Inorganic Materials (v.47, #12)

A method has been developed for the extraction of single 71Ge atoms from the gallium target of a Ga-Ge neutrino detector. The key features of this chemical process stem from the extremely low content of the element to be extracted in the sample (n × 10−27 at %), the large sample weight (up to n × 103 kg), the limited time available for the extraction and measurement of the extracted atoms (≤20 h), and small permissible loss (≤0.1%) of the target material at high degrees of 71Ge extraction (≥90%). The method involves forced generation and maintenance of a disperse system of liquid gallium droplets with an oxide surface film in an acid-peroxide solution. The small droplet size ensures a rapid 71Ge transfer from the bulk target to a small amount of gallium oxide. The 71Ge passes from the oxide film to the solution, is concentrated, and converts to germane, which is delivered to a proportional counter. We have assessed the completeness of germanium extraction in relation to process conditions. The results, in particular the completeness of extraction, have been verified in experiments with Ga + Ge mixtures at germanium concentrations of 10−4 and 10−17 to 10−16 wt %. The adequacy of the approaches used to develop the technology of the Ga-Ge detector is supported by satisfactory agreement between the solar neutrino fluxes obtained with gallium and gallium-chloride detectors.

Magnetic properties of oriented p-Cd0.947Mn0.053GeAs2 single crystals at pressures of up to 7 GPa by A. Yu. Mollaev; I. K. Kamilov; R. K. Arslanov; V. M. Novotortsev; S. F. Marenkin; U. Z. Zalibekov; T. R. Arslanov; I. V. Fedorchenko (1295-1297).
The magnetic susceptibility and transverse magnetoresistance of p-Cd0.947Mn0.053GeAs2 single crystals have been measured at hydrostatic pressures p < 7 GPa. The crystals are shown to undergo a pressure-induced metamagnetic phase transition and to have a negative magnetoresistance.

Phase separation of Mn2Sb at high pressures and temperatures by V. S. Goncharov; V. M. Ryzhkovskii (1298-1301).
The intermetallic compound Mn2Sb (tetragonal structure, Cu2Sb type) was exposed to high pressures (4 to 8 GPa) and temperatures (up to 2300 K) for 10 min and was shown to phase-separate to Mn3Sb and Mn1.5Sb at certain processing temperatures, pressures, and durations.

Phase relations in the TlInS2-TlYbS2 system and electrical properties of Tl2InYbS4 crystals by F. M. Seyidov; E. M. Kerimova; N. Z. Gasanov (1302-1305).
We have studied phase relations in the TlInS2-TlYbS2 system and showed that it contains a congruently melting compound of composition Tl2InYbS4 (1: 1 ratio of the constituent sulfides). According to X-ray diffraction results, the compound Tl2InYbS4 crystallizes in tetragonal symmetry. Temperature-dependent electrical conductivity and Hall data for Tl2InYbS4 single crystals demonstrate that this compound is a p-type semiconductor with a band gap of 1.60 eV. The temperature variation of the carrier Hall mobility in Tl2InYbS4 corresponds to carrier scattering by acoustic phonons.

The Cu-Tl-Se system has been studied at temperatures from 300 to 420 K using emf measurements with Cu4RbCl3I2 as a Cu+ ion conducting solid electrolyte. The emf data have been used to map out the subsolidus phase diagram of the Cu-Tl-Se system in the composition region Tl2Se-CuTlSe-CuSe-Se. We have calculated the partial molar thermodynamic functions of the copper in the alloys and the standard thermodynamic functions of formation and standard entropies of the ternary compounds CuTlSe2, CuTlSe, and Cu2TlSe2. The results confirm that the thermodynamic properties of copper-containing ternary systems can be studied using the approach in question even when they contain an element (thallium in this study) located to the left of copper in the electrochemical series.

Photoelectric properties of TlIn0.98Pr0.02Se2 crystals and resistors by E. M. Gojaev; A. M. Nazarov; E. A. Allakhyarov (1311-1313).
It is shown that heat treatment and uniaxial compression along the [001] axis increase the photosensitivity of TlIn0.98Pr0.02Se2 crystals and markedly shift their photosensitivity range to longer wavelengths.

Thermoelectric properties of n-Bi2Te2.7Se0.3〈I,In〉 crystals by T. E. Svechnikova; I. Yu. Nikhezina; M. A. Korzhuev (1314-1318).
n-Bi2Te2.7Se0.3〈I〉 single crystals additionally doped with indium (0.1–2.0 mol % In2Te3) have been grown by Czochralski pulling through a floating crucible. As the In2Te3 content of the growth charge increases to 0.2 mol %, the thermoelectric figure of merit (Z) of the crystals increases from 0.0029 to 0.0031 K−1 and Z max shifts to higher temperatures by ∼30 K. Increasing the In2Te3 content to 2 mol % sharply reduces Z max to 0.002 K−1 and shifts the maximum to lower temperatures. This behavior of the thermoelectric figure of merit can be understood in terms of the nonmonotonic variation of electron mobility with indium and iodine concentrations in the crystals.

Growth and self-organization of nanostructures on interlayer surfaces of A 2 V B 3 VI layered crystals by A. N. Georgobiani; A. M. Pashaev; B. G. Tagiev; F. K. Aleskerov; O. B. Tagiev; K. Sh. Kakhramanov (1319-1323).
This paper examines the formation of arrays of interlayer nanostructures in layered crystals grown by directional solidification and the Bridgman method. Sb2Te3 and Bi2Te3 layers are shown to contain steplayered structures with nanostructured islands on them. Atomic force microscope images of interlayer nanostructures in such crystals are analyzed in terms of the physics of fractals and self-organization processes.

Properties of aminosilane precursors for the preparation of Si-C-N films by S. V. Sysoev; L. D. Nikulina; M. L. Kosinova; V. I. Rakhlin; I. P. Tsirendorzhieva; A. V. Lis; M. G. Voronkov (1324-1329).
R n Si(NEt2)4 − n aminosilanes have been synthesized by reacting the R n SiCI4 − n (R = H, CH3; n = 1, 2) organylchlorosilanes with diethylamine. Using IR, UV, and NMR (1H, 13C, and 29Si) spectroscopies and elemental analysis, we have identified the reaction products and determined their spectroscopic characteristics. Vapor pressure measurements have been used to determine the saturated vapor pressure as a function of temperature and calculate the thermodynamic characteristics of vaporization. Thermodynamic modeling of chemical vapor deposition processes has been performed with the aim of predicting the phase composition of the deposit as a function of the nature of the precursor and process conditions.

Synthesis and structure of BN coatings on SiC nanofibers by P. M. Silenko; A. M. Shlapak; O. F. Pilipchuk; P. N. D’yachkov; Yu. M. Solonin (1330-1333).
The Gibbs potential has been calculated as a function of temperature for a number of BN synthesis reactions. Detailed studies of BN chemical vapor deposition on SiC nanofibers were used to develop a technique for BN coating production from nontoxic precursors. The optimal synthesis temperature was 1300°C. Transmission electron microscopy characterization of the BN/SiC nanocables thus produced showed that the coatings were 10–20 nm thick and had a hexagonal structure.

Hydrogen absorption by transition metals is analyzed in terms of crystal-field theory. A proton occupying interstitial sites in the crystal lattice of a metallic absorbent is assumed to split fivefold degenerate d-orbitals of the metal. The proposed scheme of the filling of these orbitals accounts for the good absorption properties of the d 1d 5 metals, the hydrogen absorption behavior of chromium and manganese, and the change in the thermodynamic parameters of the absorption process after the appearance of paired electrons in the electronic spectrum of the metals. We consider the influence of zero-point vibrations of hydrogen atoms incorporated into interstices of the crystal lattice of metals on some aspects of hydrogen absorption.

We have studied the reflection spectra of opal photonic crystals with air-or ethanol-filled pores at different diameters of the silica spheres. An experimental technique has been proposed which enables identification of both the first and second photonic band gaps in the reflection spectrum of opal. The ability to observe the second band gap allowed us to derive a dispersion relation for the refractive index of the infiltrated substance. The calculations were performed using a model for a one-dimensional periodic layered medium with two refractive indices. We obtained ω(k) dispersion curves for electromagnetic waves in a photonic crystal (at normal incidence). The ω(k) dispersion law was used to find a dispersion relation for the reflectance of the photonic crystal.

Effect of mechanical activation on the properties of natural zeolites by V. A. Nikashina; A. N. Streletskii; I. V. Kolbanev; I. N. Meshkova; V. G. Grinev; I. B. Serova; T. S. Yusupov; L. G. Shumskaya (1341-1346).
We have examined the effect of mechanical activation on the Sr2+ and Cu2+ ion exchange selectivity of Russian natural zeolites: clinoptilolite-containing tuffs and chabazite concentrates. We have studied their structural changes and thermal properties and determined the specific surface area and porosity of the mechanically activated zeolites. At specific milling energies below 0.5–0.7 kJ/g, the dominant process is disintegration of zeolite particles and changes in their bulk porosity. At higher milling energies, amorphization prevails. Our results demonstrate that, in the initial stage of activation, one can markedly raise the Sr2+ selectivity of some zeolites (e.g., by 16 times for Shivyrtuiskoe clinoptilolites and by 300 times for chabazite) and increase the Cu2+ selectivity (by 40 to 100 times), which will persist at high specific milling energies.

Structure of Sr1 − x Pb x FeO3 − δ (0 < x < 0.5) perovskite-like materials by I. V. Belen’kaya; O. A. Savinskaya; M. A. Neklyudova; A. P. Nemudry (1347-1355).
We have synthesized Sr1 − x Pb x FeO3 − δ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) perovskite-like materials and studied their structure by X-ray diffraction, Mössbauer spectroscopy, and electron microscopy. According to the X-ray diffraction data, the Pb solubility limit in the perovskite structure is x ≈ 0.15. The materials with x = 0.05 and 0.1 contained Pb1.33Sr0.67Fe2O5 inclusions 10–30 nm in size. Using chronopotentiometry and temperature-programmed desorption, we have estimated oxygen mobility in the materials with x = 0.05 and 0.1. The results demonstrate that Pb doping increases oxygen mobility in the strontium-ferrite-based materials.

Electrical conductivity of LaCo x Fe1 − x O3 − δ and LaLi0.1Co x Fe0.9 − x O3 − δ (0 ≤ x ≤ 0.4) oxides by S. I. Vecherskii; S. N. Tabatchikova; B. D. Antonov; V. A. Biryukov (1356-1360).
We have studied the effect of Co and Li concentrations on the phase composition and electrical conductivity of LaCo x Fe1 − x O3 − δ and LaLi0.1Co x Fe0.9 − x O3 − δ perovskite-like oxides synthesized in air at 1470 K. Single-phase materials with an orthorhombic crystal structure were obtained in the range 0 ≤ x ≤ 0.3. The composition dependences of conductivity have a minimum at x c = 0.1 and 0.2, respectively. In the range x > 0.1, the conductivity of LaCo x Fe1 − x O3 − δ increases with increasing Co concentration for T > 700 K and decreases for T < 600 K. The conductivity of La(Li0.1Co x Fe0.9 − x )O3 − δ in the range 0 ≤ x ≤ 0.1 and for x ≥ 0.2 increases with Co concentration throughout the temperature range studied.

We report the synthesis of Sr0.8Ce0.2Mn1 − y Co y O3 − δ (y = 0.3, 0.4) solid solutions, which have a tetragonal perovskite structure (sp. gr. I4/mcm) with unit-cell parameters a = 0.53998(1) nm, c = 0.76404(1) nm, and V = 0.22273(4) nm3 at y = 0.3 and a = 0.54054(6) nm, c = 0.7644(6) nm, and V = 0.22335(4) nm3 at y = 0.4. The presence of cobalt in the octahedral sites of the Sr0.8Ce0.2Mn1 − y CoyO3 − δ (y = 0.3, 0.4) solid solutions reduces their antiferromagnetic ordering temperature and induces a transition to a spin glass state.

Nanostructured phase formation in CeO2/LaAlO3 and CeO2/(Ni-W) prepared by deposition from metalorganic solutions by Yu. Ya. Tomashpolsky; N. V. Sadovskaya; L. F. Rybakova; S. Yu. Kholopova; Yu. V. Borisov (1367-1371).
We have studied nanoscale structural evolution processes and phase formation in barrier cerium oxide layers grown from methacrylate solutions on lanthanum aluminate and a nickel-tungsten tape by dip coating. The layers were characterized by atomic force microscopy, scanning electron microscopy, precision electron diffraction, X-ray microanalysis, and X-ray diffraction (including texture analysis). We have investigated nanostructured morphological forms of buffer cerium oxide layers in all synthesis steps: liquid-phase, pyrolytic, and crystalline. We have established a granular character of the nanostructure and determined the type of orientation of the films: 〈111〉 texture with a 〈200〉 additional orientation. Optimal conditions for the synthesis of a barrier layer several tens of nanometers in thickness are proposed.

Thermal decomposition of natural dolomite by A. I. Rat’ko; A. I. Ivanets; A. I. Kulak; E. A. Morozov; I. O. Sakhar (1372-1377).
We have studied thermal modification of natural dolomite chips, which has allowed us to optimize conditions for the preparation of supports for manganese oxide catalysts with appropriate physicochemical properties (elevated carbon dioxide partial pressure and calcination temperature no higher than 800°C).

We have studied the electrical properties of (1 − x)(Ba,Y)TiO3 · xPbTiO3-based solid solutions containing different percentages of low-melting glass. The materials were prepared by solid-state reactions, sintered in air at temperatures from 1100–1300°C, and characterized by complex impedance measurements in wide frequency and temperature ranges. The results demonstrate that the positive temperature coefficient of resistance effect in these materials, containing different percentages of low-melting glass, is contributed mainly by both the grain boundaries and surface layer. With increasing glass content, the ratio of the maximum resistivity to the minimum resistivity increases and the influence of the surface layer on the positive temperature coefficient of resistance effect becomes stronger. With increasing glass content, the grainboundary potential barrier height in the (1 − x)(Ba,Y)TiO3 · xPbTiO3 materials increases.

Synthesis and laser-excited IR luminescence of Y1 − x Yb x PO4 solid solutions by O. Ya. Manashirov; A. N. Georgobiani; V. B. Gutan; E. M. Zvereva; A. N. Lobanov (1384-1390).
We have determined the composition range of solid solutions in the binary system YPO4-YbPO4 and identified the key trends in the composition dependence of their IR Stokes luminescence intensity and decay time in the range 0.96–1.1 μm. The results were used to develop a new narrow-band IR phosphor, YPO4:Yb3+. Under 0.940-μm laser excitation, this phosphor offers an increased IR Stokes luminescence intensity in the range 0.96–1.1 μm (about twice as high as that of the well-known commercially available phosphors L-54 and FSD-546-2), with an afterglow time of 1700–1800 μs.

Cation mobility in Li1 + x Ti2 − x Cr x (PO4)3 NASICON-type phosphates by A. I. Svitan’ko; S. A. Novikova; D. V. Safronov; A. B. Yaroslavtsev (1391-1395).
Li1 + x Ti2 − x Cr x (PO4)3 NASICON-type materials have been prepared and characterized by X-ray diffraction, scanning electron microscopy, and impedance spectroscopy. The results demonstrate that Cr3+ doping increases the ionic conductivity of LiTi2(PO4)3 within the single-phase region of the doped material, which extends to x = 0.7. From temperature-dependent ionic conductivity data, the activation energy for lithium transport through interstitial sites and the enthalpy of defect formation in LiTi2(PO4)3 are estimated at 30.0 ± 0.5 and 56 ± 1 kJ/mol, respectively.

High-pressure/high-temperature synthesis, crystal structure, and electrical properties of CaCu3 − x Fe x V4O12 by N. I. Kadyrova; Yu. G. Zainulin; A. P. Tyutyunnik; N. V. Mel’nikova; I. S. Ustinova (1396-1401).
A perovskite-like compound of composition CaCu3 − x Fe x V4O12 (x = 0.7−1.0) has been synthesized at high pressures (p = 5.0−8.0 GPa) and temperatures (t = 1000−1300°C). Its crystal structure has been determined by X-ray diffraction (sp. gr. $$Imar 3$$ , Z = 2, a = 7.3051(5) angles have been evaluated. The electrical conductivity of the high-pressure phase CaCu2FeV4O12 exhibits metallic behavior.

Structure refinement and thermal stability of creedite by D. A. Ksenofontov; Yu. K. Kabalov; N. V. Zubkova; R. R. Shiyapova (1402-1405).
The crystal structure of the mineral creedite (hydrous calcium aluminum sulfate fluoride, Ca3Al2(F,OH)10(SO4) · 2H2O) has been determined by Rietveld powder diffraction analysis. X-ray diffraction data obtained in the temperature range from 25 to 470°C indicate that the crystal structure of creedite is stable up to 390°C. We have measured the unit-cell parameters of creedite as functions of temperature and determined its thermal expansion coefficients. Above 390°C, the mineral decomposes.