Phase Equilibria in the YFeO3 – YCoO3 System in Air

Received: 14.03.2021. Revised: 10.04.2021. Accepted: 11.04.2021. Available online: 13.04.2021.YFe1-xСоxO3 solid solutions were prepared by glycerol-nitrate technique. The homogeneity range of solid solutions was studied within the temperature range 1173 – 1573 K. A continues series of solid solution below the decomposition temperature of YСоO3, which was shown to be equal to 1266 + 6 K, begins to narrow at higher temperatures and becomes equal to 0 ≤ x ≤ 0.1 at 1573 K. The phase diagram of the YFeO3 – YСoO3 system in the “T – composition” coordinates was divided into three fields. Similar to the parent ternary oxides, all single-phase YFe1-xСоxO3 solid solutions possess orthorhombically distorted perovskite structure (Pnma space group). Unusual behavior of orthorhombic distortions in YFe1-xСоxO3 with temperature was explained by probable changes in spin state of Co3+ ions.This work was supported in parts by the Ministry of Sci-ence and Higher Education of Russian Federation (№ АААА-А20-120061990010-7) and A.V.B. was supported with a stipend for young scientists and PhD students from the President of Russian Federation (№ SP-3689.2019.1)

Phase Behavior of Aqueous Na-K-Mg-Ca-CI-NO3 Mixtures: Isopiestic Measurements and Thermodynamic Modeling

A comprehensive model has been established for calculating thermodynamic properties of multicomponent aqueous systems containing the Na{sup +}, K{sup +}, Mg{sup 2+}, Ca{sup 2+}, Cl{sup -}, and NO{sub 3}{sup -} ions. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300 C and concentrations ranging from infinite dilution to the fused salt limit. The model has been parameterized using a combination of an extensive literature database and new isopiestic measurements for thirteen salt mixtures at 140 C. The measurements have been performed using Oak Ridge National Laboratory's (ORNL) previously designed gravimetric isopiestic apparatus, which makes it possible to detect solid phase precipitation. Water activities are reported for mixtures with a fixed ratio of salts as a function of the total apparent salt mole fraction. The isopiestic measurements reported here simultaneously reflect two fundamental properties of the system, i.e., the activity of water as a function of solution concentration and the occurrence of solid-liquid transitions. The thermodynamic model accurately reproduces the new isopiestic data as well as literature data for binary, ternary and higher-order subsystems. Because of its high accuracy in calculating vapor-liquid and solid-liquid equilibria, the model is suitable for studying deliquescence behavior of multicomponent salt systems

MARKET DYNAMICS OF PRODUCTION-ECONOMIC SYSTEM. II. Transitions between production states. Elements of risk theory

The methods of theoretical micro-economy were used to investigate the spontaneous transitions between enterprise’s production states in the regime of the goods’ commercial off-load. The economical mechanisms of spontaneous transitions are viewed, some characteristics of transitions are introduced, and equations for their probability are found. It is shown that under the given conditions most probable are the transitions with the loss of capital assets corresponding to the technological and etrepreneural risks and, in particular, bankruptcy risks. The average coefficient of capital assets loss is found as a function of the system evolution period, total supply and workshop processes period. The economic meaning of the obtained resulted is discussed

Phase equilibria, crystal structure and properties of complex oxides in the Nd2O3-SrO-CoO system

International audienceThe phase equilibria in the 1/2Nd(2)O(3)-SrO-CoO system were systematically studied at 1373 K in air. The intermediate phases formed in the 1/2Nd(2)O(3)-SrO-CoO system at 1373 K in air are Nd1-xSrxCoO3-delta (0.0 <= x <= 0.5 with orthorhombic structure, sp. gr. Pbnm and 0.6 <= x <= 0.95 whose structure was detected as cubic according to XRD sp. gr. Pm3m, but shown to be tetragonal by TEM due to the oxygen vacancy ordering), Nd2-ySryCoO4-delta (0.6 <= y <= 1.1 with tetragonal K2NiF4-type structure, sp. gr. I4/mmm) and Nd2-zSrzO3 (0.0 <= z <= 0.15 with hexagonal structure, sp. gr. P-3m1). The unit cell parameters for the single phase samples were refined by the Rietveld analysis. The changes of oxygen content in Nd1-xSrxCoO3-delta (0.6 <= x <= 0.95) and Ruddlesden-Popper oxide Nd2-ySryCoO4-delta were examined by TGA. All were found to be oxygen deficient phases. High-temperature dilatometry allows calculating the thermal expansion coefficient and evaluating the chemical expansion coefficient at high temperature. The projection of isothermal-isobaric phase diagram for the Nd-Sr-Co-O system at 1373 K in air to the compositional triangle of metallic components has been constructed. The phase equilibria in the studied Nd-Sr-Co-O system were compared to La-Sr-Co-O and Nd-M-Co-O (M=Ca and Ba)