Vol 52, No 1 (2016)

The effect of oxygen partial pressure on the dimensions of SrTi_0.7Fe_0.3O_{3 ± δ} strontium ferrotitanate (perovskite structure) and Ca₁₂Al₁₄O_{33 ± δ} calcium aluminate (mayenite structure) samples has been studied by dilatometry. The observed considerable variations in dimensions are characteristic of electronic–ionic mixed conductors with the perovskite structure. The effect observed in mayenite is substantially weaker, which can be understood in terms of specific features of its structural framework, made up of hollow, closed structural elements.

Four compounds with the general formula GdM^IICoO_3.5 (M^II = Mg, Ca, Sr, Ba) have been prepared for the first time by high-temperature solid-state reactions between gadolinium(III) oxide, cobalt(II) oxide, and alkaline-earth carbonates. Their crystal class and unit-cell parameters have been determined by X-ray diffraction.

Nanocrystalline antimony-doped ([Sb]/([Sb] + [Sn]) = 0–2 at %) SnO₂ powders have been synthesized by coprecipitation from solution. The composition, crystal structure, and microstructural parameters of the powders, as well as the antimony distribution in them, have been studied by laser mass spectrometry, X-ray diffraction, low-temperature nitrogen adsorption measurements, and IR spectroscopy. The reaction of the synthesized materials with oxygen has been studied in situ by electrical conductance measurements. Oxygen chemisorption on the surface of unmodified SnO₂ leads to predominant formation of the molecular species O_2(ads)^-. Increasing the Sb concentration in the SnO²‹Sb› samples increases the fraction of the monatomic species O_2(ads)^-, which can be explained in terms of a combination of crystal-chemical and electronic factors.

We have demonstrated the feasibility of producing a disperse Fe–Al–Cr polymetallic system through a contact exchange in chloride-containing aqueous solutions and investigated the processes that take place on aluminum microparticles in aqueous solutions containing ions of appropriate metals. It has been shown that the system is a precursor of intermetallic phases that result from high-temperature processes, in particular from spark plasma sintering.

Titanium oxyhydrate nanoparticles have been prepared via tetrabutoxytitanium hydrolysis. The addition of a stabilizing component (acetylacetone) to tetrabutoxytitanium prior to hydrolysis in a mixture of water and ethanol made it possible to sharply reduce the hydrolysis rate. Boiling at 100°C converted amorphous titanium oxyhydrate sol into nanocrystalline anatase with a crystallite size of 3.5 nm. According to scanning electron microscopy data, the TiO₂ particles were spherical in shape and ranged in size from 90 to 290 nm. The material was characterized by X-ray diffraction, simultaneous thermal analysis, electron microscopy, and dynamic light scattering.

We have synthesized CdTe–MgTe samples in the composition range 0–30 mol % MgTe. The composition dependence of the unit-cell parameter of the Cd_1–xM_xTe solid solutions has been obtained for the first time. The lattice parameter of cadmium telluride (sphalerite structure) has been shown to decrease almost linearly in the range 0 ≤ x ≤ 0.20. The 78-K cathodoluminescence spectra of the Cd_1–xMg_xTe (0 < x ≤ 0.15) solid solutions heat-treated under vacuum in order to remove the excess tellurium contain strong lines in the edge emission region, due to a transition from the conduction band to a shallow acceptor level.

The crystallization mechanism of chlorine-containing fluorohafnate glasses with the compositions (65–56)HfF₄ · (20–x)BaF₂ · xBaCl₂ · 4LaF₃ · (3–y)AlF₃ · yInF₃ · (5–18)NaF has been studied by X-ray diffraction and differential thermal analysis. The results demonstrate that characteristic features of the glasses are a decrease in glass transition temperature and the precipitation of fine-particle crystalline chloride phases at temperatures below the crystallization temperature of their fluoride analogs. We have studied the effect of the Cl/F ratio in the glass batch and the melt cooling rate on the crystallization behavior of the glasses and determined the heat treatment temperature and time for the formation of transparent glassceramic materials. The luminescence properties of Er³⁺-doped fluoride and fluorochloride glasses and glassceramics prepared from them have been investigated in the 1.5-µm range.

This paper examines the possibilities of using nanoionics principles in developing the technology of novel materials for electrochemical power generation. We analyze data on ceramic membranes with increased oxygen or lithium ion conductivity for cathodes of lithium ion batteries and components of solid oxide fuel cells. It is shown that, to improve the power characteristics of such electrochemical devices, use can be made of completely amorphous nanocomposites produced using synthetic techniques that take into account controlled incommensurability of the structures of interacting components. We assess the potential advantages of using the concepts of “mixed” and nonautonomous phases forming in eutectic and eutectoid systems obtained using electrochemically active inorganic structures.