Moroz M. Thermodynamic properties of chalcogenides and chalcohalides of some transition metals and phase diagrams of the systems based thereon

The thesis is devoted to the establishment of the formula composition, synthesis conditions and thermodynamic properties of compounds of separate sections of the equilibrium T–x space of the chalcogenide and chalcohalide systems Ag–BII–XVI, Ag–XVI–YVII, Ag–BII–DIV–XVI, Ag–BII–XVI–YVII, and Ag–DIV–XVI–YVII (BII = Zn, Cd, Hg, Fe; DIV = Ge, Sn, Pb; XVI = S, Se, Te; YVII = Cl, Br, I) at T<600 K. The XRD, DTA, and DSC-TG methods were used to investigate the phase diagrams of parts of the systems. A new scientific approach was proposed to determine phase equilibria in the three- and four-element systems at temperatures with kinetic obstacles to achieving equilibrium. Chalcogenides (AgFeS2, Ag2FeS2, Ag2FeSe2, Ag2FeTe2, low-temperature modifications of AgFeSe2, AgFeTe2, Ag2FeSnS4, Ag2FeSn3S8, Ag2FeGeSe4, Ag2FeSnSe4, Ag2FePbSe4, and Ag2FeGeTe4) and chalcohalides (Ag23Te12Cl, Ag5Te2Cl, Ag10Te4Cl3, Ag19Te6Cl7, Ag19Te6Br7, Ag3TeBr, Ag5Te2Br, Ag10Te4Br3, Ag23Te12Br, and Ag7SnSe5Br) were synthesized for the first time by the low-temperature method. From the temperature dependences of EMF of investigated cells, the principal thermodynamic functions (Gibbs energy, enthalpy, and entropy) of 30 ternary and quaternary compounds were determined for the first time. Analytical equations of temperature changes of heat capacities are found for some of them and enthalpies of polymorphic transformations are calculated. The possibility of estimating the metastable state of phases at T<600 K has been established.