Influence of cation Si4+↔Ge4+ and P5+↔Ge4+ sub-stitution on the mechanical parameters of single crystals Ag7(Si1–xGex)S5I and Ag6+x(P1–xGex)S5I

Herein we present the results of microhardness investigations aimed at monocrystalline samples of Ag 7 (Si 1–x Ge x )S 5 I (0, 0.2, 0.4, 0.6, 0.8, 1) and Ag 6+x (P 1–x Ge x )S 5 I (0, 0.25, 0.5, 0.75, 1) solid solutions. The dependence of microhardness H on the load P and composition were investigated. It has been observed that the microhardness dependence on the applied load is characterized by a tendency to decrease with increasing the load. It indicates a presence of “normal” size effect in both Ag 7 (Si 1–x Ge x )S 5 I and Ag 6+x (P 1–x Ge x )S 5 I (0, 0.25, 0.5, 0.75, 1) solid solutions. The revealed size effects of hardness in single crystals of Ag 7 (Si 1–x Ge x )S 5 I and Ag 6+x (P 1-x Ge x )S 5 I solid solutions have been analyzed within the framework of the gradient theory of plasticity. The corresponding parameters of the model of geometrically necessary dislocations have been determined.