Phase equilibria in the Ag8GeS6-Ag8GeTe6 and Ag8GeSe6-Ag8GeTe6 systems were studied using differential thermal analysis and powder X-ray diffraction technique. The T-x phase diagrams were constructed. It has been found that both systems are partially quasi-binary and are characterized by the formation of continuous series of substitutional solid solutions between Ag8GeTe6 and high-temperature cubic modifications of Ag8GeS6 and Ag8GeSe6. When solid solutions are formed, the temperatures of polymorphic phase transitions of these compounds decrease. This leads to the stabilization of the ion-conducting cubic phase in the 40 mol% Ag8GeTe6 range of compositions at room temperature and below. The regions of homogeneity based on Ag8GeS6 and Ag8GeSe6 are 15 and 10 mol.%, respectively. The crystal lattice parameters of the identified solid solutions were calculated from the XRD data, and their linear dependence on the composition is shown

Argyrodite family compounds and phases based on them are valuable ecologically friendly functional materials that exhibit a number of functional propreties, such as thermoelectric, photoelectric, optical, and other. On the other hand, having Cu+ and Ag+ ion conductivity, they are ionic conductors, and can be used as electrochemical sensors, electrodes, or electrolyte materials in solid-state batteries, displays, etc. In the present paper, phase relations in the Ag8SiS6–Ag8SiTe6 system were studied by differential thermal analysis and X-ray diffraction phase techniques and a T-x phase diagram was constructed. It is established that the system is quasi-binary and is characterized by the formation of a continuous series of substitutional solid solutions between Ag8SiTe6 and HT- Ag8SiS6 compounds. With the formation of solid solutions, the temperature of the polymorphic transition of the Ag8SiS6 decreases. This leads to the stabilization of the ion-conducting cubic phase in the range of compositions 30 mol. % Ag8SiTe6 at room temperature and below. The homogeneity regions based on RT-Ag8SiS6 are 10 mol. %. According to XRD data, the crystal lattice parameters of the obtained solid solutions were calculated and a their linear dependence on the composition is shown