Inorganic Materials (v.48, #10)

Composition and reactivity of porous silicon nanopowders by A. S. Len’shin; V. M. Kashkarov; D. L. Goloshchapov; P. V. Seredin; K. Polumestnaya; E. V. Maraeva; S. Soldatenko; Yu. Yurakov; E. P. Domashevskaya (965-970).
We have studied the chemical reactivity of silicon powders with distilled water. Nanopowders were prepared through electrochemical etching of silicon wafers, followed by grinding of the porous layer. The composition of the chemical bonds in the powders was determined by IR spectroscopy. The particle size of the powders was evaluated using transmission electron microscopy and nitrogen thermodesorption measurements. According to potentiometry data, the powders differ in their reactivity with water, which can be understood in terms of the particle composition and size.

Properties of silicon prepared from plant raw materials by L. A. Zemnukhova; A. E. Panasenko; G. A. Fedorishcheva; A. M. Ziatdinov; N. V. Polyakova; V. G. Kuryavyi (971-976).
High-purity X-ray amorphous silicon dioxide samples have been prepared by hydrolyzing siliconcontaining plants in a 0.1 N HCl solution, followed by calcination at 700°C in air. Reducing the silica with metallic magnesium, we obtained silicon, which was then purified by sequential washings with hydrochloric, hydrofluoric, and sulfuric acids and water. The fine silicon powder thus prepared, up to 97.6% in purity, ranging in color from light brown to dark brown, was characterized by X-ray diffraction and IR spectroscopy. According to total external reflection X-ray fluorescence, electron probe microanalysis, and chemical analysis data, the major impurities in the powder were silicon dioxide, iron (within 0.45%), titanium (within 0.10%), calcium (within 0.088%), and manganese (within 0.031%). According to scanning electron microscopy data, the silicon obtained has the form of spongy material ranging in pore size from 50 to 200 nm.

Dislocations in manganese-doped InSb by V. P. Sanygin; A. V. Filatov; A. D. Izotov; O. N. Pashkova (977-983).
Electron probe X-ray microanalysis data for quenched InSb〈Mn〉 samples demonstrate that most of the manganese goes to doping of dislocations in the semiconductor lattice. The manganese-doped dislocations in InSb determine the magnetic and electrical properties of the material at room temperature and above. According to magnetic measurements, this is accompanied by the formation of several magnetic phases. Codoping of InSb with manganese and zinc with the aim of neutralizing one of the magnetic phases allowed us to obtain a ferromagnetic semiconductor with a Curie temperature of 320 K.

We have constructed the T-x phase diagram of the TlGaS2-TlFeS2 system (simple eutectic system, eutectic at 80 mol % TlFeS2 with a melting point of 953 K). The system contains limited series of monoclinic solid solutions based on the ternary end-members. At an annealing temperature of 933 K, the TlGaS2-based solid solution extends to 5 mol % TlFeS2 and the TlFeS2-based solid solution extends to ≅10 mol % TlGaS2. We have examined the effect of partial iron substitution for gallium on the optical properties of melt-grown single crystals of the TlGaS2-based solid solutions and determined their band gap as a function of temperature and Fe concentration.

Properties of AgInSe2 films grown by magnetron sputtering by M. A. Abdullaev; A. K. Akhmedov; D. Kh. Magomedova; P. P. Khokhlachev (987-990).
n-Type AgInSe2 films 0.5 to 0.9 μm thick were grown by dc magnetron sputtering. As targets, we used AgInSe2 crystals grown by a modified Bridgman process using high-purity precursors. The crystal structure, morphology, electrical conductivity, and Hall coefficient of the films were studied at various temperatures. We determined the optimal growth and annealing temperatures of the films (500 and 250°C, respectively). Using structures based on the films, we obtained the spectral dependences of their photoresponse, established the nature of interband transitions in the films, and evaluated their band gap. The ability to vary electrical and optical properties with no changes in stoichiometry is of interest for concentrated solar power applications.

A process has been proposed for the fabrication of microcrystalline thermoelectric materials based on PbTe-SnTe solid solutions by compacting and hot-pressing fine powders prepared through the thermal decomposition of lead acetate trihydrate and tin oxalate in the presence of tellurium powders. We analyze the mechanism of the thermal decomposition of the powder mixtures, resulting in the formation of Pb1 − x Sn x Te particles, and examine the influence of cold compaction, heat treatment, and hot pressing on the grain composition, electrical conductivity, and Seebeck coefficient of materials prepared by pressing the powders.

Nanocomposite based on modified multiwalled carbon nanotubes: Fabrication by an oriented spinning process and electrical conductivity by A. A. Babaev; P. P. Khokhlachev; Yu. A. Nikolaev; E. I. Terukov; A. B. Freidin; R. A. Filippov; A. K. Filippov; N. K. Manabaev (997-1000).
We have produced nanocomposite films consisting of modified multiwalled carbon nanotubes (MWCNTs) and a polymer (MWCNT/polymer weight ratio of 95/5). The nanocomposite has been applied to a paper substrate by an oriented spinning process from a liquid phase. The resistivity of the films has been measured as a function of temperature in the range 20–140°C along and across the preferential orientation direction of the nanotubes in the nanocomposite. The results point to an irreversible transition from semiconducting to metallic behavior of the conductivity of the films.

This paper presents an experimental study of the effect of laser irradiation on the magnetic properties of an amorphous Fe73.7Nb2.4Cu1.0Si15.5B7.4 alloy. We have measured its magnetic susceptibility and paramagnetic Curie temperature and assessed the response of the key magnetic parameters of the material to laser irradiation. The results of magnetic measurements are analyzed in conjunction with X-ray diffraction data.

Antireflective coatings based on SiO2 nanoparticles by S. V. Eskin; I. D. Kosobudskiy; A. B. Zhimalov; N. M. Ushakov; D. M. Kulbatskiy; S. V. German (1006-1011).
Single-layer antireflective coatings, produced by sol-gel method on soda-lime glass substrates, were studied. Optimal parameters of the silica sols synthesis and coating procedure of the antireflective coatings based on SiO2 nanoparticles on soda-lime glasses for producing composite glasses with high optical transmittance within the visible range of wavelengths were obtained.

Sulfated SnO2 As a high-performance catalyst for alkene oligomerization by L. L. Yurkova; S. A. Lermontov; V. P. Kazachenko; V. K. Ivanov; A. S. Lermontov; A. E. Baranchikov; L. P. Vasil’eva (1012-1019).
Nanoparticulate (3–5 nm) sulfated tin dioxide shows high catalytic activity for the oligomerization of isobutylene, hexene-1, and cyclohexene. The acidity (Hammett acidity function H 0) of sulfated stannia reaches H 0 = −16.04. We have studied the effect of synthesis conditions on the physicochemical and functional properties of sulfated SnO2.

Pulsed laser deposition of conductive indium tin oxide thin films by I. A. Petukhov; A. N. Shatokhin; F. N. Putilin; M. N. Rumyantseva; V. F. Kozlovskii; A. M. Gaskov; D. A. Zuev; A. A. Lotin; O. A. Novodvorsky; A. D. Khramova (1020-1025).
Thin indium tin oxide (ITO) films have been grown on quartz glass substrates by pulsed laser deposition. The influence of ablation target composition and deposition conditions on the growth rate, optical transmission spectra, and carrier mobility and concentration of the films has been examined. The average surface roughness of the ITO films grown at substrate temperatures above 300°C is 2 nm. The films grown at an oxygen partial pressure of 5 mTorr using ablation targets with Sn/(In + Sn) = 5% possess high transmission (85-95%) in the visible range and low resistivity (1.8 × 10−4 Ω cm).

Electrical and optical properties of TiO2 and TiO2:Fe thin films by M. N. Solovan; P. D. Maryanchuk; V. V. Brus; O. A. Parfenyuk (1026-1032).
TiO2 and TiO2:Fe thin films have been grown by electron beam evaporation and the influence of doping and heat treatment on their electrical and optical properties has been studied.

X-Ray luminescence of polycrystalline TbO2-doped Li2B4O7 by P. P. Puga; K. P. Popovych; P. S. Danilyuk; V. N. Krasylynec; G. D. Puga; I. I. Turok; V. A. Kel’man; I. I. Chichura (1033-1038).
This paper examines the effect of doping level on the X-ray luminescence of TbO2-doped polycrystalline lithium tetraborate. It is shown that, when interpreting such spectra, it is convenient to proceed from the terms of free activator and constituent ions. We demonstrate that the emission lines of Tb3+ in doped polycrystalline lithium tetraborate are effectively excited in the band between 350 and 650 nm, which is predominantly due to electron transitions from the 5 D 3 and 5 D 4 excited states to spin-orbital levels of the 7 F J ground multiplet. The emission lines of lithium and boron in single-crystal and polycrystalline undoped lithium tetraborate are effectively excited in the band between 274 and 550 nm.

Crystal structure and lattice defects of La x MnO3 + δ by T. N. Tarasenko; A. S. Mazur; O. F. Demidenko; G. I. Makovetskii; K. I. Yanushkevich (1039-1043).
We report the synthesis of polycrystalline La x MnO3 + δ (x = 0.815, 0.90, 0.94, 0.97, 1.0) samples and their crystal structure at 300 K. All of the samples are single-phase and have an orthorhombically distorted (Pnma) perovskite structure. Also possible is that some of the samples have a rhombohedrally distorted $$left( {Rar 3c} ight)$$ structure. The unit-cell parameters of La0.90MnO3 differ most significantly from those of the x = 1.0 material. We have assessed the structural imperfection of the samples (cation vacancy concentration) and proposed overall chemical formulas of the manganites that take into account structural defects. Comparison of the X-ray and measured (hydrostatic weighing) densities of the samples demonstrates that their relative density increases with decreasing lanthanum content.

Levitation jet synthesis of nickel ferrite nanoparticles by M. V. Kuznetsov; Yu. G. Morozov; O. V. Belousova (1044-1051).
Pseudospherical nickel ferrite particles 25 to 70 nm in average size were prepared by a crucibleless aerosol method through cocondensation of Fe and Ni vapors in an inert-gas flow containing a small amount of air. The particles were characterized by transmission electron microscopy, X-ray microanalysis, X-ray diffraction, BET measurements, and vibrating-sample and SQUID magnetometry. The results were used to optimize process parameters for the preparation of particles with a tailored size, specific surface area, and saturation magnetization. A dc electric field applied to the condensation zone can serve to improve the phase purity of nickel ferrite nanoparticles, reduce their size, and change their Curie temperature.

Ca2.8Ln0.2Co4O9 + δ (Ln = La, Nd, Sm, Tb-Er) solid solutions have been prepared via a citrate route and their structural parameters have been determined. Their thermal expansion, thermoelectric power, thermal conductivity, and electrical conductivity have been measured above room temperature. The results demonstrate that all of the materials obtained are p-type semiconductors. Their unit-cell parameters decrease with a decrease in the ionic radius of the Ln3+ cation substituted for Ca2+, and their thermoelectric power increases with an increase in the number of f electrons of the Ln3+ cation. We have determined the electron and phonon contributions to the thermal conductivity of the materials and evaluated the thermoelectric power factor and thermoelectric figure of merit of the oxide ceramics. The highest thermoelectric power factors are offered by the Ca2.8Tb0.2Co4O9 + δ and Ca2.8Er0.2Co4O9 + δ solid solutions: 0.27 and 0.29 mW/(m K2), respectively, at T = 1100 K.

Synthesis of yttrium-containing organoalumoxanes by G. I. Shcherbakova; P. A. Storozhenko; N. B. Kutinova; D. V. Sidorov; M. S. Varfolomeev; M. G. Kuznetsova; M. V. Polyakova; A. E. Chernyshev; A. I. Drachev; G. Yu. Yurkov (1058-1063).
Organoalumoxanes containing yttrium oxane groups, hydrolytically stable in air, and soluble in organic solvents have been synthesized for the first time. The composition of the yttrium-containing organoalumoxanes has been determined by 1H and 27Al nuclear magnetic resonance spectroscopy, IR spectroscopy, scanning electron microscopy, X-ray diffraction, thermogravimetry, and elemental analysis.