Phase equilibria and thermodynamic properties of saturated solid solutions based on the compounds BiSeI, Bi19Se27I3, and BiI3 in the Ag–Bi–Se–I system

Abstract

We have studied phase relations in the AgI–BiI3–Se–Bi2Se3 region of the Ag–Bi–Se–I system for T ≤ 530 K and derived equations of overall potential-forming reactions involving the phases BiSeI, Bi19Se27I3, and BiI3. The reactions were brought about in electrochemical cells of the form C |Ag| Ag3GeS3I glass |D| C (where C stands for an inert (graphite) electrode, Ag and D denote the electrodes of the cell, D is a mechanical mixture of four phases in the system under investigation, and Ag3GeS3I glass is a membrane with purely ionic (Ag+) conductivity). The linear temperature dependences of EMF for the cells in the range 485–510 K were used to calculate the standard thermodynamic functions of the compounds BiSeI, Bi19Se27I3, and BiI3.