Electrical Conductivity of Silver Sulfide

TLDR

Mixed electronic and ionic conduction in silver sulfide is examined, emphasizing how terminal conditions can suppress either component and alter the ionic‑to‑electronic current ratio. The study introduces a new method to independently measure ionic and electronic conductivities as functions of the silver component’s chemical potential ζ. The method measures conductivities independently by accounting for the differing contributions of electrons and ions to ζ below and above the 177 °C transition. Electronic conductivity follows an exp(Bζ) dependence on chemical potential, with B shifting abruptly from e/kT below 177 °C to e/2kT above, reflecting a transition from dissolved silver atoms to dissociated ions and electrons.

Abstract

Mixed electronic and ionic conduction in silver sulfide is examined. The importance of terminal conditions which may affect the ratio of ionic to electronic currents in experimental measurements is emphasized. In particular, either the electronic or ionic components can be completely suppressed. This is the basis of a new method of measuring the ionic and electronic conductivities independently, as functions of the chemical potential ζ of the silver component. The electronic conductivity is found to vary as expBζ both above and below the transition at 177°C. However, the coefficient B changes abruptly from e/kT below the transition to e/2kT above. This result can be understood theoretically in terms of the following picture: Excess silver is present mainly as dissolved atoms below the transition and as dissociated ions and electrons above. In the former case, only the electrons contribute to ζ, whereas in the latter there is a contribution both from the electrons and the ions.