bluuebunny/crossref_metadata_2025_split huggingface dataset:
Group II-VI Downconverting Phosphors
Authors: Valdna V. , Gavrish T. , Hue J. , Mellikov E. , Mere A. 
Published: April 2011

ABSTRACTThe efficiency of group II-VI solid solutions doped with chlorine and copper as X-ray downconverting phosphors for photodetectors is investigated. It is found that the phosphors based on the group II-VI compounds and prepared in oxygen-free medium can increase the photodetectors sensitivity to X-ray radiation more than one order of magnitude and enhance the photodetectors photovoltage versus X-ray radiant flux characteristic linearity.
Early Transition Metal Oxides and a Pinch of Salt: New Synthetic Routes to Titanates and Niobates
Authors: Geselbracht M. J. , Scarola R. J. , Ingram D. , Green C. , Caldwell J. H. 
Published: April 2011

AbstractMolten salts have traditionally been used as recrystallizing solvents for the crystal growth of mixed metal oxides. In recent years, many examples of the direct preparation of mixed metal oxides from molten salt solutions have been reported. We have been exploring the use of chloride melts as a reaction media to prepare complex early transition metal oxides. Specific examples of new synthetic routes to interesting titanates and niobates will be presented. In one case, we have prepared a series of layered niobate perovskite solid acids from molten salts at temperatures well below those traditionally used in solid state syntheses. In the second case, we have discovered a new synthetic route to a poorly characterized reduced calcium titanate that is otherwise very difficult to make. The synthesis and characterization of these two classes of compounds will be described.
Controlling Defects in Double-Layer Cuprates by Chemical Modifications
Authors: Salvador P. A , Greenwood K. B. , Otzschi K. , Koenitzer J. W , Dabrowski B. M. , Poeppelmeier K. R. , Mason T. O. 
Published: April 2011

AbstractIn-situ high temperature electrical conductivity and thermopower have been measured simultaneously on a number of ordered perovskite-like oxides containing double CUO4/2 sheets. Equilibrium measurements have been conducted as a function of oxygen partial pressure, temperature and chemical substitution in order to understand the relationships between the chemical architecture and the transport and defect properties. Data for LaBa2Cu2NbO8 and LaCa2Cu2GaO7 are presented and compared with those of known triple perovskite superconductors, Y1−xCaxSr2Cu2GaO7 and YBa2Cu3O7−δ, and several quadruple perovskites, Ln′Ln″Ba2Cu2M2O11 (Ln = Lanthanide, Y; M = Sn, Ti). These materials belong to a general family of superconductors which are constructed from similar ‘active’ layers (double perovskite blocks of square-pyramidal copper-oxygen sheets), and interleaved with fixed valence cations in perovskite-like ‘conditioning’ layers. Similarities in the transport properties of the non-superconducting and superconducting materials at elevated temperatures are illustrated, and the amount and types of defects, including carrier concentrations, are correlated with the internal chemistry and inner architecture of each material.
Optical Properties of Lanthanide -Containing Halide-Modified Zinc Tellurite Glasses
Authors: Sidebottom D. L. , Hruschka Michael A. , Potter B. G. , Brow Richard K. , Hudgens James J. 
Published: April 2011

AbstractAs part of an ongoing investigation to characterize the properties and structure of zinc halide-tellurium oxide glasses, we report preliminary measurements of the optical properties of several Nd- and Er-doped tellurites. Measurements include florescence lifetimes and estimates of the theoretical radiative lifetimes (as obtained by traditional Judd-Ofelt analysis of optical absorption spectra) as well as phonon sideband studies sensitive to vibrational characteristics near the rare earth ion. The response of these optical features to the substitution of alternative halides is examined.
New Nonlinear Optical Crystals of KTiOPo4 (KTP) Family
Authors: Chani V. l. , Shimamura K. , Endo S. , Fukuda T. 
Published: April 2011

AbstractPhase formation and crystal growth conditions for different combinations of cations corresponding to chemical formula of KTP were studied. Preparation of new Ti-less arsenates which arc isostructural with KTP is reported. In the single crystals grown Ti4+ cations were completely substituted with M2+ + Nb5+ (M = Mg, Zn) or M3+ + Nb5+ (M = Al, Cr, Ga, Fe, In) cation couples. The crystals were prepared by spontaneous crystallization using flux method. The structure analysis was made by X-ray powder diffraction technique. The crystals composition was measured by electron probe microanalysis (EPMA). Second harmonic generation (SHG) effect was studied by the powder technique with a pulsed YAG:Nd laser (1064 nm). SHG signal of the crystals was found to be slightly greater than that of KTiOAsO4 (KTA).
Optical Second Harmonic Generation in Transparent Tellurite Glass-Ceramics Containing BaTiO3
Authors: Tanaka Katsuhisa , Kuroda Hisako , Hirao Kazuyuki , Soga Naohiro 
Published: April 2011

AbstractOptical second harmonic generation has been observed in transparent tellurite glass-ceramics of Ba0-TiO2-TeO2 system. BaTiO3 and unidentified crystalline phase precipitate from 15BaO·15TiO2·7OTeO2 glass. The temperature of maximum rate of nucleation for these crystalline phases is estimated to be 380°C. The BaTiO3 crystal precipitated is a cubic phase with lattice parameter of 0.4045 nm, which is slightly larger than the value reported in the JCPDS cards. The optical second harmonic intensity of the present transparent tellurite glass-ceramics is comparable to the intensity of poled tellurite glasses although the BaTiO3 phase precipitated is cubic and the crystal face is randomly oriented in the glass-ceramics. For instance, the second harmonic intensity of the present transparent tellurite glass-ceramics is about twice as large as that of 20WO3·80TeO2 glass poled at 280°C under the external electric field of 3 kV, the second-order nonlinear coefficient, d33, of which is 0.10 pm/V.
Application of Photostimulable Phosphor, Imaging Plate :BaFBr:Eu2+, to Image Storing for UV-VUV Radiations
Authors: Katto Masahito , Ohnishi Shunshiro , Kurioka Yutaka , Takigawa Yasuo , Kurosawa Kou 
Published: April 2011

AbstractAn imaging plate containing photostimulable phosphor material, BaFBr:Eu2+, was found to be applicable to store images for nanosecond pulses as well as quasi-continuous radiations in 4 – 35 eV photon energy range. The sensitivity, which was defined as photostimulated luminescence intensity for a given incident photon number increased with the photon energy and had a peak at 6.2 eV. The intensity of the luminescence was confirmed to increase in proportion to incident photon numbers of the radiation. The readout system was improved and then pattern images were successfully restored. The resolution of imaging plate was found to be lower than 100 μm with our system, which depends on the intensity of a He-Ne laser for restoring images.
Crystal Growth of Ca3(Li,Nb,Ga)5O12 Garnets from Melt
Authors: Chani V. l. , Myu Y. , Shimamura K. , Saiki Y. , Fukuda T. 
Published: April 2011

AbstractSingle crystals of Ca3(Li,Nb,Ga)5O12 garnets have been grown from stoichiometric melts by micro-pulling down and Czochralski methods using Pt crucibles. It was found that the mixture of oxides with atomic ratio Ca : Li : Nb : Ga = 3 : 0.275 : 1.775 : 2.95 correspond to the garnet composition which melts congruenlly at about 1450°C. Solid state reaction data of the compounds related with this material are also reported. Lattice parameter of all Ca3(Li,Nb,Ga)5O12 crystals grown was about 1.254 nm. Transparent and bubble-free crystals of Ca3LixNb1.5+xGa(3.5+x)Ga(3.5−2x)O12 (x = 0.25 and 0.275) were grown by Czochralski technique in air. An optical transmission spectrum of the crystals was studied. No absorption was detected in 400–1200 nm wavelength range.
Electron Transport Phenomena in NiS2−xSex Single Crystals
Authors: Yao X. , Ehrlich S. , Liedlb G. , Hogan T. , Kannewurf C. , Honig J. M. 
Published: April 2011

AbstractStructural studies, electrical resistivity, and Seebeck coefficient measurements are reported in the range 4.2 − 300 K for single crystals of NiS2−xSex (0 ≤ x ≤ 0.71) grown from a Te melt. Over the entire temperature and composition ranges there are no large scale structural changes concomitant to a variety of magnetic ordering phenomena, and to a changeover from insulating to metallic characteristics as x increases. Thus, the evolution in transport characteristics with x can be studied without interference from the lattice; moreover, the electron count is unaffected by substitution of Se for S. The existence of anomalous peaks in resistivity as a function of temperature is attributed to significant electron correlation phenomena which allow the entropy of charge carrier to play a dominant role. The complex temperature dependence of the Seebeck coefficient is attributed to the participation of both electrons and holes in charge transport.
The Narrow-Band System La1-xSrxTiO3
Authors: Hays Charles C. , Goodenough John B. , Marken John T. 
Published: April 2011

AbstractMagnetic, transport, and structural data on polycrystalline samples of the system La1-xSrxTiO3, 0 ≤ x ≤ 0.8, show an abrupt, but apparently smooth, transition from p-type polaronic conduction in a canted-spin antiferromagnetic system for x ≤ 0.04 to metallic, mass-enhanced Pauli paramagnetic behavior for x ≥ 0.1 with evidence for a spin glass and a discontinuous drop in TN in the transition range. We interpret these results as a manifestation of the coexistence of two distinguishable electronic domains within a single crystallographic phase as a result of cooperative displacements of the oxygen atoms.
Synthesis of A1–xA'xNbO3 (A=Na+, K+; A'= La3+, Sr2+) and its Electrical Properties
Authors: Sugimoto W. , Tahara T. , Sugahara Y. , Kuroda K. 
Published: April 2011

AbstractPolycrystalline samples of A1–xA'xNbO3 (A=Na+, K+; A'= La3+, Sr2+) were prepared by solid-state reactions and the relationship between the structure and electrical properties was examined. Single-phase products were obtained for Na1–xLaxNbO3 (x ≤0.1), K1–xLaxNbO3 (x ≤0.15), Na1–xSrxNbO3 (x ≤0.3), and K1–xSrxNbO3 (x ≤0.5). The structures of the sodium-containing compounds and potassium-containing compounds were indexed according to a pseudocubic and cubic symmetry, respectively. The resistivity measurements showed semiconductive behavior for the lanthanum-containing samples. The strontium-containing samples showed semiconducting properties for x ≤0.2, while a transition to metallic conduction at low temperature was observed for x >0.2.
Low Temperature Magnetic Properties of Some New High-Pressure Perovskite Phases of Iron II: Observation of Novel Slow Paramagnetic Relaxation in CaFe2Ti2O6 and CaFe3Ti4O12
Authors: Reiff W. M. , Leinenweber K. , Parise J. 
Published: April 2011

AbstractResults of iron-5 7 Mössbauer spectroscopy and ac and dc susceptibility study of the double perovskite phases, CaFeTi2O6 (A) and CaFe3Ti4O12 (B) are presented. Both phases exhibit spectral broadening effects with decreasing temperature and incipient magnetic hyperfine splitting attributable to novel slow paramagnetic relaxation at the tetrahedral and square planar sites of (A) and the square planar sites of (B). The temperature dependence of magnetic moment for (A) corresponds to classical single ion zero field splitting, while that of (B) indicates antiferromagnetic exchange interactions. There is no evidence of cooperative long range magnetic order in these materials.
Effects of Non-Stoichiometry on Anisotropic Magnetic Properties in CuFeO2+δ Single Crystals
Authors: Hasegawa M. , Zhao T. R. , Bartashevich M. I. , Takei H. , Goto T. 
Published: April 2011

AbstractEffects of non-stoichiometry on anisotropie magnetic states in CuFeO2 with a so-called delafosite structure have been investigated using CuFeO2+δ (δ=-0.061, -0.026, 0.014, 0.085) single crystals. Each single crystal is grown using the floating zone method in each controlled atmosphere and found to have good quality. All crystals show two anisotropie successive antiferromagnetic transitions in the temperature dependence of magnetic susceptibilities. The higher antiferromagnetic transition temperature is not affected by the non-stoichiometry. On the other hand, the lower one shows distinct effects of the non-stoichiometry, depending on the kind of oxygen defects. Oxygen deficiency leads to an increase in TN2, while excess oxygen leads to a decrease. It is also found that all samples show clear anisotropie step anomalies in the magnetization curve up to 38 T and that the anomalies and hystereses depend on the nonstoichiometry.
Effect of Hydrostatic Pressure (≤2GPa) on the Transport Properties in Perovskite-Type Oxides
Authors: Itoh M. , Yu J-D. , Nishi K. , Katsumata T. , Inaguma Y. , Huang T. 
Published: April 2011

AbstractA clamp-type hydrostatic pressure device for the measurement of properties of perovskite-related compounds under pressure was established in our laboratory and applied to the measurements of resistivity, AC susceptibility, Hall effect and ionic conductivity. In usual perovskite-type oxides, loading of a pressure of 1 GPa (lOkbar) corresponds to a contraction of interionic distance as large as 0.2%. This small value is not enough to evaluate the whole scheme of phase transition behavior for perovskite-type oxides but very effective for the observation of changes in interactions between electrons and ions. Some problems concerned with this method have been pointed out.
High-Resolution Electron Microscopy of Magnetic Dielectric Oxides in the Bao:TiO2Fe2O3 System
Authors: Bendersky L. A. , Vanderah T. A. , Roth R. S. 
Published: April 2011

AbstractIn a recent work on phase equilibria relations in the BaO:Fe2O3:TiO2 system the existence of sixteen ternary compounds was confirmed. Most of the new found compounds apparently have a new structural type. In this work we employed electron diffraction and high-resolution microscopy in attempt to understand the structures of the new compounds. Since the present work was done on the compounds prepared by solid-state reaction, it also provides a correlation with a single-crystal x-ray work on some of the similar compounds prepared by crystallization from a melt.
La2Zr2O7 Formation Between Yttria-Stabilized Zirconia and La0.85Sr0.15MnO3 at 1373 K
Authors: Mitterdorfer A. , Gauckler L. J. 
Published: April 2011

AbstractOxygen ion conducting yttria-stabilized zirconia and perovskite-type Sr-doped LaMnO3 have been widely used as solid electrolyte and cathode materials in solid oxide fuel cells. The electrochemical properties of the cathode depend largely on the nanostructure and the phase composition of the interface between cathode and electrolyte. Interfaces between single crystals of 9.5mol% Y2O3-stabilized ZrO2 and porous La0.85Sr0.15MnyO3 (y = 0.95…1.10) were investigated. Atomic force microscopy was used for interface studies of YSZ single crystals after removal of sintered perovskite cathodes. High resolution transmission electron microscopy, electron diffraction and electrochemical impedance spectroscopy were employed for interface characterization. Pyrochlore-type lanthanum zirconate formed at the interface during sintering at 1100°C. Nucleation, growth kinetics, and morphology were largely depending on cathode stoichiometry. Lanthanum zirconate formation was retarded in case of A-site deficient perovskite.
Ionic Distribution in Rare Earth Ion-Doped Na+ β"- Alumina
Authors: Wang Yuhu , Cormack Alastair N. 
Published: April 2011

AbstractStructure of β"-alumina has been studied through atomistic simulation. Distribution of Mg2+ in the spinel blocks, Na+ as well as Nd3+ in the conduction planes have been calculated and compared with the structure models derived experimentally. Mg2+ ions, as the stabilizer of β"-alumina structure, prefer to occupy the tetrahedral Al(2) sites in the spinel block. Two configurations for Mg2+ distribution are proposed. Due to the presence of Mg2+, oxygen ions in or adjacent to the conduction plane, O(5), O(4) and O(3), are slightly displaced from their original sites, leading to the removal of the local symmetry at the mO site. Strongly affected by the Mg2+ distribution, Nd3+ions, originally introduced into the BR site in the conduction plane, are found to move towards the distorted mid-oxygen sites, which is in excellent agreement with the previous estimate from spectroscopie study.
Preparation and Electrical Conductivity Measurement of LiSbO3Thin Films
Authors: Ozawa K. , Sakka Y. , Amano M. 
Published: April 2011

AbstractLiSbO3thin films have been prepared by the sol-gel process with metal alkoxides using a spin-coating method. The (Oll)-oriented and randomly oriented LiSbO3thin films are obtained by the precursor film crystallizing under an atmosphere of a flowing mixture of water vapor and oxygen, and an air atmosphere, respectively. The two different atmospheres also affect the crystallization temperature of the films. The electrical conductivity of the (Oll)-oriented LiSbO3thin film is approximately one order of magnitude larger than that of the randomly oriented LiSbO3thin film in the temperature range of 380 to 600°C.
A Comparative Study of Lithium and Sodium Insertion in Two Block Structure Type Phases, W3Nb14O44 and W4Nb26O77
Authors: Fuentes Antonio F. , Martinez De La Cruz A. , Torres-Martinez Leticia M. 
Published: April 2011

AbstractA comparative study of lithium insertion in W4Nb26O77 and W3Nb14O44, two block structure type phases, has been carried out. This process is, in both cases, reversible for a similar number of lithium ions incorporated to total metal atoms ratio (Li/ΣM), 1.15 in W3Nb14O44 and 1.23 in W4Nb26O77. No significant structural changes are seen by X-ray diffraction upon insertion. Sodium insertion in W3Nb14O44 has been also studied observing a substantial reduction on the number of ions incorporated when compared with lithium (Na/ΣM: 0.03).
Chemical Reactivity Between Sialon Ceramics and Iron-Based Alloys
Authors: Vleugels J. , Van Der Biest O. 
Published: April 2011

AbstractThe chemical interaction of a number of SiAlON ceramic - iron-based alloy combinations is studied by means of static interaction couple experiments at 1200 °C. During the interaction, silicon and nitrogen from the ceramic dissolve and diffuse into the iron alloy, whereas the remaining aluminium and oxygen form Al2O3 particles. The rate controlling step of the interaction was identified and the influence of alloying elements in the iron-based alloy as well as the chemical composition of the ceramic on the reactivity was investigated. The relative reactivity measured in the interaction couples was compared with the measured wear of the ceramics in turning of steels. The predictive capabilities of the results of the interaction couple experiments on the actual cutting tool performances in turning operations is highlighted.
Reactivity of Chrysotile Asbestos in Acids: Mechanism of Transformation to Silicon Dioxide Hemihydrate Upon Leaching of Magnesium
Authors: Vaillancourt Anne , Denes Georges , Le Van Mao Raymond 
Published: April 2011

AbstractAcid leaching chrysotile asbestos results in a stepwise loss of magnesium which reduces the strain locally. This results in a partial unwiding of the structural sheets which makes possible further leaching. Strong acids are used for a coarse brutal attack of the chrysotile structure, whereas weak acids allow a fine control of the magnesium leaching degree required to have the adequate properties of the partially leached asbestos which is used for the preparation of zeolites with enhanced catalytic properties. The final material is not carcinogenic. The leached materials were characterized by atomic absorption spectrometry, bulk density and BET specific surface area measurements, and X-ray diffraction.
Atomic and Electronic Structure of the Corundum (0001) Surface
Authors: Puchin V. E. , Kotomin E. A. , Shluger A. L. 
Published: April 2011

AbstractThe electronic structure and geometry of the Al terminated corundum (0001) surface were studied using a slab model within the ab-initio Hartree-Fock technique. The distance between the top Al plane and the next O basal plane is found to be considerably reduced on relaxation (by 0.57 Å, i.e. by 68% of the corresponding interlayer distance in the bulk). An interpretation of experimental photoelectron spectra (UPS Hel) and metastable impact electron spectra (MIES) is given. Calculated projected densities of states exhibit a strong dependence on the relaxation of surface atoms.
Microstructural Characterization of an Oriented Silicalite Film
Authors: Lovallo M. C. , Tsapatsis M. 
Published: April 2011

ABSTRACTThe crystal orientation of a submicron silicalite membrane is examined using standard x-ray diffraction and pole-figure analyses. Results indicate that the crystals in the molecular sieving layer are preferentially oriented with both straight and sinusoidal channel networks of the zeolite parallel to the membrane surface. This requires that transport across the membrane proceed down the c-axis of the crystals which can occur by jumping between the two channel networks. EDAX data confirms that the molecular sieving layer is the pure silica zeolite silicalite.
Use of Graphite Nanofibers as a Novel Catalyst Support Medium for Hydrogenation Reactions
Authors: Park C. , Rodriguez N. M. , Baker R. T. K. 
Published: April 2011

ABSTRACTIn this investigation we elected to use the hydrogenation of 1-butene as probe reactions in an attempt to monitor any possible changes in catalytic behavior resulting from supporting 5 wt.% nickel on different types of carbon nanofibers compared to the performance of the same metal loading on more traditional carriers, including γ-Al2O3 and active carbon. In all cases the carbon nanofiber supported nickel particles are found to exhibit superior activity and significant changes in selectivity to that found from the same metal supported on traditional carriers.
High-Energy Mechanical Synthesis of Nanophase Fluorite-Structured Mixed Oxide Catalysts with a High Redox Activity
Authors: Primavera Alessandra , Trovarelli Alessandro , Jordillorca  , Terribile Daniela , de Leitenburg Carla , Dolcetti Giuliano 
Published: April 2011

ABSTRACTA series of nanostructured, highly defective, ternary solid solutions containing CeO2, ZrO2, and MnO2 or CuO were prepared by high-energy mechanical milling of individual components. Morphological and redox properties were studied by XRD, HRTEM and temperature-programmed reduction techniques. It was shown that the introduction of small amounts of copper and manganese strongly promotes the redox behavior of cerium at lower temperatures in comparison with CeO2 and CeO2-ZrO2. High temperature treatment of up to 1400K was also shown to further promote overall redox capacity without affecting low-temperature redox behavior. Moreover, evidence is provided to show that Cu and Mn are dissolved within the CeO2 lattice structure. Addition of dopants enhances catalytic redox properties in the oxidation of CO at low temperatures, which is associated with the high concentration of oxygen vacancies that form on the introduction of aliovalent elements into the ceria-zirconia lattice.
Materials Science: A Driver for Innovation in Applied Catalysis
Authors: Maxwell I. E. , Lednor P. W. 
Published: April 2011

ABSTRACTThis paper suggests that materials science is an important driver for innovation in applied catalysis. A wide range of catalytic materials is discussed in support of this thesis, with porosity as a common theme, and covering micro, meso and macro-porous materials. Applications of these materials is also wide-ranging, covering processes for the manufacture of fine chemicals or petrochemicals, and in oil refining, natural gas conversion and environmental processes. Further im-provents in the rate of innovation can be expected from new partnerships which are being formed, both at business and research levels.