The effect of heterovalent P+5 ⇆ Si+4 substitution on the microhardness of Ag7+x(P1-xSix)S6 single crystals

Herein, we present the results of the microhardness investigations of Ag7+x(P1-xSix)S-6 (x = 0, 0.1, 0.25, 0.5, 0.75, 1) single crystals. The influence of composition x on the dependence of microhardness on the applied load was investigated. The study was carried out within a wide range of the applied loads 0.05...2 N. It has been found that an increase in the load on the indenter leads to a monotonic nonlinear decrease in the values of microhardness in all studied samples. This indicates a "normal" indentation size effect. The observed effect in Ag7+x(P1-xSix)S-6 single crystals at various x was described using the geometrically necessary dislocations model. The corresponding parameters of the geometrically necessary dislocations model were determined. The influence of ionic radii and electronegativity of structural polyhedra elements of Ag7+x(P1-xSix)S-6 solid solutions was discussed.