Inorganic Materials (v.44, #10)

A mechanism of quasi-one-dimensional vapor phase growth of Si and GaP whiskers by V. A. Nebol’sin; A. A. Shchetinin (1033-1040).
Using vapor phase growth, we have studied the conditions and mechanisms of Si and GaP whisker growth on (111) and (100) substrates in the presence of Au, Cu, Ni, and Pt as metal solvents. Our experimental data demonstrate that the rate of whisker growth is unaffected by the nature and orientation of the substrate and that the liquid droplet wets the (111) singular face of the growth front. The three-phase line of contact acts as a source of steps on the singular face of the growth front under the droplet. Based on the present results, a physicochemical mechanism of quasi-one-dimensional vapor-droplet-solid whisker growth has been proposed and substantiated.

Cluster ferromagnetism in Mn-doped InSb by V. A. Ivanov; O. N. Pashkova; E. A. Ugolkova; V. P. Sanygin; R. M. Galéra (1041-1046).
We have studied cluster ferromagnetism in InSb〈Mn〉 and have refined kinematic exchange theory with application to such diluted magnetic semiconductors.

Effect of SH-containing ligands on the growth of CdS nanoparticles by N. G. Piven; Yu. B. Khalavka; L. P. Shcherbak (1047-1051).
Cadmium sulfide nanoparticles have been synthesized via precipitation from solution, using thioglycolic acid (TGA) and L-cysteine as stabilizing agents. The nanoparticle size has been evaluated using the absorption spectra of the solutions, dynamic light scattering data, and transmission electron microscopy. The L-cysteine-stabilized nanoparticles are smaller and more uniform in size compared to the TGA-stabilized nanoparticles. The effect of synthesis temperature on nanoparticle growth has been studied. With increasing synthesis temperature, the average radius of the nanoparticles increases, which is accompanied by their aggregation and broadening of their size distribution.

Effect of hydrogen on the stability of isovalently doped ZnSe crystals by L. P. Gal’chinetskii; B. V. Grinev; N. G. Starzhinskii; A. Ya. Dulfan; V. D. Ryzhikov (1052-1056).
We present thermodynamic analysis of the relative stability of V ZnZniXSe defect complexes (radioluminescence centers in ZnSe(XSe) crystals) toward reactions with hydrogen in the temperature range 300 to 1300 K and analysis of reactions between the surface of ZnSe(XSe) crystals and air that lead to hydrogen diffusion into the bulk of the crystal. The results, supported by experimental data, indicate that the stability of the complexes and the chemical stability of ZnSe(XSe) crystals toward reactions with hydrogen increase in the order OSe < SSe < TeSe.

Heat capacity of the n-Bi2Te2.88Se0.12 and p-Bi0.52Sb1.48Te3 solid solutions by Yu. I. Shtern; A. S. Malkova; A. S. Pashinkin; V. A. Fedorov (1057-1059).
The heat capacity of the n-Bi2Te2.88Se0.12 and p-Bi0.52Sb1.48Te3 solid solutions has been measured from 360 to 600 K. The data, represented in the form C p = a + bT + cT −2, have been used to evaluate the thermodynamic functions of the solid solutions in the range 298.15 to 600 K.

Phase equilibria in the system Tl2Te-SnTe-TlBiTe2 by M. B. Babanly; G. B. Dashdieva; F. N. Guseinov (1060-1065).
The phase equilibria in the system Tl2Te-SnTe-TiBiTe2 (A) have been studied using differential thermal analysis, x-ray diffraction, and microhardness measurements. We have constructed the T-x phase diagrams along the SnTe-TlBiTe2, SnTe-Tl9BiTe6, and Tl4SnTe3-TlBiTe2 joins, the 600-and 800-K sections of the phase diagram of system A, and its liquidus diagram. The results demonstrate that the system contains broad ranges of Tl5Te3-structured and SnTe-based solid solutions (δ and γ1 phases, respectively). There are also relatively small fields of the Tl2Te-based phase (α) and low-and high-temperature TlBiTe2-based solid solutions (γ2 and γ′2). The liquidus surface of system A comprises the primary crystallization fields of the δ, γ1, and γ′2 phases. The liquidus of the α phase is degenerate. The ternary eutectic between the δ, γ1, and γ′2 phases melts at 755 K.

Lattice parameter fluctuations and atomic displacements from equilibrium positions in PbTe1−x Cl x solid solutions have been studied by x-ray diffraction. Both parameters are shown to increase with chlorine content, reaching 0.026 and 0.045 Å, respectively.

Homogeneity ranges of Tl5Te2Cl and Tl5Te2Br by M. B. Babanly; M. I. Chiragov; Yu. A. Yusibov (1069-1075).
This paper systematizes phase-diagram data for the Tl-TlCl(Br)-Te systems and presents their 500-K subsolidus phase diagrams. Tl5Te2Cl and Tl5Te2Br (Tl5Te3 structure) are shown to be nonstoichiometric compounds with wide homogeneity ranges, which have been accurately determined using emf measurements, x-ray diffraction, and microhardness tests. Using emf data for reversible concentration cells with a thallium electrode, we have evaluated the partial thermodynamic functions of the thallium in the alloys studied, the standard thermodynamic functions of formation of Tl5Te2Cl and Tl5Te2Br, and their standard entropies. The crystal chemistry of these phases of variable composition is discussed in relation to the Tl5Te3 structure.

The Bi-Te-I system has been studied by differential thermal analysis, x-ray diffraction, and emf measurements in the temperature range 300–400 K using concentration cells of the type (−)Bi(s) | glycerol + KI + BiI3 | Bi-Te-I(s)(+). The results have been used to construct the 300-K section of the Bi-Te-I phase diagram. The existence of the ternary compounds BiTeI, Bi2TeI, and Bi4TeI1.25 has been confirmed, and the position of the phase fields involving these compounds has been accurately determined. Using emf data, we have evaluated the partial thermodynamic functions (Δ $$ ar G $$ , Δ $$ ar H $$ , and Δ $$ ar S $$ ) of the bismuth in the alloys studied, the standard thermodynamic functions of formation of the ternary compounds, and their standard entropies.

Electrochemical preparation of germane by V. V. Turygin; M. K. Smirnov; N. N. Shalashova; A. V. Khudenko; S. V. Nikolashin; V. A. Fedorov; A. P. Tomilov (1081-1085).
Germane has been prepared through the electrochemical reduction of the germanate anion in alkaline solutions with a current efficiency of 40–45%. Active solution circulation in the cathodic zone and the use of an Sn or Cd cathode are shown to raise the germane yield. The current density and initial solution concentration have a weak effect on the reduction process.

A new type of nanostructure in Si/C composite electrodes for lithium-ion batteries by M. A. Bruk; V. A. Bespalov; B. A. Loginov; V. B. Loginov; Nikolai A. Degtyarev; Nikita A. Degtyarev; I. D. Zefirov; V. A. Kal’nov; A. V. Klochikhina; T. L. Kulova; Yu. E. Roginskaya; A. V. Skundin (1086-1090).
The composition and structure of thin-film Si/C composite anodes produced by alternately depositing controlled amounts of silicon and carbon using magnetron plasma sputtering have been determined by atomic force microscopy, x-ray diffraction, and optical spectroscopy (Raman and UV through IR specular reflectance spectra). The silicon-to-carbon volume ratio in the films was varied from 39.5: 60.5 to 87: 13, and their thickness ranged from 100 to 480 nm. The surface of the films was found to have a nanogranular structure, which had not been reported previously for Si/C composites. This morphology is atypical of structureless silicon layers deposited under the same conditions but is similar to the nanostructure of a thin carbon film consisting of grains uniform in shape and size (D av = 20–25 nm). Reducing the carbon content of the composites from 60 to 36% increases the grain size from 25 to 45–50 nm. At high silicon contents (near 80%), the nanostructure of the composites is less homogeneous: in addition to nanograins, there are structureless silicon zones. The homogeneity of the nanostructure depends on the Si: C ratio and the sequence and thicknesses of the deposited Si and C layers. Thin (104–173 nm) films containing more than 30% carbon (they have isolated silicon clusters) reveal the highest activity for the lithium intercalation-deintercalation process. Their Raman spectra show strong luminescence characteristic of silicon nanoparticles less than 5–6 nm in size. This effect is missing in the thicker films, in which the silicon forms an infinite cluster and which have a stronger tendency to degrade.

Thermodynamic properties of Mn-Y-Si(Ge, Sn, Pb, C) melts by V. S. Sudavtsova; N. V. Kotova (1091-1096).
The effect of Group IVA elements on the integral enthalpy of mixing of Mn-Y-Si(Ge, Sn, Pb, C) melts has been studied using the mixing enthalpies of Mn-Y-Si(Ge) melts determined earlier by calorimetry at 1770 ± 5 K. Since the thermochemical properties of Mn-Y-C(Sn, Pb) melts are unexplored, they have been calculated by the Bonnier-Caboz method using reliable data for the constituent binary systems. To this end, we have performed critical evaluation of the phase diagrams and thermochemical data for the constituent binary systems and have compared the enthalpies of formation of solid Δf H and liquid Δmix H binary alloys. The results indicate that, among liquid Mn-Y-IVA alloys, the formation of Mn-Y-Ge melts is the most exothermic. The thermochemical properties of all the ternary alloys examined are determined by the properties of the Y-Si(Ge, Sn, Pb, C) constituent binary systems, which have the highest exothermic mixing enthalpies.

We have studied the effect of neutron irradiation in a nuclear reactor on the high-frequency IR absorption spectra of quartz glasses. Three groups of bands were identified in the range 1400–2300 cm−1 (at 1610, 1910, and 2270 cm−1), and one group, in the range 2870–2970 cm−1. The effects of neutron dose, ambient atmosphere, and sample geometry on these bands have been assessed. The results have been correlated with the irradiation-induced changes in the fundamental modes of the glass network and the luminescent and structural properties of the glasses. Mechanisms have been proposed for the radiation-induced changes in the spectral characteristics of some of the absorption bands. We assume activation of some combined frequencies at v > 1400 cm−1 and local vibrations in the impurity region of the spectrum. High neutron doses produce marked changes in the IR spectrum, which seem to be associated with structural changes in the glass. The likely mechanism of such changes is discussed.

Preparation of ceria and yttria nanopowders via thermal decomposition of oxalates, carbonates, and hydroxides by A. A. Titov; M. A. Klimenko; E. G. Goryacheva; N. L. Opolchenova; N. N. Stepareva; N. P. Sokolova (1101-1104).
Ceria and yttria nanopowders have been prepared through thermal decomposition of various precursors. The nature of precursors has been shown to have a significant effect on the microstructure of the powders. The stability of the powders to particle (crystallite) growth has been studied as a function of heat-treatment temperature and duration.

A size distribution function of magnetite nanoparticles has been selected among known distribution functions that well represent the frequency polygon of the nanoparticles. Normal and lognormal distribution functions are shown to provide more accurate representations for the initial and final portions of the size distribution of magnetite nanoparticles. We have determined the transition diameter of magnetite nanoparticles which corresponds to a transition from a normal to a lognormal distribution function and have constructed a composite distribution function consisting of normal and lognormal distribution functions, which accurately represents the size distribution of the magnetite nanoparticles. The distribution moments and magnetization curve calculated using this distribution function agree well with the moments calculated using the frequency polygon of the magnetite nanoparticles and with the experimentally determined magnetization curve.

Lithium ion conductivity of LiLaO2-Li2ZrO3 solid solutions by M. I. Pantyukhina; Z. S. Martem’yanova; N. N. Batalov (1110-1114).
The limits of the LiLaO2-and Li2ZrO3-based solid solutions in the LiLaO2-Li2ZrO3 system have been determined: 0–10 mol % Li2ZrO3 and 0–5 mol % LiLaO2, respectively. We have studied the transport properties (electronic conductivity, temperature and composition dependences of conductivity and activation energy) of lithium lanthanate and the solid solutions in the LiLaO2-Li2ZrO3 system. Conduction in LiLaO2 is likely due to lithium ion transport through a polyhedral network.

Electric-field effect on crystal growth in the Li3PO4-Li4GeO4-Li2MoO4-LiF system by D. A. Ksenofontov; L. N. Dem’yanets; A. K. Ivanov-Schitz (1115-1120).
We have studied the electric-field effect on crystallization processes in the Li3PO4-Li4GeO4-Li2MoO4-LiF system. In zero field, Li3+x P1−x Ge x O4 (x = 0.31) crystals were grown on the cathode under the conditions of this study. At low applied voltages (≤ 0.5 V), we obtained Li2MoO4, Li2GeO3, and Li1.3Mo3O8. In the range V = 0.5–1 V, crystals of Li3+x P1−x Ge x O4 solid solutions with x = 0.17, 0.25, 0.28, 0.29, and 0.36 were obtained. An applied electric field was shown to reduce the melting temperature of the starting mixtures and the crystallization onset temperature.

Hydrothermal synthesis and photoluminescence behavior of Eu-doped GdVO4 by Dalai Jin; Hong Yang; Gaosong Ding; Xiaojing Yu; Lina Wang; Yifan Zheng (1121-1124).
Eu3+ doped GdVO4 was successfully prepared by a simple hydrothermal method. It was characterized by x-ray diffraction and scanning electron microscopy, which revealed that the GdVO4:Eu3+ was tetragonal (zircon-type structure). Photoluminescence spectra revealed that there was efficient energy transfer from the GdVO4 host to the Eu3+, and the GdVO4:Eu3+ crystal exhibited a strong red emission peaked at 616 nm due to the Eu3+ 5 D 0-7 F 2 transition. The hydrothermal route is proposed for synthesizing a red luminescent GdVO4:Eu3+ phosphor as an economical technique.

Phase composition and optical properties of thin films based on lanthanum and tungsten oxides by V. A. Logacheva; A. N. Lukin; Yu. A. Tikhonova; A. A. Lynov; D. M. Pribytkov; A. M. Khoviv (1125-1129).
We have studied the phase composition and optical properties of 150-to 500-nm-thick films based on lanthanum and tungsten oxides, produced by magnetron sputtering followed by heat treatment at 773 K in vacuum and flowing oxygen. The oxide films have been found to have high transmission in the range 250 to 900 nm and an absorption band between 190 and 250 nm. Analysis of their absorption edge indicates that its complex structure is due to the presence of several phases. The energies of direct transitions evaluated from the spectra of the films coincide with the band gaps of the phases present in the films.

We have optimized the composition of porous glass-ceramic supports compatible with conducting ceramics and have developed a procedure for the fabrication of such supports. High-shrinkage-potential porous supports in the form of dead-end tubes have been shown to be best suited for designing multilayered selective ceramic membranes. We have assessed the effects of various modifiers on the shrinkage curve of such supports. The factors that play a central role in determining the properties of supports have been identified: the amount of burnout additives determines the macroporosity, the addition of low-melting clay influences the shrinkage potential, leaching influences the microporosity, impregnation with a lanthanum salt determines the shape of the shrinkage curve and reactivity, and modification with Al2O3 sol determines the heat resistance of the supports.

Properties of Na0.875Li0.125NbO3 ceramics by O. Yu. Kravchenko; L. A. Reznichenko; G. G. Gadzhiev; L. A. Shilkina; S. N. Kallaev; O. N. Razumovskaya; Z. M. Omarov; S. I. Dudkina (1135-1150).
The structural, dielectric, and thermal properties of the Na0.875Li0.125NbO3 solid solution doped with strontium and other elements have been studied in wide temperature and frequency ranges. The material has been shown to undergo a sequence of phase transitions accompanied by anomalies in its structural, dielectric, and thermal properties. The observed low-frequency dispersion of its dielectric permittivity is attributed to the effect of electrical conductivity.

Luminescence of Pb2+ in MAl2B2O7 (M = Ca, Sr) by İlhan Pekgözlü; Sülin Taşcıǡlu; Ayhan Menger (1151-1154).
Pb2+ doped SrAl2B2O7 was prepared by solution combustion synthesis. The synthesized material was determined by powder XRD. The photoluminescence properties of the synthesized phosphor were investigated at room temperature using a spectrofluorometer. The emission peak of Pb2+ doped SrAl2B2O7 was observed at 420 nm upon excitation at 277 nm. The Stokes shift of SrAl2B2O7:Pb2+ was calculated to be 12 292 cm−1. The luminescence behavior of Pb2+ in both SrAl2B2O7 and CaAl2B2O7 was discussed.