Semiconducting behavior in the liquid Ag-As₂X₃ system (X:Te, Se)

Measurements of the electrical conductivity, magnetic susceptibility and thermoelectric power have been carried out on liquid Ag-As₂Te₃ and Ag-As₂Te₃ systems. The liquid Ag-As₂Te₃ system exhibits a deep minimum of the electrical conductivity, diamagnetic peak of the magnetic susceptibility and rapid drop of the positive thermoelectric power at the stoichiometric composition of Ag₆As₂Te₃, reflecting the occurrence of the metal-semiconductor transition. The liquid Ag₆As₂Te₃ system also has the diamagnetic peak of magnetic susceptibility and sign reversion of thermoelectric power near the composition of Ag₆As₂Te₃. However, the electrical conductivity in the selenide system indicates a negative temperature dependence like metals and takes a maximum value at this composition. The observed results have been discussed with the help of the pseudogap model developed by Enderby and Barnes. In this result, the unusual behavior of electrical conductivity in the selenide system has been deduced to be associated with the conduction and valence band edge-parameters rather than the pseudogap width.