Thermochemical properties of selected ternary phases in the Ag-Bi-S system

Thermodynamic properties of the equilibrium phases matildite (beta-AgBiS2), schapbachite (alpha-AgBiS2), and pavonite (AgBi3S5) with their stoichiometric variations have been studied. The ternary phase AgBiS2 was synthesized from the pure binary sulfides, and characterized by the SEM-EDS and X-ray powder diffraction techniques. Thermal analysis of the synthesized phase was done by the differential scanning calorimetry and thermogravimetry techniques. Based on the calorimetric measurements, phase transformation and melting temperatures as well as enthalpies of AgBiS2 have been determined. Thermodynamic properties of both AgBiS2 and AgBi3S5, including their stoichiometric variations at saturations of bismuth and sulfur, have been compiled and critically evaluated. Heat capacities of both phases have been estimated with two different estimation methods. The estimated results have been compared with the available experimental literature data. Despite the fact that the estimation methods are partly based on assumptions, the obtained values are generally in reasonable agreement with the available literature data. The obtained results are presented and discussed.