Inorganic Materials (v.44, #8)

Mass spectrometric study of GaInPAsSb/GaSb heterostructures by A. V. Blagin; D. P. Valyukhov; L. S. Lunin; R. V. Pigulev; I. M. Khabibulin (793-795).
The composition and thickness of GaInPAsSb five-component layers grown on GaSb substrates by temperature-gradient liquid phase crystallization and liquid phase epitaxy and the heterojunction width have been determined by secondary neutral mass spectrometry. The heterostructures have been compared from the viewpoint of technological applications.

Effect of cation vacancies on the thermal conductivity of GdS x solid solutions by S. M. Luguev; N. V. Lugueva; V. V. Sokolov (796-799).
The thermal conductivity of GdS x solid solutions (Th3P4 structure) has been measured between 80 and 400 K. In all of the solid solutions studied, lattice thermal conductivity prevails. The high-temperature thermal conductivity of GdS1.500 is due not only to the phonon mechanism but also to radiative heat transport. At x < 1.49, filling of cation vacancies increases the electronic component, whose contribution rises with increasing Gd content.

Phase equilibria in Ag-Ga-S films and kinetics of AgGaS2 crystallization by D. I. Ismailov; A. Ch. Mamedova (800-803).
The phase compositions of films produced by coevaporation and sequential evaporation of Ag, Ga, and S have been determined. The phases identified in the films grown at room temperature are Ag2S, GaS, Ga2S3, and AgGaS2. The kinetics of phase transformations in thin amorphous AgGaS2 films have been studied by dynamic electron diffraction. The dimensionality of growth during amorphous AgGaS2 crystallization and the activation energies for nucleation and crystallite growth have been evaluated.

Electrical properties of electrodeposited CdTe thin films by M. N. Mamedov; A. Sh. Aliev (804-806).
The electrical properties of electrodeposited CdTe thin films have been studied. The temperature-dependent electrical conductivity data obtained have been used to determine the conductivity type and semiconductor parameters (E g, B, and α) of the films.

Bi, Te, and Bi-Te nanoparticles in opal matrices by S. N. Ivicheva; Yu. F. Kargin; E. Yu. Buslaeva; G. Yu. Yurkov (807-812).
Bi, Te, and Bi2Te3 nanoparticles have been prepared by reducing bismuth salts, telluric acid, and their decomposition products with supercritical isopropanol in opal pores.

Fabrication of gold nanoparticles using luminol as a reductive and protective reagent by Baoqiang Lv; Xiaodong Su; Yang Li; Yi Li; Jianfei Mao; Dan Xiao (813-817).
An easy and simple reaction is employed to synthesize ligand-protected gold nanoparticles. In this reaction, luminol is used as a reductive and protective reagent to prepare gold nanoparticles in aqueous solution. It includes two steps: chemiluminescence and formation of gold nanoparticles. The formation processes were monitored by resonance light scattering spectroscopy, and the results were observed by transmission electron microscopy and x-ray photoelectron spectroscopy. Highly stable gold nanoparticles about 110 ± 2 nm in size can be readily obtained. A new insight into the design of water-soluble ligand-protected gold nanoparticles for biomedical, analytical, and catalytic applications has been provided.

High-temperature ordering-phase separation transition in the Fe50Co50 alloy by N. V. Lomova; I. N. Shabanova; Yu. I. Ustinovshikov (818-822).
High-temperature (above 1200°C) B2 ordering has been detected in the Fe50Co50 alloy by selected area electron diffraction. X-ray photoelectron spectroscopy data indicate that the transition from phase separation to ordering is accompanied by changes in both the d-electron valence band spectrum (ordering increases 3d-electron localization at the Fe atoms) and the 3s core level spectrum (phase separation increases the exchange interaction between the electron spins of the partially filled 3d shell and ionized 3s shell of the Fe and Co atoms). We conclude that an ordering-phase separation transition occurs not only at 730°C but also at a temperature slightly above 1200°C.

Band structure of silicon carbide nanotubes by E. V. Larina; V. I. Chmyrev; V. M. Skorikov; P. N. D’yachkov; D. V. Makaev (823-834).
Using the linear augmented cylindrical wave method in the muffin-tin approximation, we have calculated the band structure of (n, n) and (n, 0) silicon carbide nanotubes for n = 5–10. In the range n = 7–10, (n, n) nanotubes are semiconductors, and their band gap decreases steadily with increasing n: 0.28 eV at n = 7, 0.26 eV at n = 8, 0.19 eV at n = 9, and 0.11 eV at n = 10. Nanotubes with n = 5 and 6 are metallic. At n = 7–9, (n, 0) nanotubes are semiconductors, and their band gap increases steadily with n: 0.39 eV at n = 7, 0.46 eV at n = 8, and 0.62 eV at n = 9. Nanotubes with n = 5 and 6 have metallic conductivity according to our results.

Preparation and optical properties of silver nanoparticles in R-phycoerythrin, a protein matrix by O. D. Bekasova; A. A. Brekhovskikh; A. A. Revina; V. T. Dubinchuk (835-841).
Ag+ chemisorption by R-phycoerythrin in an aqueous solution is shown to lead to the formation of silver nanoparticles, without the need for a reductant of Ag+. According to electron-microscopic results, most of the nanoparticles are elongated, (3 ± 0.5) × (6 ± 2) nm in dimensions. Also present are cubic Ag crystallites 22.5 nm in size (standard deviation of ±5.9 nm) and aggregates 53 × 48 nm in dimensions (standard deviation of ±8.8 × 8 nm). The absorption spectrum of the Ag nanoparticles in R-phycoerythrin is typical of small nanoparticles. Their fluorescence spectrum shows peaks of individual nanoparticles (450 nm) and fractal aggregates (630 and 670 nm). The fluorescence intensity of the Ag nanoparticles and their aggregates is an order of magnitude higher in comparison with other matrices.

Effect of mechanical processing on the dissolution rate of MgO by N. F. Kosenko; L. A. Vinogradova; M. A. Smirnova (842-845).
The kinetics of MgO dissolution after attrition grinding have been studied using photometry and pH measurements. The dissolution rate constant, limiting magnesium ion concentration, and solution pH have been shown to pass through a maximum at a certain attrition time. The effect of attrition time on the dissolution rate is interpreted in terms of the surface condition and aggregation of the powder particles.

Synthesis of ZnO nanotetrapods by O. A. Lyapina; A. N. Baranov; G. N. Panin; A. V. Knotko; O. V. Kononenko (846-852).
ZnO tetrapods have been grown on silicon substrates by chemical vapor deposition, and the effect of synthesis conditions on their morphology and size has been studied. The cathodoluminescence spectra of the tetrapods show two emissions characteristic of ZnO, in the UV and green spectral regions. Their relative intensities depend on the vapor composition during synthesis and annealing conditions. A mechanism of tetrapod growth at significant supersaturations is discussed.

Preparation of ceria nanoparticles by D. V. Drobot; A. V. Chub; V. V. Voronov; P. P. Fedorov; V. K. Ivanov; O. S. Polezhaeva (853-855).
Ceria nanoparticles (D = 2.4−6.9 nm) with the fluorite structure have been prepared via oxidative precipitation of cerium from a solution of a rare-earth chloride mixture, followed by acid washing.

Titanium-to-rutile oxidation kinetics in the direct-oxidation fabrication of thin-wall ceramics by K. A. Solntsev; V. Yu. Zufman; N. A. Alad’ev; S. V. Shevtsov; A. S. Chernyavskii; A. P. Stetsovskii (856-862).
The oxidation kinetics of titanium preforms for the direct-oxidation fabrication of thin-wall ceramics have been studied in the temperature range 750–1100°C using titanium plates up to 5 mm in thickness. Empirical relations for the kinetics of these processes have been obtained. The preform weight has been shown for the first time to influence the oxidation rate of titanium and the amount of forming rutile, which is inconsistent with the known patterns of metal oxide formation. One possible mechanism of rutile formation during the direct-oxidation fabrication of thin-wall ceramics is considered.

Optical properties of undoped and Yb3+-doped YAl3(BO3)4 crystals by I. T. Bodnar; V. V. Filippov; N. V. Kuleshov; N. I. Leonyuk; V. V. Mal’tsev; O. V. Pilipenko (863-865).
The ordinary and extraordinary refractive indices of nominally undoped and Yb3+-doped (7 at %) YAl3(BO3)4 crystals have been measured in the visible range at temperatures from 20 to 400°C. The refractive indices are found to increase with temperature. The thermo-optic coefficients are on the order of ∼10−6. The temperature dependences of the refractive indices show a number of anomalies, suggestive of an incommensurate system exhibiting devil’s staircase behavior.

Green and red upconversion emissions of Er3+/Yb3+-codoped SrTiO3 powder prepared by a polymeric precursor method by F. C. D. Lemos; J. E. C. da Silva; D. M. A. Melo; M. S. C. Câmara; P. S. de Lima; C. E. J. Carneiro (866-869).
Ultrafine Er3+/Yb3+-codoped SrTiO3 (SEYT) powders in cubic form have been prepared by a poly-meric precursor method. The single phase perovskite for the obtained material was observed at low temperature. An efficient infrared-to-visible conversion in SEYT perovskite will be reported. Visible emissions at 550 and 663 nm corresponding to the 2S3/24I15/2 and 4F9/24I15/2 transitions, respectively, were observed under continuous wave excitation at 980 nm. An enhancement of the visible upconversion luminescence in Er3+/Yb3+ codoped samples was confirmed due to efficient energy transfer from Yb3+ to Er3+ ions. The quadratic pump power dependence of these emissions indicated the contribution of two photons to the upconversion process.

Quality of KDP crystals grown on point seeds by a novel rapid growth method by E. L. Kim; V. I. Katsman; V. V. Vorontsov; V. N. Portnov; V. N. Trushin; K. A. Markov (870-875).
Structural perfection of KDP single crystals grown on point seeds by a rapid growth method has been studied by selective etching, UV spectroscopy, x-ray topography, a conoscopic method (to assess anomalous birefringence), rocking-curve analysis, and resistivity measurements. Etching results indicate that the dipyramid growth sectors are less homogeneous. The zonal structure is more pronounced in the peripheral parts of the crystals, that is, in the final stages of rapid growth. In spite of the sectorial and zonal inhomogeneities, the crystals are superior in quality to those prepared by other rapid growth methods.

Electrical conductivity of Cs3PO4 doped with trivalent cations by S. S. Stroev; E. I. Burmakin; G. Sh. Shekhtman (876-881).
Cs3 − 3x M x PO4 (M = Sc, Y, La, Sm, Nd) solid electrolytes have been synthesized, their phase composition has been determined, and their electrical conductivity has been measured as a function of temperature. In all of the systems, we have identified cesium orthophosphate based solid solutions. Above ∼550°C, the solid solutions are isostructural with the high-temperature, cubic phase of Cs3PO4. They offer high cesium ion conductivity owing to the formation of cesium vacancies via 3Cs+ → M3+ substitutions and the decrease in phase transition temperature. The conductivity of the synthesized solid solutions, (4.8−5.6) × 10−3 S/cm at 300°C and (1.6−1.9) × 10−1 S/cm at 800°C, is at the level of earlier studied Cs3 − 2x M x II PO4 solid electrolytes.

Potassium ion conducting K2 − 2x Fe2 − x P x O4 solid electrolytes by E. I. Burmakin; G. Sh. Shekhtman (882-885).
Potassium ion conducting solid electrolytes based on potassium monoferrite have been prepared by substituting pentavalent phosphorus cations for Fe3+. The highest conductivity of K2 − 2x Fe2 − x P x O4 is achieved in the range x = 0.05−0.10: 7.1 × 10−3 S/cm at 300°C and 1.6 × 10−1 S/cm at 700°C. The rise in the conductivity of KFeO2 upon phosphorus doping is due to the formation of potassium vacancies.

Facile preparation of Ag2V4O11 nanoparticles via low-temperature molten salt synthesis method by Xiaoyu Cao; Lingling Xie; Hui Zhan; Yunhong Zhou (886-889).
Nanosized Ag2V4O11 powders have been prepared via the low-temperature molten salt method using LiNO3 as a reaction medium. The powders have been characterized by x-ray diffraction and transmission electron microscopy. The discharge properties of the powders have been assessed by the galvanostatic discharge test using CR2016 coin cells. The powder made at 300°C for 2 h is composed of nearly spherical particles about 40 nm in size. The discharge test shows that the powders prepared by the low-temperature molten salt method exhibit high discharge capacities.

The carbothermic reduction of NiO, CoO, CuO, MoO3, and the MMoO4 (M = Ni, Co, Cu) molybdates has been studied by thermogravimetry. The results demonstrate that the reactivity of the molybdates with solid carbon, the sequence of reduction reactions, and the composition of reaction intermediates are determined by the reactivity of the constituent oxides, which decreases in the order CuO > MoO3 > NiO > CoO. The reaction intermediates in the reduction of CuMoO4 are Cu6Mo5O18 and Cu2Mo3O10, and those in the reduction of CoMoO4 are Co2Mo3O8 and CoMoO3. NiMoO4 is reduced without oxide intermediates. The reactions of CuMoO4 and NiMoO4 with solid carbon lead to selective reduction of the molybdates to metals (Cu or Ni) and molybdenum oxides (MoO2 and MoO3 − x ). In the reactions of NiMoO4 and CoMoO4 with CO gas, the metals are formed at comparable rates, which favors the formation of metal solid solutions, intermetallic phases, and mixed carbides.

The nonstoichiometric phase La1 − y Ca y F3 − y with a LaF3-related structure has been studied by electron diffraction. In addition to diffraction features corresponding to twinning on the (001) and {1 $$ ar 2 $$ 0} planes, typical of LaF3, evidence has been found for twinning on the {101} and {102} planes. This behavior is accounted for by the formation of ordering domains with an ordering direction inclined to mirror planes. It seems likely that ordering domains determine many of the properties of nonstoichiometric phases.

Thermo-and photostimulated luminescence of CaI2-based crystals by S. S. Novosad; I. S. Novosad (900-904).
We systematize earlier and new data on the effect of oxygen and hydrogen impurities on recombination processes in CaI2 crystals by jointly examining their roentgeno-, thermo-, and photostimulated luminescence spectra. The 90-K emission spectra of CaI2 crystals are shown to consist of at least five bands. The 395-nm emission is assumed to be due to radiative decay of (HI)* heteronuclear excitons. The 520-nm luminescence is attributable to iodine-vacancy-bound anion excitons. The thermostimulated luminescence peaks observed in the temperature range 90–150 K are due to the thermal dissociation of V k and H hole centers. The 90-K photostimulated luminescence of CaI2-based crystals is shown to be excited in the electronic stage of the recombination process.

PTCR ceramics produced from oxalate-derived barium titanate by V. N. Shut; S. V. Kostomarov; A. V. Gavrilov (905-910).
BaTiO3 powders with an average crystallite size from 68 to 2000 nm have been prepared by calcining barium titanyl oxalate at temperatures from 700 to 1150°C, and their morphology and recrystallization kinetics have been studied. The powders have been used to produce positive temperature coefficient of resistance (Ba,Ca,Pb)TiO3 ceramics, and the microstructure and electrical properties of the ceramics have been investigated. The results indicate that improving the crystallinity of the barium titanate powder suppresses recrystallization in the ceramics, increases their resistivity, and has a significant effect on their resistance jump and electric strength. We have identified the optimal temperature range of barium titanyl oxalate calcination, which insures the highest electric strength of PTC thermistors with a resistance of 31 Ω. The corresponding crystallite size of the barium titanate powder is ≃200 nm.