ac conductivity studies in single and mixed alkali vanadophosphate glasses

Two different series of vanadophosphate glasses doped with sodium and sodium–potassium were investigated for ac conductivity in the frequency range 500 Hz to 500 kHz and temperature range 300–660 K. Mott's small polaron hopping has been used to explain the temperature dependence of electrical conductivity. The change over of conduction mechanism, occurring at 0.16 mole fraction of Na2O from predominantly electronic to ionic has been observed in single alkali glasses. The mixed alkali effect, in terms of electrical conductivity and activation energies associated with it, has been observed to be occurring at 0.12 mole fraction of second alkali (K2O) content in mixed alkali glasses. The results have been discussed.