Obtaining of disordered highly ionic conductive Ag7+x(P1-xSix)S6 single crystalline materials

For the first time, bulk single crystals of the Ag7+x(P1-xSix)S6 solid solution were obtained via directional crystallization from the melt. The crystal structure of the Ag7+x(P1-xSix)S6 solid solution was determined by the Rietveld method. It was demonstrated that Ag7+x(P1-xSix)S6 solid solutions crystallize in two crystal systems – cubic and orthorhombic, and different SG: P213, F-43m and Pna21. The grown crystals were studied by SEM and EDS methods. The electrical parameters of Ag7+x(P1-xSix)S6 were studied in wide frequency and temperature ranges. Established that Ag7+x(P1-xSix)S6 solid solutions exhibit an increase in ionic conductivity compared to the initial compounds. Among the studied solid solutions, the Ag7.25P0.75Si0.25S6 sample demonstrated the highest conductivity with values reaching σion = 2.9 × 10–2 S/cm. The lowest activation energy value (Ea(ion) = 0.2 eV) is also observed for the given composition of solid solutions. The mechanism of ion transport is considered within the context of limiting distances and position occupancy.