Conductivity and dielectric behavior of NaPO3-ZnO-V2O5 glasses

A series of zinc-phosphate glass containing different concentrations of V2O5 ((80 - x) NaPO3 + 20 ZnO + x V2O5 (x = 0-25 mol%)) was prepared by melt quenching method and analyzed by differential scanning caloremetry (DSC) and impredance spectroscopy. The electrical properties of these samples were measured using ac impedance spectroscopy technique over a frequency range of 10 Hz to 13 MHz at several temperatures in the range of 323-673 K. The ac conductivity, dc conductivity, dielectric constant and loss factors were obtained from these measurements. Constant-phase elements (CPE) are used in equivalent electrical circuits for the fitting of experimental impedance data. The impedance spectra have also indicated that the conduction is predominantly polaronic in nature. The frequency and temperature dependence of the electrical modulis as well as dielectric loss parameters have exhibited a relaxation character attributed to the vanadyl complexes. The relaxation effects have been analyzed by the graphical method. From this analysis, it has been established that there is a spread of relaxation times. The results have been further discussed quantitatively in the light of different valance states of vanadium ions with the aid of the data on spectroscopic properties. The frequency dependence of the electric conductivity was found to follow a simple power law behavior, in accordance with the relation sigma(ac)(omega) = sigma(0) + Lambda(1).omega(s)(2), where s(1) and s(2) are smaller than 1. The thermal activation energies for the electronic conduction were estimated on the basis of the Arrhenius plots. (C) 2014 Published by Elsevier B.V.