DC conductivity in single and mixed alkali vanadophosphate glasses

Three different series of single and mixed alkali vanadium phosphate glasses have been prepared by a melt quench method. DSC studies were carried out on few of these samples and their glass transition temperatures were determined. The glass transition temperatures were found to decrease with alkali content in single alkali systems and increase with second alkali content in mixed alkali systems. The dc electrical conductivity has been measured as a function of temperature. The data has been analyzed in the light of Mott’s small polaron hopping model and activation energies were determined. In one set of single alkali glasses activation energies were found to increase with alkali content and in another set of single alkali systems a transition from predominantly electronic to ionic conduction has been observed above 0.16 mol fraction of alkali content. The mixed alkali glasses have shown higher activation energies and lower conductivities compared to single alkali doped glasses and this has been attributed to a mixed alkali influence on the electrical conduction in these systems.