Inorganic Materials (v.44, #9)

Planar buried crescent InP/InGaAsP/InP heterostructure on p-InP by M. G. Vasil’ev; A. M. Vasil’ev; A. A. Shelyakin (913-917).
A process is described for liquid phase epitaxy of mesa stripe buried crescent InP/InGaAsP/InP heterostructures with a p-n-p-n/ZnSe leakage current blocking structure. The process enables the fabrication of 1.3-μm light-emitting diodes with a low threshold current, stable fundamental transverse mode operation, and high output power. When mounted with the mesa stripe up, the diodes offer an emission power above 30 mW.

Chromium diffusion in GaAs in an open system by M. V. Ardyshev; I. A. Prudaev; O. P. Tolbanov; S. S. Khludkov (918-921).
We have studied chromium diffusion from a surface layer produced by thermal evaporation into n-type GaAs in a flowing inert-reducing atmosphere. The temperature dependences of the Cr diffusivity and solubility in GaAs are well represented by Arrhenius equations with D 0 = 1.7 × 10−2 cm2/s and Q D = 1.43 eV for the diffusivity and C Cr 0 = 8.9 × 1021 cm−3 and Q Cr = 1.22 eV for the solubility.

The short-range order in thin amorphous Bi2S3 films grown under ordinary conditions and in an applied electric field of 3000 V/cm has been studied. The interatomic distances obtained are r 1 = 0.23 nm, r 2 = 0.345 nm, and r 3 = 0.45 nm, and the corresponding coordination numbers are n 1 = 4, n 2 = 6, and n 3 = 5.88. The coordination numbers and the ratios r 3/r 1 = 1.96 and r 2/r 1 = 1.5 indicate that the atoms in amorphous Bi2S3 are in tetrahedral and octahedral coordination. In the films grown in an electric field, the near neighbor distances are slightly shorter.

The temperature dependences of the thermal expansion coefficient and isothermal compressibility for TlGaSe2(1 − x)S2x (x = 0.1, 0.2) solid solutions show an anomaly attributable to a second-order phase transition. The thermal expansion data have been used to evaluate the Debye characteristic temperature Θ, rms atomic displacement, and specific heat difference of the solid solutions.

X-ray diffraction study of ternary layered compounds in the PbSe-Bi2Se3 system by L. E. Shelimova; O. G. Karpinskii; V. S. Zemskov (927-931).
The pseudobinary system PbSe-Bi2Se3 has been studied by x-ray diffraction using cleaved single-crystal specimens and powders, and the compositions of the layered compounds existing in this system have been refined. The monoclinic cell parameters of the compounds Pb5Bi6Se14 and Pb5Bi12Se23, belonging to the [(PbSe)5] m [(Bi2Se3)3] n homologous series, have been determined.

Electron diffraction study of the short-range order in amorphous Yb1 − x Sm x As4Se7 films by E. Sh. Hajiev; A. I. Madadzade; D. I. Ismailov (932-934).
The electron scattering intensity of amorphous Yb1−x Sm x As4Se7 films was measured up to S max = 112 nm−1. The intensity data were Fourier-transformed to convert to an atomic radial distribution function and determine the short-range order parameters of the amorphous films.

New thallium neodymium tellurides by S. Z. Imamalieva; F. M. Sadygov; M. B. Babanly (935-938).
The phase equilibria in the composition region Tl2Te-Tl2Te3-Nd2Te3-NdTe of the Tl-Nd-Te system have been studied by differential thermal analysis and x-ray diffraction, and the 500-K section of its phase diagram has been mapped out. The ternary compounds identified are Tl9NdTe6, Tl4NdTe3, Tl6Nd4Te9, Tl4Nd6Te11, Tl2NdTe3, TlNdTe3, and TlNd3Te6. X-ray powder diffraction data indicate that the compounds Tl9NdTe6 and Tl4NdTe3 are structural analogs of Tl5Te3 and have tetragonal cell parameters a = 8.855 Å, c = 13.010 Å and a = 8.858 Å, c = 12.998 Å, respectively (sp. gr. I4/mcm, Z = 4). Tl9NdTe6 and Tl4NdTe3 are phases of variable composition (δ-phase), and their fields cover most of the Tl2Te-Tl5Te3-Tl4NdTe3 composition triangle. The structure of Tl5Te3 and its ternary analogs is discussed, and the conclusion is drawn that, in spite of the broad field of the δ-phase, Tl9NdTe6 and Tl4NdTe3 are daltonides, i.e., distinct chemical compounds.

Application of the embedded-atom method to liquid copper by D. K. Belashchenko; Yu. V. Zhuravlev (939-945).
A procedure for calculating the embedded-atom method (EAM) potential with the use of diffraction data for the metal near its melting point has been applied to copper at temperatures from 1423 to 7400 K. In optimizing the parameters of the EAM potential, we used the pair correlation functions of copper at 1423 and 1873 K, the thermodynamic properties of liquid copper under ordinary conditions, and flash heating and shock compression results. Molecular dynamics simulation with the EAM potential adequately represents the thermodynamic properties and structural characteristics of liquid copper up to 1873 K. The simulated 1423-K bulk modulus is close to the experimentally determined one. At low pressures, the self-diffusion coefficient rises as a power law function of temperature with an exponent close to 2.10. The simulated melting point of copper, 1384 ± 3 K, is close to the actual one. Simulations were performed at temperatures of up to 7400 K and densities a factor of 1.6 higher than the normal one. The melting point was evaluated at pressures of up to 50 GPa. The EAM potential obtained is suitable for the liquid phase but fails to accurately describe properties of crystalline copper.

Electrochemical arsenic extraction from nonferrous metals industry waste by V. V. Turygin; M. K. Smirnov; A. V. Smetanin; E. G. Zhukov; V. A. Fedorov; A. P. Tomilov (946-953).
We have developed physicochemical approaches to processing of arsenic-containing nonferrous metals industry waste with the use of sulfuric acid stripping followed by electrochemical arsenic extraction. Our results indicate the possibility of producing crude and high-purity arsenic; metallic zinc; and Sn, Pb, Sb, Cd, and Cu concentrates. A combined process has been developed for the preparation of 99.9999%-pure arsenic.

Determination of oxygen in W-C-Co nanopowders by P. V. Krasovskii; Yu. V. Blagoveshchenskii; K. V. Grigorovich (954-959).
The oxygen content of W-C-Co nanopowders produced by plasma reduction of WO3, followed by low-temperature carburization in hydrogen has been determined by carrier gas hot extraction. The oxygen in adsorbed water, carbon-oxygen complexes weakly bound to the surface, and surface oxides (WO x and CoO x ) has been determined separately. Freshly prepared, passivated WC and WC + 8% Co powders with a specific surface area of 6–11 m2/g were found to contain 0.03–0.07 μg/cm2 of oxygen, not counting adsorbed water. Strongly bound oxygen in the form of surface oxides accounts for at least 80% of the total oxygen. These oxygen contents are equivalent to surface coverages from 1.2 to 2.5 oxygen monolayers (monolayer density of 1015 at/cm2). The water content varies from 0.15 to 0.3%, which corresponds to a water film no thicker than a monolayer. All of the water is physisorbed. The products of the plasma reduction of WO3 have a complex phase composition (W2C, WC1 − x , W, α-WC) and a specific surface area from 21 to 24 m2/g. In spite of the high content of the readily oxidizable phases W and W2C, the plasma-synthesized mixtures have submonolayer surface coverages with oxygen. They are protected from air oxidation by thin (one to three monolayers) pyrolytic carbon films, while the small amount of oxygen present originates from unreacted particles. In dry air, the powders oxidize insignificantly. At 100% humidity, stoichiometric WC powders are the most stable, while WC + 8% Co shows the lowest stability. The oxidation rate of W-C powders is proportional to the overall content of W and W2C.

Effect of chemical etching on the luminescent properties of zinc oxide nanorods by A. N. Gruzintsev; A. N. Red’kin; E. E. Yakimov; C. Barthou (960-964).
Vertically aligned ZnO nanorods grown on (100) Si substrates have been found to have a polycrystalline zinc oxide underlayer. After etching in a hydrochloric acid solution, the nanorods had smaller dimensions and pointed ends. As shown by exciton spectroscopy, the nanorods had a higher structural perfection and better luminescent properties in comparison with the underlayer. The 4.2-K luminescence spectra of the nanorods exhibit violet emission due to bound and interacting excitons. The low-temperature edge emission of the ZnO underlayer is shown to consist of lines due to electron-hole plasma recombination.

Composition and structure of hafnia films on silicon by T. P. Smirnova; V. V. Kaichev; L. V. Yakovkina; V. I. Kosyakov; S. A. Beloshapkin; F. A. Kuznetsov; M. S. Lebedev; V. A. Gritsenko (965-970).
Ellipsometry, electron microscopy, and x-ray photoelectron spectroscopy data indicate that, during HfO2 deposition onto silicon, the native oxide reacts with the HfO2 deposit to form an amorphous intermediate layer which differs in refractive index (≃1.6) from both HfO2 (1.9–2.0) and SiO2 (1.46). Thermodynamic analysis of the Si-SiO2-HfO2-Hf system shows that Si is in equilibrium with Si/HfO2 − y only at low oxygen pressures. Starting at a certain oxygen pressure (equivalent to the formation of a native oxide layer), the equilibrium phase assemblage is Si/HfSiO4/HfO2 − y .

The effect of fast-neutron irradiation on the structure of fused silica has been studied by IR reflection spectroscopy in a wide range of neutron fluences, from 1017 to 1021 n/cm2. The spectral characteristics of the bending and stretching modes of the bridge bonds in silica have been shown to be nonlinear functions of neutron fluence. The kinetics of radiation-induced changes in the optical properties of silica in the UV through visible spectral region have been analyzed in relation to those in its structure and microscopic characteristics. A strong correlation has been found between the dose dependences of the optical and structural properties of silica, such as the 465-nm luminescence intensity, the intensity and position of the amorphous halo, the reflectivity and frequency of the IR bands at 1125 and 480 cm−1, the density of the material, and its ionic polarizability. We assume that there is a threshold dose in the range 1019 to 1020 n/cm2 which produces sharp changes in the optical and structural properties of SiO2 due to a transition to a metamict-like state. An analytical expression has been derived for the radiation-induced changes in the intensity of the first halo. The driving force and mechanism of the radiation-induced structural changes in fused SiO2 have been tentatively identified.

Silica aerogels were made by sol-gel techniques using tetraethoxysilane, followed by drying under ambient pressure. BET and XRD results show that the silica aerogels have a high inner surface area and are amorphous. Laser granularity analysis shows that the average particle size of silica aerogels is less than 20 μ m and that they have mesoporous structure. The surface chemical modification was confirmed by FTIR spectroscopy. The thermal stability of the hydrophobic aerogels was studied from 25 to 1200°C. The hydrophobic nature of the aerogels could be maintained up to around 500° C. Above this temperature, the aerogels become hydrophilic.

SO2 chemisorption on SnO2〈Sb〉 by M. V. Vinokurova; A. A. Vinokurov; L. E. Derlyukova (980-985).
We have studied SO2 chemisorption on antimony-doped SnO2 samples annealed at 200 and 600°C. Increasing the annealing temperature from 200 to 600°C makes the sample surface more homogeneous. In the range 100–200°C, the electrical conductivity of the samples air-annealed at 600°C increases in proportion with the amount of absorbed SO2. Doping with 0.2 at % Sb ensures the largest increase in conductivity upon chemisorption.

Chlorine impurity content of Bi2O3 and GeO2 by E. V. Polyakova; O. V. Shuvaeva; A. I. Saprykin (986-989).
Bismuth(III) and germanium(IV) oxides are used as precursors for the crystal growth of bismuth orthogermanate. The chlorine content of the starting oxides is critical to the engineering performance of this material. We propose a simple, high-speed technique for determining the chlorine content of bismuth(III) and germanium(IV) oxides, down to 5 × 10−4 wt %, using capillary electrophoresis.

Magnetic nanocomposites of mixed oxides of iron and barium synthesized under different oxidative environments by Shalima Gupta; Sajdha; H. N. Sheikh; B. L. Kalsotra; N. Kumar; S. Kumar (990-1008).
Synthesis of nanocomposites of mixed oxides of iron and barium in a copolymer matrix of aniline and formaldehyde using a chemical route at room temperature is reported. X-ray diffraction, infrared, 57Fe Mossbauer studies, and scanning electron microscopy on as-synthesized samples, as well as samples obtained on heating at different temperatures, are described. X-ray diffraction, 57Fe Mossbauer, and scanning electron microscopy show the formation of nanoparticles of barium ferrites in the polymer matrix. These studies further show the formation of solid solution of iron and barium oxide on heating the samples at temperatures from 400 to 700°C. From the Mossbauer and x-ray diffraction studies, it has been found that γ-Fe2O3, which normally transforms into α-Fe2O3 on heating at 500°C, persists up to 700°C in the present samples containing barium ions. Infrared studies indicate that the polymeric backbone is strongly influenced by different reaction conditions and lead to variable magnetic character in the heated samples.

The physicochemical properties of (1 − x)CsH2PO4/xSiP y O z (x = 0.2–0.7) composites containing fine-particle silicon phosphates as heterogeneous additives have been studied at different humidities. The introduction of silicon phosphates suppresses the superionic phase transition of CsH2PO4 and increases the low-temperature conductivity of the materials, which depends significantly on humidity. The CsH2PO4-SiP y O z materials offer high conductivity (∼3 × 10−3 to 10−2 S/cm at ∼110–230°C) at low water vapor pressures (3 mol % H2O). Amorphization of the CsH2PO4 in the composites markedly changes its thermodynamic properties. The effect of long-term isothermal holding (210°C, 3 mol % H2O) on the conductivity of the composites has been studied.

Magnetic susceptibility and effective magnetic moment of the Nd3+ and Co3+ ions in NdCo1 − x Ga x O3 by N. N. Lubinskii; L. A. Bashkirov; A. I. Galyas; S. V. Shevchenko; G. S. Petrov; I. M. Sirota (1015-1021).
The magnetic susceptibility of NdCo1 − x Ga x O3 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.8, 0.9, 1) has been measured at temperatures from 80 to 950 K. The effective magnetic moments (μeff) due to the magnetic moments of the Co3+ and Nd3+ ions have been determined in the temperature ranges of Curie-Weiss behavior, 130–370 and 600–940 K, and have then been used, together with the effective magnetic moment of Nd3+ (3.62μB or 4.20μB), to evaluate the effective magnetic moment of Co3+ in NdCo1 − x Ga x O3. For the solid solutions with $$ mu _{eff Co^{3 + } } $$ < 2.83μB, we have determined the fractions of intermediate-and low-spin Co3+ ions. In the range 2.83μB < $$ mu _{eff Co^{3 + } } $$ < 4.90μB, we have determined the fraction of high-spin Co3+ ions. The results indicate that, in the temperature range 130–370 K, the Co3+ ions in NdCo1 − x Ga x O3 with x = 0, 0.5, 0.8, and 0.9 are in the intermediate-and high-spin states, and the fraction of high-spin Co3+ ions gradually increases from 10% at x = 0 to 67% at x = 0.9. In the solid solutions with x = 0.1, 0.2, 0.3, and 0.7, more than half of the Co3+ ions are in the low-spin state, and the rest are in the intermediate-spin state. In the temperature range 600–940 K, the Nd3+ ions are in the ground and excited states, with theoretically predicted of $$ mu _{eff Nd^{3 + } } $$ of 3.62μB and 5.52μB, respectively. Because of the significant uncertainty in $$ mu _{eff Nd^{3 + } } $$ in this temperature range, $$ mu _{eff Co^{3 + } } $$ has been determined less accurately compared to the range 130–370 K.

BaFe12O19 films produced from BaFe2O4/α-Fe2O3 heterostructures by V. V. Pan’kov; A. I. Stognii; V. D. Koshevar; V. A. Ketsko (1022-1025).
BaFe12O19 hexaferrite films have been produced on thermally oxidized single-crystal silicon (SiO2/Si) substrates by sequential ion-beam sputtering of BaFe2O4 and α-Fe2O3 targets in an argon-oxygen atmosphere. Their crystal structure has been studied, and the origin of the impurity phases forming during heat treatment has been identified. The results show that heat treatment may lead to the formation of eutectic melts. As a result, the hexaferrite films may contain spherulites.

Effect of iron oxides on the fabrication and properties of continuous glass fibers by E. A. Moiseev; S. I. Gutnikov; A. P. Malakho; B. I. Lazoryak (1026-1030).
We have studied the effect of iron oxides (0–10 wt % in terms of FeO) on the fabrication conditions and properties of continuous Fe-containing glass fibers and have determined the temperature ranges of fiber fabrication. A relationship between the iron oxide content of glass and the fiber fabrication temperature has been established. Using differential scanning calorimetry and x-ray diffraction, we have investigated the effect of glass composition on the glass transition temperature and temperature range of crystallization of the fibers. At high iron oxide contents (5–10 wt %), the first to crystallize is magnetite, otherwise quartz appears first. Increasing the heat-treatment temperature leads to crystallization of pigeonite, augite, enstatite, anorthite, and labradorite.