Thermodynamics of silicon sulphides and zinc sulphide

Abstract

The equilibrium constant and standard free energy change for the reactions: 2 ZnS(s)⇌2 Zn(g)+ S₂(g)(1), ZnS(s)+ Si(s)⇌Zn(g)+ SiS(g)(2) have been measured around 1000°C by a transportation method. The following free energies were obtained ΔG°= 178 900–92.4 T cal mol^–1 <1293 K (1a), ΔG°= 172 500–87.4 T cal mol^–1 >1293 K (1b), ΔG°= 101 700–65.7 T cal mol^–1 <1293 K (2a), ΔG°= 98 500–63.2 T cal mol^–1 >1293 K. (2b) By combination, the free energy change for reaction (3) is obtained: 2Si(s)+ S₂(g)= 2 SiS(g)(3), ΔG°= 24 500–39.0 T cal mol^–1 Combined with results of other investigators the free energy of formation of SiS₂(s, l, g) is estimated.