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

We have studied phase relations in the AgI–BiI 3 –Se–Bi 2 Se 3 region of the Ag–Bi–Se–I system for T ≤ 530 K and derived equations of overall potential-forming reactions involving the phases BiSeI, Bi 19 Se 27 I 3 , and BiI 3 . The reactions were brought about in electrochemical cells of the form C |Ag| Ag 3 GeS 3 I 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 Ag 3 GeS 3 I 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, Bi 19 Se 27 I 3 , and BiI 3 .