ac relaxation in silver vanadate glasses

Abstract

The frequency dependent ac conductivity of semiconducting silver vanadate glasses has been studied in the temperature range 87--423 K and in the frequency range 10 Hz--2 MHz. The experimental results have been analyzed with reference to various theoretical models based on quantum mechanical tunneling and classical barrier hopping. The analysis shows that the temperature dependence of the ac conductivity is consistent with the overlapping large polaron tunneling model at temperatures below 275 K in the measured frequency range. The frequency exponent data show a departure from the theoretically expected values above 275 K. A scaling of the conductivity spectra with respect to temperature is attempted for these glasses at high temperatures. It is observed that at temperatures above 275 K the conductivity spectra show a time-temperature superposition principle consistent with the temperature independence of the frequency exponent in this temperature region.