Inorganic Materials (v.47, #7)

Preparation of single-crystal 29Si by A. V. Gusev; V. A. Gavva; E. A. Kozyrev; A. M. Potapov; V. G. Plotnichenko (691-693).
A process has been developed for the preparation of single-crystal 29Si from 29Si-enriched silane. A silicon single crystal has been grown with a 29Si content over 99.9 at %. The oxygen and carbon concentrations in the crystal are under 1 × 1016 cm−3, and its resistivity exceeds 1 kΩ cm.

Ultrapurification of 76Ge-enriched GeH4 by distillation by S. A. Adamchik; A. D. Bulanov; P. G. Sennikov; M. F. Churbanov; A. Yu. Sozin; O. Yu. Chernova; I. A. Kosheleva; O. Yu. Troshin (694-696).
76Ge-enriched germane has been ultrapurified by low-temperature distillation. The nature and concentration of molecular impurities in the germane samples were determined by gas chromatography/mass spectrometry, high-resolution Fourier transform IR spectroscopy, and gas chromatography. The distillate contains no more than 10−5 mol % hydrocarbons, 10−4 mol % carbon dioxide, 10−3 to 10−1 mol % digermane and trigermane, and <3 × 10−5 mol % other impurities. A distinctive feature of the impurity composition of the isotopically enriched germane samples is the presence of silicon tetrafluoride and sulfur hexafluoride impurities.

This paper describes the fabrication of a red-orange-emitting (Zn,Cd)S:(Ag,In,Sb) cathodoluminescent phosphor which offers enhanced brightness at a low excitation voltage. The effects of antimony and chlorine added to the starting mixture as coactivators are analyzed. The largest brightness gain, observed at C Sb/C Ag ≃ 1.3, is probably due to the formation of Ag+-Sb3+ associates. Increasing the C Sb/C Ag ratio to above ≃ 2.2 leads to quenching of luminescence.

Phase equilibria in the Tl2Se-PbSe system and growth and properties of Tl4PbSe3 single crystals by T. O. Malakhovska-Rosokha; M. Yu. Sabov; I. E. Barchii; E. Yu. Peresh (700-702).
The T-x phase diagram of the Tl2Se-PbSe system has been mapped out. The system contains a congruently melting compound (803 K) of composition Tl4PbSe3, which forms a continuous series of solid solutions with Tl2Se. Tl4PbSe3 single crystals have been grown by directional solidification, and their physicochemical and thermoelectric properties have been studied. Tl4PbSe3 crystals have high thermopower (α T ) and thermoelectric figure of merit (Z T ).

Phase equilibria and glass formation in the AsSe-MnSe system by I. I. Aliev; T. M. Il’yasly; Sh. A. Gasangulieva; C. A. Veliyev (703-706).
The phase equilibrium in the AsSe-MnSe system has been studied using physicochemical characterization techniques (differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements), and its phase diagram has been mapped out. The system is shown to be a pseudobinary join of the ternary system Mn-As-Se. At AsSe: MnSe = 1: 1, the system contains a compound of composition MnAsSe2, which melts incongruently at 750°C. The glass-forming region extends to 15 mol % MnSe. We have examined the crystallization behavior of the glasses. Solid AsSe dissolves up to 2 mol % MnSe, and solid MnSe dissolves up to 2.5 mol % AsSe.

Thermodynamic and quasi-chemical modeling of point defects in CdTe〈I〉 by D. M. Freik; I. V. Gorichok; U. M. Pysklynets (707-711).
The carrier concentration and the densities of predominant point defects in CdTe〈I〉 crystals have been calculated as functions of two-step annealing parameters using quasi-chemical and thermodynamic modeling. We have identified the dominant native and impurity defect species, which govern the electrical properties of the material, and proposed a compensation model that takes into account not only native defects, I Te + substitutional defects, and their complexes with native point defects, such as (V Cd 2− I Te + ), and (V Cd 2− 2I Te + )0, but also DX centers. The equilibrium constants of formation of the V Cd 2− I Te + ), defect complex and center have been evaluated.

PbTe-Bi2Te3-Te system studied by EMF measurements by M. B. Babanly; A. V. Shevel’kov; F. N. Guseinov; D. M. Babanly (712-716).
The Pb-Bi-Te system has been studied in the composition region PbTe-Bi2Te3-Te at temperatures from 300 to 430 K using emf measurements on reversible concentration cells of the type $( - )PbTe(s)|liquid electrolyte, Pb^{2 + } |(Pb - Bi - Te)(s)( + ).$ . The subsolidus phase diagram inferred from the emf data includes the ternary compounds PbBi6Te10, PbBi4Te7, Pb2Bi6Te11, and PbBi2Te4 of the nPbTe · mBi2Te3 homologous series. Best fit equations for the temperature-dependent emf data were used to determine the partial thermodynamic functions ( $overline {Delta G} $ , $overline {Delta H} $ , and $overline {Delta S} $ ) of the PbTe in the alloys. Using these partial molar functions, subsolidus phase diagram data for the PbTe-Bi2Te3-Te system, and relevant data for PbTe and Bi2Te3, we calculated the standard thermodynamic functions of formation and standard entropies of the above ternary compounds.

We have studied composite electrolytic coatings grown from a nickeling electrolyte containing detonation synthesis nanodiamond. The results demonstrate that the surface composition of nanodiamond particles influences the structure and properties of the coatings. The use of nanodiamond with a surface modified by nickel compounds raises the microhardness and wear resistance of the nickel coatings, without degrading their plasticity.

This paper examines the effect of the chemical and phase compositions of nonstoichiometric titanium carbide prepared by self-propagating high-temperature synthesis on the electrical and thermophysical properties of polymer compounds. Doping of titanium carbide with trace amounts of nitrogen raises the conductivity of the polymer compounds. The addition of epoxy to the polymer matrix markedly reduces the thermal expansion of the material. The proposed materials can be used at temperatures of up to 300–350°C.

Microstructure of TaC coatings on carbon fibers by N. I. Baklanova; T. M. Zima; A. V. Utkin; A. T. Titov (728-732).
This paper examines the possibility of modifying the surface of carbon fibers with tantalum carbide via reactive chemical vapor deposition at temperatures from 800 to 1000°C. We have studied the surface morphology and topography of the coatings on carbon fibers and determined their phase composition by a variety of physicochemical characterization techniques, including X-ray diffraction, high-resolution scanning electron microscopy, and atomic force microscopy. The strength of the modified fibers has been measured at room temperature. The results demonstrate that the coatings are continuous and uniform in thick-ness along and across the monofilaments, with good surface adhesion. The microstructure and surface topography of the coatings depend on the deposition time and temperature.

Nb3Sn-based superconducting helicoids by V. N. Kolosov; A. A. Shevyrev (733-739).
A procedure is proposed for the fabrication of superconducting helicoids which includes consecutive electrodeposition of Nb and Nb3Sn layers from molten salts onto the surface of a plane-turn copper tape helix.

Vapor-phase synthesis of aligned zinc oxide nanorod arrays on various substrates by A. N. Red’kin; A. N. Gruzintsev; E. E. Yakimov; O. V. Kononenko; D. V. Roshchupkin (740-745).
Zinc oxide nanorod arrays have been grown on Si(100), Si(111), and glass substrates by low-pres-sure chemical vapor deposition from elemental zinc and oxygen. Under the experimental conditions of this study, nanorods grow along the c-axis and are predominantly normal to the substrate surface, independent of the crystallographic orientation of the substrate. The cathodoluminescence spectra of all the samples obtained show one strong emission band in the UV spectral region, due to free-exciton recombination, which attests to good stoichiometry of the ZnO nanocrystals. The uniformity of the arrays correlates with the density of nanorods per unit area and their thickness.

Mechanism of ZnO heterolayer formation on ZnSe substrates by V. P. Makhniy; S. V. Khusnutdinov; R. Jakeła (746-748).
We have studied the mechanism of ZnO formation on ZnSe substrates. The results demonstrate that, varying process parameters, one can grow ZnO heterolayers of controlled thickness on ZnSe substrates.

Surface morphology and electrical resistance of the oxide film on InSe by V. M. Katerynchuk; Z. D. Kovalyuk (749-752).
Experimental evidence is presented that air oxidation of InSe crystals produces a native oxide layer which possesses not dielectric but conductive properties and is separated from the semiconductor substrate by a potential barrier. The surface resistance of oxide films grown on InSe across and along the C axis has been measured as a function of oxidation time and temperature. The results demonstrate that the surface resistance of the films varies significantly only during the first five minutes of oxidation. Subsequently, the surface resistance remains almost constant at 100–150 Ω/□. The surface morphology of the native oxide on InSe has been studied by atomic force microscopy. The oxide surface is shown to be nanotextured due to nanospikes normal to the substrate surface. The influence of oxidation temperature and time on the dynamics of the surface morphology of the oxide layer (the lateral dimensions, height, and density of nanospikes) is examined.

Composition, microstructure, and properties of anatase and η-TiO2 nanoparticles by G. M. Kuz’micheva; E. V. Savinkina; M. G. Chernobrovkin; D. N. Titov; P. A. Demina; L. N. Obolenskaya; L. G. Bruk; A. G. Yakovenko (753-758).
Nanoparticulate anatase and η-TiO2 prepared via a sulfate route have been shown (using powder X-ray diffraction, scanning electron microscopy, X-ray microanalysis, and IR spectroscopy) to differ in micro- and nanoparticle size and elemental composition. The degree of As(V), V(V), and Bi(III) extraction from aqueous solutions (for the last element, a content below its maximum allowable concentration has been reached) using nanoparticulate titania adsorbents depends on their composition, crystal structure, crystallinity, and microstructure. The synthesized anatase and η-TiO2 powders are shown to be potentially attractive carriers of PdCl2-CuCl2/TiO2 catalysts for low-temperature carbon monoxide oxidation in air.

This paper presents thermodynamic assessment of the Sm-Ba-O system and its constituent binaries using available experimental data. Analytical expressions are derived for the Gibbs energy of Sm2BaO4, Sm4Ba3O9, and the liquid. The BaO-SmO1.5 phase diagram at oxygen partial pressures of 1 Pa and 21 kPa is calculated.

Mechanochemical synthesis of γ-LiAlO2 studied by 6Li and 27Al NMR and synchrotron X-Ray diffraction by V. P. Isupov; O. A. Kharlamova; L. E. Chupakhina; M. R. Sharafutdinov; D. F. Khabibulin; O. B. Lapina (763-767).
The structural transformations accompanying the mechanochemical synthesis of fine-particle γ-LiAlO2 have been studied by 6Li and 27Al NMR and in situ X-ray diffraction. Mechanical activation of a mixture of aluminum hydroxide and lithium carbonate in an AGO-2 planetary mill results not only in size reduction, intermixing, and partial amorphization of the starting materials but also in the mechanochemical synthesis of a carbonate form of aluminum lithium hydroxide. Subsequent heat treatment of the mechanically activated mixture leads to the release of water and carbon dioxide molecules and the formation of an X-ray amorphous phase containing aluminum in octahedral and tetrahedral oxygen coordination. The X-ray amorphous material converts to gamma lithium aluminate through an intermediate phase.

Mechanisms of solid-state reactions underlying the synthesis of phase-pure lithium niobate by M. N. Palatnikov; N. V. Sidorov; V. T. Kalinnikov (768-773).
LiNbO3 formation in the Li2CO3-Nb2O5 system has been studied by thermal analysis, X-ray diffraction, IR spectroscopy, and mass spectrometry with the aim of gaining insight into the mechanisms of solid-state reactions underlying the synthesis of single-phase lithium niobate.

Structure and dielectric properties of (1 − x)BiFeO3 · x(KBi)1/2TiO3 perovskite solid solutions by A. V. Pushkarev; N. M. Olekhnovich; Yu. V. Radyush (774-778).
(1 − x)BiFeO3 · x(KBi)1/2TiO3 ceramics have been prepared by solid-state reactions. The system has been shown to contain a continuous series of perovskite solid solutions. In the composition ranges x < 0.4, 0.4 < x < 0.9, and x > 0.9, the solid solutions have rhombohedral, orthorhombic, and tetragonal structures, respectively. The observed compositional phase transitions are accompanied by sharp changes in unit-cell volume. We describe the dielectric properties of the orthorhombic solid solutions, which demonstrate that these materials exhibit relaxor behavior.

Dielectric and piezoelectric properties of (1 − 2x)BiScO3 · xPbTiO3 · xPbMg1/3Nb2/3O3 (0.30 ≤ x ≤0.46) solid solutions by A. A. Bush; K. E. Kamentsev; A. M. Lavrent’ev; A. G. Segalla; Yu. K. Fetisov (779-785).
We have synthesized ceramic samples of (1 − 2x)BiScO3 · xPbTiO3 · xPbMg1/3Nb2/3O3 perovskite solid solutions with 0.30 ≤ x ≤ 0.46 and studied their structural, dielectric, and piezoelectric properties. At x = 0.40, the system has a morphotropic phase boundary between tetragonal (x > 0.40) and rhombohedral (x < 0.40) solid solutions. The dielectric permittivity and loss tangent of the solid solutions have been measured at temperatures from 100 to 800 K and frequencies from 0.1 to 200 kHz. The maximum in the permittivity of the solid solutions lies in the range 390–440 K. With increasing BiScO3 content, features characteristic of fer-roelectric relaxors emerge and become more pronounced. Near the morphotropic phase boundary, the piezoelectric charge coefficients d 33 and d 31 of the solid solutions reach 410 and 150 pC/N, respectively, and their radial-mode mechanical Q drops to 22, which makes these materials potential candidates for a number of applications.

We have studied the physicochemical and physical properties of a langbeinite-structure cesium cadmium molybdate (sp. gr. P213, Z = 4, a = 11.239(1) Å). It has very low thermal expansion and possesses piezoelectric properties. We have constructed the section of the longitudinal piezoelectric surface for Cs2Cd2(MoO4)3 by a plane containing a threefold axis (body diagonal), along which the piezoelectric modulus has the highest value: 5.8 × 10−12 C/N.

Effect of mechanical activation time on the reactivity of wolframite concentrates by E. V. Bogatyreva; A. G. Ermilov; T. A. Sviridova; O. S. Savina; K. V. Podshibyakina (791-797).
A direct method has been tested for evaluating the energy stored during mechanical activation in the wolframite phase of standard and low-grade wolframite concentrates. The activation energy change has been shown to be influenced by the type of energy stored. Our results confirm that the energy stored during mechanical activation in the form of surface energy influences the leaching behavior of the concentrate. We have studied the effect of the surface energy stored in the wolframite phase during mechanical activation on the tungsten extraction into solution through low-temperature alkaline leaching. A relationship has been derived between the tungsten extraction into solution through alkaline leaching and the surface energy stored in the wolframite phase.

Gamma-induced defects in BaFI crystals by I. Nuritdinov; B. T. Atashov; A. B. Uteniyazova; K. Turdanov (798-800).
We have studied gamma-induced defects in BaFI crystals. To gain insight into the origin of the observed induced absorption bands, we analyzed the dose dependence of the concentration of color centers. The results lead us to assign the 205-nm absorption band to α(F) centers, the 270-nm band to F i 0 centers, the 370-nm band to I i 0 centers, the bands around 480 nm to F(F) centers, and the 610-nm band to F(I) centers.

Optical properties of Tm3+-doped TeO2-WO3 glasses by A. N. Shushunov; V. A. Novikov; I. A. Grishin (801-805).
Tm3+-doped TeO2-WO3 glasses have been prepared and their absorption spectra have been measured in the visible to IR (up to 7 μm) spectral region. Luminescence measurements have shown that the glasses have emission bands at 1.45 and 1.8 μm. An attempt was made to remove OH groups from the glasses using KBF4 and an inert atmosphere during the glass preparation. The results demonstrate that a low OH content can be achieved only by combining these approaches. The 1.8-μm emission intensity in “dry” glass is a factor of 6 higher than that in the OH-containing glasses. The relevant Judd-Ofelt parameters have been calculated.

Preparation of Pb2B5O9Br-based nonlinear optical glass-matrix composites by B. V. Egorova; V. A. Dolgikh; S. Yu. Stefanovich; P. S. Berdonosov; A. V. Garshev (806-809).
Borate halide glasses have been prepared by quenching melts with the stoichiometric composition Pb2B5O9Br, an excess of B2O3, PbBr2, or Pb2B5O9Cl additions, and their glass transition and crystallization temperatures have been determined. The glasses were annealed at different temperatures to give glass-matrix composites comprising a bromine-deficient matrix and microscopic crystalline Pb2B5O9Br particles. The composites exhibit second harmonic generation, and the signal intensity correlates with the surface morphology of the materials.