Diffuse reflectance spectroscopy of solid solutions in the Ag7PS6-Ag8GeS6 system

Abstract

Samples of Ag7+x(P1–xGex)S6 (x = 0, 0.1, 0.25, 0.33, 0.5, 0.75, 1.0) solid solutions were obtained in the form of microcrystalline powders by grinding in an agate mortar. The diffuse reflectance spectra of the obtained Ag7+x(P1–xGex)S6 samples were studied in the spectral range 200 to 1400 nm at 293 K. The spectral dependences were analyzed using multilevel approximation by applying the Kubelka–Munk function and the Tauc method. It has been found that for Ag7+x(P1 xGex)S6 solid solutions, a red shift of the reflection edge beginning is observed with increasing the Ge content. The pseudo-gap values of Ag7+x(P1–xGex)S6 solid solutions was estimated by the Tauc method. It was found that the heterovalent cationic substitution P+5 → Ge+4 within the anionic sublattice leads to a monotonic nonlinear decrease in the pseudo-gap values.