Volume 62, Nº 8 (2017)

New complex oxides of composition Pr_1–yCa_yFe_{0.5 + x}(Mg_0.25Mo_0.25)_0.5–xO₃, 0.0 ≤ x ≤ 0.1, 0.42 ≤ y ≤ 0.8 having an orthorhombically distorted perovskite structure have been prepared. The thermal expansion and electric conductivity of the new phases have been studied in the temperature range between 100–900°C. The results of our study imply that thin films of the oxides studied can be treated as electrode materials for symmetric solid-oxide fuel cells.

The effects caused by modifying additives, namely nonionic surfactants (Tween 80 and Neonol AF 9-6) and oxides (B₂O₃ and HfO₂), on the rheology, film formation, and phase formation in the yttrium aluminum silicate system prepared by sol–gel technology were studied. The effect of 1 wt % HfO₂ additions on the activation energy of crystallization was studied.

4-Hydroxysalicylidene-2-furfurylimine HL⁴ and complex МоО₂Cl₂ · 2HL⁴ were prepared. The HL⁴ structure was determined by X-ray crystallography. The two crystallographically nonequivalent molecules have similar structures and are in zwitterionic form.

The effect of 4d-metal dopants on the densities of states of hexagonal TiO₂ nanotubes has been calculated by the linearized augmented cylindrical wave method. It has been demonstrated that the substitution of Nb, Mo, Tc, or Pd atoms for a part of Ti atoms leads to a decrease in the band gap width of the material due to the formation of impurity levels in the band gap of TiO₂. Doping TiO₂ nanotubes with these metals is a promising way to produce materials for electrodes for electrochemical photolysis of water. Doping with Y, Rh, or Ag leads to the displacement of the absorption edge from the UV to the visible range owing to a considerable broadening of the valence and conduction band edges; Zr, Ru, and Cd have a lower disturbing effect on the electronic levels of TiO₂.

Hitherto unprepared ABCO₄ compounds (where A and B stand for tervalent metals (r_A ≥ r_B) and C stands for a divalent metal) are predicted. Criteria are found to predict the possibility for these compounds to crystallize in some type of structure (K₂NiF₄, CaFe₂O₄, YbFe₂O₄, or spinel) at room temperature and atmospheric pressure. The prediction is based only on the properties of elements and simple oxides. A special software system for computer-aided analysis of information is used for calculations involving pattern recognition based on use case.

2-Amino-1-ethylbenzimidazole (L¹) adducts with copper(II), cobalt(II), and zinc(II) chelates of N,N,S tridentate tosylamino-functionalized mercaptopyrazole-containing Schiff base (H₂L), resulting from condensation of 2-tosylaminoaniline with 1-phenyl-3-methyl-4-formylpyrazole-5-thiol, with the general formula [ML · L¹] were obtained by electrochemical method. The structure and composition of the complexes were confirmed by the data of C, H, N elemental analysis, IR and ¹H NMR spectroscopy, and magnetochemical and X-ray spectral measurements. The mononuclear structure of the copper(II) adduct with coordination bond located on the pyridine type endocyclic nitrogen atom of 2-amino-1-ethylbenzimidazole was proved by X-ray diffraction.

Phase equilibria in the Nd–Co–Fe–O system were systematically studied at 1373 K in air. The homogeneity range and crystal structure of solid solution NdCo_1–xFe_xO₃ (0.0 ≤ x ≤ 1.0) have been studied by the X-ray powder diffraction method. The structural parameters of complex oxides have been refined by the full-profile Rietveld method. It was shown that all oxides reveal practically stoichiometric oxygen composition within the entire temperature range under investigation. The values of thermal expansion coefficients for the cobaltites NdCo_1–xFe_xO₃ (x = 0.3, 0.7) have been calculated within the wide temperature range in air. Chemical stability of NdCo_1–xFe_xO₃ (x = 0.3, 0.7) in respect to the solid electrolyte materials (Ce_0.8Sm_0.2O_2–δ and La_0.88Sr_0.12Ga_0.82Mg_0.18O3-δ) was examined. Electrical conductivity of NdCo_1–xFe_xO₃ (x = 0.3, 0.7) was measured as a function of temperature within the range 300–1373 K in air. It was shown that substitution of cobalt for iron leads to the decrease of conductivity. The isothermal-isobaric cross-section of the phase diagram for the Nd–Co–Fe–O system at 1373 K in air has been presented.

The phase and chemical compositions of precipitates formed in the system Zn(VO₃)₂–HCl–VOCl₂–H₂O at pH 1−3, molar ratio V⁴⁺: V⁵⁺ = 0.1−9, and 80°C were studied. It was shown that, within the range 0.4 ≤ V⁴⁺: V⁵⁺ ≤ 9, zinc vanadate with vanadium in a mixed oxidation state forms with the general formula Zn_xV⁴⁺_yV⁵⁺_2-yO₅ ∙ nH₂O (0.005 ≤ x ≤ 0.1, 0.05 ≤ y ≤ 0.3, n = 0.5−1.2). Vanadate Zn_xV₂O₅ ∙ nH₂O with the maximum tetravalent vanadium content (y = 0.30) was produced within the ratio range V⁴⁺: V⁵⁺ = 1.5−9.0. Investigation of the kinetics of the formation of Zn_xV₂O₅ ∙ nH₂O at pH 3 determined that tetravalent vanadium ions VO2+ activate the formation of zinc vanadate, and its precipitation is described by a second-order reaction. It was demonstrated that, under hydrothermal conditions at pH 3 and 180°C, zinc decavanadate in the presence of VOCl₂ can be used as a precursor for producing V₃O₇ ∙ H₂O nanorods 50–100 nm in diameter.

Composition and stability of triglycine complexes with Cu(II) ions in a wide range of concentration ratios at T = 298.15 K and I = 0.2 (KNO₃) have been determined by potentiometric method. Existence of CuHL²⁺, CuHL₂₊, CuH₂L²⁺², CuL⁺, CuH_–1L, CuH_–2L–, CuH_–3L^2–, CuL₂, CuH_-1L^-₂, and CuH_–2L^2-₂, species has been established.

We report the results of our studies of the protolytic and coordination equilibria of formation of mono- and polynuclear heteroligand complexonates containing cobalt(II) and nickel(II) salts and EDTA, as well as monoamine complexons, such as iminodiacetic acid and hydroxyethyliminodiacetic acid. The experimental data obtained by absorption spectrophotometry were processed using the mathematical models that allowed us to assess the probability of existence of a broad range of complex species in the solution and to select the species sufficient for the experimental data to be reconstituted from them. The compositions of the polynuclear heteroligand cobalt(II) and nickel(II) complexonates were determined. The pH ranges of their existence were found; the equilibrium constants of the reactions and the stability constants of the resulting complexes were calculated. An assumption is made about their structure.