Phase Equilibria and Thermodynamic Properties of Selected Compounds in the Ag–Ga–S–AgBr System for Modern Application in Energy Conversion Devices

The phase equilibria of the Ag–Ga–S–AgBr system in the part GaS–Ga ₂S ₅–AgBr–Ag ₂S below 600 K were investigated by the modified electromotive force (EMF) method using the Ag ⁺ catalysts as small nucleation centers of equilibrium phases. Division of the GaS–Ga ₂S ₅–AgBr–Ag ₂S was carried out with the participation of the following compounds Ag ₂S, GaS, Ga ₂S ₃, AgBr, Ag ₉GaS ₆, AgGaS ₂, Ag ₃SBr, Ag ₃Ga ₂S ₄Br, and Ag ₂₇Ga ₂S ₁₂Br ₉. Reactions were performed by applying electrochemical cells (ECs) with the structure: (−) IE | NE | SSE | R{Ag ⁺} | PE | IE (+), where IE is the inert electrode (graphite powder), NE is the negative electrode (silver powder), SSE is the solid-state electrolyte (glassy Ag ₃GeS ₃Br), PE is the positive electrode, R{Ag ⁺} is the region of Ag ⁺ diffusion into PE. The measured EMF and temperature values of ECs were used to determine the standard thermodynamic functions of the compounds Ag ₃Ga ₂S ₄Br and Ag ₂₇Ga ₂S ₁₂Br.