Conductivity and dielectric relaxations in Bi_2O_3-doped phospho- vanadate glasses

摘要

This work mainly focus on the study of electrical conductivity of the ternary glass system. In this paper electronic conduction in Bi2O3 doped phospho-vanadate glasses are discussed. Electrical conductivity measurements for both ac and dc were carried over a range of frequency (40Hz to 10MHz) and temperature (433-500K). Transition metal ions (TMI) play very important role in the electrical properties of phosphate glasses. Two different valence states present in these TMI determine the electrical properties. In phospho-vanadate glasses conduction mechanism uses small polaron hopping of electrons between V4+ and V5+ states in vanadium glasses. Small polaron hopping between these states describes the investigated glasses are electronic conductors. Variation of different hopping parameters with Bi2O3 mol% and with temperature is discussed. Modifier role of bismuth oxide leading to the enhancement of conductivity of investigated glasses with decreasing concentration of V2O5 mol%. X-ray diffraction technique used to check the glassy nature of the investigated glass system. The Cole-Cole plots depict conduction is single type (electronic). The dc and ac conductivity values were found to increase with increasing Bi2O3 content. Fitting data to Almond type behavior ac conductivity analysis is done. Furthermore study of scaling behavior is also done using stretched exponents. The values of investigated ternary glasses lie in the range of 0.6-0.62 and seems to be almost constant but for base glass it is 0.68. The dielectric loss (tan) values were found to decrease with increasing Bi2O3 content.