey to Vegard's law for Ts = 1373 and 1473 K. SEM analysis shows orthorhombic grains of 0.514 μm × 1 μm mean dimensions. MCC1 and MCC2 tests, performed on minerals sintered at 1373 K, indicate that the most durable one is that containing 9.50 wt% Sr. MCC1 test gave 6.998·10-6 g/cm2 d of Sr, and MCC2 2.143·10-4 g/cm2 d of Ce. The temperature favors the Sr dissolution to the detriment of Ce. The Ca dissolution rate reaches 1.002·10-6 to 2.005·10-6 g/cm2 d.

  13. Magnesium and cadmium in covalently bonded networks. Synthesis and structure of AETMg and AETCd (AE = Ca, Sr; T = Pd, Ag, Pt, Au) with TiNiSi type structure and the solid solution Yb2-xPtMgx

    International Nuclear Information System (INIS)

    The equiatomic intermetallic compounds AETMg and AETCd (AE = Ca, Sr; T = Pd, Ag, Pt, Au) and the whole solid solution Yb2-xPtMgx were synthesized from the elements in sealed niobium tubes in a high-frequency or a muffle furnace. All samples were characterized on the basis of their powder X-ray diffraction patterns. The structures of SrAuCd, CaPdCd, CaPtCd, CaPdMg, SrPtMg, CaAg1.017Mg0.983, SrAg1.032Mg0.968, and Yb1.792PtMg0.208 were refined on the basis of single-crystal X-ray diffractometer data. Some of the crystals showed small homogeneity ranges. All compounds crystallize with the orthorhombic TiNiSi type structure, space group Pnma. The crystal chemistry is briefly discussed and variations in chemical bonding as a result of the electronegativity of the transition metal are described. (orig.)

  14. Application of the Functional Theory in studying the adsorption of carbon monoxide on the TiO2 rutile surface of 110, defected surface and the surface modified by some metallic ions

    International Nuclear Information System (INIS)

    Density functional theory (DFT) is used to investigate properties of TiO2 (110) surface with defects and metal-doped TiO2. The results of our calculations of structure of TiO2 surface have been shown in good agreement with those of experiments and other ab-initio calculations. The differences of band structure between TiO2 (110) and TiO2 surface defected show that visible light can excite surface with defects easily. We also investigate density of states (DOS) of metal-doped surface (Li, Ca, Sc, V, Mo, Mn, Fe, Co, Ni) and find that the Mo-doped surface has very small band gap (∼ 0 eV). This surface may have higher photo-chemical activity in visible light. (author)

  15. Fabrication of (111)-oriented Ca{sub 0.5}Sr{sub 0.5}IrO{sub 3}/SrTiO{sub 3} superlattices—A designed playground for honeycomb physics

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, Daigorou [Department of Physics, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Matsuno, Jobu [RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198 (Japan); Takagi, Hidenori [Department of Physics, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Max-Plank-Institute for solid state research, Heisenbergstrasse 1, Stuttgart 70569 (Germany)

    2015-04-01

    We report the fabrication of (111)-oriented superlattice structures with alternating 2m-layers (m = 1, 2, and 3) of Ca{sub 0.5}Sr{sub 0.5}IrO{sub 3} perovskite and two layers of SrTiO{sub 3} perovskite on SrTiO{sub 3}(111) substrates. In the case of m = 1 bilayer films, the Ir sub-lattice is a buckled honeycomb, where a topological state may be anticipated. The successful growth of superlattice structures on an atomic level along the [111] direction was clearly demonstrated by superlattice reflections in x-ray diffraction patterns and by atomically resolved transmission electron microscope images. The ground states of the superlattice films were found to be magnetic insulators, which may suggest the importance of electron correlations in Ir perovskites in addition to the much discussed topological effects.

  16. Low-temperature sintered ZnNb{sub 2}O{sub 6}–CaTiO{sub 3} ceramics with near-zero τ{sub f}

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Mei; Li, Yuxia [Key Laboratory for Robot and Intelligent Technology of Shandong Province, College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590 (China); Dou, Gang, E-mail: dougang521@163.com [Key Laboratory for Robot and Intelligent Technology of Shandong Province, College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590 (China); Gong, Shuping [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-10-15

    The phases, microstructure and microwave dielectric properties of ZnNb{sub 2}O{sub 6}–xCaTiO{sub 3} ceramics with BaCu(B{sub 2}O{sub 5}) glass additions prepared by solid state reaction method were charactered by using X-ray diffraction, Scanning electron microscopy and Advantest network analyzer. The τ{sub f} of ZnNb{sub 2}O{sub 6} was modified to near 0 ppm °C{sup −1} by incorporating CaTiO{sub 3} with opposite τ{sub f} values on the basis of Lichtenecker empirical rule. The microwave dielectric properties of ZnNb{sub 2}O{sub 6}–xCaTiO{sub 3} (x = 8.0 wt.%) samples with BaCu(B{sub 2}O{sub 5}) glass additives sintered in 900–1000 °C were investigated, and the results indicated that the behaviors of the ε{sub r} and Q × f were associated with the sintering temperature and the amount of BaCu(B{sub 2}O{sub 5}) glass. The sintering temperature of the ceramics was reduced to 950 °C from 1175 °C. Addition of 5.0 wt.% BaCu(B{sub 2}O{sub 5}) glass in ZnNb{sub 2}O{sub 6}–xCaTiO{sub 3} (x = 8.0 wt.%) ceramics sintered at 950 °C showed excellent dielectric properties of ε{sub r} = 20.2, Q × f = 14,100 GHz (f = 7.3 GHz) and τ{sub f} = 0 ppm °C{sup −1}. Moreover, the material had a chemical compatibility with silver, which represented a promising candidate materials for low-temperature-co-fired ceramics applications. - Highlights: • The τ{sub f} of ZnNb{sub 2}O{sub 6} was modified to near 0 ppm °C{sup −1} by incorporating CaTiO{sub 3}. • The sintering temperature of ZnNb{sub 2}O{sub 6}–xCaTiO{sub 3} ceramics with BCB was reduced to 950 °C. • The good dielectric properties of ε{sub r} = 20.2, Q × f = 14,100 GHz, τ{sub f} = 0 ppm °C{sup −1} were achieved. • It represented a promising candidate materials for LTCC applications.

  17. Structural properties of CaTi1-x(Nb2/3Li2/3)xO3-δ (CNLTO) and CaTi1-x(Nb1/2Ln1/2)xO3 (Ln=Fe (CNFTO), Bi (CNBTO)), modified dielectric ceramics for microwave applications

    International Nuclear Information System (INIS)

    This paper presents an investigation of the structural characteristics of Nb1/2Bi1/2 (CNBTO), Nb1/2Fe1/2 (CNFTO) and Nb2/3Li1/3 (CNLTO) substitution into the B-site of calcium titanate ceramics. The modified CaTiO3 (CTO) ceramics were prepared by the conventional solid-state method. The compounds were investigated, by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDXS). The X-ray analysis shows that all samples have an orthorhombic structure. The refinement analysis of all samples were also performed and discussed in this paper. For all studied samples, a Raman mode at 805 cm-1 was detected and its intensity increases as the substitution increases. The dielectric permittivity and loss at microwave frequencies (MW) were investigated. The CNLTO phase, present the highest dielectric constant (k=35.8) at 3.9 GHz with loss (tg α=7x10-3). The lowest value of k=25.7 (f=4.8 GHz) and tg α=3x10-3, was obtained for the CNFTO phase. These measurements confirm the possible use of such material for microwave devices like dielectric resonator antennas.

  18. CaCu{sub 3}Ti{sub 4}O{sub 12} thin films on conductive oxide electrode: A comparative study between chemical and physical vapor deposition routes

    Energy Technology Data Exchange (ETDEWEB)

    Catalano, Maria R.; Malandrino, Graziella [Dipartimento di Scienze Chimiche, Universita di Catania, and INSTM, UdR Catania, Viale A. Doria 6, 95125 Catania (Italy); Bongiorno, Corrado [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy); Toro, Roberta G. [Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Via dei Taurini, 19, 00185 Roma (Italy); Fiorenza, Patrick [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy); Bodeux, Romain [Laboratoire LEMA, UMR 6157 CNRS/CEA, Universite F. Rabelais, Parc de Grandmont, 37200 Tours (France); STMicroelectronics, R and D, Rue Pierre et Marie Curie, 37000 Tours (France); Wolfman, Jerome; Gervais, Monique; Lambert, Cecile Autret; Gervais, Francois [Laboratoire LEMA, UMR 6157 CNRS/CEA, Universite F. Rabelais, Parc de Grandmont, 37200 Tours (France); Lo Nigro, Raffaella, E-mail: raffaella.lonigro@imm.cnr.it [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Dielectrics growth and characterization is one of the most hot topics of materials science and microelectronics. Black-Right-Pointing-Pointer CaCu{sub 3}Ti{sub 4}O{sub 12} perovskite, recently, demonstrated to possess peculiar dielectric properties (Science, 2001, 293, 673-676). Black-Right-Pointing-Pointer To date no deep discussion on the growth processes, properties and perspective of CCTO thin films has been proposed. Black-Right-Pointing-Pointer Our paper is an effective example of interdisciplinarity, since the comparison between PLD and MOCVD has been addressed. Black-Right-Pointing-Pointer Great attention has been paid to CaCu{sub 3}Ti{sub 4}O{sub 12} film/substrate interfaces since dielectric properties are strongly affected. - Abstract: Metal Organic Chemical Vapor Deposition (MOCVD) and Pulsed Laser Deposition (PLD) techniques have been used for the growth of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) thin films on La{sub 0.9}Sr{sub 1.1}NiO{sub 4}/LaAlO{sub 3} (LSNO/LAO) stack. (1 0 0) oriented CCTO films have been formed through both deposition routes and film complete structural and morphological characterizations have been carried out using several techniques (X-ray diffraction, scanning electron microscopy, energy-filtered transmission electron microscopy). The comparative study demonstrated some differences at the CCTO/LSNO interfaces depending on the adopted deposition technique. Chemical/structural modification of the LSNO electrode probably occurred as a function of the different oxygen partial pressure used in the PLD and MOCVD processes.

  19. Trends in electronic structures and structural properties of MAX phases: a first-principles study on M(2)AlC (M = Sc, Ti, Cr, Zr, Nb, Mo, Hf, or Ta), M(2)AlN, and hypothetical M(2)AlB phases.

    Science.gov (United States)

    Khazaei, Mohammad; Arai, Masao; Sasaki, Taizo; Estili, Mehdi; Sakka, Yoshio

    2014-12-17

    MAX phases are a large family of layered ceramics with many potential structural applications. A set of first-principles calculations was performed for M(2)AlC and M(2)AlN (M = Sc, Ti, Cr, Zr, Nb, Mo, Hf, or Ta) MAX phases as well as for hypothetical M(2)AlB to investigate trends in their electronic structures, formation energies, and various mechanical properties. Analysis of the calculated data is used to extend the idea that the elastic properties of MAX phases can be controlled according to the valence electron concentration. The valence electron concentrationcan be tuned through the various combinations of transition metal and nonmetal elements. PMID:25419878

  20. Magnetic and charge ordering properties of Bi0.2Ca0.8Mn0.9X0.1O3 (where X = Ti, Cr, Fe, Co, Ni, Cu)

    International Nuclear Information System (INIS)

    Highlights: ► Structural, magnetic and transport properties of Bi0.2Ca0.8Mn0.9X0.1O3 (where X = Ti, Cr, Fe, Co, Ni, Cu) have been studied. ► TCO decreases by ∼10 K and ∼33 K, in Ni2+ and Cu2+ doped samples, while it increases by 42 K in Ti4+ doped sample. ► In case of Fe3+, Co3+ and Cr3+ doped samples charge-ordering (CO) completely disappears. ► Furthermore, the enhancement in resistivity in all the doped samples with respect to undoped one has been observed. ► The magnetic exchange interactions between Mn and doped ions explain magnetic and electrical properties. - Abstract: Structural, magnetic and transport properties of Bi0.2Ca0.8Mn0.9X0.1O3 (where X = Ti, Cr, Fe, Co, Ni, Cu) have been investigated. The parent sample Bi0.2Ca0.8MnO3 (BCMO) exhibits robust charge-ordered antiferrromagnetic (COAFM) phase with charge ordering temperature (TCO) ∼155 K and AFM Neel temperature (TN) ∼105 K. TCO decreases by ∼10 K and ∼33 K, respectively, in Ni2+ and Cu2+ doped samples, while it increases by 42 K in Ti4+ doped sample. In case of Fe3+, Co3+ and Cr3+ doped samples charge-ordering (CO) completely melts. The paramagnetic (PM) to ferromagnetic (FM) transition temperatures (TC) of doped samples have lower values as compared to undoped one. In addition, a spin glass (SG) state is observed in all the samples and the magnetic state at T C is akin to a cluster glass (CG) for undoped and Ni, Cu, Ti doped samples formed due to the presence of FM clusters in COAFM matrix. Furthermore, the enhancement in resistivity in all the doped samples with respect to undoped one has been observed. Based on the present study it has been proposed that the disorder induced by doping on the Mn site and magnetic exchange interactions between Mn and doped ions play a key role in explaining magnetic and electrical properties.

  1. New tumor-associated antigen SC6 in pancreatic cancer

    Institute of Scientific and Technical Information of China (English)

    Min-Pei Liu; Xiao-Zhong Guo; Jian-Hua Xu; Di Wang; Hong-Yu Li; Zhong-Min Cui; Jia-Jun Zhao; Li-Nan Ren

    2005-01-01

    AIM: To examine the concentration of a new antigen SC6 (SC6-Ag) recognized by monoclonal antibody (MAb)in patients with pancreatic cancer and other malignant or benign diseases and to understand whether SC6-Ag has any clinical significance in distinguishing pancreatic cancer from other gastrointestinal diseases.METHODS: Six hundred and ninety-five serum specimens obtained from 115 patients with pancreatic cancer, 154 patients with digestive cancer and 95patients with non-digestive cancer were used and classified in this study. Serum specimens obtained from 140 patients with benign digestive disease and 89 patients with non-benign digestive disease served as controls. Ascites was tapped from 16 pancreatic cancer patients, 19 hepatic cancer patients, 16 colonic cancer patients, 10 gastric cancer and 6 severe necrotic pancreatitis patients. The samples were quantitated by solid-phase radioimmunoassay. The cut-off values (CV)of 41, 80, and 118 U/mL were used.RESULTS: The average intra- and interassay CV detected by immunoradiometric assay of SC6-Ag was 5.4% and 8.7%, respectively. The sensitivity and specificity were 73.0% and 90.9% respectively. The levels in most malignant and benign cases were within the normal upper limit. Among the 16 pancreatic cancer cases, the concentration of SC6-Ag in ascites was over the normal range in 93.8% patients. There was no significant difference in the concentration of SC6-Ag.Decreased expression of SC6-Ag in sera was significantly related to tumor differentiation. The concentration of SC6-Ag was higher in patients before surgery than after surgery. The specificity of SC6-Ag and CA19-9 was significantly higher than that of ultrasound and computer tomography (CT) in pancreatic cancer patients. Higher positive predictive values were indicated in 92.3% SC6-Ag and 88.5% CA19-9, but lower in 73.8% ultrasound and 76.2% CT.CONCLUSION: The combined test of SC6-Ag and CA19-9 may improve the diagnostic rate of primary cancer. The detection of

  2. Structural studies of CaAl{sub 12}O{sub 19}, SrAl{sub 12}O{sub 19}, La{sub 2/3+δ}Al{sub 12-δ}O{sub 19}, and CaAl{sub 10}NiTiO{sub 19} with the hibonite structure; indications of an unusual type of ferroelectricity

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jun; Medina, Elena A.; Sleight, Arthur W.; Subramanian, M.A. [Oregon State University, Corvallis, OR (United States). Dept. of Chemistry; Stalick, Judith K. [National Institute of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research

    2016-08-01

    Various oxides with the hibonite structure were synthesized and structurally analyzed using powder neutron diffraction. The structure of CaAl{sub 12}O{sub 19} at 298 and 11 K shows dipoles that are apparently too dilute to order unless subjected to a suitable electric field. Magnetoplumbites, such as BaFe{sub 12}O{sub 19}, are isostructural with hibonite. These compounds possess ferromagnetic properties, which combined with the electric dipoles may influence multiferroic behavior. Our SrAl{sub 12}O{sub 19} sample showed two distinct hexagonal phases, a major phase with the normal hibonite structure and a minor phase having a closely related structure. Our sample of the defect hibonite phase La{sub 2/3+δ}Al{sub 12-δ}O{sub 19} shows a distinctly higher δ value (0.25) vs. that reported (∝ 0.15) for samples made from the melt. Finally, we used to advantage the negative scattering length of Ti to determine the site occupancies of Ni and Ti in CaAl{sub 10}NiTiO{sub 19}.

  3. SC tuning fork

    CERN Multimedia

    The tuning fork used to modulate the radiofrequency system of the synchro cyclotron (SC) from 1957 to 1973. This piece is an unused spare part. The SC was the 1st accelerator built at CERN. It operated from August 1957 until it was closed down at the end of 1990. In the SC the magnetic field did not change with time, and the particles were accelerated in successive pulses by a radiofrequency voltage of some 20kV which varied in frequency as they spiraled outwards towards the extraction radius. The frequency varied from 30MHz to about 17Mz in each pulse. The tuning fork vibrated at 55MHz in vacuum in an enclosure which formed a variable capacitor in the tuning circuit of the RF system, allowing the RF to vary over the appropriate range to accelerate protons from the centre of the macine up to 600Mev at extraction radius. In operation the tips of the tuning fork blade had an amplitude of movement of over 1 cm. The SC accelerator underwent extensive improvements from 1973 to 1975, including the installation of a...

  4. Homogeneous interface-type resistance switching in Au/La0.67Ca0.33MnO3/SrTiO3/F(:)SnO2heterojunction memories

    Institute of Scientific and Technical Information of China (English)

    Zhang Ting; Ding Ling-Hong; Zhang Wei-Feng

    2012-01-01

    La0.67Ca0.33MnO3 thin films are fabricated on fluorine-doped tin oxide conducting glass substrates by a pulsed laser deposition technique with SrTiO3 used as a buffer layer.The current-voltage characteristics of the heterojunctions exhibit an asymmetric and resistance switching behaviour.A homogeneous interface-type conduction mechanism is also reported using impedance spectroscopy.The spatial homogeneity of the charge carrier distribution leads to fieldinduced potential-barrier change at the Au-La0.67Ca0.33MnO3 interface and a concomitant resistance switching effect.The ratio of the high resistance state to the low resistance state is found to be as high as 1.3 × 104% by simulating the AC electric field.This colossal resistance switching effect will greatly improve the signal-to-noise ratio in nonvolatile memory applications.

  5. Electrical and piezoelectric properties of BiFeO3 thin films grown on SrxCa1−xRuO3-buffered SrTiO3 substrates

    KAUST Repository

    Yao, Yingbang

    2012-06-01

    (001)-oriented BiFeO 3 (BFO) thin films were grown on Sr xCa 1-xRuO 3- (SCRO; x = 1, 0.67, 0.33, 0) buffered SrTiO 3 (001) substrates using pulsed laser deposition. The microstructural, electrical, ferroelectric, and piezoelectric properties of the thin films were considerably affected by the buffer layers. The interface between the BFO films and the SCRO-buffer layer was found to play a dominant role in determining the electrical and piezoelectric behaviors of the films. We found that films grown on SrRuO 3-buffer layers exhibited minimal electrical leakage while films grown on Sr 0.33Ca 0.67RuO 3-buffer layers had the largest piezoelectric response. The origin of this difference is discussed. © 2012 American Institute of Physics.

  6. Angular properties of pure and Ca-substituted YBa2Cu3O7-δ superconducting thin films grown on SrTiO3 and CeO2 buffered Al2O3 substrates

    International Nuclear Information System (INIS)

    In this work transport properties of superconducting 10 at.% Ca-substituted YBCO thin films grown on (1 0 0)-SrTiO3 single crystal substrate (STO) and superconducting pure and 10 at.% Ca-substituted YBCO thin films grown on CeO2 buffered Al2O3 substrates (CAO) have been analyzed as a function of the temperature, applied magnetic field and angle between magnetic field direction and the direction normal to the film surfaces. Particularly, the angular analysis provides an easy way to discriminate between isotropic point defects and correlated pinning sites. Despite the intragrain pinning mechanisms remained unaffected by Ca substitution, a detrimental effect on grain boundary properties clearly emerged for 10 at.% Ca concentration. This effect is enhanced in sample grown on CeO2 buffered sapphire where a more disturbed grain boundary is expected resulting in an enhancement of the correlated pinning, already observed in pure YBCO films grown on CAO, and in a reduction of the intrinsic pinning efficiency

  7. Determination of self attenuation coefficient and relative TL efficiency of CaSO{sub 4}:Dy, LiF:Mg,Cu,P and LiF:Mg,Ti TLDs - An alternate approach

    Energy Technology Data Exchange (ETDEWEB)

    Bakshi, A.K., E-mail: akbakshi123@yahoo.com; Chatterjee, S.; Palani Selvam, T.; Joshi, V.J.; Chougaonkar, M.P.

    2011-10-01

    Highlights: {yields} Relative TL efficiency in the energy range 10-34 keV has been determined using an alternate approach for CaSO{sub 4}:Dy disc, MTS disc and MCP-N chip. {yields} For CaSO{sub 4}:Dy disc, it was found that light attenuation coefficient increases with the proportion of CaSO{sub 4}:Dy phosphor in the disc. {yields} The light attenuation coefficient of MTS disc and MCP-N chip was found to be 23.4 and 45.5 cm{sup -1}, respectively. {yields} Relative TL efficiency in the photon energy range of 10-34 keV for MTS discs and MCP-N chips matches well with the reported values in the literature. - Abstract: Self attenuation of TL and relative TL efficiency of polytetra fluoro ethylene (PTFE) embedded CaSO{sub 4}:Dy disc, LiF:Mg,Ti (MTS) disc and LiF:Mg,Cu,P (MCP-N) chip were determined in the present study for photons of energy 10-34 keV. The relative TL efficiency was determined using an alternative approach in which ratio of experimental response and corrected theoretical response was used instead of measuring the absolute TL emission in photon counting mode. For CaSO{sub 4}:Dy disc, it was found that with increasing the proportion of CaSO{sub 4}:Dy phosphor in the disc, the light attenuation coefficient increases. The light attenuation coefficient of MTS disc and MCP-N chip was found to be 23.4 and 45.5 cm{sup -1}, respectively. The relative TL efficiency in the photon energy range of 10-34 keV for MTS discs and MCP-N chips, evaluated in the present study matches well with the reported values in the literature.

  8. Cyclotron production of 44Sc: From bench to bedside

    International Nuclear Information System (INIS)

    Introduction: 44Sc, a PET radionuclide, has promising decay characteristics (T1/2 = 3.97 h, Eβ+av = 632 keV) for nuclear imaging and is an attractive alternative to the short-lived 68Ga (T1/2 = 68 min, Eβ+av = 830 keV). The aim of this study was the optimization of the 44Sc production process at an accelerator, allowing its use for preclinical and clinical PET imaging. Methods: 44CaCO3 targets were prepared and irradiated with protons (~ 11 MeV) at a beam current of 50 μA for 90 min. 44Sc was separated from its target material using DGA extraction resin and concentrated using SCX cation exchange resin. Radiolabeling experiments at activities up to 500 MBq and stability tests were performed with DOTANOC by investigating different scavengers, including gentisic acid. Dynamic PET of an AR42J tumor-bearing mouse was performed after injection of 44Sc-DOTANOC. Results: The optimized chemical separation method yielded up to 2 GBq 44Sc of high radionuclidic purity. In the presence of gentisic acid, radiolabeling of 44Sc with DOTANOC was achieved with a radiochemical yield of ~ 99% at high specific activity (10 MBq/nmol) and quantities which would allow clinical application. The dynamic PET images visualized increasing uptake of 44Sc-DOTANOC into AR42J tumors and excretion of radioactivity through the kidneys of the investigated mouse. Conclusions: The concept “from-bench-to-bedside” was clearly demonstrated in this extended study using cyclotron-produced 44Sc. Sufficiently high activities of 44Sc of excellent radionuclidic purity are obtainable for clinical application, by irradiation of enriched calcium at a cyclotron. This work demonstrates a promising basis for introducing 44Sc to clinical routine of nuclear imaging using PET

  9. Effect of doping by Bi and Ca on ferroelectric properties and relaxor character in the (Ba1-xCax)1-3y/2BiyTiO3 solid solution

    Science.gov (United States)

    Zaghouene, H.; Bahri, F.; Boujelbene, M.; Khemakhem, H.; Simon, A.

    2012-10-01

    The temperature dependence of the real and imaginary parts of dielectric permittivity for (Ba1-xCax)1-3y/2BiyTiO3 solid solution prepared using the solid-state reaction technique, suggests that the relaxor character in this solid solution depends strongly on the Bi than on the Ca doping percent.X-ray diffraction analysis show that Bi doping can be fully incorporated into the perovskite lattice of (Ba1-xCax)TiO3. Doping with Bi causes remarkable shift of the maximum of dielectric permittivity (Tm) at low temperatures and the evolution of ɛ‧r exhibiting strong frequency dispersion. For some compositions, we have observed a typical behavior of a well-known relaxors. On the other hand, we pointed out that the relaxor character is linked principally to the nature of the substituting element and not to the heterogeneity in general. So the Ca element does not have the same effect as the Bi one.

  10. Broadband near-infrared quantum-cutting by cooperative energy transfer in Yb3+–Bi3+ co-doped CaTiO3 for solar cells

    International Nuclear Information System (INIS)

    Highlights: • Broadband NIR QC CaTiO3:Yb3+,Bi3+ phosphor has been firstly developed. • Co-doping with Bi3+, it enhanced the Yb3+ emission intensity by a factor of 10. • This phosphor could efficiently convert 300–480 nm light to ∼1000 nm light. • The ET processes were involved in CET via two photons QC process. - Abstract: An efficient near-infrared (NIR) quantum-cutting (QC) process which converts broadband ultraviolet-blue into NIR via downconversion (DC) has been demonstrated in CaTiO3:Yb3+,Bi3+ phosphors for the first time. These phosphors are valuable for use in crystalline Si (c-Si) solar cells, because they efficiently convert 300–480 nm light that is not fully utilized by existing c-Si solar cells into ∼1000 nm NIR light that can be sufficiently absorbed by solar cells. Co-doping with 15% Bi3+ ions, a significant enhancement in Yb3+ NIR integrated emission intensity by a factor of 10 is realized. The phosphors were characterized with the photoluminescence excitation (PLE) and the photoluminescence (PL) spectra evidence the presence of energy transfer (ET) processes from Bi3+-related charge transfer state to Yb3+ ions. The dependence of Yb3+ luminescent intensity on the excitation power was also measured and it demonstrates that the ET processes involve cooperative energy transfer (CET) via two photons QC processes

  11. Structure and ferroelectric studies of (Ba{sub 0.85}Ca{sub 0.15})(Ti{sub 0.9}Zr{sub 0.1})O{sub 3} piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Venkata Ramana, E., E-mail: venkataramanaesk@rediffmail.com [I3N-Aveiro, Department of Physics, University of Aveiro, Aveiro 3810 193 (Portugal); Mahajan, A. [Department of Materials and Ceramics Engineering, University of Aveiro, Aveiro 3810 193 (Portugal); Graça, M.P.F.; Mendiratta, S.K.; Monteiro, J.M.; Valente, M.A. [I3N-Aveiro, Department of Physics, University of Aveiro, Aveiro 3810 193 (Portugal)

    2013-10-15

    Graphical abstract: - Highlights: • (Ba{sub 0.85}Ca{sub 0.15})(Ti{sub 0.9}Zr{sub 0.1})O{sub 3} (BCTZO) ceramic was synthesized by the ceramic method. • In situ XRD and Raman spectra showed the phase transition of BCTZO around 360 K. • The ceramics showed a tunability of 82% at 40 kV cm{sup −1} electric field. • BCTZO exhibited good quality factor of 111 at microwave frequencies. • Piezoforce microscopy studies indicated the switchability of ferroelectric domains. - Abstract: We have synthesized and studied the structural and ferroelectric properties of lead-free 0.5(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3}–0.5Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} ceramics in the temperature region of its ferroelectric transition. The synthesized material showed high dielectric constant, low loss and good pyroelectric figure of merit. From the temperature dependent X-ray diffraction measurements, we determined the tricritical point to be in the temperature range of 303–400 K. The dielectric measurements indicate a diffuse ferroelectric phase transition (DPT) around 360 K in agreement with the X-ray measurements. We studied the evolution of Raman spectra with temperature to understand the nature of phase transition in BaTiO{sub 3} (BTO) and the BCTZO. The results indicates that the transition of ferroelectric–paraelectric state is not sharp as in the case of BTO and the polar state persists through the paraelectric state. In general, our study indicates that there are ferroelectric domains of nanometer size beyond the commonly defined transition temperature. The observation of local piezoelectric hysteresis loop indicated the existence of intrinsic ferroelectric property of the ceramic at the nanoscale. The ceramics exhibited electric field tunable dielectric properties with a tunability of 82% at an applied DC field of 40 kV cm{sup −1}, low dielectric loss of 0.001 and room temperature pyroelectric coefficient of 6 × 10{sup −8} C cm{sup −2} K{sup −1} and the

  12. Formation cross sections of 43Sc, 44Sc and 46Sc isotopes in the 45Sc + 3He reaction

    International Nuclear Information System (INIS)

    In the experiments performed on the 3He-ion beam irradiation scandium targets at the U-120M cyclotron of the Institute of Nuclear Physics of the Czech Academy of Sciences, Rez, 45Sc(3He, αn)43Sc, 45Sc(3He,α)44Sc and 45Sc(3He, 2p)46Sc reactions were investigated in the 3He energy range from 5 to 24 MeV. To determine the yield of resulting Sc isotope, activation technique was used. A measurement of γ-activity induced in the target was carried out using HPGe-detector of high resolution. Despite the low binding energy of 3He and positive values of Q-reactions leading to the formation of 44Sc and 46Sc isotopes, the behavior of excitation functions for the formation of these isotopes is different from the behavior of excitation functions for deuterons. Cross sections for 44Sc reach their maximum at the Coulomb barrier of the reaction. This is due to the fact that the stable core of 4He forms in the reaction in addition to 44Sc

  13. Structural and electronic properties of ScSb, ScAs, ScP and ScN

    Energy Technology Data Exchange (ETDEWEB)

    Tebboune, AbdelGhani; Belbachir, A.H. [Departement de physique, Universite des Sciences et Technologie Mohamed Boudiaf d' Oran, 31000 Oran (Algeria); Rached, Djamel [Applied Materials Laboratory, Centre de Recherches (ex-CFTE), Universite de Sidi Bel Abbes, 22000 Sidi Bel Abbes (Algeria); Benzair, AbdelNour [Departement de Physique, Universite de Sidi Bel Abbes, 22000 Sidi Bel Abbes (Algeria); Sekkal, Nadir [Departement de Physique-Chimie, Ecole Normale Superieure de l' Enseignement Technique, BP 1523, El M' Naouer, 31000 Oran (Algeria); Computational Materials Science Laboratory, Departement de Physique, Institut de Sciences Exactes, Universite de Sidi Bel Abbes, 22000 Sidi Bel Abbes (Algeria); Physia-Laboratory, BP 47 (RP), 22000 Sidi Bel Abbes (Algeria)

    2006-10-15

    The structural and electronic properties of ScSb, ScAs, ScP and ScN III-V materials are investigated within a version of the first-principles full potential linear Muffin-Tin orbitals method (FPLMTO) that enables an accurate treatment of the interstitial regions. At high pressure, the transition from rocksalt (B1) to CsCl (B2) structure is found to be possible. The zinc blende phase is also investigated and is found to give a semiconductor behavior with a wide bandgap to all our materials. The latter is direct at X for ScAs, ScSb, ScP. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Structural and electronic properties of ScSb, ScAs, ScP and ScN

    International Nuclear Information System (INIS)

    The structural and electronic properties of ScSb, ScAs, ScP and ScN III-V materials are investigated within a version of the first-principles full potential linear Muffin-Tin orbitals method (FPLMTO) that enables an accurate treatment of the interstitial regions. At high pressure, the transition from rocksalt (B1) to CsCl (B2) structure is found to be possible. The zinc blende phase is also investigated and is found to give a semiconductor behavior with a wide bandgap to all our materials. The latter is direct at X for ScAs, ScSb, ScP. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Bioactivity studies on TiO2-bearing Na2O–CaO–SiO2–B2O3 glasses

    International Nuclear Information System (INIS)

    Soda lime silica borate glasses mixed with different concentrations of TiO2 are synthesized by the melt-quenching technique. As a part of study on bioactivity of these glasses, the samples were immersed in simulated body fluid (SBF) solution for prolonged times (~ 21 days) during which weight loss along with pH measurements is carried out at specific intervals of time. The XRD and SEM analyses of post-immersed samples confirm the formation of crystalline hydroxyapatite layer (HA) on the surface of the samples. To assess the role of TiO2 on the formation of HA layer and degradability of the samples the spectroscopic studies viz. optical absorption and IR spectral studies on post- and pre-immersed samples have been carried out. The analysis of the results of degradability together with spectroscopic studies as a function of TiO2 concentration indicated that about 6.0 mol% of TiO2 is the optimal concentration for achieving better bioactivity of these glasses. The presence of the maximal concentration octahedral titanium ions in this glass that facilitates the formation of HA layer is found to be the reason for such a higher bioactivity. - Highlights: • Soda lime silica borate glasses mixed with TiO2 are synthesized. • Bioactivity of the glasses is studied by immersing them in SBF solution. • XRD and SEM studies indicated the formation of hydroxyapatite layer on the surface. • Quantum of degradability is the highest in the glasses mixed with 6.0 mol% of TiO2. • The results are analyzed using IR and optical absorption studies

  16. High Permittivity (1 - x)Ba(Zr(0.2)Ti(0.8))O3 - x(Ba(0.7)Ca(0.3))TiO3 (x = 0.45) Epitaxial Thin Films with Nanoscale Phase Fluctuations.

    Science.gov (United States)

    Scarisoreanu, Nicu D; Craciun, Floriana; Moldovan, Antoniu; Ion, Valentin; Birjega, Ruxandra; Ghica, Corneliu; Negrea, Raluca F; Dinescu, Maria

    2015-11-01

    Epitaxial (1 - x)Ba(Ti0.8Zr0.2)TiO3 - x(Ba0.7Ca0.3)TiO3, x = 0.45 (BCZT 45), thin films have been deposited on (001) SrTiO3 (STO) and (001/100) SrLaAlO4 (SLAO) substrates by pulsed laser deposition. X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) confirmed the epitaxial growth of the films. A high structural quality has been evidenced for the BCZT/STO films. Geometric phase analysis (GPA) associated with the HRTEM enabled us to obtain microstrain analysis and the in-plane and out-of-plane lattice parameter variation on different areas. Tetragonality ratio fluctuations at nanoscale level which are relevant for the existence of nanodomains have been evidenced on the BCZT/STO films. The in-plane dielectric constant has been measured on interdigital electrodes deposited by lift-off technique on the top of the films. High values of dielectric permittivity (>3000) combined with low dielectric loss (reading domains during topography scanning. PMID:26488203

  17. RECTIFYING AND MAGNETORESISTANCE PROPERTIES OF THE HETEROJUNCTION COMPOSED OF La1/8 Ca7/8 MnO3 AND NB-DOPED SrTiO3%La1/8Ca7/8MnO3/Sr0.95Nb0.05TiO3异质结的整流特性和磁输运性质

    Institute of Scientific and Technical Information of China (English)

    王能语; 周桃飞; 李广

    2007-01-01

    在5%Nb掺杂的SrTiO3衬底上用磁控溅射法外延生长了La1/aCa7/aMnO3薄膜形成异质结,该异质结有类似于传统P-n结的整流特性.磁场下扩散电压减小,当温度低于130 K以下,扩散电压的减小非常明显.这和在此温度以下,La1/8Ca7/aMnO3出现自旋倾斜态密切相关.我们计算出异质结的结电阻和磁致电阻(MR),在不同大小的正负偏压,不同磁场下,都得到负的MR值.我们给出界面附近的La1/8Ca7/8MnO3的能带结构并分析了外加磁场对洪德耦合,Jahn-Teller畸变等机制的作用,来解释该异质结的磁输运行为.结果有助于了解高Ca掺杂锰氧化物异质结的性质.%A heterojunction composed of La1/8 Ca7/8 MnO3 and Nb-doped SrTiO3 was fabricated, which shows rectifying characteristic like conventional p-n junctions. The diffusion voltage is slightly decreased under magnetic fields at high temperature and the effect of magnetic fields is more obvious at temperatures below 130 K, at which spin canting state appears in La1/8Ca7/8MnO3. A negative magnetoresistance was found in this heavily Ca-doped manganite heterojunction due to the majority spin carriers (MASCs) transport at the manganite-titanate interface. An energy band structure employing both Jahn-Teller distortion and Hund's coupling of electrons at the interface is used to explain the MASCs' magneto-transport behaviors.

  18. Structural phase transition in early growth of Bi2Sr2CaCu2O8+x films on SrTiO3 substrates

    Science.gov (United States)

    Abrecht, M.; Ariosa, D.; Onellion, M.; Margaritondo, G.; Pavuna, D.

    2002-02-01

    We used pulsed laser deposition, with a Bi2Sr2CaCu2O8+x target, to grow films ranging from (1/4) to 10 unit cells thick. We studied these films, and reference Bi2Sr2CaCu2O8+x single crystal samples, using angle-integrated photoemission, core level photoemission, and x-ray diffraction. The data indicate that all films exhibit a metallic-like Fermi edge in the photoemission data. More strikingly, a structural phase transition occurs at a nominal Bi2Sr2CaCu2O8+x thickness of approximately one unit cell, converting the precursor Bi2O2.33 highly coherent thin film into a Bi2Sr2CaCu2O8+x structure.

  19. Magnetic dipole moment of the doubly closed-shell plus one proton nucleus $^{49}$Sc

    CERN Multimedia

    Gaulard, C V; Walters, W; Nishimura, K; Muto, S; Bingham, C R

    It is proposed to measure the magnetic moment of $^{49}$Sc by the Nuclear Magnetic Resonance on Oriented Nuclei (NMR-ON) method using the NICOLE on-line nuclear orientation facility. $^{49}$Sc is the neutron rich, doubly closed-shell, nucleus $^{48}$Ca plus one proton. Results will be used to deduce the effective g-factors in the $^{48}$Ca region with reference to nuclear structure and meson exchange current effects.

  20. Morphotropy, isomorphism, and polymorphism of Ln{sub 2}M{sub 2}O{sub 7}-based (Ln = La-Lu, Y, Sc; M = Ti, Zr, Hf, Sn) oxides

    Energy Technology Data Exchange (ETDEWEB)

    Shlyakhtina, A. V., E-mail: annash@chph.ras.ru [Russian Academy of Sciences, Semenov Institute of Chemical Physics (Russian Federation)

    2013-07-15

    Structural studies of compounds of variable composition and measurements of their conductivity have made it possible to identify new oxygen-ion-conducting rare-earth pyrochlores, Ln{sub 2}Ti{sub 2}O{sub 7} (Ln = Dy-Lu) and Ln{sub 2}Hf{sub 2}O{sub 7} (Ln = Eu, Gd), with intrinsic high-temperature oxygen ion conductivity (up to 1.4 Multiplication-Sign 10{sup -2} S/cm at 800 Degree-Sign C). Twenty six systems have been studied, and more than 50 phases based on the Ln{sub 2}M{sub 2}O{sub 7} (Ln= La-Lu; M = Ti, Zr, Hf) oxides have been synthesized and shown to be potential oxygen ion conductors. The morphotropy and polymorphism of the Ln{sub 2}M{sub 2}O{sub 7} (Ln = La-Lu; M = Ti, Zr, Hf) rare-earth pyrochlores have been analyzed in detail for the first time. Thermodynamic and kinetic (growth-related) phase transitions have been classified with application to the pyrochlore family.

  1. Determination of self attenuation coefficient and relative TL efficiency of CaSO 4 :Dy, LiF:Mg,Cu,P and LiF:Mg,Ti TLDs - An alternate approach

    Science.gov (United States)

    Bakshi, A. K.; Chatterjee, S.; Palani Selvam, T.; Joshi, V. J.; Chougaonkar, M. P.

    2011-10-01

    Self attenuation of TL and relative TL efficiency of polytetra fluoro ethylene (PTFE) embedded CaSO 4:Dy disc, LiF:Mg,Ti (MTS) disc and LiF:Mg,Cu,P (MCP-N) chip were determined in the present study for photons of energy 10-34 keV. The relative TL efficiency was determined using an alternative approach in which ratio of experimental response and corrected theoretical response was used instead of measuring the absolute TL emission in photon counting mode. For CaSO 4:Dy disc, it was found that with increasing the proportion of CaSO 4:Dy phosphor in the disc, the light attenuation coefficient increases. The light attenuation coefficient of MTS disc and MCP-N chip was found to be 23.4 and 45.5 cm -1, respectively. The relative TL efficiency in the photon energy range of 10-34 keV for MTS discs and MCP-N chips, evaluated in the present study matches well with the reported values in the literature.

  2. Composition dependence of ferroelectric and piezoelectric properties of epitaxial (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} thin films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Q.R.; Wang, D.Y., E-mail: dy.wang@unsw.edu.au; Luo, B.C.; Ding, R.; Lorenzen, D.L.; Li, S.

    2015-03-15

    Highlights: • Epitaxial (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT–xBCT) thin films were successfully grown on (0 0 1)-oriented SrTiO{sub 3} (STO) substrates by pulsed laser deposition (PLD). • Both structural and physical properties of BZT–xBCT thin films exhibited strong composition dependence. • An MPB-like behaviour was found at around x = 0.5 with highest dielectric, ferroelectric and piezoelectric properties. • The piezoelectric coefficients of our BZT–0.5BCT thin films were in upper range of the existing piezoelectric thin film materials. - Abstract: Lead-free (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT–xBCT) (x = 0.3, 0.4, 0.5, 0.6, 0.7) thin films were deposited on SrRuO{sub 3} (SRO)-electroded (0 0 1)-oriented SrTiO{sub 3} (STO) single crystal substrates by pulsed laser deposition (PLD). X-ray diffraction and selected area electron diffraction (SAED) patterns verified epitaxial growth for all the thin films. High ferroelectric activities were evidenced by the well-defined polarization-electric field hysteresis loops. Both structural and physical properties of the thin films demonstrated a strong composition dependence and an MPB-like behaviour was found at around x = 0.5, which is in agreement with that of its bulk counterparts. The superior ferroelectric and piezoelectric responses were attained at x = 0.5 with remanent polarization P{sub r} of 17.8 μC/cm{sup 2} and piezoelectric coefficient d{sub 33} of 100 ± 5 pm/V.

  3. A polaronic stacking fault defect model for CaCu{sub 3}Ti{sub 4}O{sub 12} material: an approach for the origin of the huge dielectric constant and semiconducting coexistent features

    Energy Technology Data Exchange (ETDEWEB)

    Bueno, Paulo R; Tararan, Ronald; Parra, Rodrigo; Joanni, Ednan; Ramirez, Miguel A; Ribeiro, Willian C; Longo, Elson; Varela, Jose A, E-mail: prbueno@iq.unesp.b [Laboratorio Interdisciplinar de Eletroquimica e Ceramica Instituto de Quimica, Departamento de Fisico-Quimica, Universidade Estadual Paulista, Araraquara, SP, CEP 14800-900 (Brazil)

    2009-03-07

    This paper proposes a polaronic stacking fault defect model as the origin of the huge dielectric properties in CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) materials. The model reconciles the opposing views of researchers on both sides of the intrinsic versus extrinsic debate about the origin of the unusually high values of the dielectric constant measured for CCTO in its various forms. Therefore, by considering stacking fault as the origin of the high dielectric constant phenomena, it was shown that the internal barrier layer capacitance mechanism is enhanced by another similar, but different in nature, mechanism that operates in the nanoscale range due to polaron defects associated with stacking fault, a mechanism that was referred to as nanoscale barrier layer capacitance (NBLC). The NBLC approach explains the origin of the CCTO's huge dielectric constant coexisting with semiconducting features.

  4. Influence of CuO addition and sintering temperature on microwave dielectric properties of Ca0.99Zn0.01La4Ti5O17 ceramics for application in stacked patch antenna

    International Nuclear Information System (INIS)

    In this study, the microwave dielectric properties of Ca0.99Zn0.01La4Ti5O17 (CZLTO) ceramics have been investigated. It is found that the X-ray diffraction pattern exhibited no phase difference with 0.5 wt % CuO additive at different sintering temperatures. The maximum value of the dielectric constant and the quality factor Q x f can be obtained with 0.5 wt % CuO additive and sintered at 1450degC for 4 h. A πf of -8.16 ppm/degC was measured for CZLTO ceramics with 0.5 wt % CuO sintered at 1450degC for 4 h. The measurement results for a stacked patch antenna at 2.45 GHz are presented. With this technique, a 3.3% bandwidth (return loss 11 bandwidth. (author)

  5. Domain wall motion and electromechanical strain in lead-free piezoelectrics: Insight from the model system (1 − x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 using in situ high-energy X-ray diffraction during application of electric fields

    International Nuclear Information System (INIS)

    The piezoelectric compositions (1 − x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 (BZT-xBCT) span a model lead-free morphotropic phase boundary (MPB) between room temperature rhombohedral and tetragonal phases at approximately x = 0.5. In the present work, in situ X-ray diffraction measurements during electric field application are used to elucidate the origin of electromechanical strain in several compositions spanning the tetragonal compositional range 0.6 ≤ x ≤ 0.9. As BCT concentration decreases towards the MPB, the tetragonal distortion (given by c/a-1) decreases concomitantly with an increase in 90° domain wall motion. The increase in observed macroscopic strain is predominantly attributed to the increased contribution from 90° domain wall motion. The results demonstrate that domain wall motion is a significant factor in achieving high strain and piezoelectric coefficients in lead-free polycrystalline piezoelectrics

  6. Broadband near-infrared quantum-cutting by cooperative energy transfer in Yb{sup 3+}–Bi{sup 3+} co-doped CaTiO{sub 3} for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Li-Tian; Chen, Jun-Qiang; Deng, Chao; Tang, Li; Chen, Dong-Ju; Meng, Jian-Xin, E-mail: tmjx@jnu.edu.cn; Cao, Li-Wei

    2015-08-15

    Highlights: • Broadband NIR QC CaTiO{sub 3}:Yb{sup 3+},Bi{sup 3+} phosphor has been firstly developed. • Co-doping with Bi{sup 3+}, it enhanced the Yb{sup 3+} emission intensity by a factor of 10. • This phosphor could efficiently convert 300–480 nm light to ∼1000 nm light. • The ET processes were involved in CET via two photons QC process. - Abstract: An efficient near-infrared (NIR) quantum-cutting (QC) process which converts broadband ultraviolet-blue into NIR via downconversion (DC) has been demonstrated in CaTiO{sub 3}:Yb{sup 3+},Bi{sup 3+} phosphors for the first time. These phosphors are valuable for use in crystalline Si (c-Si) solar cells, because they efficiently convert 300–480 nm light that is not fully utilized by existing c-Si solar cells into ∼1000 nm NIR light that can be sufficiently absorbed by solar cells. Co-doping with 15% Bi{sup 3+} ions, a significant enhancement in Yb{sup 3+} NIR integrated emission intensity by a factor of 10 is realized. The phosphors were characterized with the photoluminescence excitation (PLE) and the photoluminescence (PL) spectra evidence the presence of energy transfer (ET) processes from Bi{sup 3+}-related charge transfer state to Yb{sup 3+} ions. The dependence of Yb{sup 3+} luminescent intensity on the excitation power was also measured and it demonstrates that the ET processes involve cooperative energy transfer (CET) via two photons QC processes.

  7. A 45Sc-NMR and DFT calculation study of crystalline scandium compounds

    Science.gov (United States)

    Bräuniger, Thomas; Hofmann, Andreas J.; Moudrakovski, Igor L.; Hoch, Constantin; Schnick, Wolfgang

    2016-01-01

    A series of scandium compounds, namely ScPO4, ScOF, Li3Sc(BO3)2, and CaSc2O4, were prepared according to procedures described in the literature, and then characterised by powder X-ray diffraction and solid-state 45Sc-NMR spectroscopy. By computer fitting, the quadrupolar interaction parameters χ and η, as well as the isotropic chemical shifts δiso were extracted from the NMR spectra. For comparison and site assignment of 45Sc, density functional theory (DFT) calculations of the EFG tensor were carried out with the CASTEP code. For the compounds with a well-defined formal coordination number (CN), a convincing linear correlation between CN and isotropic chemical shift could be established.

  8. Correlative characterization of primary Al3(Sc,Zr) phase in an Al–Zn–Mg based alloy

    International Nuclear Information System (INIS)

    Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al3(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al3(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al3(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al3(Sc,Zr) phases. Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al3(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al3(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al3Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al3(Sc,Zr) particle enhances the heterogeneous nucleation of Al3(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al3(Sc,Zr) phases were observed within the α-Al matrix. • A layer by layer growth within primary Al3(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al3Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al3(Sc,Zr)

  9. Sol-gel synthesis of quaternary (P2O5)55-(CaO)25-(Na2O)(20-x)-(TiO2) x bioresorbable glasses for bone tissue engineering applications (x = 0, 5, 10, or 15).

    Science.gov (United States)

    Foroutan, Farzad; Walters, Nick J; Owens, Gareth J; Mordan, Nicola J; Kim, Hae-Won; de Leeuw, Nora H; Knowles, Jonathan C

    2015-08-01

    In the present study, we report a new and facile sol-gel synthesis of phosphate-based glasses with the general formula of (P2O5)55-(CaO)25-(Na2O)(20-x)-(TiO2) x , where x = 0, 5, 10 or 15, for bone tissue engineering applications. The sol-gel synthesis method allows greater control over glass morphology at relatively low processing temperature (200 °C) in comparison with phosphate-based melt-derived glasses (~1000 °C). The glasses were analyzed using several characterization techniques, including x-ray diffraction (XRD), (31)P magic angle spinning nuclear magnetic resonance ((31)P MAS-NMR), Fourier transform infrared (FTIR) spectroscopy and energy-dispersive x-ray (EDX) spectroscopy, which confirmed the amorphous and glassy nature of the prepared samples. Degradation was assessed by measuring the ion release and pH change of the storage medium. Cytocompatibility was also confirmed by culturing osteoblast-like osteosarcoma cell line MG-63 on the glass microparticles over a seven-day period. Cell attachment to the particles was imaged using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results revealed the potential of phosphate-based sol-gel derived glasses containing 5 or 10 mol% TiO2, with high surface area, ideal dissolution rate for cell attachment and easily metabolized dissolution products, for bone tissue engineering applications. PMID:26306553

  10. Magneto-transport properties of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction

    Indian Academy of Sciences (India)

    P Raychaudhuri; C Mitra; K Dorr; K H Muller; G Kobernik; R Pinto

    2002-05-01

    Hole-doped rare-earth manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 both show a metal–insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance. In an earlier publication we have reported the rectifying characteristic of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal–insulator transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La0.7Ce0.3MnO3 could be a minority spin carrier ferromagnet. The implication of this observation is discussed.

  11. Microstructure of epitaxial La0.7Ca0.3MnO3 thin films grown on LaAlO3 and SrTiO3

    International Nuclear Information System (INIS)

    Epitaxial La0.7Ca0.3MnO3 (LCMO) thin films of a thickness ∼170 nm were grown on (001) LaAlO3 (LAO) and (001) SrTiO3 (STO) substrates by pulsed laser deposition. Transmission electron microscopy and associated techniques have been applied to investigate the microstructures introduced by lattice mismatch that are responsible for the observed differences in properties between these two films. Numerous secondary phase rods were observed in both films. For the LCMO/LAO film, Ca-deficient secondary-phase rods originated in the film after a thickness of about 25 nm and were found to be responsible for relieving in-plane compressive stress during the island growth. In the case of STO substrate, however, almost all of secondary-phase rods initiated at the film-substrate interface. The lattice mismatch between LCMO and STO is relaxed into regions of good coherent fit separated by such secondary phases, possibly resulting from interfacial reaction. The two types of substrates lead to the formation of two different crystallographic domain structures in the LCMO films. The film on LAO exhibits an almost pure [110] out-of-plane texture with 90 degree sign domains in plane. In contrast, the film grown on STO consists of mixed domains of [001] and [110] orientations and is dominated by [001] texture. (c) 2000 American Institute of Physics

  12. Elastic and inelastic {alpha}-scattering cross-sections obtained with the 44 MeV fixed energy Saclay cyclotron on separated targets of {sup 24}Mg, {sup 25}Mg, {sup 26}Mg, {sup 40}Ca, {sup 46}Ti, {sup 48}Ti, {sup 50}Ti, {sup 52}Cr, {sup 54}Fe, {sup 56}Fe, {sup 58}Fe, {sup 58}Ni, {sup 60}Ni, {sup 62}Ni, {sup 64}Ni, {sup 63}Cu, {sup 65}Cu, {sup 64}Zn, {sup 112}Sn, {sup 114}Sn, {sup 116}Sn, {sup 118}Sn, {sup 120}Sn, {sup 122}Sn, {sup 124}Sn and {sup 208}Pb using the Saclay fixed-energy cyclotron; Sections efficaces differentielles elastiques et inelastiques obtenues par diffusion de particules {alpha} de 44 MeV sur des cibles de {sup 24}Mg, {sup 25}Mg, {sup 26}Mg, {sup 40}Ca, {sup 46}Ti, {sup 48}Ti, {sup 50}Ti, {sup 52}Cr, {sup 54}Fe, {sup 56}Fe, {sup 58}Fe, {sup 58}Ni, {sup 60}Ni, {sup 62}Ni, {sup 64}Ni, {sup 63}Cu, {sup 65}Cu, {sup 64}Zn, {sup 112}Sn, {sup 114}Sn, {sup 116}Sn, {sup 118}Sn, {sup 120}Sn, {sup 122}Sn, {sup 124}Sn et {sup 208}Pb au cyclotron a energie fixe de saclay

    Energy Technology Data Exchange (ETDEWEB)

    Bruge, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires. Departement de physique nucleaire, service de physique nucleaire a moyenne energie

    1967-01-01

    This report contains elastic and inelastic {alpha}-scattering cross-sections obtained with the 44 MeV fixed energy Saclay cyclotron on Mg, Ca, Ti, Cr, Fe, Ni, Co, Zn, Sn and Pb enriched targets. (author) [French] Ce rapport contient les tableaux des sections efficaces differentielles obtenues par diffusion elastique et inelastique des particules {alpha} de 44 MeV, fournies par le cyclotron a energie fixe de Saclay, sur des cibles d'isotopes separes de Mg, Ca, Ti, Cr, Fe, Ni, Co, Zn, Sn et Pb. (auteur)

  13. Absolute transition probabilities in Sc I and Sc II

    International Nuclear Information System (INIS)

    Absolute atomic transition probabilities for emission lines from 70 levels in Sc I and Sc II are reported. The transition probabilities are from emission branching ratios measured using the 1.0-m Fourier-transform spectrometer at the National Solar Observatory. Radiative lifetimes, measured using time-resolved laser-induced fluorescence, provide the normalization for converting the branching ratios to absolute transition probabilities. These results are compared with other experimental and theoretical transition probabilities

  14. Extinction in SC galaxies

    Science.gov (United States)

    Giovanelli, Riccardo; Haynes, Martha P.; Salzer, John J.; Wegner, Gary; da Costa, Luiz N.; Freudling, Wolfram

    1994-06-01

    We analyze the photometric properties of a sample of Sbc-Sc galaxies with known redshifts, single-dish H I profiles, and Charge Coupled Device (CCD) I band images. We derive laws that relate the measured isophotal radius at muI = 23.5, magnitude, scale length, and H I flux to the face-on aspect. We find spiral galaxies to be substantially less transparent than suggested in most previous determinations, but not as opaque as claimed by Valentijn (1990). Regions in the disk farther than two or three scale lengths from the center are close to completely transparent. In addition to statistically derived relations for the inclination dependence of photometric parameters, we present the results of a modeling exercise that utilizes the 'triplex' model of Disney et al. (1989) to obtain upper limits of the disk opacity. Within the framework of that model, and with qualitative consideration of the effects of scattering on extinction, we estimate late spiral disks at I band to have central optical depths tauI(0) less than 5 and dust absorbing layers with scale heights on the order of half that of the stellar component or less. We discuss our results in light of previous determinations of internal extinction relations and point out the substantial impact of internal extinction on the scatter of the Tully-Fisher relation. We also find that the visual diameters by which large catalogs are constructed (UGC, ESO-Uppsala) are nearly proportional to face-on isophotal diameters.

  15. Monitor of SC beam profiles

    CERN Multimedia

    1977-01-01

    A high-resolution secondary emission grid for the measurement of SC beam profiles. Modern techniques of metal-ceramic bonding, developed for micro-electronics, have been used in its construction. (See Annual Report 1977 p. 105 Fig. 12.)

  16. Composition-driven phase boundary and electrical properties in (Ba0.94Ca0.06)(Ti1-xMx)O3 (M = Sn, Hf, Zr) lead-free ceramics.

    Science.gov (United States)

    Zhao, Chunlin; Wang, Hui; Xiong, Jie; Wu, Jiagang

    2016-04-12

    In this study, we systematically investigated the composition dependence of the phase structure, microstructure, and electrical properties of (Ba0.94Ca0.06)(Ti1-xMx)O3 (M = Sn, Hf, Zr) ceramics synthesised by the conventional solid-state reaction method. The phase boundary type strongly depends on the composition, and then different electrical properties were exhibited. The addition of Hf and Zr can more quickly shift phase transition temperatures (TR-O and TO-T) to a higher temperature with respect to Sn, leading to the formation of different phase boundaries. In addition, different phase boundaries can also be affected by their doped contents. The R-O and O-T phase boundaries can be shown in the Sn-doped ceramics with x = 0.10, and the R-O phase boundary can exist in the Hf (x = 0.07) or Zr (x = 0.075)-doped ceramics. A high piezoelectric property of d33 = 600 pC N(-1) can be achieved in the Sn-doped ceramics due to the involvement of converging R-O/O-T phase boundaries, an enhanced ferroelectric performance with Pr = 14.54 μC cm(-2) and Ec = 1.82 kV cm(-1) can be attained in the Zr-doped ceramics, and Hf would benefit from obtaining a large strain behaviour (∼0.20%). We believe that the electrical properties and the related physical mechanisms of BaTiO3-based ceramics can be well unveiled by studying their chemical modification behavior. PMID:26952807

  17. Evaluation of the thermoluminescent detector answers of CaSO{sub 4}:Dy, LiF:Mg,Ti and micro LiF:Mg,Ti in photon clinical beams dosimetry using water simulator; Avaliacao da resposta de detectores termoluminescentes de CaSO4:Dy, LiF:Mg,Ti e microLiF:Mg,Ti na dosimetria de feixes clinicos de fotons utilizando simulador de agua

    Energy Technology Data Exchange (ETDEWEB)

    Matsushima, Luciana C.; Veneziani, Glauco R.; Campos, Leticia L., E-mail: lmatsushima@usp.b, E-mail: veneziani@ipen.b, E-mail: lcrodri@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (GMR/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Gerencia de Metrologia das Radiacoes; Sakuraba, Roberto K.; Cruz, Jose C. da, E-mail: rsakuraba@einstein.b, E-mail: jccruz@einstein.b [Sociedade Beneficente Israelita Brasileira, Sao Paulo, SP (Brazil). Hospital Albert Einstein (HAE)

    2011-10-26

    This paper perform the comparative study of thermoluminescent answer of calcium sulfate dosemeter doped with dysprosium (DaSO{sub 4}:Dy) produced by the IPEN, Sao Paulo, with answer of lithium fluoride dosemeters doped with magnesium and titanium (LiF:Mg, Ti) in the dosimetry of clinical beams of photons (6 and 15 MV) by using water simulator object. Dose-answer curves were obtained for gamma radiation of cobalt-60 in the air and in conditions of electronic equilibrium (plate of PMMA), and clinical photons of CLINAC model 2100C accelerators of the two evaluated hospitals: Hospital das Clinicas of the Faculty of Medicine of Sao Paulo university and Hospital Albert Einstein. It was also evaluated the sensitivity and reproduction of the three dosemeters

  18. Local distortions in La0.7Ca0.3Mn1-bAbO3 (A=Ti and Ga) colossal magnetoresistance samples: Correlations with magnetization and evidence for cluster formation

    International Nuclear Information System (INIS)

    X-ray absorption fine structure (XAFS) measurements as a function of temperature have been carried out at the Mn K edge for La0.7Ca0.3Mn1-xTixO3 and La0.7Ca0.3Mn1-yGayO3 (x and y=0.01 to 0.10) and correlated with transport and magnetization measurements. Most samples exhibit colossal magnetoresistance (CMR) at low temperature. The magnetization data show a concentration dependence: the ferromagnetic phase transition broadens as x or y increases, and both the transition temperature Tc and the saturated magnetization decrease with increasing dopant concentration. The transport measurements show that the resistivity increases as x or y increases, and that the resistivity peak, which we associated with the metal-to-insulator (MI) transition temperature TMI, moves rapidly to lower temperatures with x or y. In contrast to the La1-aCaaMnO3 materials, for which the resistivity peak normally occurs very close to Tc, TMI is usually far below Tc for these cosubstituted materials. The increase in resistivity well below Tc strongly suggests the formation of clusters. We also find that TMI has a much smaller magnetic field dependence than that for La1-aCaaMnO3 CMR materials. The XAFS data show that a non-Debye broadening, associated with polaron formation, also develops as T approaches Tc, as observed for other CMR samples, but the magnitude of this extra broadening, Δσ2, decreases with x or y, with a larger effect for Ti than for Ga. We find that for a given type of dopant, the resistivity peak occurs when σ2 is decreased to a specific value that is essentially independent of concentration and that this corresponds to nearly the same value of the sample magnetization. These results indicate that the addition of either Ga or Ti distorts the local Mn-O environment which likely promotes cluster formation. Measurements of the absorption edge shift as a function of x for these materials do not quite follow the calculated edge positions based on concentrations, possibly suggesting

  19. MODELS FOR METAL-POOR STARS WITH ENHANCED ABUNDANCES OF C, N, O, Ne, Na, Mg, Si, S, Ca, AND Ti, IN TURN, AT CONSTANT HELIUM AND IRON ABUNDANCES

    Energy Technology Data Exchange (ETDEWEB)

    VandenBerg, Don A.; Dotter, Aaron [Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, B.C. V8W 3P6 (Canada); Bergbusch, Peter A. [Department of Physics, University of Regina, Regina, Saskatchewan S4S 0A2 (Canada); Ferguson, Jason W. [Department of Physics, Wichita State University, Wichita, KS 67260-0032 (United States); Michaud, Georges; Richer, Jacques [Departement de Physique, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada); Proffitt, Charles R., E-mail: vandenbe@uvic.ca, E-mail: Aaron.Dotter@gmail.com, E-mail: pbergbusch@accesscomm.ca, E-mail: proffitt@stsci.edu, E-mail: Jason.Ferguson@wichita.edu, E-mail: michaudg@astro.umontreal.ca, E-mail: jacques.richer@umontreal.ca [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2012-08-10

    Recent work has shown that most globular clusters have at least two chemically distinct components, as well as cluster-to-cluster differences in the mean [O/Fe], [Mg/Fe], and [Si/Fe] ratios at similar [Fe/H] values. In order to investigate the implications of variations in the abundances of these and other metals for H-R diagrams and predicted ages, grids of evolutionary sequences have been computed for scaled solar and enhanced {alpha}-element metal abundances, and for mixtures in which the assumed [m/Fe] value for each of the metals C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti has been increased, in turn, by 0.4 dex at constant [Fe/H]. These tracks, together with isochrones for ages from Almost-Equal-To 5 to 14 Gyr, have been computed for -3.0 {<=} [Fe/H] {<=}-0.6, with helium abundances Y = 0.25, 0.29, and 0.33 at each [Fe/H] value, using upgraded versions of the Victoria stellar structure program and the Regina interpolation code, respectively. Turnoff luminosity versus age relations from isochrones are found to depend almost entirely on the importance of the CNO cycle, and thereby mainly on the abundance of oxygen. Since C, N, and O, as well as Ne and S, do not contribute significantly to the opacities at low temperatures and densities, variations in their abundances do not impact the predicted T{sub eff} scale of red giants. The latter is a strong function of the abundances of only Mg and Si (and Fe, possibly to a lesser extent) because they are so abundant and because they are strong sources of opacity at low temperatures. For these reasons, Mg and Si also have important effects on the temperatures of main-sequence stars. Due to their low abundances, Na, Ca, and Ti are of little consequence for stellar models. The effects of varying the adopted solar metals mixture and the helium abundance at a fixed [Fe/H] are also briefly discussed.

  20. MODELS FOR METAL-POOR STARS WITH ENHANCED ABUNDANCES OF C, N, O, Ne, Na, Mg, Si, S, Ca, AND Ti, IN TURN, AT CONSTANT HELIUM AND IRON ABUNDANCES

    International Nuclear Information System (INIS)

    Recent work has shown that most globular clusters have at least two chemically distinct components, as well as cluster-to-cluster differences in the mean [O/Fe], [Mg/Fe], and [Si/Fe] ratios at similar [Fe/H] values. In order to investigate the implications of variations in the abundances of these and other metals for H-R diagrams and predicted ages, grids of evolutionary sequences have been computed for scaled solar and enhanced α-element metal abundances, and for mixtures in which the assumed [m/Fe] value for each of the metals C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti has been increased, in turn, by 0.4 dex at constant [Fe/H]. These tracks, together with isochrones for ages from ≈5 to 14 Gyr, have been computed for –3.0 ≤ [Fe/H] ≤–0.6, with helium abundances Y = 0.25, 0.29, and 0.33 at each [Fe/H] value, using upgraded versions of the Victoria stellar structure program and the Regina interpolation code, respectively. Turnoff luminosity versus age relations from isochrones are found to depend almost entirely on the importance of the CNO cycle, and thereby mainly on the abundance of oxygen. Since C, N, and O, as well as Ne and S, do not contribute significantly to the opacities at low temperatures and densities, variations in their abundances do not impact the predicted Teff scale of red giants. The latter is a strong function of the abundances of only Mg and Si (and Fe, possibly to a lesser extent) because they are so abundant and because they are strong sources of opacity at low temperatures. For these reasons, Mg and Si also have important effects on the temperatures of main-sequence stars. Due to their low abundances, Na, Ca, and Ti are of little consequence for stellar models. The effects of varying the adopted solar metals mixture and the helium abundance at a fixed [Fe/H] are also briefly discussed.

  1. Microstructures and Microwave Dielectric Properties of (1-x(Sr0.2Nd0.208Ca0.488TiO3- xNd(Ti0.5Mg0.5O3 Ceramics with High Quality Factor

    Directory of Open Access Journals (Sweden)

    QU Jing-Jing, WEI Xing, JING Ben-Qin, LIU Fei, YUAN Chang-Lai

    2015-11-01

    Full Text Available (1-x(Sr0.2Nd0.208Ca0.488TiO3-xNd(Ti0.5Mg0.5O3 (0.3≤x≤0.4, SNCT-NTMx ceramics were prepared by solid sate reaction technique. In addition, the crystal structure, microstructures, sintering properties, and microwave dielectric properties of the SNCT-NTMx ceramics were investigated. These results showed that an orthorhombic perovskite structure with a minor amount of unknown secondary phase was formed in the ceramics with the compositions of 0.3≤x≤0.35. Additionally, the content of the second phase gradually increased with increasing x valueup to 0.4. For the SNCT-NTMx ceramics with an increase in NTM content, the dielectric constant (εr decreased, while the quality factor (Q×f effectively improved, and the temperature coefficient of resonant frequencies (τf gradually shifted to negative direction. An optimized microwave dielectric properties with εr ~ 50.1, Q×f ~ 44, 910 GHz and τf ~–1.7×10-6/℃ could be obtained for the ceramics with x = 0.35 after being sintered at 1520℃ for 4 h.

  2. Investigation of the structural, optical and dielectric properties of highly (1 0 0)-oriented (Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20})TiO{sub 3} thin films on LaNiO{sub 3} bottom electrode

    Energy Technology Data Exchange (ETDEWEB)

    Pontes, D.S.L. [Laboratorio Interdisciplinar de Eletroquimica e Cerâmica, Department of Chemistry, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil); Pontes, F.M., E-mail: fenelon@fc.unesp.br [Department of Chemistry, Universidade Estadual Paulista, P.O. Box 473, 17033-360 Bauru, São Paulo (Brazil); Chiquito, A.J. [NanO LaB, Transporte Eletrônico em Nanoestruturas, Department of Physics, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil); Longo, E. [Laboratorio Interdisciplinar de Eletroquimica e Cerâmica, Department of Chemistry, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil); Institute of Chemistry, Universidade Estadual Paulista, Araraquara, São Paulo (Brazil)

    2014-07-01

    Highlights: • Highly (h 0 0) oriented LNO and PCST thin films were grown on LAO(1 0 0) substrate. • PCST/LNO/LAO structure shown classic ferroelectric–paraelectric phase transition. • PCST/LNO/LAO structure shows superior dielectric properties. • PCST/LAO films showed a direct allowed optical transition. - Abstract: Highly (1 0 0)-oriented Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3}/LNO/LAO structure was fabricated using a chemical deposition process via spin-coating technique. XRD revealed that both LNO and Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3} films grown on LAO(1 0 0) substrate and LNO/LAO(1 0 0) structure were crystallized to be highly (h 0 0)-oriented, respectively. AFM images revealed smooth surfaces, spherical-shaped grains and a crack-free surface with a roughness of about 3–7 nm. The tetragonal perovskite phase was confirmed by Raman spectroscopy for Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3}/LNO/LAO and Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3}/LAO structures. The optical transmittance of 340 nm thick Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3} films on a LAO(1 0 0) substrate exhibited an average transmittance above 80% in the wavelength range of 500–1000 nm and an optical band gap E{sub g} of 3.56 and 2.87 eV for the direct and indirect transition processes, respectively. The Au/Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3}/LNO/LAO structure has a hysteresis loop with remnant polarization, P{sub r}, of 12 μC/cm{sup 2}, and a coercive field, E{sub c}, of 46 kV/cm for an electric field at 370 kV/cm along with a dielectric constant over 1200.

  3. A comparative study of the different sample decomposition procedures for three common lithium minerals: a scheme for the accurate elemental analysis of Li, Na, K, Rb, Cs, Mg, Ca, Mn, Al, Fe, and Ti using FAAS and ICP-AES

    International Nuclear Information System (INIS)

    An analytical procedure is developed for the elemental analysis of some lithium minerals and validated using standard reference samples of National Bureau of Standard, subsequently applied to natural lithium minerals obtained from field areas of southern region, Bangalore. The common lithium minerals are spodumene, petalite and lepidolite, and the Li2O content ranges from 4% to 8%. Three different sample decomposition procedures such as (i) fusion with ammonium bi-fluoride (ii) a mixture of ammonium bi-fluoride and ammonium sulphate and (iii) acid digestion with hydrofluoric acid and nitric acid mixture were studied and compared. Fusion with ammonium bi-fluoride was studied earlier. The elements Li, Na, K, Rb and Cs in the samples are determined by FAAS, and ICP-AES was used for other elements (Al, Fe, Mn, Mg, Ca, Ti, Be, Nb) determination. The results obtained for three international reference materials, such as, Spodumene NBS 181, Petalite, NBS 182 and Lepidolite NBS 183 are in good agreement with the recommended values, which indicates the accuracy of the proposed scheme of analysis. Authors have also estimated the values for Al, Fe, Mn, Mg, Ca, Na and K for these reference materials which were not reported earlier. The advantages of fusion with ammonium bi fluoride alone or a mixture of ammonium bi fluoride and ammonium sulphate are: (i) no alkali metal is contributed from the flux, (ii) majority of other refractory minerals which are present in minor or trace quantities were are also decomposed completely. Therefore, it gives an indication of the presence of other associated pegmatite minerals during the analysis. The proposed method is accurate and reproducibility is characterized by 2 to 5% RSD, depending on the concentration of the elements in the sample. (author)

  4. Magnetoelectric properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 - CoFe2O4 particulate composites

    Science.gov (United States)

    Paul Praveen, J.; Vinitha Reddy, M.; Das, Dibakar

    2016-05-01

    0.7[(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3)]-0.3[CoFe2O4] multiferroic particulate ceramic composite with (0-3) connectivity has been synthesized by wet chemical methods. BCZT-CFO composite showed both polarization-electric field and magnetic hysteresis loops simultaneously at room temperature. A high dielectric constant of 2160 and tangent loss factor of 0.6 has been obtained. Magnetoelectric (ME) voltage coefficient (αME =dE/dH) of the composite was measured as a function of applied d.c magnetic field at different frequencies. At resonance frequency (365kHz) the composite showed a maximum αME of 102mV/cm.Oe. It was observed that the transverse ME coefficient is 1.8 times higher than the longitudinal ME coefficient. The magnetoelectric properties of this composite has been studied in detail in this work and correlated with its structure.

  5. Dual-band LTCC antenna based on 0.95Zn2SiO4-0.05CaTiO3 ceramics for GPS/UMTS applications

    Institute of Scientific and Technical Information of China (English)

    窦刚; 李玉霞; 郭梅

    2015-01-01

    In this paper, we present a compact low-temperature co-fired ceramic (LTCC) dual-band antenna by using the elec-tromagnetic coupling effect concept for global positioning system (GPS) and universal mobile telecommunication system (UMTS) applications. The overall dimension of the antenna is 8.6 mm × 13.0 mm × 1.1 mm. It consists of double meander lines and a via hole line. The top meander line operates at the upper band, and the bottom radiating patch is designed for the lower band. The via-hole line is employed to connect the double meander lines. Because of the effect of the coupled line, total dimension of the proposed antenna is greatly reduced. With the 2.5:voltage standing wave ratio (VSWR) impedance bandwidth definition, the lower and upper bands have the bandwidths of 110 MHz and 150 MHz, respectively. The pro-posed antenna is successfully designed, simulated, and analyzed by a high frequency structure simulator (HFSS). And the antenna is manufactured by using the 0.95Zn2SiO4-0.05CaTiO3 ceramics (εr=7.1, tanδ =0.00038) that is prepared by ourselves. The results show that the antenna is compact, efficient, and of near omnidirectional radiation pattern.

  6. Effect of grain boundary layer strain on the magnetic and transport properties of (100- x) La 0.7Ca 0.3MnO 3/( x) BaTiO 3 composites showing enhanced magnetoresistance

    Science.gov (United States)

    Bose, Esa; Taran, S.; Karmakar, S.; Chaudhuri, B. K.; Pal, S.; Sun, C. P.; Yang, H. D.

    2007-07-01

    A ferromagnetic/ferroelectric composite system, viz. (100- x)La 0.7Ca 0.3 MnO 3 [LCMO]/( x) BaTiO 3 [BTO] (with x=0.0%, 1.0%, 5.0%, 7.5%, 10.0% and 15.0%, in wt%) has been synthesized and the temperature-dependent DC magnetization M( T), resistivity ρ( T), magnetoresistance (MR), and thermoelectric power S( T) have been studied. Both metal-insulator transition temperature ( TMI) and the corresponding Curie temperature ( TC) decrease whereas peak resistivity at TMI increases as x is enhanced from 0.0% to 10.0%. For x>10.0%, this trend of variation is reversed. A maximum three-fold increase of magnetoresistance (MR) is observed (for sample with x=10.0%) due to the addition of ferroelectric (non-magnetic) perovskite BTO (compared to the mother compound LCMO). Interestingly, thermoelectric power S( T) shows a pronounced depression (dip) near the magnetic transition region for the composite samples. The above results have been analyzed considering strain induced by the LCMO/BTO grain boundary layer (BL).

  7. Effect of grain boundary layer strain on the magnetic and transport properties of (100-x) La0.7Ca0.3MnO3/(x) BaTiO3 composites showing enhanced magnetoresistance

    International Nuclear Information System (INIS)

    A ferromagnetic/ferroelectric composite system, viz. (100-x)La0.7Ca0.3 MnO3 [LCMO]/(x) BaTiO3 [BTO] (with x=0.0%, 1.0%, 5.0%, 7.5%, 10.0% and 15.0%, in wt%) has been synthesized and the temperature-dependent DC magnetization M(T), resistivity ρ(T), magnetoresistance (MR), and thermoelectric power S(T) have been studied. Both metal-insulator transition temperature (T MI) and the corresponding Curie temperature (T C) decrease whereas peak resistivity at T MI increases as x is enhanced from 0.0% to 10.0%. For x>10.0%, this trend of variation is reversed. A maximum three-fold increase of magnetoresistance (MR) is observed (for sample with x=10.0%) due to the addition of ferroelectric (non-magnetic) perovskite BTO (compared to the mother compound LCMO). Interestingly, thermoelectric power S(T) shows a pronounced depression (dip) near the magnetic transition region for the composite samples. The above results have been analyzed considering strain induced by the LCMO/BTO grain boundary layer (BL)

  8. Investigating the effect of SiO2-TiO 2-CaO-Na 2O-ZnO bioactive glass doped hydroxyapatite: characterisation and structural evaluation.

    Science.gov (United States)

    Yatongchai, Chokchai; Wren, Anthony W; Curran, Declan J; Hampshire, Stuart; Towler, Mark R

    2014-07-01

    The effects of increasing bioactive glass additions, SiO2-TiO2-CaO-Na2O-ZnO up to 25 wt% in increments of 5 wt%, on the physical and mechanical properties of hydroxyapatite (HA) sintered at 900, 1000, 1100 and 1200 °C for 2 h was investigated. Increasing both the glass content and the temperature resulted in increased HA decomposition. This resulted in the formation of a number of bioactive phases. However the presence of the liquidus glass phase did not result in increased densification levels. At 1000 and 1100 °C the additions of 5 wt% glass resulted in a decrease in density which never recovered with increasing glass content. At 1200 °C a cyclic pattern resulted from increasing glass content. There was no direct relationship between strength and density with all samples experiencing no change or a decrease in strength with increasing glass content. Weibull statistics displayed no pattern with increasing glass content. PMID:24748516

  9. Lead-free Ba{sub 0.8}Ca{sub 0.2}(Zr{sub x}Ti{sub 1−x})O{sub 3} ceramics with large electrocaloric effect

    Energy Technology Data Exchange (ETDEWEB)

    Asbani, B. [LPMC, Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens Cédex (France); LMCN, F.S.T.G. Université Cadi Ayyad, BP 549 Marrakech (Morocco); Dellis, J.-L.; Lahmar, A.; Gagou, Y.; El Marssi, M., E-mail: mimoun.elmarssi@u-picardie.fr [LPMC, Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens Cédex (France); Courty, M.; Djellab, K. [LRCS, UMR7314, Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens Cédex (France); Amjoud, M.; Mezzane, D. [LMCN, F.S.T.G. Université Cadi Ayyad, BP 549 Marrakech (Morocco); Kutnjak, Z. [Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia)

    2015-01-26

    The electrocaloric effect was investigated in lead-free Zr doped Ba{sub 0.8}Ca{sub 0.2}(Zr{sub x}Ti{sub 1−x})O{sub 3} (BCTZ) ceramics synthesized by a conventional sintering process. Room-temperature x-ray diffraction analysis showed that the tetragonal structure is obtained in BCTZ for x ≤ 0.08 and a pseudo cubic phase for x > 0.08. The dielectric spectroscopy and calorimetry revealed that the Curie temperature decreases as a consequence of Zr doping and that the BCTZ exhibits a first order ferroelectric phase transition. The electrocaloric effect was determined by the calculation of the electrocaloric change of temperature (ΔT) using the Maxwell relation based on the P–E hysteresis loops measured at different temperatures. A large electrocaloric responsivity ΔT/ΔE = 0.34 × 10{sup −6 }Km/V was found for x = 0.04, which significantly exceeds of values found so far in other lead-free electrocaloric materials.

  10. In-situ Electric Field-Induced Modulation of Photoluminescence in Pr-doped Ba0.85Ca0.15Ti0.90Zr0.10O3 Lead-Free Ceramics

    Science.gov (United States)

    Sun, Hai Ling; Wu, Xiao; Chung, Tat Hang; Kwok, K. W.

    2016-06-01

    Luminescent materials with dynamic photoluminescence activity have aroused special interest because of their potential widespread applications. One proposed approach of directly and reversibly modulating the photoluminescence emissions is by means of introducing an external electric field in an in-situ and real-time way, which has only been focused on thin films. In this work, we demonstrate that real-time electric field-induced photoluminescence modulation can be realized in a bulk Ba0.85Ca0.15Ti0.90Zr0.10O3 ferroelectric ceramic doped with 0.2 mol% Pr3+, owing to its remarkable polarization reversal and phase evolution near the morphotropic phase boundary. Along with in-situ X-ray diffraction analysis, our results reveal that an applied electric field induces not only typical polarization switching and minor crystal deformation, but also tetragonal-to-rhombohedral phase transformation of the ceramic. The electric field-induced phase transformation is irreversible and engenders dominant effect on photoluminescence emissions as a result of an increase in structural symmetry. After it is completed in a few cycles of electric field, the photoluminescence emissions become governed mainly by the polarization switching, and thus vary reversibly with the modulating electric field. Our results open a promising avenue towards the realization of bulk ceramic-based tunable photoluminescence activity with high repeatability, flexible controllability, and environmental-friendly chemical process.

  11. Elastic properties of perovskite ATiO{sub 3} (A = Be, Mg, Ca, Sr, and Ba) and PbBO{sub 3} (B = Ti, Zr, and Hf): First principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Pandech, Narasak; Limpijumnong, Sukit, E-mail: sukit@sut.ac.th [School of Physics and NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); Thailand Center of Excellence in Physics (ThEP Center), Commission on Higher Education, Bangkok 10400 (Thailand); Sarasamak, Kanoknan [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand)

    2015-05-07

    The mechanical properties of perovskite oxides depend on two metal oxide lattices that are intercalated. This provides an opportunity for separate tuning of hardness, Poisson's ratio (transverse expansion in response to the compression), and shear strength. The elastic constants of series of perovskite oxides were studied by first principles approach. Both A-site and B-site cations were systematically varied in order to see their effects on the elastic parameters. To study the effects of A-site cations, we studied the elastic properties of perovskite ATiO{sub 3} for A being Be, Mg, Ca, Sr, or Ba, one at a time. Similarly, for B-site cations, we studied the elastic properties of PbBO{sub 3} for B being Ti, Zr, or Hf, one at a time. The density functional first principles calculations with local density approximation (LDA) and generalized gradient approximation (GGA) were employed. It is found that the maximum C{sub 11} elastic constant is achieved when the atomic size of the cations at A-site and B-site are comparable. We also found that C{sub 12} elastic constant is sensitive to B-site cations while C{sub 44} elastic constant is more sensitive to A-site cations. Details and explanations for such dependencies are discussed.

  12. Improved Electrical Properties of Low-Temperature Sintered Cu Doped Ba0.99Ca0.01Zr0.02Ti0.98O3 Ceramics

    Science.gov (United States)

    Zhang, Yong; Sun, Huajun; Chen, Wen

    2016-06-01

    In this study, a series of Ba0.99Ca0.01Zr0.02Ti0.98O3-x mol.% Cu (BCZT-xCu) ceramics were fabricated with a conventional solid state reaction method. The effects of sintering temperature and doping level of Cu ions on the microstructure development and electrical properties were studied systematically. The optimal sintering temperature could be lowered by 200°C compared to pure BCZT ceramics, due to the addition of Cu. Optimized properties were obtained for BCZT-2.0 mol.% Cu ceramics sintered at 1250°C, showing improved ferroelectric properties with a high remnant polarization (P r = 8.25 μC/cm2) and a low coercive field (E c = 0.395 kV/mm). Of particular significance is that the dielectric properties were found to show high thermal stability. The dielectric constant ( {ɛr } ) is within the scope of 1900-2350, while the dielectric loss (tanδ) is in the range of 1.15-2.2% within a temperature range of 30-105°C. In general, the BCZT-2.0Cu ceramics mainly display the characteristic of normal ferroelectrics.

  13. Elastic properties of perovskite ATiO3 (A = Be, Mg, Ca, Sr, and Ba) and PbBO3 (B = Ti, Zr, and Hf): First principles calculations

    International Nuclear Information System (INIS)

    The mechanical properties of perovskite oxides depend on two metal oxide lattices that are intercalated. This provides an opportunity for separate tuning of hardness, Poisson's ratio (transverse expansion in response to the compression), and shear strength. The elastic constants of series of perovskite oxides were studied by first principles approach. Both A-site and B-site cations were systematically varied in order to see their effects on the elastic parameters. To study the effects of A-site cations, we studied the elastic properties of perovskite ATiO3 for A being Be, Mg, Ca, Sr, or Ba, one at a time. Similarly, for B-site cations, we studied the elastic properties of PbBO3 for B being Ti, Zr, or Hf, one at a time. The density functional first principles calculations with local density approximation (LDA) and generalized gradient approximation (GGA) were employed. It is found that the maximum C11 elastic constant is achieved when the atomic size of the cations at A-site and B-site are comparable. We also found that C12 elastic constant is sensitive to B-site cations while C44 elastic constant is more sensitive to A-site cations. Details and explanations for such dependencies are discussed

  14. Microstructural characterization and interactions in Ti- and TiH2-hydroxyapatite vacuum sintered composites

    Directory of Open Access Journals (Sweden)

    Marcelo Teresa Maria

    2006-01-01

    Full Text Available Titanium/hydroxyapatite (HAP composites are candidate materials for biomedical applications as implants and hard tissue substitutes since they combine the good mechanical properties and biocompatibility of Ti with the excellent HAP bioactivity and osteointegration. In powder metallurgy processing of these composites, HAP decomposition promoted by Ti during powder sintering is found. In a previous work Ti-50v%HAP greens of 60% theoretical density (dT were vacuum sintered at 1150 degreesC and formation of CaO and Ca4O(PO42 (TTCP resulting from the HAP decomposition, as well as Ti4P3 at the Ti/HAP interfaces was obtained. In the present work those composites are compared with similar ones processed from TiH2 as a substitute for Ti which were also vacuum sintered at 1150 degreesC from greens with 60 to 86%dT. For the lower %dT, the compounds formed were CaO, TTCP and Ti4P3 and for the higher %dT ones, besides those same products, CaTiO3, Ti5P3 and a phase containing Ti, Ca and P were detected.

  15. Batievaite-(Y), Y2Ca2Ti[Si2O7]2(OH)2(H2O)4, a new mineral from nepheline syenite pegmatite in the Sakharjok massif, Kola Peninsula, Russia

    Science.gov (United States)

    Lyalina, L. M.; Zolotarev, A. A.; Selivanova, E. A.; Savchenko, Ye. E.; Krivovichev, S. V.; Mikhailova, Yu. A.; Kadyrova, G. I.; Zozulya, D. R.

    2016-05-01

    Batievaite-(Y), Y2Ca2Ti[Si2O7]2(OH)2(H2O)4, is a new mineral found in nepheline syenite pegmatite in the Sakharjok alkaline massif, Western Keivy, Kola Peninsula, Russia. The pegmatite mainly consists of nepheline, albite, alkali pyroxenes, amphiboles, biotite and zeolites. Batievaite-(Y) is a late-pegmatitic or hydrothermal mineral associated with meliphanite, fluorite, calcite, zircon, britholite-group minerals, leucophanite, gadolinite-subgroup minerals, titanite, smectites, pyrochlore-group minerals, zirkelite, cerianite-(Ce), rutile, behoite, ilmenite, apatite-group minerals, mimetite, molybdenite, and nickeline. Batievaite-(Y) is pale-cream coloured with white streak and dull, greasy or pearly luster. Its Mohs hardness is 5-5.5. No cleavage or parting was observed. The measured density is 3.45(5) g/cm3. Batievaite-(Y) is optically biaxial positive, α 1.745(5), β 1.747(5), γ 1.752(5) (λ 589 nm), 2V meas. = 60(5)°, 2V calc. = 65°. Batievaite-(Y) is triclinic, space group P-1, a 9.4024(8), b 5.5623(5), c 7.3784(6) Å, α 89.919(2), β 101.408(2), γ 96.621(2)°, V 375.65(6) Å3 and Z = 1. The eight strongest lines of the X-ray powder diffraction pattern [d(Å)(I)(hkl)] are: 2.991(100)(11-2), 7.238(36)(00-1), 3.061(30)(300), 4.350(23)(0-1-1), 9.145(17)(100), 4.042(16)(11-1), 2.819(16)(3-10), 3.745(13)(2-10). The chemical composition determined by electron probe microanalysis (EPMA) is (wt.%): Nb2O5 2.25, TiO2 8.01, ZrO2 2.72, SiO2 29.96, Al2O3 0.56, Fe2O3 0.43, Y2O3 11.45, La2O3 0.22, Ce2O3 0.33, Nd2O3 0.02, Gd2O3 0.07, Dy2O3 0.47, Er2O3 1.07, Tm2O3 0.25, Yb2O3 2.81, Lu2O3 0.45, CaO 24.98, MnO 1.31, MgO 0.01, Na2O 1.13, K2O 0.02, F 2.88, Cl 0.19, H2O 6.75 (determined on the basis of crystal structure data), O = (F,Cl) -1.25, total 97.09 wt.%. The empirical formula based on the EPMA and single-crystal structure analyses is (Y0.81Ca0.65Mn0.15Zr0.12Yb0.11Er0.04Fe3+ 0.04Ce0.02Dy0.02Lu0.02La0.01Tm0.01)Σ2.00((H2O)0.75Ca0.70□0.55)Σ2.00Ca2.00(□0.61Na0.25( H2O

  16. Al-Cu based welding wire with minor Sc-Zr alloying and its application

    Institute of Scientific and Technical Information of China (English)

    尹志民; 郭飞跃; 潘青林; 宋练鹏

    2003-01-01

    A kind of Al-Cu-(Sc, Zr, Mn, Ti, V, B) welding wire was developed by adding minor Sc, Zr, Mn, V, B, and was used for welding 2195 aluminum alloy plate with a thickness of 2 mm. Mechanical properties and microstructure of welding wire and welding joint were studied. The results show that strength coefficient of the welding joint is 0.70 and the weakest area lies in the softened zone of HAZ. It is indicated that this welding wire adding minor Sc, Zr, Mn, V, B is an ideal welding wire for 2195 Al-Li alloy plate. The high strength of the weld comes from grain-refining strengthening and precipitation strengthening of Al2Cu, Al3Sc and Al3Zr.

  17. Microwave dielectric properties of (1 − x)Mg{sub 0.95}Zn{sub 0.05}TiO{sub 3}–(x)Ca{sub 0.6}La{sub 0.8/3}TiO{sub 3} ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Rajput, Shailendra Singh [Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India); Keshri, Sunita, E-mail: s_keshri@bitmesra.ac.in [Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India); Gupta, Vibha Rani [Department of Electronics and Communication Engineering, Birla Institute of Technology, Mesra, Ranchi 835215 (India)

    2013-03-05

    Highlights: ► This report presents the microwave dielectric properties of (1 − x)MZT–(x)CLT samples. ► The 0.79MZT-0.21CLT composite sample shows a nearly zero τ{sub f} ∼ −0.8 ppm/°C. ► A dielectric resonator antenna has been fabricated using 0.79MZT-0.21CLT sample. ► The probe fed DRA provides higher gain as compared to the microstrip line fed DRA. -- Abstract: In this paper the structural and microwave dielectric properties of the (1 − x)(Mg{sub 0.95}Zn{sub 0.05})TiO{sub 3}–(x)(Ca{sub 0.6}La{sub 0.8/3})TiO{sub 3} ceramic composites have been investigated with the variation of x as well as sintering temperature. The grown samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy analysis. The Rietveld analysis of the XRD data has been carried out for structure refinement of the phases. The relative permittivity (∊{sub r}), quality factor (Q) and temperature coefficient of resonant frequency τ{sub f} of the grown samples have been thoroughly studied. Out of all samples of this series, the sample with x = 0.21 shows excellent dielectric properties with ∊{sub r}∼26.26, Q × f ∼ 60,738 GHz (at 6.44 GHz) and a nearly zero τ{sub f} ∼ −0.8 ppm/°C. Two types of dielectric resonator antennas with different feeding mechanisms have been fabricated using this sample to study their performance. The experimental results have been compared with the simulated results obtained using Ansoft High Frequency Structure Simulator software.

  18. Rotary condenser for SC2

    CERN Multimedia

    1975-01-01

    During 1975 the SC2 performance was improved among other things by redesigning some of the elements of the ROTCO (Annual Report 1975, p. 55). The photo shows an interior wiew of the housing of the rotary condenser and of the sixteen sets of shaped stator blades.

  19. Quaternary equilibrium diagrams ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}-(CaO, MgO, TiO{sub 2}). A powerful tool for the development of new materials by reaction sintering; Diagramas de equilibrio cuaternarios ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}- (CaO, MgO, TiO{sub 2}). Una poderosa herramienta para el desarrollo de nuevos materiales por sinterizacion reactiva

    Energy Technology Data Exchange (ETDEWEB)

    Moya, J. S.; Bartolome, J. F.; Pena, P.

    2011-07-01

    In this paper we set out, discuss and evaluate the work on Mullite-zirconia composites obtained by reaction sintering led and inspired by Salvador de Aza on the basis of ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}-(CaO, MgO, TiO{sub 2}) multicomponent phase equilibrium diagrams. We analyze their impact on different areas of ceramic science and technology such as refractory grogs, aluminum industry, etc. The possible fields of future applications such as dental prosthesis replacing partially stabilized zirconia materials with rare earths are also reported. (Author) 42 refs.

  20. 45Ti extraction using hydroxamate resin

    DEFF Research Database (Denmark)

    Gagnon, K.; Severin, Gregory; Barnhart, T. E.;

    2012-01-01

    As an attractive radionuclide for positron emission tomography, this study explores the extraction and reactivity of 45Ti produced via the 45Sc(p,n)45Ti reaction on a GE PETtrace. Using a small hydroxamate column, we have demonstrated an overall recovery of >50% of 45Ti in ~1 mL of 1M oxalic acid....... Conditions for reacting with desferal were also explored, with effective specific activities up to 38 GBq/μmol obtained....

  1. Atomistic modeling of ternary additions to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt and Ni-Ti-Hf shape memory alloys

    International Nuclear Information System (INIS)

    The behavior of ternary and quaternary additions to NiTi shape memory alloys is investigated using a quantum approximate method for the energetics. Ternary additions X to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt, and Ni-Ti-Hf alloys, for X=Au, Pt, Ir, Os, Re, W, Ta,Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Zn, Cu, Co, Fe, Mn, V, Sc, Si, Al and Mg are considered. Bulk properties such as lattice parameter, energy of formation, and bulk modulus of the B2 alloys are studied for variations due to the presence of one or two simultaneous additives.

  2. Atomistic modeling of ternary additions to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt and Ni-Ti-Hf shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mosca, H.O., E-mail: hmosca@cnea.gov.ar [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, B1650KNA San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Bozzolo, G. [Loyola University Maryland, 4501 N. Charles St., Baltimore, MD 21210 (United States); Grosso, M.F. del [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, B1650KNA San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, CONICET (Argentina)

    2012-08-15

    The behavior of ternary and quaternary additions to NiTi shape memory alloys is investigated using a quantum approximate method for the energetics. Ternary additions X to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt, and Ni-Ti-Hf alloys, for X=Au, Pt, Ir, Os, Re, W, Ta,Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Zn, Cu, Co, Fe, Mn, V, Sc, Si, Al and Mg are considered. Bulk properties such as lattice parameter, energy of formation, and bulk modulus of the B2 alloys are studied for variations due to the presence of one or two simultaneous additives.

  3. Approaching compositional limits of perovskite - type oxides and oxynitrides by synthesis of Mg0.25Ca0.65Y0.1Ti(O,N)3, Ca1-xYxZr(O,N)3 (0.1 ≤ x ≤ 0.4), and Sr1-xLaxZr(O,N)3 (0.1 ≤ x ≤ 0.4)

    Science.gov (United States)

    Widenmeyer, Marc; Peng, Chen; Baki, Aykut; Xie, Wenjie; Niewa, Rainer; Weidenkaff, Anke

    2016-04-01

    Partial substitution of cations and anions in perovskite-type materials is a powerful way to tune the desired properties. The systematic variation of the cations size, the partial exchange of O2- for N3- and their effect on the size of the optical band gap and the thermal stability was investigated here. The anionic substitution resulted in the formation of the orthorhombic perovskite-type oxynitrides Mg0.25Ca0.65Y0.1Ti(O,N)3, Ca1-xYxZr(O,N)3, and Sr1-xLaxZr(O,N)3. A two-step synthesis protocol was applied: i) (nano-crystalline) oxide precursors were synthesized by a Pechini method followed by ii) ammonolysis in flowing NH3 at T = 773 K (Ti) and T = 1273 K (Zr), respectively. High-temperature synthesis of such oxide precursors by solid-state reaction generally resulted in phase separation of the different A-site cations. Changes of the crystal structures were investigated by Rietveld refinements of the powder XRD data, thermal stability by DSC/TG measurements in oxygen atmosphere, oxygen and nitrogen contents by O/N analysis using hot gas extraction technique, and optical band gaps by photoluminescence spectroscopy. By moving from Mg0.25Ca0.65Y0.1Ti(O,N)3 via Ca1-xYxZr(O,N)3 to Sr1-xLaxZr(O,N)3, the degree of tilting of the octahedral network is reduced, as observed by an increase in the B-X-B angles caused by the simultaneously increasing effective ionic radius of the A-site cation(s). In general, increasing substitution levels on the A-site (Y3+ and La3+) are accompanied by an enhanced replacement of O2- by N3-. In all three systems, this anionic substitution resulted in a reduction of the optical band gap by approximately 1 eV (Ti) and up to 2.1 eV (Zr) compared to the respective oxides. For Mg0.25Ca0.65Y0.1Ti(O,N)3 an optical band gap of 2.2 eV was observed, appropriate for a solar water splitting photocatalyst. The Zr-based oxynitrides required a by a factor of 2 higher nitrogen contents to significantly reduce the optical band gap and the measured values of 2

  4. Instrumental neutron-activation analysis applications in the assessment of Al, Ca, Dy, K, Mg, Na, Ti, and V contents in soils of the adjacent Khamar-Daban mountain range

    International Nuclear Information System (INIS)

    Full text: With consideration of predominating winds in the region, the Baikal Pulp and Paper Complex (BPPC) is likely to be a key source of industrial air emissions on the southern shore of the Baikal Lake to the North-East of the Baikalsk city. About thirty years ago on-going drying of dark coniferous forests growing on the North- Western slopes of the Khamar-Daban Range to the North-East of the Complex was revealed. Numerous biogeocenoses surveys of impaired and drying forests allowed to concluding on the primary impact of BPPC air emissions. The presence of toxic chemicals is reasoned by solid fuel combustion at the BPPC heat and power plant (HPP). Solid fuel burning is known to release a wide range of chemicals, including heavy metals, into the atmospheric air. Their excessive concentrations are also likely to produce negative impact on various ecosystems, including land-based. Indirect retrospective assessment of the regional pollution level is achievable through a survey focused on environment objects that accumulate both major, minor, and trace elements present in industrial air emissions. Topsoil is a more appropriate subject for such surveys. Contaminants are retained in soil for significantly longer time than in other biosphere components - most likely eternally. Soil serves as a mighty absorber of many chemical elements. It retains them in topsoil, which is the most fertile soil layer. As research subjects were used topsoil samples taken on the Khamar-Daban mounts to the North-East of BPPC at a height of about 1200 - 1500 m above sea level in two areas located 11 and 84 km away, respectively. For chemical element content analysis soil samples were taken from topsoil 4 cm thick as an average mixed sample. Mass fractions of 9 chemical elements (Al, Ca, Dy, K, Mg, Mn, Na, Ti and V) were measured by the instrumental neutron activation analysis using short-lived radionuclides. Ampoules with soil samples were irradiated in the thermal column of the IRT

  5. CaMn0.875Ti0.125O3 as oxygen carrier for chemical-looping combustion with oxygen uncoupling (CLOU)—Experiments in a continuously operating fluidized-bed reactor system

    KAUST Repository

    Rydén, Magnus

    2011-03-01

    Particles of the perovskite material CaMn0.875Ti0.125O3 has been examined as oxygen carrier for chemical-looping with oxygen uncoupling, and for chemical-looping combustion of natural gas, by 70h of experiments in a circulating fluidized-bed reactor system. For the oxygen uncoupling experiments, it was found that the particles released O2 in gas phase at temperatures above 720°C when the fuel reactor was fluidized with CO2. The effect increased with increased temperature, and with the O2 partial pressure in the air reactor. At 950°C, the O2 concentration in the outlet from the fuel reactor was in the order of 4.0vol%, if the particles were oxidized in air. For the chemical-looping combustion experiments the combustion efficiency with standard process parameters was in the order of 95% at 950°C, using 1000kg oxygen carrier per MW natural gas, of which about 30% was located in the fuel reactor. Reducing the fuel flow so that 1900kg oxygen carrier per MW natural gas was used improved the combustion efficiency to roughly 99.8%. The particles retained their physical properties, reactivity with CH4 and ability to release gas-phase O2 reasonably well throughout the testing period and there were no problems with the fluidization or formation of solid carbon in the reactor. X-ray diffraction showed that the particles underwent changes in their phase composition though. © 2010 Elsevier Ltd.

  6. Dual-band LTCC antenna based on 0.95Zn2SiO4-0.05CaTiO3 ceramics for GPS/UMTS applications

    Science.gov (United States)

    Dou, Gang; Li, Yu-Xia; Guo, Mei

    2015-10-01

    In this paper, we present a compact low-temperature co-fired ceramic (LTCC) dual-band antenna by using the electromagnetic coupling effect concept for global positioning system (GPS) and universal mobile telecommunication system (UMTS) applications. The overall dimension of the antenna is 8.6 mm × 13.0 mm × 1.1 mm. It consists of double meander lines and a via hole line. The top meander line operates at the upper band, and the bottom radiating patch is designed for the lower band. The via-hole line is employed to connect the double meander lines. Because of the effect of the coupled line, total dimension of the proposed antenna is greatly reduced. With the 2.5: voltage standing wave ratio (VSWR) impedance bandwidth definition, the lower and upper bands have the bandwidths of 110 MHz and 150 MHz, respectively. The proposed antenna is successfully designed, simulated, and analyzed by a high frequency structure simulator (HFSS). And the antenna is manufactured by using the 0.95Zn2SiO4-0.05CaTiO3 ceramics (εr = 7.1, tanδ = 0.00038) that is prepared by ourselves. The results show that the antenna is compact, efficient, and of near omnidirectional radiation pattern. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20133718120009), the Natural Science Foundation of Shandong Provence, China (Grant Nos. ZR2013FQ002 and ZR2014FQ006), the China Postdoctoral Science Foundation (Grant No. 2014M551935), the Qingdao Municipality Postdoctoral Science Foundation, China, and the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents, China (Grant Nos. 2013RCJJ042 and 2014RCJJ052).

  7. Resistive switching mechanisms in random access memory devices incorporating transition metal oxides: TiO2, NiO and Pr0.7Ca0.3MnO3

    International Nuclear Information System (INIS)

    Resistance change random access memory (RRAM) cells, typically built as MIM capacitor structures, consist of insulating layers I sandwiched between metal layers M, where the insulator performs the resistance switching operation. These devices can be electrically switched between two or more stable resistance states at a speed of nanoseconds, with long retention times, high switching endurance, low read voltage, and large switching windows. They are attractive candidates for next-generation non-volatile memory, particularly as a flash successor, as the material properties can be scaled to the nanometer regime. Several resistance switching models have been suggested so far for transition metal oxide based devices, such as charge trapping, conductive filament formation, Schottky barrier modulation, and electrochemical migration of point defects. The underlying fundamental principles of the switching mechanism still lack a detailed understanding, i.e. how to control and modulate the electrical characteristics of devices incorporating defects and impurities, such as oxygen vacancies, metal interstitials, hydrogen, and other metallic atoms acting as dopants. In this paper, state of the art ab initio theoretical methods are employed to understand the effects that filamentary types of stable oxygen vacancy configurations in TiO2 and NiO have on the electronic conduction. It is shown that strong electronic interactions between metal ions adjacent to oxygen vacancy sites results in the formation of a conductive path and thus can explain the 'ON' site conduction in these materials. Implication of hydrogen doping on electroforming is discussed for Pr0.7Ca0.3MnO3 devices based on electrical characterization and FTIR measurements.

  8. Low-temperature sintering and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]3- δ with glass frit added

    Science.gov (United States)

    In, Chi-Seung; Yeo, Dong-Hun; Shin, Hyo-Soon; Nahm, Sahn; Choi, Won-Youl

    2015-04-01

    In accordance with the trend for mobile terminals to be high intensity and to have thinner layers, low temperature co-fired ceramics (LTCC) materials with outstanding dielectric loss characteristics and diverse dielectric constants have been in demand, and the need for high-strength materials that can withstand external shocks has increased. Ca[(Li1/3Nb2/3)1- x Ti x ]O3- δ (CLNT) has a quality factor over 14,000 and τ f ≤ 10 when the dielectric constant is 41 ˜ 46, but its sintering temperature is high at 1150 °C. Therefore, it cannot be used as a LTCC component. This study aimed to lower the sintering temperature to 900 °C by adding a low-melting-point glass such as B2O3·SiO2·BaO and B2O3·SiO2·Al2O3. As the glass content in CLNT was increased from 10 wt% to 20 wt%, the density and the Q·f0 property decreased, and the dielectric constant rose. When B2O3·SiO2·BaO was added to CLNT at 15 wt%, the dielectric constant was found to be 27, the Q·f0 property to be 3470, and the τ f to be -18 ppm/°C. When B2O3·SiO2·Al2O3 was added to CLNT at 10 wt%, the dielectric constant was 20, the Q·f0 property was 3990, and the τ f was -15 ppm/°C. As such, in both cases, excellent dielectric properties were observed.

  9. The non-ohmic and dielectric behavior evolution of CaCu{sub 3}Ti{sub 4}O{sub 12} after heat treatments in oxygen-rich atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Qiaoli [College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou 450011 (China); Li Tao, E-mail: hnlt529@163.com [Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Chen Zhenping; Xue Renzhong; Wang Yongqiang [Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the percent of oxygen at grain boundaries of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the dielectric properties of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the non-ohmic behaviors of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can enhance the potential barrier of CCTO ceramics. Black-Right-Pointing-Pointer We have explained behavior between the permittivity and the non-ohmic characteristics of CCTO ceramics by the Schottky potential barrier theory. - Abstract: CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics pellets were prepared using the solid-state reaction method, and then they were heat-treated at different temperatures in oxygen-rich atmosphere. The effect of heat treatments on the non-ohmic behaviors and dielectric properties were investigated. EDS analysis results indicate that the percent of oxygen at grain boundaries of CCTO ceramics heat-treated in oxygen-rich atmosphere increases markedly with the rise of temperature and approaches saturation state at about 850 Degree-Sign C. The breakdown voltage and nonlinear coefficient also exhibit an increase trend with the rise of temperature. In addition, the calculated results manifest that the height of Schottky potential barrier is closely related to the oxygen content at the grain boundaries. The permittivity and dielectric loss of samples heat-treated present a relatively intense decrease with the rise of temperature. But the permittivity has a behavior just reverse to the non-ohmic characteristics, which can be explained by the Schottky potential barrier theory.

  10. Physical conditions in CaFe interstellar clouds

    OpenAIRE

    Gnacinski, P.; Krogulec, M.

    2007-01-01

    Interstellar clouds that exhibit strong Ca I and Fe I lines were called CaFe clouds. The ionisation equilibrium equations were used to model the column densities of Ca II, Ca I, K I, Na I, Fe I and Ti II in CaFe clouds. The chemical composition of CaFe clouds is that of the Solar System and no depletion of elements onto dust grains is seen. The CaFe clouds have high electron densities n=1 cm^-3 that leads to high column densities of neutral Ca and Fe.

  11. Structure property relationships in the ATi2O4 (A=Na, Ca) family of reduced titanates

    International Nuclear Information System (INIS)

    Reduced titanates in the ATi2O4 (A=Li, Mg) spinel family exhibit a variety of interesting electronic and magnetic properties, most notably superconductivity in the mixed-valence spinel, Li1+x Ti2-x O4. The sodium and calcium analogs, NaTi2O4 and CaTi2O4, each differ in structure, the main features of which are double rutile-type chains composed of edge-sharing TiO6 octahedra. We report for the first time, the properties and band structures of these two materials. XANES spectroscopy at the Ti K-edge was used to probe the titanium valence. The absorption edge position and the pre-edge spectral features observed in the XANES data confirm the assignment of Ti3+ in CaTi2O4 and mixed-valence Ti3+/Ti4+ in NaTi2O4. Temperature-dependent resistivity and magnetic susceptibility studies are consistent with the classification of both NaTi2O4 and CaTi2O4 as small band-gap semiconductors, although changes in the high-temperature magnetic susceptibility of CaTi2O4 suggest a possible insulator-metal transition near 700 K. Band structure calculations agree with the observed electronic properties of these materials and indicate that while Ti-Ti bonding is of minimal importance in NaTi2O4, the titanium atoms in CaTi2O4 are weakly dimerized at room temperature. -- Graphical abstract: Normalized titanium K-edge XANES spectra confirm mixed-valence for NaTi2O4 with an edge energy intermediate between Ti3+ oxides such as CaTi2O4, MgTi2O4 and Ti2O3, and Ti4+ containing oxides such as TiO2

  12. Radiative lifetimes of even- and odd-parity levels in Sc I and Sc II

    International Nuclear Information System (INIS)

    Time-resolved laser-induced fluorescence on atomic and ionic beams is used to measure radiative lifetimes for 77 odd- and even-parity levels of Sc I and Sc II. Time-of-flight selection of slow Sc atoms is demonstrated to minimize error in long lifetimes, an error that arises because escape from the observing region before radiating. High-lying even-parity levels in Sc I and Sc II are excited by using two-step laser excitation

  13. Search for beta sup - and beta sup -beta sup - decays of sup 4 sup 8 Ca

    CERN Document Server

    Bakalyarov, A; Barabash, A; Briançon, C; Brudanin, V; Egorov, V; Hubert, F; Hubert, P; Kovalik, A; Lebedev, V I; Rukhadze, N I; Stekl, I; Umatov, V; Vylov, T D

    2002-01-01

    A sup 4 sup 8 CaCO sub 3 powder sample containing 20.18 g of sup 4 sup 8 Ca was measured for 797 h with a 400 cm sup 3 low-background HPGe detector. New limits on decays of sup 4 sup 8 Ca were obtained. For single beta transitions to sup 4 sup 8 Sc the limits are equal to 0.71x10 sup 2 sup 0 y, 1.1x10 sup 2 sup 0 y, and 0.82x10 sup 2 sup 0 y for transitions to the ground state, excited 5 sup + and 4 sup + states, respectively. The new limits on double beta decay to excited states of sup 4 sup 8 Ti are equal to 0.47x10 sup 2 sup 0 y, 1.1x10 sup 2 sup 0 y, and 0.90x10 sup 2 sup 0 y for transitions to the first 2 sup + , second 2 sup + and first 0 sup + excited states, respectively. All limits are given at the 90% CL.

  14. Xemilofiban: SC 54684A, xemlofiban.

    Science.gov (United States)

    2003-01-01

    Xemilofiban [SC 54684, SC 54684A (HCl), xemlofiban], a glycoprotein IIb/IIIa antagonist, is an orally available prodrug of a non-peptide mimetic of the tetrapeptide RGDF. It is converted to the active metabolite, SC 54701 (the free base form of SC 54701A). Development was initiated by Searle (Monsanto). Searle became part of Pharmacia Corporation, which was acquired by, and merged into, Pfizer in April 2003. Searle had co-development and co-marketing agreements with Sankyo in Japan; these have been discontinued. In January 2003, Pharmacia donated the intellectual property for xemilofiban to Western Michigan University. In February 2003, Western Michigan University granted an exclusive worldwide licence of xemilofiban to VDDI Pharmaceuticals (formerly Virtual Drug Development Inc.). Xemilofiban was in a phase III clinical trial, the Evaluation of Xemilofiban in Controlling Thrombotic Events (EXCITE) trial, with Searle (Monsanto) in the US and Europe for the treatment of thrombosis in patients with unstable angina pectoris and acute myocardial infarction undergoing angioplasty. However, as xemilofiban demonstrated no significant clinical benefit, Searle discontinued its development. In Japan, Sankyo discontinued the development of xemilofiban for thrombosis at phase II following Searle's decision to drop the project. VDDI Pharmaceuticals plans to develop xemilofiban in cardiovascular disorders following on from the phase III studies completed by Pharmacia; a restructured dosing schedule and narrowed patient selection will be used. VDDI has research facilities worldwide and will utilise facilities in Ireland for the European clinical development programme; research facilities in the Southwest Michigan Innovation Center are planned while the head office of VDDI is based in Tennessee. Xemilofiban is in phase III development for the treatment of cardiovascular disease in conjunction with percutaneous coronary intervention. PMID:14584975

  15. An orange emitting phosphor Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe with pure garnet phase for warm white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Yaoqing [Engineering Research Center of Advanced Glasses Manufacturing Technology, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China); School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Zhang, Qinghong [Engineering Research Center of Advanced Glasses Manufacturing Technology, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China); Xu, Jiayue [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Li, Yaogang, E-mail: yaogang_li@dhu.edu.cn [Engineering Research Center of Advanced Glasses Manufacturing Technology, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China); Wang, Hongzhi, E-mail: wanghz@dhu.edu.cn [Engineering Research Center of Advanced Glasses Manufacturing Technology, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China)

    2015-09-15

    A new silicate garnet phosphor, Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe was synthesized by a high temperature solid-state reaction under reductive atmosphere. X-ray diffraction (XRD) showed that the powder was pure garnet phase. The emission and excitation spectrum indicated that the Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe phosphors could absorb blue light in the spectral range of 400–550 nm efficiently and exhibit bright yellow–orange emission in the range of 520–750 nm. With the increase of Ce{sup 3+} concentration, the emission band of Ce{sup 3+} showed a red shift. Interestingly, the concentration quenching occurred when the Ce{sup 3+} concentration exceeded 4 mol%. The temperature-dependent luminescent properties of the phosphors were discussed and the Lu{sub 1.96}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:0.04Ce phosphors showed good performances in color temperature (2430 K) and potential applications for warm white LEDs. - Graphical Abstract: This image shows that the phosphor of Lu{sub 1.96}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:0.04Ce can generate a uniform yellow tint under natural light illumination and emit orange–red light when excited by blue light. With a fixed 467 nm emission light, warm white light can be produced by this phosphor, which indicates that the phosphor is potentially applicable in warm white light emitting diodes based on GaN chips. - Highlights: • A new silicate garnet phosphor was synthesized by solid-state method. • Secondary phases can be avoided when a small amount of Si{sup 4+} were replaced by Ti{sup 4+}. • A broad emission band of Ce{sup 3+} in the phosphors was described. • The phosphors are potentially applicable in warm white light emitting diodes.

  16. Isospin-symmetry-hindered branch of 42Sc β-decay

    International Nuclear Information System (INIS)

    The branching fraction for the isospin-symmetry-hindered positron decay of 42Sc to 42Ca (1.837 MeV) was measured to be (6.3+-2.6)x105 by observation of delayed γ-rays. This branch alone corresponds to a reduction of the superallowed ground-state Fermi strength by (0.043+-0.018)%. The 42Sc sources were produced by the 42Ca(p,n)42Sc reaction at 7.7 MeV. The measured branching agrees with Coulomb-mixing calculations by Rappleyea and Kunz and by Towner, but is smaller than other calculations. This result is of interest in connection with the intercomparison of the superallowed 0+ → 0+ pure Fermi decays, which determine the effective vector coupling constant of nuclear β-decay. (Auth.)

  17. Effect of minor Sc and Zr addition on grain refinement of as-cast AI-Zn-Mg-Cu alloys

    Institute of Scientific and Technical Information of China (English)

    He Yongdong; Zhang Xinming; Cao Zhiqiang

    2009-01-01

    The optical microscopy and scanning electron microscopy as well as energy dispersive spectroscopy were employed to investigate the influence of joint addition of Sc and Zr on grain refinement of AI-Zn-Mg-Cu alloys.Results show that the addition of 0.20% Sc has a little effect on grain refinement because Sc is mainly dissolved into the matrix and hardly any primary Al3Sc particles are precipitated. The alloy with addition of 0.30% Sc and 0.16%Zr has more equiaxed grains than that of others,giving cast grain sizes as fine as 13μm. This is because the Sc substitutes for AI atom in the AI-Zr crystal cell and forms AI-Sc-Zr unit cell,which grows and becomes AI3(Scx,Zr1.x)particle,acting as a nucleus for the formation of a-AI. The addition of 0.04% Ti and 0.008% B makes the grain size drop from 250 μm to 50 μm. Its refinement effect is less than the 13 μm achieved by the alloy including 0.30% Sc and 0.16% Zr.

  18. Magnetic and charge ordering properties of Bi{sub 0.2}Ca{sub 0.8}Mn{sub 0.9}X{sub 0.1}O{sub 3} (where X = Ti, Cr, Fe, Co, Ni, Cu)

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Kamlesh [Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667 (India); Vaithyanathan, V.; Inbanathan, S.S.R. [Post Graduate and Research Department of Physics, The American College, Madurai 625002 (India); Varma, G.D., E-mail: gdvarfph@iitr.ernet.in [Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

    2012-08-25

    Highlights: Black-Right-Pointing-Pointer Structural, magnetic and transport properties of Bi{sub 0.2}Ca{sub 0.8}Mn{sub 0.9}X{sub 0.1}O{sub 3} (where X = Ti, Cr, Fe, Co, Ni, Cu) have been studied. Black-Right-Pointing-Pointer T{sub CO} decreases by {approx}10 K and {approx}33 K, in Ni{sup 2+} and Cu{sup 2+} doped samples, while it increases by 42 K in Ti{sup 4+} doped sample. Black-Right-Pointing-Pointer In case of Fe{sup 3+}, Co{sup 3+} and Cr{sup 3+} doped samples charge-ordering (CO) completely disappears. Black-Right-Pointing-Pointer Furthermore, the enhancement in resistivity in all the doped samples with respect to undoped one has been observed. Black-Right-Pointing-Pointer The magnetic exchange interactions between Mn and doped ions explain magnetic and electrical properties. - Abstract: Structural, magnetic and transport properties of Bi{sub 0.2}Ca{sub 0.8}Mn{sub 0.9}X{sub 0.1}O{sub 3} (where X = Ti, Cr, Fe, Co, Ni, Cu) have been investigated. The parent sample Bi{sub 0.2}Ca{sub 0.8}MnO{sub 3} (BCMO) exhibits robust charge-ordered antiferrromagnetic (COAFM) phase with charge ordering temperature (T{sub CO}) {approx}155 K and AFM Neel temperature (T{sub N}) {approx}105 K. T{sub CO} decreases by {approx}10 K and {approx}33 K, respectively, in Ni{sup 2+} and Cu{sup 2+} doped samples, while it increases by 42 K in Ti{sup 4+} doped sample. In case of Fe{sup 3+}, Co{sup 3+} and Cr{sup 3+} doped samples charge-ordering (CO) completely melts. The paramagnetic (PM) to ferromagnetic (FM) transition temperatures (T{sub C}) of doped samples have lower values as compared to undoped one. In addition, a spin glass (SG) state is observed in all the samples and the magnetic state at T < T{sub C} is akin to a cluster glass (CG) for undoped and Ni, Cu, Ti doped samples formed due to the presence of FM clusters in COAFM matrix. Furthermore, the enhancement in resistivity in all the doped samples with respect to undoped one has been observed. Based on the present study it has

  19. Diagramas de equilibrio cuaternarios ZrO2-Al2O3-SiO2-(CaO, MgO, TiO2). Una poderosa herramienta para el desarrollo de nuevos materiales por sinterización reactiva

    OpenAIRE

    Moya, J.S.; Bartolomé, J. F.; Peña, P.

    2011-01-01

    En este articulo se exponen, discuten y evalúan los trabajos que sobre materiales de Mullita-Circona obtenidos por sinterización reactiva dirigió e inspiro Salvador de Aza sobre la base de los diagramas de equilibrio de fase multicomponentes ZrO2-Al2O3-SiO2-(CaO, MgO, TiO2). Se analiza su impacto en distintas áreas de la ciencia y tecnología cerámicas tales como chamotas refractarias, industria del aluminio, etc. También se proponen posibles campos de aplicación futura como es el ...

  20. Exploration of R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge): Structural Motifs, the novel Compound Gd2AlGe2 and Analysis of the U3Si2 and Zr3Al2 Structure Types

    Energy Technology Data Exchange (ETDEWEB)

    Sean William McWhorter

    2006-05-01

    In the process of exploring and understanding the influence of crystal structure on the system of compounds with the composition Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} several new compounds were synthesized with different crystal structures, but similar structural features. In Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, the main feature of interest is the magnetocaloric effect (MCE), which allows the material to be useful in magnetic refrigeration applications. The MCE is based on the magnetic interactions of the Gd atoms in the crystal structure, which varies with x (the amount of Si in the compound). The crystal structure of Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} can be thought of as being formed from two 3{sup 2}434 nets of Gd atoms, with additional Gd atoms in the cubic voids and Si/Ge atoms in the trigonal prismatic voids. Attempts were made to substitute nonmagnetic atoms for magnetic Gd using In, Mg and Al. Gd{sub 2}MgGe{sub 2} and Gd{sub 2}InGe{sub 2} both possess the same 3{sup 2}434 nets of Gd atoms as Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, but these nets are connected differently, forming the Mo{sub 2}FeB{sub 2} crystal structure. A search of the literature revealed that compounds with the composition R{sub 2}XM{sub 2} (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge) crystallize in one of four crystal structures: the Mo{sub 2}FeB{sub 2}, Zr{sub 3}Al{sub 2}, Mn{sub 2}AlB{sub 2} and W{sub 2}CoB{sub 2} crystal structures. These crystal structures are described, and the relationships between them are highlighted. Gd{sub 2}AlGe{sub 2} forms an entirely new crystal structure, and the details of its synthesis and characterization are given. Electronic structure calculations are performed to understand the nature of bonding in this compound and how electrons can be accounted for. A series of electronic structure calculations were performed on models with the U{sub 3}Si{sub 2} and Zr{sub 3}Al{sub 2} structures, using Zr and A1 as

  1. The temporoammonic input to the hippocampal CA1 region displays distinctly different synaptic plasticity compared to the Schaffer collateral input in vivo: significance for synaptic information processing

    Directory of Open Access Journals (Sweden)

    Ayla eAksoy Aksel

    2013-08-01

    Full Text Available In terms of its sub-regional differentiation, the hippocampal CA1 region receives cortical information directly via the perforant (temporoammonic path (pp-CA1 synapse and indirectly via the tri-synaptic pathway where the last relay station is the Schaffer collateral-CA1 synapse (Sc-CA1 synapse. Research to date on pp-CA1 synapses has been conducted predominantly in vitro and never in awake animals, but these studies hint that information processing at this synapse might be distinct to processing at the Sc-CA1 synapse. Here, we characterized synaptic properties and synaptic plasticity at the pp-CA1 synapse of freely behaving adult rats. We established that field excitatory postsynaptic potentials at the pp-CA1 have longer onset latencies and a shorter time-to-peak compared to the Sc-CA1 synapse. LTP (> 24h was successfully evoked by tetanic afferent stimulation of pp-CA1 synapses. Low frequency stimulation evoked synaptic depression at Sc-CA1 synapses, but did not elicit LTD at pp-CA1 synapses unless the Schaffer collateral afferents to the CA1 region had been severed. Paired-pulse responses also showed significant differences. Our data suggest that synaptic plasticity at the pp-CA1 synapse is distinct from the Sc-CA1 synapse and that this may reflect its specific role in hippocampal information processing.

  2. Strain dependence of the electronic properties of LaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Moon, S. J. [Hanyang University, Seoul (Korea, Republic of); Kim, Y. S. [Seoul National University, Seoul (Korea, Republic of)

    2014-11-15

    We report on the transport and the core-level X-ray photoemission spectroscopy data of fully strained LaTiO{sub 3} thin films grown on GdScO{sub 3} and SrTiO{sub 3} substrates. We observed that LaTiO{sub 3} thin film grown on GdScO{sub 3} showed insulating behavior but that grown on SrTiO{sub 3} exhibited a metallic character. We found that while the La 4d photoemission spectra of the two films were nearly the same, their Ti 2p and O 1s data revealed a difference. Our results suggest that strain induced changes in the Ti-O bonding play an important role in the electronic properties of LaTiO{sub 3} thin films.

  3. 46 CFR 7.70 - Folly Island, SC to Hilton Head Island, SC.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Folly Island, SC to Hilton Head Island, SC. 7.70 Section... BOUNDARY LINES Atlantic Coast § 7.70 Folly Island, SC to Hilton Head Island, SC. (a) A line drawn from the southernmost extremity of Folly Island to latitude 32°35′ N. longitude 79°58.2′ W. (Stono Inlet Lighted...

  4. Soft spin dipole giant resonances in 40Ca

    CERN Document Server

    Stuhl, L; Csatlos, M; Marketin, T; Litvinova, E; Adachi, T; Algora, A; Daeven, J; Estevez, E; Fujita, H; Fujita, Y; Guess, C; Gulyas, J; Hatanaka, K; Hirota, K; Ong, H J; Ishikawa, D; Matsubara, H; Meharchand, R; Molina, F; Okamura, H; Perdikakis, G; Rubio, B; Scholl, C; Suzuki, T; Susoy, G; Tamii, A; Thies, J; Zegers, R; Zenihiro, J

    2013-01-01

    High resolution experimental data has been obtained for the 40,42,44,48Ca(3He,t)Sc charge exchange reaction at 420 MeV beam energy, which favors the spin-isospin excitations. The measured angular distributions were analyzed for each state separately, and the relative spin dipole strength has been extracted for the first time. The low-lying spin-dipole strength distribution in 40Sc shows some interesting periodic gross feature. It resembles to a soft, dumped multi-phonon vibrational band with $\\hbar\\omega$= 1.8 MeV, which might be associated to pairing vibrations around $^{40}$Ca.

  5. Soft spin-dipole resonances in 40Ca

    International Nuclear Information System (INIS)

    High resolution experimental data has been obtained for the 40,42,44,48Ca(3He,t)Sc charge exchange reaction at 420 MeV beam energy, which favors the spin-isospin excitations. The measured angular distributions were analyzed for each state separately, and the relative spin dipole strength has been extracted for the first time. The low-lying spin-dipole strength distribution in 40Sc shows some interesting periodic gross feature. It resembles to a soft, damped multi-phonon vibrational band with hω= 1.8 MeV, which might be associated to pairing vibrations around 40Ca.

  6. Angular properties of pure and Ca-substituted YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting thin films grown on SrTiO{sub 3} and CeO{sub 2} buffered Al{sub 2}O{sub 3} substrates

    Energy Technology Data Exchange (ETDEWEB)

    Augieri, A. [ENEA Research Center, Via E. Fermi 45, 00044 Frascati, Rome (Italy)], E-mail: augieri@frascati.enea.it; Celentano, G. [ENEA Research Center, Via E. Fermi 45, 00044 Frascati, Rome (Italy); Ciontea, L. [Technical university of Cluj-Napoca, Str. C. Daicoviciu 15, 3400 Cluj-Napoca (Romania); Galluzzi, V. [ENEA Research Center, Via E. Fermi 45, 00044 Frascati, Rome (Italy); Gambardella, U. [INFN-LNF, Via E. Fermi 40, 00044 Frascati, Rome (Italy); Halbritter, J. [IHM, FZK, Postfach 3640, 76021 Karlsruhe (Germany); Petrisor, T. [Technical university of Cluj-Napoca, Str. C. Daicoviciu 15, 3400 Cluj-Napoca (Romania); Rufoloni, A.; Vannozzi, A. [ENEA Research Center, Via E. Fermi 45, 00044 Frascati, Rome (Italy)

    2007-09-01

    In this work transport properties of superconducting 10 at.% Ca-substituted YBCO thin films grown on (1 0 0)-SrTiO{sub 3} single crystal substrate (STO) and superconducting pure and 10 at.% Ca-substituted YBCO thin films grown on CeO{sub 2} buffered Al{sub 2}O{sub 3} substrates (CAO) have been analyzed as a function of the temperature, applied magnetic field and angle between magnetic field direction and the direction normal to the film surfaces. Particularly, the angular analysis provides an easy way to discriminate between isotropic point defects and correlated pinning sites. Despite the intragrain pinning mechanisms remained unaffected by Ca substitution, a detrimental effect on grain boundary properties clearly emerged for 10 at.% Ca concentration. This effect is enhanced in sample grown on CeO{sub 2} buffered sapphire where a more disturbed grain boundary is expected resulting in an enhancement of the correlated pinning, already observed in pure YBCO films grown on CAO, and in a reduction of the intrinsic pinning efficiency.

  7. The xerocytosis of Hb SC disease.

    Science.gov (United States)

    Ballas, S K; Larner, J; Smith, E D; Surrey, S; Schwartz, E; Rappaport, E F

    1987-01-01

    Patients with Hb SC disease were found to have microcytic and hyperchromic red cell indices despite mild reticulocytosis. Iron deficiency anemia was ruled out by the finding of normal serum ferritin levels. In order to determine whether the microcytosis was due to coexistent alpha-thalassemia, restriction endonuclease mapping was performed on genomic DNA extracted from peripheral blood leukocytes. Patients with Hb SC disease had microcytic indices despite the presence of a full complement of four alpha-genes (alpha alpha/alpha alpha), suggesting that the microcytosis may be due to cellular dehydration (or xerocytosis), since the mean corpuscular hemoglobin concentration in Hb SC disease patients was significantly higher than in controls. This possibility was investigated further by the determination of RBC cation content. RBC Na levels were similar in SC and normal red cells. Hb SC RBCs, however, had significantly reduced K levels. These findings show that RBC cation content, and thus cell water, is decreased in Hb SC disease. The decreased RBC K level in the presence of normal cellular Na concentration suggests selective K loss that is not due to inhibition of the Na K pump. Ouabain-insensitive K+ efflux was increased to four times normal in SC cells. Cell dehydration was confirmed by the demonstration of increased high-density RBCs on discontinuous Stractan density gradients and by osmotic gradient ektacytometry. Cellular dehydration and its sequelae were worse in CC erythrocytes and milder in AC cells than in Hb SC red cells. Taken together, these data indicate that in Hb SC disease the RBCs are severely dehydrated and typically microcytic and hyperchromic. Hb SC RBCs seem to be dehydrated due to selective K loss. These findings suggest a functional interrelationship between Hb SC, the red cell membrane, and cation regulation. PMID:2947642

  8. rotor of the SC rotating condenser

    CERN Multimedia

    1974-01-01

    The rotor of the rotating condenser was installed instead of the tuning fork as the modulating element of the radiofrequency system, when the SC accelerator underwent extensive improvements between 1973 to 1975 (see object AC-025). The SC was the first accelerator built at CERN. It operated from August 1957 until it was closed down at the end of 1990.

  9. Influence of Li2CO3 and V2O5 combined additions on the sintering and dielectric properties of Ca0.5Sr0.5TiO3 ceramics prepared from powders synthesized by sol-gel method

    Directory of Open Access Journals (Sweden)

    Nouara Lamrani

    2014-06-01

    Full Text Available In this work, we have studied the influence of lithium carbonate (Li2CO3 associated with the vanadium oxide (V2O5 on sintering and dielectrics properties of Ca0.5Sr0.5TiO3 ceramic materials obtained from nanopowder synthesized by sol-gel method. The nanopowder was obtained by controlled mixing of titanium butoxide dissolved in butanol-2 and acetic acid with a saturated aqueous solution of calcium acetate and strontium carbonate and subsequent drying of the formed gel at 80 °C and calcination at 1100 °C. The synthesized nanopowder was mixed with different amount of additives, and then uniaxally pressed and sintered in air atmosphere at temperature determined by dilatomertic measurements. The pure Ca0.5Sr0.5TiO3 sample obtained by this process required a sintering temperature around 1500 °C. The addition of Li2CO3 combined with V2O5 improved sinterability and caused a shift of dilatimeric shrinkage curve to much lower temperatures. Thus, dense ceramics (98% of theoretical density were obtained at sintering temperature ≤ 1300 °C. The effect of adding Li2CO3-V2O5 on the structure of ceramics and the dielectric properties is discussed and show that type I dielectric properties (linear variation of the permittivity are conserved, but with an increase of dielectric loss.

  10. Academic Training - Pulsed SC Magnets

    CERN Multimedia

    Françoise Benz

    2006-01-01

    2005-2006 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 2, 3, June 29, 30, 31 May, 1, 2 June 11:00-12:00 - Auditorium, bldg 500 Pulsed SC Magnets by M. Wilson Lecture 1. Introduction to Superconducting Materials Type 1,2 and high temperature superconductors; their critical temperature, field & current density. Persistent screening currents and the critical state model. Lecture 2. Magnetization and AC Loss How screening currents cause irreversible magnetization and hysteresis loops. Field errors caused by screening currents. Flux jumping. The general formulation of ac loss in terms of magnetization. AC losses caused by screening currents. Lecture 3. Twisted Wires and Cables Filamentary composite wires and the losses caused by coupling currents between filaments, the need for twisting. Why we need cables and how the coupling currents in cables contribute more ac loss. Field errors caused by coupling currents. Lecture 4. AC Losses in Magnets, Cooling and Measurement Summary of all loss mech...

  11. Cs3ScCl6

    Directory of Open Access Journals (Sweden)

    Matthew D. Ward

    2014-06-01

    Full Text Available Crystals of tricaesium scandium(III hexachloride were obtained as a side product from the reaction of U, SnCl2, Sc, and S in a CsCl flux at 1073 K. Cs3ScCl6 crystallizes in the Rb3YCl6 structure type. The asymmetric unit comprises three Cs sites, two Sc sites, and six Cl sites, all of which have site symmetry 1, except for the two Sc sites that have site symmetries of 2 and -1, respectively. The structure is composed of isolated [ScCl6]3− octahedra that are surrounded by Cs+ cations. Two Cs+ cations have interactions with eight Cl− anions, while the third has interactions with ten Cl− anions.

  12. Cs3ScCl6.

    Science.gov (United States)

    Ward, Matthew D; Ibers, James A

    2014-06-01

    Crystals of tricaesium scandium(III) hexa-chloride were obtained as a side product from the reaction of U, SnCl2, Sc, and S in a CsCl flux at 1073 K. Cs3ScCl6 crystallizes in the Rb3YCl6 structure type. The asymmetric unit comprises three Cs sites, two Sc sites, and six Cl sites, all of which have site symmetry 1, except for the two Sc sites that have site symmetries of 2 and -1, respectively. The structure is composed of isolated [ScCl6](3-) octa-hedra that are surrounded by Cs(+) cations. Two Cs(+) cations have inter-actions with eight Cl(-) anions, while the third has inter-actions with ten Cl(-) anions. PMID:24940185

  13. Photon stimulated desorption investigations of positive ions of MgO, TiO2, Yb2O3, Nd2O3, H2O/Si(100), CaF2/Si and of H2O, CO and NO on Yb and Nd in the energy range 14 eV up to 800 eV

    International Nuclear Information System (INIS)

    Photon-stimulated desorption of positive ions from surfaces has been studied with synchrotron radiation in the photon energy range 14 -800 eV of the 'FLIPPER'-monochromator using a time-of-flight mass spectrometer. TiO2, as a prototype of a maximal valency ionic compound, shows a strong desorption of O+- in the photon energy range of the Ti 3 p → 3d- and Ti 2p → 3d-resonance as well as at the 0 1s-excitation due to intraatomic respectively intraatomic Auger decays, which is in agreement with the Knotek-Feibelman model. The desorption of F+ from CaF2-covered silicon is found to follow the respective excitation and decay processes in Ca and F. In addition, the very large cross section for the F+ desorption causes a radiation damage by photons of more than about 30 eV. The adsorbate system H2O/Si (100) needs a multiple electron excitation to show a significant desorption setting in only 30 eV above the 0 1s threshold. The rare earth metals Yb and Nd covered with O2, H2O, CO or NO exhibit a competitive desorption of O+ partly due to intraatomic Auger decays caused by single electron excitations and partly due to multiple electron excitations. The variation of the 0+ yield with regard to the different adsorbates on Yb and Nd is unexpectedly low. A detailed investigation was concerned with thin oxidized Mg-films and differently prepared MgO-single-crystals. Here we found a very efficient desorption of O+ and H+ resulting from the excitation of O 1s-surface-excitons. In addition, the strong hole-hole-interaction energy of crystalline MgO appears to be responsible for a suppressed O+-signal in the energy range of the Mg 2p-excitation. (orig./BHO)

  14. Bioactivity studies on TiO{sub 2}-bearing Na{sub 2}O–CaO–SiO{sub 2}–B{sub 2}O{sub 3} glasses

    Energy Technology Data Exchange (ETDEWEB)

    Jagan Mohini, G. [Department of Physics, Andhra Loyola College, Vijayawada 520 008, Andhra Pradesh (India); Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522 510, A.P. (India); Sahaya Baskaran, G. [Department of Physics, Andhra Loyola College, Vijayawada 520 008, Andhra Pradesh (India); Ravi Kumar, V. [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522 510, A.P. (India); Piasecki, M. [Institute of Physics, J. Dlugosz University, Al. Armii Krajowej 13/15, Czestochowa (Poland); Veeraiah, N., E-mail: nvr8@rediffmail.com [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522 510, A.P. (India)

    2015-12-01

    Soda lime silica borate glasses mixed with different concentrations of TiO{sub 2} are synthesized by the melt-quenching technique. As a part of study on bioactivity of these glasses, the samples were immersed in simulated body fluid (SBF) solution for prolonged times (~ 21 days) during which weight loss along with pH measurements is carried out at specific intervals of time. The XRD and SEM analyses of post-immersed samples confirm the formation of crystalline hydroxyapatite layer (HA) on the surface of the samples. To assess the role of TiO{sub 2} on the formation of HA layer and degradability of the samples the spectroscopic studies viz. optical absorption and IR spectral studies on post- and pre-immersed samples have been carried out. The analysis of the results of degradability together with spectroscopic studies as a function of TiO{sub 2} concentration indicated that about 6.0 mol% of TiO{sub 2} is the optimal concentration for achieving better bioactivity of these glasses. The presence of the maximal concentration octahedral titanium ions in this glass that facilitates the formation of HA layer is found to be the reason for such a higher bioactivity. - Highlights: • Soda lime silica borate glasses mixed with TiO{sub 2} are synthesized. • Bioactivity of the glasses is studied by immersing them in SBF solution. • XRD and SEM studies indicated the formation of hydroxyapatite layer on the surface. • Quantum of degradability is the highest in the glasses mixed with 6.0 mol% of TiO{sub 2.} • The results are analyzed using IR and optical absorption studies.

  15. Large electrostrictive effect and bright upconversion luminescence in Er-modified 0.92(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}–0.08(Ba{sub 0.90}Ca{sub 0.10})(Ti{sub 0.92}Sn{sub 0.08})O{sub 3} lead-free ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoli; Wu, Meihua; Diao, Wenxin; Zhang, Bing; Hao, Jigong, E-mail: haojigong@lcu.edu.cn; Xu, Zhijun; Chu, Ruiqing

    2015-10-01

    In this study, a new lead-free luminescent electrostrictive material has been obtained by introducing trivalent Er{sup 3+} as the activator into 0.92(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}–0.08(Ba{sub 0.90}Ca{sub 0.10})(Ti{sub 0.92}Sn{sub 0.08})O{sub 3} (BNT–0.08BCST). A high, purely electrostrictive effect (the electrostrictive coefficient Q{sub 33} reaches up to 0.028 m{sup 4}/C{sup 2}) with exceptionally good fatigue resistance (up to 10{sup 6} cycles) and thermostability (25–140 °C) is obtained in 0.2 mol%Er-modified BNT–0.08BCST ceramics. Besides the excellent electrostrictive properties, Er{sup 3+}-modified BNT–0.08BCST samples exhibit a strong green-red upconversion emission, and the emission intensities are strongly dependent on the doping concentration, which reaches the optimal value as the doping concentration is 0.4 mol%. These results suggest that this kind of material may have potential application as a multifunctional device by integrating its excellent upconversion luminescence and electrostrictive properties.

  16. Elastic ion scattering of 40Ca and 48Ca by 208Pb nuclei

    International Nuclear Information System (INIS)

    The elastic ion scattering of 40Ca and 40Ar at 302 MeV and of 48Ca and 48Ti at 252 MeV by 208Pb nuclei has been investigated. The data obtained have been analyzed in terms of the classical model for elastic scattering. The distances of closest approach for classical Rutherford trajectories have been measured for 40Ca and 48Ca to differ by 0.19 fm, which corresponds to the normal radius growth defined by the function R approximately r0Asup(1/3)

  17. Electronic Structures of S/C-Doped TiO2 Anatase (101) Surface: First-Principles Calculations

    OpenAIRE

    2014-01-01

    The electronic structures of sulfur (S) or carbon (C)-doped TiO2 anatase (101) surfaces have been investigated by density functional theory (DFT) plane-wave pseudopotential method. The general gradient approximation (GGA) + U (Hubbard coefficient) method has been adopted to describe the exchange-correlation effects. All the possible doping situations, including S/C dopants at lattice oxygen (O) sites (anion doping), S/C dopants at titanium (Ti) sites (cation doping), and the coexisting of an...

  18. Platinum determination by instrumental neutron activation analysis with special reference to the spectral interference of Sc-47 on the platinum indicator nuclide Au-199

    DEFF Research Database (Denmark)

    Alfassi, Z.B.; Probst, T.U.; Rietz, B.

    A method of instrumental neutron activation analysis (INAA) is developed for the determination of platinum by the Au-199 daughter of Pt-199 in the presence of the spectral interference from the Sc-47 daughter of Ca-47. The contributions of the Pt and Ca signals to the integral 157-161 keV peak were...

  19. SC-FDMA for mobile communications

    CERN Document Server

    Abd El-Samie, Fathi E

    2013-01-01

    SC-FDMA for Mobile Communications examines Single-Carrier Frequency Division Multiple Access (SC-FDMA). Explaining this rapidly evolving system for mobile communications, it describes its advantages and limitations and outlines possible solutions for addressing its current limitations. The book explores the emerging trend of cooperative communication with SC-FDMA and how it can improve the physical layer security. It considers the design of distributed coding schemes and protocols for wireless relay networks where users cooperate to send their data to the destination. Supplying you with the re

  20. Effect of scandium on structure and hardening of Al–Ca eutectic alloys

    International Nuclear Information System (INIS)

    The phase composition, structure and hardening of alloys in the aluminium corner of the Al–Ca–Sc system were studied in the range up to 10% Ca and up to 1% S≿. The experimental study (optical, scanning and transmission electron microscopy with electron-microprobe analysis, differential thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was shown that only phases of the binary systems (Al4Ca and Al3Sc) might be in equilibrium with the aluminium solid solution. It was shown that the (Al) + Al4Ca eutectic had a much finer structure as compared with the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. The influence of the annealing temperature within the range up to 600 °C on the structure and hardness of the Al–Ca–Sc experimental alloys was studied. It was determined that the maximum hardening corresponded to the annealing at 300 °C, which was due to the precipitation of Al3Sc nanoparticles with their further coarsening. With an example of an Al-7.6% Ca-0.3% Sc model experimental alloy, a principal possibility of manufacturing aluminium casting alloys based on the (Al) + Al4Ca eutectic was demonstrated. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of casting. - Highlights: • Al–Ca–Sc phase diagram in aluminum corner. • Formation of Al3Sc nanoparticles in eutectic (Al) + Al4Ca during heating at 300–450 °C. • Hardening and thermal stability of proposed (Al–Ca–Sc) and commercial (Al–Si–Mg, 356 type) eutectic alloys