Thermodynamic Properties of a High-Temperature Ag8SiSe6 Modification and Ag8Si1 – xSnxSe6 Solid Solutions Studied by the EMF Method with Solid Electrolyte

The thermodynamic properties of a high-temperature (HT) modification of Ag8SiSe6 and solid solutions Ag8Si1 – xSnxSe6 are studied using the EMF method with the solid Ag+-conducting electrolyte Ag4RbI5. Based on the EMF measurements of concentration cells such as $$\left( {-} \right){\text{Ag}}\left( {\text{s}} \right)\left| {{\text{A}}{{{\text{g}}}_{{\text{4}}}}{\text{Rb}}{{{\text{I}}}_{{\text{5}}}}\left( {\text{s}} \right)} \right|\left( {{\text{Ag}{-}\text{in alloy}}} \right)\left( + \right)\,\,\,\,\,\,\,\,\,(1)$$ the linear equations for the temperature dependence of EMF are obtained in the temperature interval of 300–450 К and the partial thermodynamic functions of silver in alloys are calculated. Based on the data on solid-state equilibria in the system Ag–Si–Sn–Se, the equations for the potential-generating reactions responsible for these partial molar functions are obtained and the integral thermodynamic functions of formation and entropy are calculated for the HT-Ag8SiSe6 and solid solutions with a composition x = 0.2, 0.4, 0.6, and 0.8.