AC conductivity in Li2O and Li2O-K2O doped vanado-tellurite glasses

Abstract

In the present study, two sets of vanado-tellurite glasses doped with Li2O and Li2O-K2O have been prepared by the melt quenching method. AX conductivity was measured using in the frequency range 50Hz to 5MHz and temperature from 300 to 525K. By non-linear regressional analysis of the measured total conductivity, dc and ac components and frequency exponent, s, were determined. In both the series of glasses, the conductivity increased with increasing frequency and decreased with increasing alkali content. The temperature dependence of conductivity has been analyzed using Mott's small polaron hopping model and the high temperature activation energies were determined. The activation energy decreased with increasing Li2O content in single alkali glasses and with increase in K2O content in mixed alkali glasses. The frequency exponent, s, was observed to be nonlinearly varying with temperature and it has been looked at in terms of Correlated Barrier Hopping and Quantum Mechanical Tunneling models. By scaling the conductivity isotherms and drawing master curves, the time-temperature superposition principle has been verified in both the series of glasses. It is for the first time that the alkali doped vanado-tellurite glasses are reported for ac conductivity in the frequency range 50Hz-5MHz, and the data has been subjected to thorough analysis. © 2009 IOP Publishing Ltd.