Thermodynamic properties of saturated solid solutions of Ag7SnSe5Br and Ag8SnSe6 compounds in the Ag-Sn-Se-Br system measured by the EMF method

Triangulation of the Ag-Sn-Se-Br system in the part of Ag2Se-SnSe-SnSe2-AgBr was carried out using the X-ray diffraction and differential thermal analysis methods. The spatial position of the established four-phase regions regarding figurative point of silver was used in order to write the equations of virtual potential-forming chemical reactions. Potential-forming processes were performed in electrochemical cells (ECCs) of the type (−) C |Ag| Ag3GeS3Br glass |D| C (+) where C are the inert (graphite) electrodes; Ag and D are the electrodes of the ECCs; D represents the equilibrium four-phase alloys, and Ag3GeS3Br glass is a membrane with purely ionic Ag+ conductivity. The linear dependencies of the EMF of cells on temperature in the range of 480-520 К have been used in order to calculate the standard thermodynamic values of saturated solid solutions of Ag7SnSe5Br and Ag8SnSe6 compounds in the four-element part of the Ag-Sn-Se-Br system.