Experimental thermodynamic study of the equilibrium phase AgBi 3S5 by an improved EMF method

Abstract

A thermodynamic study of the equilibrium phase assemblages AgBi 3S5-Bi2S3-S/Bi was made by an EMF-technique. The ternary phase was synthesized from the pure Ag2S and Bi2S3 in an evacuated silica ampoule, and ground into powder before mixing with appropriate compositions of Bi2S 3 and S or Bi. The phase mixtures were pressed into different pellets, in a series of experiments. Together with pieces of pure Ag-foil and the electrolytic pellets of superionic conductor RbAg4I5 or AgI, the pellets were assembled to form the galvanic cells Pt(-) | Ag | RbAg4I5 | AgBi3S5 + Bi 2S3 + S + (C) | Pt(+) and Pt(-) | Ag | AgI | AgBi 3S5 + Bi2S3 + Bi | C | Pt(+). The EMF-measurements were made in a temperature range 299.15-594.15 K. In this paper, the thermodynamic functions for the formation of pavonite (AgBi 3S5) at sulfur and bismuth saturation have been determined. The obtained results are in agreement with some of the available literature values. Furthermore, new experimental thermodynamic data of bismuth-saturated pavonite (AgBi3+xS5; 0 < x < 0.14), in the temperature range 299.15-594.15 K, were determined. © 2013 Elsevier B.V. All rights reserved.