Inorganic Materials (v.45, #9)

The conceptual base, current state, and relevant trends of investigations in the chemistry of high-purity substances are examined.

Phase transformation of p-Cd1 − x Mn x GeAs2 single crystals at 5.5 GPa by A. Yu. Mollaev; I. K. Kamilov; R. K. Arslanov; U. Z. Zalibekov; S. A. Varnavskii; S. F. Marenkin (961-964).
The electrical resistivity and Hall coefficient of oriented single-crystal p-Cd1 − x Mn x GeAs2 samples have been measured at high pressures. The results indicate that the crystals undergo a reversible structural transformation at 5.5 GPa, which is independent on the sample orientation.

Photoelectrochemical properties of TiO2/CdS heterostructures by A. Sh. Aliev; M. N. Mamedov; M. T. Abbasov (965-967).
The photoelectrochemical properties of TiO2, CdS, and TiO2/CdS anodes have been studied. The results demonstrate that, under illumination, CdS anodes are subject to photocorrosion, and Cd2+ ions pass into solution. Corrosion-resistant films of TiO2 prevent CdS photocorrosion, and the CdS/TiO2 system exhibits good photosensitivity in the visible range.

Phase equilibria in ternary reciprocal systems based on IV–VI compounds by A. A. Volykhov; L. V. Yashina; M. E. Tamm; A. V. Ryzhenkov (968-974).
Using the experimental data obtained in this study, literature data, and a unified thermodynamic model, we have calculated the T − x − y phase diagrams of all the pseudoternary reciprocal systems formed by the Group 14 metal chalcogenides: Sn, Pb ‖ S, Se; Sn, Pb ‖ S, Te; and Sn, Pb ‖ Se, Te.

Interlayer nanoparticles of copper, nickel, and silver in Bi2Te3 by F. K. Aleskerov; S. Sh. Kakhramanov (975-979).
According to electronic micropictures and results of roentgen diffractometry (RD) in the Bi2Te3 metal system, nanodimensional fragments are formed in the van der Waals slot Te(1)-Te(1). These structural vacuum nanoreactors are filled not only with metal nanoparticles (Cu, Ni, and Ag) but also with formed semiconductor nanofragments and fractal surfaces on their basis. They are formed upon adhesion of diffusing atoms according to a mechanism specific to the known solid fractal structures. Their analysis based on the physical concept of fractals formed upon deposition of atoms in unlimited volume on crystal faces is carried out.

Dielectric properties of diamond powder by S. M. Gavrilkin; K. B. Poyarkov; B. V. Matseevich; S. S. Batsanov (980-981).
A method for measuring the dielectric permittivity of diamond powder is developed. It is shown that variation of particle sizes of diamond powder can purposefully change its dielectric properties.

We present a detailed study of the pyrolytic synthesis of nanofibrous carbon materials (NCMs) from ethanol and various water-ethanol mixtures on a nickel catalyst at temperatures from 400 to 700°C. In the synthesis from 96% ethanol, the initial deposition rate increases with temperature, but this is accompanied by a substantial decrease in catalyst life. The addition of water to the reaction system considerably increases the catalyst life. One possible reason for this is that water vapor prevents carbonization of the catalyst particles. At the same time, above 600°C the rate of NCM deposition from a 50% water-ethanol mixture is considerably slower. At 550°C and lower temperatures, the rate of NCM deposition from water-ethanol mixtures (based on ethanol consumption) changes insignificantly. Our results demonstrate that NCMs can be synthesized even from very dilute (down to 10 vol %) aqueous ethanol solutions. The participation of water vapor in chemical processes that take place in the reaction zone is discussed.

Synthesis and characterization of nano-scale alumina on single walled carbon nanotube by O. M. Kalfa; Ö. Yalçinkaya; A. R. Türker (988-992).
In this study, nano-scale crystalline alumina was synthesized on single walled carbon nanotube by sol-gel method for using as a sorbent for solid phase extraction of trace metals. The characterization of the synthesized nanocomposite material was performed by scanning electron microscope, transmission electron microscope and X-ray diffractometer methods. It was proved that the obtained composite material was mainly nano-scale Al2O3, and partly Mg2Al2O4 and Zn2Al2O4 on single walled carbon nanotube. In addition, the specific surface area of the material was determined and found as 165 m2/g. The adsorption capacity of the nanomaterial was also determined for cadmium(II) ions and found as 2.18 mg/g at pH 8.

Formation of nanocomposites during annealing of amorphous Fe-P-Si alloys by M. O. Anosova; Yu. V. Baldokhin; V. V. Vavilova; V. M. Ievlev; Yu. E. Kalinin; V. P. Korneev; N. A. Palii (993-997).
Annealing-induced nanocrystallization in inhomogeneous, clusterized Fe-P-Si amorphous alloys has been studied using Mössbauer effect, elastic modulus, and internal friction measurements. The results demonstrate that flash lamp processing causes the clusters in the Fe82P16S alloy to dissolve, improving its magnetic properties, whereas the clusters in the Fe78P20Si2 alloy persist, and its hardness rises significantly

Component redistribution during Nb and In/Nb film growth on single-crystal silicon by N. N. Afonin; V. A. Logacheva; A. M. Khoviv; V. M. Vakhtel’; Yu. S. Shramchenko (998-1002).
The component redistribution during the growth of Nb and In/Nb films on single-crystal silicon has been studied by Rutherford backscattering spectroscopy and X-ray diffraction. The results indicate that magnetron sputtering of indium onto niobium films gives rise to mass transfer across the Nb/Si interface and to niobium and silicon heterodiffusion, accompanied by chemical reactions and the formation of silicides. The likely reason for this is the generation of defects during the magnetron sputtering of indium.

We have studied the effect of electric-current mode on the structure and characteristics of niobium stannide coatings produced by electrochemical coreduction of niobium and tin ions at the cathode in molten salts. The results demonstrate that single-phase Nb3Sn coatings with a superconducting transition temperature T c = 17.3–17.9 K can be obtained using unsteady-current deposition. The coatings produced in galvanostatic mode and by ac deposition at a frequency of 50 Hz have a columnar grain structure. Current-reversal deposition with pulse ratios above 7–9 results in a layered microstructure with layers parallel to the substrate surface, instead of the columnar microstructure, and ensures a considerably higher critical current.

Ultrasound effect on the Czochralski growth of corundum crystals by S. D. Vyshnevskiy; E. V. Kryvonosov; L. A. Lytvynov (1009-1012).
We have studied the effect of ultrasound in the range 100–400 kHz on the Czochralski growth of corundum single crystals in a carbon-containing medium. The results demonstrate that sonication during crystal growth influences the size and density of gas bubbles in the melt. At frequencies above 350 kHz, sonication contributes to the bubble rejection at the growth front, thereby reducing the pore density in the crystal.

Optical properties of three-dimensional magnetic opal photonic crystals by V. S. Gorelik; N. I. Yurasov; V. V. Gryaznov; Yu. P. Voinov; P. P. Sverbil’; M. I. Samoilovich (1013-1017).
We have studied the optical properties of opal photonic crystals infiltrated with the M0.35Zn0.65Fe2O4 (M = Ni, Co) ferrites. The crystals consisted of amorphous SiO2 nanospheres. The visible reflectivity spectra of the crystals were used to determine parameters of their photonic band gap and their refractive index.

Structure and phase composition of oxide dispersion strengthened fcc alloys prepared via strong deformation in the Fe2O3-Fe-Ni-M (M = Ti, Zr) systems by A. V. Litvinov; V. A. Shabashov; K. A. Kozlov; N. F. Vil’danova; V. V. Sagaradze (1018-1025).
Deformation-induced Fe 2 dissolution in fcc Fe-Ni-M (M = Ti, Zr) alloys has been studied by Mössbauer spectroscopy, X-ray diffraction, and transmission electron microscopy. The results indicate that high-pressure shear deformation in Bridgman anvil cells and ball milling lead to dissolution of the low-stability oxide Fe2O3 in the fcc matrix and the formation of metallic solid solutions and secondary oxides of the alloying elements. This enables preparation of oxide dispersion strengthened Fe-Ni alloys and grain size reduction of the fcc matrix. The formation of secondary oxides occurs more actively during ball milling than during high-pressure shear deformation because of the more significant local heating of the mixture and the larger specific surface area and higher reactivity of the powder.

Electrical conductivity and thermoelectric power of LaCo1 − x Ga x O3 solid solutions by N. N. Lubinskii; L. A. Bashkirov; G. S. Petrov; S. V. Shevchenko; I. N. Kandidatova; I. M. Sirota (1026-1031).
Increasing the degree of Ga3+ substitution for Co3+ ions in LaCo1 − x Ga x O3 solid solutions (x = 0–1) considerably reduces their electrical conductivity: at T= 850 K, from 190.5 S/cm in LaCoO3 to 1.32 × 10−5 S/cm in the x = 0.95 solid solution. The anomaly in the temperature-dependent conductivity of the solid solutions, due to the broad semiconductor-metal transition, decreases with increasing x. For x ≥ 0.8, there is a very weak or no anomaly. The activation energies for conduction in the samples with x = 0.90 and 0.95 are 0.89 and 0.92 eV, respectively. At room temperature, the materials with 0 ≤ x ≤ 0.3 have a negative thermoelectric power. With increasing temperature, it increases, crosses zero between 435 and 530 K, reaches a maximum in the range 500–650 K, and decreases at higher temperatures.

Luminescence of BaSiO3 crystals doped with Er3+ and Yb3+ by A. N. Georgobiani; C. Barthou; P. Benalloul; I. B. Bakhtiyarly; K. O. Tagiev (1032-1035).
The Stokes and anti-Stokes luminescence of undoped and rare-earth-doped (Er3+ and Yb3+) BaSiO3 has been studied in the temperature range 78–450 K under excitation at 10–1000 mV. The results indicate that the emission mechanism in BaSiO3 crystals is hole recombination and that the anti-Stokes luminescence is due to consecutive sensitization; that is, the Yb3+ ions in the BaSiO3 compound act as luminescence sensitizers, and the Er3+ ions, as activators.

Detailed analysis of structural and DTA data indicates that the zeolites with the general formula AAl2Si3O10 · nH2O (A = Ba, Ca) and n = 4 crystallize in the edingtonite structure. With decreasing water content, this structure transforms first into the scolecite structure (n = 3) and then into the metascolecite structure (n = 2).

Aluminum phosphate was prepared from aluminum nitrate solution and phosphoric acid in the molar ratio of Al/P = 1/1 at pH 5, 7 and 9. Urea was added in phosphoric acid solution before mixing. These materials were used for aluminum phosphate bulks in hydrothermal hot pressing process. The chemical composition and thermal behavior of the precipitations was analyzed by inductivity coupled plasma, thermogravimetry—differential thermal analyses, X-ray diffraction, and Fourier transform infrared spectroscopy. Furthermore, materials before and after sintering by hydrothermal hot pressing process were estimated from specific surface area, pore size distribution, particle size distribution, and SEM images. The purpose of this work is to clarify the effect of pH, the addition of urea, and heating on hydrothermal hot pressing process of aluminum phosphate.

Dielectric properties of (1 − x)KNbO3 · xBiMg2/3Nb1/3O3 perovskite solid solutions by Yu. V. Radyush; N. M. Olekhnovich; A. V. Pushkarev (1053-1057).
(1 − x) KNbO3 · xBiMg2/3Nb1/3O3 ceramic materials have been prepared by solid-state reactions. The materials with x < 0.3 have been shown to be perovskite solid solutions. Their average lattice parameter increases linearly with x. Like undoped KNbO3, the solid solutions undergo a low-temperature (rhombohedral → orthorhombic) ferroelectric phase transition. The transition temperature increases almost linearly with x. The dc electrical conductivity of the ceramics exhibits Arrhenius behavior. The activation energy for conduction rises sharply near the phase transition temperature.

The stability region of orthorhombic Nd1 − x Ba x Mn1 − y Cr y O3 solid solutions in air at 1370 K has been determined. Nd0.9Ba0.1MnO3 and Nd0.9Ba0.1Mn0.7Cr0.3O3 have been shown to be close in thermal expansion to yttria-stabilized zirconia.

(1 − x)Bi(Mg1/2Ti1/2)O3 · xBiCoO ceramics have been prepared at high pressures (6 GPa) and temperatures (1370–1570 K). Perovskite solid solutions have been obtained in the composition ranges 0 < x < 0.6 and 0.8 < x < 1. The Bi(Mg1/2Ti1/2)O3-based perovskite phase (x < 0.6) has an orthorhombic structure (sp. gr. Pnnm), which persists up to the decomposition temperature of the material. The BiCoO3-based phase (x > 0.8) has a tetragonal structure (sp. gr. P4mn). In the range 0.6 < x < 0.8, the ceramics consisted of the two perovskite phases. The lattice parameters of the solid solutions with x < 0.6 are linear functions of composition. The dielectric properties of the orthorhombic solid solutions have been studied using impedance spectroscopy. The temperature dependences of dielectric permittivity ɛ′ and dielectric loss tanδ exhibit different behaviors at low and high temperatures. With increasing x, the boundary between these regions shifts from about 450 to 300 K. At high temperatures, both ɛ′ and tanδ rise steeply. The dc conductivity of the solid solutions with x < 0.6 exhibits Arrhenius behavior. The activation energies for charge transport in the ceramics studies are presented.

Thermodynamic properties of V3Te4 by A. A. Vinokurov; A. V. Tyurin; V. M. Gurevich; K. S. Gavrichev; V. P. Zlomanov (1069-1073).
The heat capacity of V3Te4 has been measured as a function of temperature using an adiabatic calorimeter, and its thermodynamic properties were evaluated. We have determined the Debye characteristic temperature and fracton dimension of crystalline V3Te4.