Thermodynamic Properties of Iron-Gallium Sulfides

Results are presented from a thermodynamic study of compounds with a layered FeGa2S4 and Fe2Ga2S5 structure. The EMF is measured for concentration chains of the type (−) FeS(solid)|glycerol + KCl + FeCl2|(Fe in alloy) (+) in the 300–390 K range of temperatures. Results from X-ray diffraction analysis and data in the literature are used to establish the nature of solid-phase equilibria in the system Fe–Ga–S in the area of compositions FeS–Ga2S3–S. The formation of the above ternary compounds and a wide range of solid solutions based on Ga2S3 is confirmed. Partial molar functions of iron in ternary alloys are determined by combining thermodynamic data calculated from measurements of the EMF and the thermodynamic functions in the literature for compounds FeS2 and FeS. These partial molar values and thermodynamic data for Ga2S3 are used to calculate the standard entropies and thermodynamic functions of the formation of compounds FeGa2S4 and Fe2Ga2S5, and of solid solutions based on Ga2S3, according to the diagram of solid phase equilibria for subsystem FeS–Ga2S3–S.