PHASE EQUILIBRIA IN THE Bi19S27I3 -“Bi19Se27I3” SYSTEM AND CHARACTERIZATION OF SOLID SOLUTIONS

The phase equilibria along the Bi19S27I3 -“Bi19Se27I3” section of the Bi2S3– Bi2Se3 -BiI3 system have been investigated based on a comparative analysis of DTA measurements, PXRD patterns, and SEM results. It has been established that the system is partially stable in the subsolidus area and forms a wide series of solid solutions (δ -phase) with a hexagonal structure based on Bi₁₉S₂₇I₃. The solubility limit based on Bi19S27I3 in this section at room temperature is ~70 mol%. The crystal lattice parameters change linearly within the homogeneity area, in accordance with Vegard's law. Compositions less enriched in Bi₁₉S₂₇I₃ consist of heterogeneous mixtures, including δ-solid solutions based on Bi₂Se₃ and BiSeI. The obtained materials are of interest as potential candidates for thermoelectric and photoelectric applications