Mechanism of Electrical Conduction in Molten Cu S-Cu Cl and Mattes

Abstract

The specific conductance and its temperature dependence were measured over the entire composition range of the molten Cu₂S-CuCI system. At a typical temperature of 1200°C, 10 mol pct of the ionically conducting CuCl reduced the specific conductance from about 77 ohm⁻¹cm⁻¹ for pure Cu₂S to about 32 ohm⁻¹cm⁻¹, and 50 mol pct CuCl reduced the conductance to that for pure CuCl—about 5 ohm⁻¹cm⁻¹. The nature of electrical conduction in molten Cu₂S, FeS, CuCl, and mixtures was studied by measuring the current efficiency of electrolysis at about 1100°C. The Cu₂S, FeS, and mattes were found to conduct exclusively by electrons, but addition of 15 wt pct CuS to Cu₂S produces a small amount of electrolysis. Addition of CuCl to Cu₂S suppresses electronic conduction, and ionic conduction reaches almost 100 pct at a CuCl concentration of about 50 mol pct. These facts are interpreted in terms of electron energy level diagrams by analogy to the situation in solids.