Electrical Conductivity of Silver Sulfide

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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.