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  • Author or Editor: G. Moiseev x
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The thermochemical properties of Cu2O3 were calculated. The stability of Cu2O3 was studied with the help of TM methods. It was shown that this oxide can exist in oxygen atmosphere (P=105 Pa) at temperatures below 380 K.

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Abstract  

The empirical regularities of the SEF for relative inorganic substances in binary and quasibinary systems (energetic and dimensional rules of linear approximation - ELAR and DLAR) are described.

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Abstract  

With help of literature data and some empirical methods the main thermochemical and thermodynamical properties were estimated for condensed GaSb, GaS, Ga2S, Ga2S3, Ga4S5, Sb2S3 and for gaseous Ga2S and SbS phases.

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Thermochemical and thermodynamical properties of HTSC phases are reviewed for the Y-Ba-Cu-O system and also presented for the newly calculated Bi-Sr-Cu-O system stressing out stoichiometric and phenomenological viewpoints. Simulated data are listed for (H 298 o-H o o, phase transformation temperatures, standard entropies, standard enthalpies of formation, heat capacities in crystalline phase, etc. Pseudobinary phase diagrams are treated showing the effect of oxygen partial pressure particularly illustrated on the (Sr, Bi, Ba)-Cu-O system.

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With the use of various calculation methods, unknown thermodynamic properties (TP) of Bi2O5 and BiO2, as well as the temperature dependencies of reduced Gibbs energy (TDRGE) were determined. With the help of thermodynamic simulation (TS) methods at 300–1500 K, common P=105 Pa the thermal decompositions of condensed Bi2O5, BiO2, Bi2O3 and BiO have been investigated in initial atmosphere of O2 and Ar. Every condensed substance was presented as the individual phase. It was found that BixOyoxides have temperature stability fields and also districts of possible mixture formation. During equilibrium heating of BixOy oxides the various types of phase transformations were observed. The characteristics of some transformations were estimated.

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A thermodynamical method for the estimation of decomposition heat in a crystal state, incongrous and congruous melting of compounds with the use of temperature dependencies of total entropies of compounds was suggested. Entropies and heats of phase transformation of YBa2Cu3O6, YBa2Cu3O7, YBa2Cu3.5O7.5, YBa2Cu4O8, YBa2Cu5O9, YBa4Cu3O8.5, Y2BaO4, Y2Ba2O5, Y2Ba4O7, Y4Ba3O9, YCuO2, Y2Cu2O5, Y2BaCu2O5, Ba2CuO3, BaCuO2, BaCu2O2, Ba3Cu5O8 were calculated. Data, obtained by the authors earlier, are discussed.

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Abstract  

A method of calculation of average heat capacities of phase transformation products of complex oxides is suggested. The method takes into account the physical state of products and the increase in the heat capacities of products due to the change of entropy at a phase transformation. Average heat capacities of products formed in a congruous melting of compounds (YCuO2 and Y4Ba3O9), in an incongruous melting of compounds (Y2Cu2O5, BaCuO2, BaCu2O2, Y2BaCuO5, YBa2Cu3O7, YBa2Cu3O6) and in a decomposition in a crystalline state of compounds (Y2BaO4, Y2Ba2O5, Y2Ba4O7, Ba2CuO3, Ba3Cu5O8, YBa2Cu3.5O7.5, YBa2Cu4O8, YBa2Cu5O9) was estimated by using three methods.

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