THE SbBiTe2Se-SbBiTe2S PHASE DIAGRAM OF THE Sb-Bi-S-Se-Te SYSTEM

Abstract

Using powder X-ray diffraction (PXRD) and differential thermal analysis (DTA), the phase equilibria of the SbBiTe2Se – SbBiTe2S section were studied, and its T-x diagram was constructed. The system is non-quasibinary, due to both initial phases melting in the temperature range. The system is stable below the solidus, which is characterized by the formation of continuous solid solutions (α-phase) with a tetradymite-like hexagonal structure. An analysis of the structural features of tetradymite and other tetradymite-like compounds shows that the substitution of atoms by related atoms is possible in all layers of the packet. In this work sulfur atoms in the central layer can be easily replaced by selenium atoms. This tendency allows us to expect the formation of the range of compositions in the BiSb-Te-Se-S system in which substitutions are realized in cationic and anionic positions. Lattice parameters were determined from the results of powder diffraction patterns. It has been established that the crystal lattice parameters of solid solutions change linearly with composition, which complies with the Vegards rule. Keywords: SbBiTe2Se – SbBiTe2S system, phase diagram, tetradymite-like structure, solid solutions, high entropy alloys.