The Ag₂S-GeS₂-P₂S₅ system at 500 K

Phase equilibria in the quasi-ternary system Ag2S-GeS2-P2S5 at 500 K (227 degrees C) were investigated by physicochemical analysis methods on 55 (plus 7 glass samples) alloys that were synthesized by direct single-temperature method. Phase diagram of the quasi-binary system Ag7PS6-Ag8GeS6 was also investigated. The limited solid solution ranges of the Ag7PS6 and Ag8GeS6 compounds are formed in the Ag7PS6-Ag8GeS6 system. The crystal structure of the two compositions was investigated by Rietveld method. The unit cell periods of the phases are: a = 1.5108 nm, b = 0.74609(7) nm, c = 1.0571(1) nm for Ag7.9P0.1Ge0.9S6, and a = 1.0403 nm for Ag7.1P0.9Ge0.1S6. Optical band gap was determined from the energy position of optical absorption edge at 293 K (20 degrees C) at a fixed value of the absorption coefficient alpha = 300 cm(-1).