Inorganic Materials (v.49, #2)
Preparation and properties of Mn1.1Sb1 − y Al y and Mn1.1Sb1 − y Si y solid solutions by M. Budzyński; V. I. Mitsiuk; V. M. Ryzhkovskii; Z. Surowiec; T. M. Tkachenka (115-119).
We have prepared Mn1.1Sb1 − y Al y (0 < y ≤ 0.2) and Mn1.1Sb1 − y Si y (0 < y ≤ 0.1) solid solutions with the B8 structure, in which the aluminum and silicon atoms substitute for antimony in the anion sublattice of manganese antimonide. Magnetic measurements have shown that substitutions within the stability region of the B8 phase have little effect on the mass magnetization and Curie temperature of the material. Mössbauer spectroscopy results confirm the anion nature of the substitutions.
Thermoelectric and mechanical properties of the Bi0.5Sb1.5Te3 solid solution prepared by melt spinning by L. D. Ivanova; L. I. Petrova; Yu. V. Granatkina; V. G. Leontyev; A. S. Ivanov; S. A. Varlamov; Yu. P. Prilepo; A. M. Sychev; A. G. Chuiko; I. V. Bashkov (120-126).
This paper reports the preparation and characterization of pressed microcrystalline materials based on a p-type Bi0.5Sb1.5Te3 solid solution produced from a melt-spun powder. We have examined the effect of melt spinning conditions (temperature, disk rotation rate, and purity of the inert gas in the heat treatment chamber) on the particle size and morphology of the powders and the microstructure and thermoelectric properties of hot-pressed samples and investigated the mechanical properties (compression and bend tests) of materials prepared by various methods. The thermoelectric properties of the materials (thermopower, electrical conductivity, and thermal conductivity) were studied at room temperature and in the range 100–700 K. The highest thermoelectric figure of merit ZT of the materials prepared by pressing the melt-spun powder was 1.3, whereas the ZT of the materials prepared by the other methods did not exceed 1.1. The higher ZT of the materials studied was due to their lower lattice thermal conductivity and slightly higher thermopower.
Synthesis and properties of antimony-doped ZnO nanorods by A. N. Baranov; A. A. Kovalenko; O. V. Kononenko; E. V. Emelin; D. V. Matveev (127-135).
This paper describes a process for the synthesis of ZnO〈Sb〉nanorods containing controlled antimony concentrations. We have optimized the synthesis of ZnO〈Sb〉nanorods to maximize their length-to-diameter ratio. The synthesis conditions and subsequent processing are shown to have a significant effect on the luminescence and transport properties of the nanorods. Planar structures based on individual nanorods were produced by electron beam lithography and their current-voltage characteristics were measured and were shown to depend on the chemical history of the nanorods.
Mechanochemical synthesis of titanium carbide using carbons of various origins by D. V. Onishchenko; V. P. Reva (136-144).
The data presented in this paper show that the limiting factors in the mechanochemical synthesis of titanium carbide from mixtures of titanium and a carbon-containing raw material are the structure of the carbon and the degree of aromaticity of the starting material. Our results demonstrate the possibility of producing mechanochemical titanium carbide using mixtures of carbon black and graphite.
Hydrogenation of Zr3Al2 in hydrogen and ammonia by V. N. Fokin; E. E. Fokina; I. I. Korobov; B. P. Tarasov (145-148).
We have identified conditions for the formation of Zr3Al2-based intermetallic hydrides through reactions with hydrogen and ammonia at temperatures from 150 to 300°C. The use of ammonia is shown to reduce the onset temperature for the formation of a hydride phase by 100°C compared to hydrogenation with hydrogen. Increasing the ammonia-Zr3Al2 reaction temperature to 500°C in the presence of NH4Cl as an activator leads to the decomposition of the intermetallic compound and the formation of finely dispersed zirconium hydride and zirconium nitride powders.
Hydrogen sorption properties of V1 − x Cr x (x = 0.1–0.5) alloys by V. N. Verbetsky; T. A. Zotov; A. V. Tatarintsev; E. A. Movlaev (149-152).
We have studied the interaction of hydrogen with vanadium-chromium alloys. Hydrogen absorption and desorption isotherms have been constructed, the stability ranges of the forming hydride phases have been determined, and the ΔH and ΔS of the reactions involved have been evaluated. X-ray diffraction characterization results indicate the formation of three hydride phases, with fcc, bcc, and hcp structures.
Morphology and crystal-chemical characteristics of cobalt and nickel nanopowders prepared by thermochemical and electrolytic methods by A. S. Kurlov; A. A. Rempel; V. I. Matrenin; A. S. Stikhin (153-158).
The phase composition and morphology of cobalt and nickel powders and nickel foam have been studied by X-ray diffraction and scanning electron microscopy. The cobalt and nickel powders prepared through solution electrolysis are shown to have a dendritic microstructure. The particle morphology of the nanostructured cobalt and nickel powders and nanostructured nickel foam can be described by a three-level (according to the particle size) model.
Properties of sol-gel derived silica membranes by T. F. Kuznetsova; S. I. Eremenko (159-164).
Silica membrane materials have been produced by sol-gel processing using tetraethyl orthosilicate as a precursor and oxyethylated fatty alcohols and alkyl phenols as templates. Using low-temperature nitrogen adsorption-desorption, we have studied the adsorption properties and microstructure of silica membranes templated around colloidal surfactant crystals. The results demonstrate that the pore structure of the membranes differs significantly from that of their bulk analogs. The silica membranes have type IV isotherms and an H1 hysteresis loop, characteristic of cylindrical mesopores. The I + IV type mixed isotherms of the bulk analogs are dominated by features of type I with an H2 or H4 hysteresis, characteristic of monodisperse bottle-shaped or slit-like mesopores, respectively.
Modified titania and titanium-containing composites as fillers exhibiting an electrorheological effect by A. N. Murashkevich; O. A. Alisienok; I. M. Zharskii; E. V. Korobko (165-171).
SiO2/TiO2 nanocomposites and individual titania (S = 30–500 m2/g) have been prepared through cohydrolysis of organomineral silicon and titanium derivatives in the presence of templates. We demonstrate that heterovalent substitution of chromium or cerium for titanium increases the thermal stability of TiO2 in terms of its crystallite size and specific surface area. After drying at 120°C, fillers based on SiO2/TiO2 composites (coprecipitated and core-shell SiO2/TiO2 particles) exhibit a significant electrorheological response due to appreciable hydrate and hydroxyl layers on the surface of the particles. Structural modification of titania also allows one to increase the electrorheological effect through an increase in specific surface and defect formation.
Synthesis and properties of dielectric (HfO2)1 − x (Sc2O3) x films by L. V. Yakovkina; T. P. Smirnova; V. O. Borisov; V. N. Kichai; V. V. Kaichev (172-178).
(HfO2)1 − x (Sc2O3) x films have been grown by chemical vapor deposition (CVD) using the volatile complexes hafnium 2,2,6,6-tetramethyl-3,5-heptanedionate (Hf(thd)4) and scandium 2,2,6,6-tetramethyl-3,5-heptanedionate (Sc(thd)3) as precursors. The composition and crystal structure of the films containing 1 to 36 at % Sc have been determined. The results demonstrate that, in the composition range 9 to 14 at % scandium, the films are nanocrystalline and consist of an orthorhombic three-component phase, which has not been reported previously. Using Al/(HfO2)1 − x (Sc2O3) x /Si test structures, we have determined the dielectric permittivity of the films and the leakage current through the insulator as functions of scandium concentration. The permittivity of the films with the orthorhombic structure reaches k = 42–44, with a leakage current density no higher than ∼10−8 A/cm2.
High-speed determination of the thickness and spectral ellipsometry investigation of films produced by the thermal oxidation of InP and V x O y /InP structures by I. Ya. Mittova; V. A. Shvets; E. V. Tomina; B. V. Sladkopevtsev; N. N. Tret’yakov; A. A. Lapenko (179-184).
Spectral ellipsometry was used to determine the thickness and optical properties of films produced by the thermal oxidation of InP and V x O y /InP structures. Comparison of the measured optical characteristics and thickness of nanofilms with high-speed ellipsometric analysis data indicates that the two methods should be used in the case of multicomponent films. Absorption in such films is shown to be due, among other factors, to the presence of unoxidized indium, which influences the optical properties of the film and the ellipsometric measurement results.
Effect of ceramic powder particle size on the electrical properties of Li0.03Na0.97Ta0.05Nb0.95O3 ceramics by M. N. Palatnikov; V. V. Efremov; N. V. Sidorov; O. B. Shcherbina; A. A. Yanichev; I. N. Efremov (185-193).
We compare the microstructure, electrical properties, and Raman spectra of ceramic samples of the Li0.03Na0.97Ta0.05Nb0.95O3 ferroelectric solid solution prepared by a conventional ceramic processing technique using ceramic powders with different particle sizes. The Li0.03Na0.97Ta0.05Nb0.95O3 solid solutions prepared from the powders of different particle sizes are shown to differ only slightly in average grain size, pore size, and porosity, but the particle size of the ceramic powder has a significant effect on their electrical properties. The difference in properties between the samples is due not so much to the difference in particle size between the parent ceramic powders as to the fact that the diffusion processes involved in solid-state synthesis may give rise to composition gradients, and grains that differ in size may differ in microstructure and composition.
Effect of doping with Pb, Ba, and Si on the properties of Y3Fe5O12 single crystals by N. V. Vorob’eva (194-197).
In doped single-crystal yttrium iron garnet, Y3Fe5O12, photoinduced changes in the cubic magnetostriction constant λ111 and coefficient (λσ) that characterizes extra stress in the material are determined by the sublattice the dopant is incorporated into. The incorporation of dopant cations into a particular crystallographic site can be controlled by adjusting the crystal growth process. Varying the process for the growth of doped Y3Fe5O12 single crystals with semiconducting properties, one can tune the type and magnitude of their photoinduced response. Since an ideal sample cannot be created in practice, and even the lowest densities of growth defects in a single crystal lead to photomagnetism, the present results suggest that, at sufficiently low temperatures, photomagnetic changes occur in almost all Y3Fe5O12 single crystals. The behavior of their photomagnetic response depends on the type of defect.
Effect of annealing on the magnetic properties of Y3Fe5O12 and Y2.95La0.05Fe4.7Ga0.3O12 films by S. A. Yur’ev; S. I. Yushchuk (198-201).
We have studied the effect of high-temperature (1273–1673 K) and low-temperature (523–873 K) anneals in air, O2, and N2 on the magnetic properties of Y3Fe5O12 and Y2.95La0.05Fe4.7Ga0.3O12 garnet ferrite films. The films, 5–15 μm in thickness, were grown on (111)-oriented gadolinium gallium garnet (Gd3Ga5O12) substrates by liquid phase epitaxy. High-temperature annealing was shown to change the saturation magnetization and increase the ferromagnetic resonance linewidth ΔH of the films. Low-temperature annealing at 723 K in flowing dry oxygen for 20 h reduces the ΔH of the ferromagnetic resonance by 18–25% and makes it insensitive to changes in temperature and ambient humidity.
Synthesis, structure, and some properties of LiNi1/3Co1/3Mn1/3O2 by A. A. Titov; Z. V. Eremenko; E. G. Goryacheva; N. P. Sokolova; N. L. Opolchenova; N. N. Stepareva; G. P. Korobko (202-208).
Crystalline LiNi1/3Co1/3Mn1/3O2 powders have been synthesized by two different procedures, using carbonate coprecipitation from sulfate and nitrate solutions, followed by two-step heat treatment of a mixture of the resultant Ni1/3Co1/3Mn1/3CO3 precursor and Li2CO3 at 500 and 900°C. The powders have been characterized by X-ray diffraction, scanning electron microscopy, and dynamic light scattering. The results demonstrate that the synthesized compounds have a hexagonally ordered, layered structure of the α-NaFeO2 type. The primary-particle (crystallite) size in the powders is 50 nm and the aggregate size is 150–250 nm. The average size of larger structures (agglomerates) is 11 and 18 μm in the powders prepared via the sulfate and nitrate routes, respectively. The chemical stability of the synthesized powders is shown to depend on the ambient medium. Prolonged storage in air leads to the formation of new, lithium-deficient phases, especially in the case of the powders prepared from nitrate solutions.
Effect of crystal structure on the luminescence properties of CaF2-PrF3 solid solutions by I. A. Boiaryntseva; A. V. Gektin; N. V. Shiran (209-213).
The structure and luminescent properties of lightly doped CaF2:Pr crystals and Ca0.65Pr0.35F2.35 solid solution have been studied. The results demonstrate that the evolution of the emission spectra of the crystals with increasing PrF3 concentration can be understood in terms of the structural changes in the fluorite solid solutions, namely, the formation of defect clusters.
Extrinsic luminescence centers in CdI2 crystals doped with PbI2 (10−4 to 1 mol %) by I. M. Bolesta; N. V. Gloskovskaya; M. R. Panasyuk; I. N. Rovetskii; L. I. Yaritskaya (214-218).
We have studied the luminescence properties of PbI2 doped (10−4 to 1 mol %) CdI2 crystals in the temperature range 4.2–90 K and those of 2H- and 4H-PbI2 crystals at 90 K. The results demonstrate that the Pb atoms produce impurity centers in the form of isolated Pb2+ ions and 4H-PbI2 nanocrystals located in the plane of the layers or along linear structural defects of CdI2. The formation of PbI2 nanocrystals was confirmed by atomic force microscopy. We discuss excitonic and electron-hole mechanisms of energy transfer to luminescence centers.
Impurity composition of molybdate-tellurite glasses prepared from mixtures precipitated from hydrochloric acid solutions of tellurium and molybdenum compounds by ammonia by A. A. Sibirkin; O. A. Zamyatin; M. F. Churbanov; A. N. Moiseev; V. G. Pimenov (219-222).
Molybdate-tellurite glasses have been prepared from precipitates obtained by adding aqueous ammonia to hydrochloric acid solutions of tellurium(IV) and molybdenum(VI) compounds. The impurity compositions of the precipitates and glasses have been determined by atomic emission spectroscopy. The results indicate that contamination with metal impurities occurs mainly in the precipitate washing step. Prolonged holding of a glass-forming melt in a porcelain crucible leads to contamination of the glass with aluminum, magnesium, and calcium.