DC conductivity of silver vanadium tellurite glasses

The mixed electronic–ionic conduction in 0.5[xAg2O–(1−x)V2O5]–0.5TeO2 glasses with x=0.1–0.8 has been investigated over a wide temperature range (70–425 K). The mechanism of dc conductivity changes from predominantly electronic to ionic within the 30⩽mol% Ag2O⩽40 range; it is correlated with the underlying change in glass structure. The temperature dependence of electronic conductivity has been analyzed quantitatively to determine the applicability of various models of conduction in amorphous semiconducting glasses. At high temperature, T>θD/2 (where θD is the Debye temperature) the electronic dc conductivity is due to non-adiabatic small polaron hopping of electrons for 0.1⩽x⩽0.5. The density of states at Fermi level is estimated to be N(EF)≈1019–1020 eV−1 cm−3. The carrier density is of the order of 1019 cm−3, with mobility ≈2.3×10−7–8.6×10−9 cm2 V−1 s−1 at 300 K. The electronic dc conductivity within the whole range of temperature is best described in terms of Triberis–Friedman percolation model. For 0.6⩽x⩽0.8, the predominantly ionic dc conductivity is described well by the Anderson–Stuart model.