The Electrical Conductivity, and the Thermodynamic and Structural Properties of Molten AgCl ‐ Ag2 S Mixtures: II . Electrical Conductivities

Abstract

The specific conductivities of molten silver chloride‐silver sulfide mixtures have been determined over the entire composition range. Pure molten silver sulfide is a good electronic conductor having a specific conductivity of 202 , with an almost negligible temperature dependence. The measured specific conductivity of pure molten silver chloride is in very close agreement with previous determinations. Silver chloride has a very low apparent activation energy for conduction. By comparison with the alkali halides, it is shown that the apparent activation energy for conduction of univalent salts is inversely proportional to their lattice energies. Dilute solutions of silver sulfide in silver chloride are ionic conductors. The specific conductivity in this region decreases and the apparent activation energy for conduction increases as the concentration of silver sulfide is increased. Above 20 mole % silver sulfide, the conductivity of the melts increases rapidly with increasing silver sulfide content and increasing temperature, as electronic conduction starts to occur. The activation energy for electronic conduction in this region is shown to be essentially composition and temperature independent. One per cent electronic conduction starts to occur at about 14 mole % silver sulfide at 750°C and at 24.5 mole % silver sulfide at 460 °C. Above 50 mole % silver sulfide the conductivity increases very rapidly, and the temperature dependence of the conductivity becomes negative. Structural changes in these melts appear to influence the electronic conduction markedly.