Russian Journal of Inorganic Chemistry最新文献

The solubility of the substances in the NaClO₃∙CO(NH₂)₂–C₂H₅NO–H₂O system was examined using a visual-polythermal method in the temperature range from –39.0 to 78.0°С. A solubility diagram was created based on the results. In the phase diagram of the system, the crystallization fields of ice, CO(NH₂)₂, NaClO₃, and C₂H₅NO, as well as a new compound NaClO₃∙CO(NH₂)₂∙C₂H₅NO, were separated. The compound was successfully isolated and confirmed to be novel based on the results of physicochemical analysis.

The existence regions of the Y_2–xMg_xFeTaO_7–δ (x = 0–0.15), Y_2–xMg_xFe_1–x/2Ta_1+x/2O_7–δ (x = 0–0.15), Y₂Fe_1–xMg_xTaO_7–δ (x = 0–0.3), and Y₂Fe_1–3/2xMg_xTa_1+x/2O_7–δ (x = 0–0.3) solid solutions were estimated. It was found that, regardless of the composition, the entry of Mg²⁺ into the crystal lattice of Y₂FeTaO₇ causes a similar distortion of the structure (space group R(bar {3}) → space group P3₁21). Based on XANES and Mössbauer spectroscopy data, it was suggested that Mg²⁺ ions occupied the eight-coordinated sites in the crystal lattice of solid solutions, displacing iron ions, while vacant yttrium sites in Y_2–xMg_xFeTaO_7–δ and Y_2–xMg_xFe_1–x/2Ta_1+x/2O_7–δ are occupied by tantalum ions. The XANES method confirmed the existence of Fe⁴⁺ ions in the Y₂FeTaO₇ solid solutions along with Fe³⁺. The simultaneous presence of the Ta⁴⁺ and Ta⁵⁺ ions ensures the electroneutrality of there crystal lattices. Herewith, the entry of Mg²⁺ does not lead to an increase in the Fe⁴⁺ concentration.

Composites MnO/C based on cubic manganese monoxide were synthesized by microwave-assisted hydrothermal treatment of an aqueous solution of potassium permanganate with ascorbic acid and subsequent annealing of the precursor in an inert atmosphere at a temperature of 500°C. It was found that the molar ratio of the reaction mixture components, Mn : C₆H₈O₆ = 1 : (0.75‒1.5), is the key parameter determining the features of composite formation. A mechanism of formation of the MnO/C composite was proposed. The maximum carbon content in the composite material was ~3 wt %. The main physicochemical characteristics of the synthesized composites were determined using powder X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy, and low-temperature nitrogen adsorption. The behavior of MnO/C as an anode material for a lithium-ion battery showed that the composite is efficient only at high current densities.

We propose a force field designed to model multi-walled WSe₂ nanotubes whose size is beyond the capabilities of ab initio methods. The parameterization of interatomic potentials is successfully tested on single-walled and double-walled nanotubes, the structure of which is determined using non-empirical calculations. This force field has been used to model the structure and stability of chiral and achiral multi-walled WSe₂ nanotubes with diameters approaching experimental values. The properties of WSe₂-based nanotubes are compared with the properties of analogous WS₂-based nanotubes calculated using the force field, which was published in the previous paper I of this series. The interwall distances obtained from the simulations are in good agreement with recent measurements of these parameters for existing WS₂ and WSe₂ nanotubes. It is found that the interwall interaction contributes to the stabilization of multi-walled nanotubes slightly more in the case of WSe₂ than in the case of WS₂. Analysis of the deviation of the nanotube shape from the cylindrical one showed a close similarity of the structure of the tubes of both compositions.

This work proposes a method for the preparation of nanostructured Er₃Fe₅O₁₂ powders, comprising the anion-exchange resin assisted coprecipitation of erbium and iron(III) ions and subsequent heat treatment of the products. Optimal conditions for the anion-exchange precipitation of a highly reactive stoichiometric precursor were determined, and the influence of the heat-treatment schedule on the yield and stability of erbium ferrite garnet nanoparticles was investigated. The prepared nanomaterials were characterized by X-ray powder diffraction analysis, electron microscopy, thermal analysis, and Mössbauer spectroscopy. This synthesis method provides iron-erbium garnet with an average particle size of 25 nm at 800°C. The discovered patterns can be used to develop new methods for the synthesis of rare-earth garnet compounds.

Quantum chemical methods have been used to calculate heteronuclear rhenium and molybdenum oxo-alkoxo complexes (Re_xMo_4–xO₆(OMe)₁₀) and oxohydroxoalkoxo complexes (Re_xMo_4–xO_6–n(ОН)_n(OMe)₁₀, n = 1, 2, 4). The core of the clusters is a rhombus composed of four metal atoms connected by bridging oxygen atoms along the sides and the short diagonal. Alkoxo groups occupy terminal positions. The structure and relative stability of the isomers corresponding to different positions of the heterometal atoms at the vertices of the rhombus have been calculated. The theoretical differences in total energies relative to the most stable isomer, the metal-metal bond lengths, bond order indices and the sum of these indices for each isomer have been determined. It has been found that in some cases, along with the bridging M–O–M' bonds, direct metal-metal bonds are also formed.

This paper presents a theoretical and experimental study of the Li⁺,K⁺||F^–,Cl^–,Br^–,({text{CrO}}_{4}^{{2 - }}) quinary reciprocal system. А phase tree of the system was constructed. It has a branched structure and includes two stable pentatopes, a stable hexatope, and a stable tetrahedron separated by two stable tetrahedra and a secant triangle. The LiF–LiCl–LiBr–Li₂CrO₄–KCl–KBr hexatope was studied experimentally by differential thermal analysis (DTA) and X-ray powder diffraction analysis (XRD). The polythermal section passing through two low–melting quaternary eutectic points included in the boundary elements of the hexatope was studied to determine the nature of physical and chemical interactions in the hexatope. Solid solutions based on lithium and potassium chlorides and lithium and potassium bromides were found to not decompose within the hexatope. The characteristics of the composition at the minimum point in the hexatope were determined. There are four crystallizing phases in the stable hexatope: LiF, Li₂CrO₄, LiCl_xBr_1‑x, and KCl_xBr_1–x.

The structural and morphological properties of samples in the Ba₂In₂O₅–Ba₂InNbO₆ eutectic system were studied when treated below and above the eutectic temperature. A narrow-extent Ba₂In_2-xNb_xO_5+x (х ≤ 0.05) solid solution and (1 − y)Ba₂In_1.95Nb_0.05O_5.05∙yBa₂InNbO₆ composites were found in the system. In the y ≥ 0.15 composites, the major phase is a stabilized structure with a disordered arrangement of oxygen vacancies. The total electrical conductivity in dry air is determined primarily by oxygen-ion transfer, and it increases for both the solid solution and the composites; the greatest increase of about two orders of magnitude is in the y = 0.15 and 0.25 composite samples treated at above-eutectic temperature. The increase in electrical conductivity is due to the combined influence of structural and morphological factors. The composites treated at above-eutectic temperature have a specific morphology. A layer of submicron-sized crystallites is formed on the surface of the grains of the major phase upon eutectic crystallization, which is responsible for the appearance of the composite electrical conductivity effect.

Reaction of zinc halides with methylurea (MeUr) in 1 : 2 ratio in aqueous solution results in formation of new coordination compounds [Zn(MeUr)₂Cl₂], [Zn(MeUr)₂Br₂], and [Zn(MeUr)₂I₂]. The new coordination compounds have been isolated and studied by X-ray powder diffraction, IR spectroscopy, and single-crystal X-ray diffraction. The structure of previously unknown polymorphic modification of zinc bromide complex with dimethylacetamide (DMA) [Zn(DMA)₂Br₂] has been studied. The complexes have molecular tetrahedral structure. The dipole moments of the zinc halide complexes with methylurea and dimethylacetamide have been calculated to be of 9.3–9.7 D and 6.6–8.2 D, respectively.

Oxofluorozirconate K₂Zr₃OF₁₂ was prepared by heating an aqueous suspension of KZrF₅. Its structure and thermal decomposition were studied by thermal analysis (DTA–TG), X-ray powder diffraction (XRD), IR and Raman spectroscopy. The complete hydrolytic decomposition of K₂Zr₃OF₁₂ at 620°C mainly yields a mixture of monoclinic K₂ZrF₆ and ZrO₂ phases. Experimental IR and Raman spectra of oxofluorozirconate K₂Zr₃OF₁₂ and its heating products were measured, systematized, and analyzed. The bands in the experimental spectra were assigned based on the results of quantum-chemical calculations.