Temperature and frequency dependent conductivity of lithium doped bismuth zinc vanadate semiconducting glassy system

The ac conductivity of bismuth zinc vanadate glasses of compositions x Li2O (100 - x) (50V(2)O(5)center dot 20 Bi2O3 center dot 30 ZnO); x = 0, 2, 4, 6, and 8 has been studied in the frequency range 10(-1) Hzb-2 MHz and in temperature range 313-533 K. The temperature and frequency dependent conductivity is found to obey Almond-West universal power law for all the studied lithium doped bismuth zinc vanadate glassy systems. Various parameters such as dc conductivity (sigma(dc)), crossover frequency (omega(H)) and frequency exponent (s) have been estimated by fitting the experimental data of ac conductivity to Almond-West universal power law. It has been observed that the ac conductivity of bismuth zinc vanadate glass system decreases with the increase in Li2O content. The ac conductivity and its frequency exponent have been analyzed in the frame work of various theoretical models. The ac conduction seems to take place via tunneling of overlapping large polarons in all the compositions.