Electrical Properties of Molten AgI-Ag₂S Mixtures

Abstract

The conductivity, σ, of molten (AgI)_1-c(Ag₂S)_c mixtures decreases rapidly on the addition of AgI to Ag₂S. The σ of molten Ag₃SI is 13 ohm^-1 · cm^-1 at the melting point. It is suggested that a deep pseudogap is caused by the addition of AgI to Ag₂S. The thermoelectric power, S^*, of liquid Ag₂S is - 77 μV/K at the melting point. The S^* of molten (AgI)_1-c(Ag₂S)_c mixtures decreases gradually with increasing AgI component and reaches a minimum value of - 135 μV/K at the composition c=0.5. Moreover, the sign of S^* on the AgI-rich side changes gradually from negative to positive with increasing AgI composition. This p-n transition was found to occur near the composition c=0.36. The change in sign of S^* may be closely related to a gradual transition from predominantly electronic conduction to ionic one. The behaviour of σ and S^* for molten (AgI)_1-c(Ag₂S)_c mixtures was analysed by using a model of conduction processes due to both electrons and silver ions.