Structural and electrical properties of lithium substituted niobo vanadate glasses doped with nickel ferrite

This article reports on the impedance spectroscopic study of lithium substituted niobo vanadate glasses and their nickel ferrite doped counterparts using Cole-Cole (Nyquist) plots and electrical conductivity analysis. The glass samples were prepared using the melt quenching technique. Differential scanning calorimetry and x-ray diffractometry were used to determine the thermal properties and the amorphous nature of the glass samples, respectively. Using impedance spectroscopy, the nature and extent of inhomogeneity were investigated and correlated with transport properties in the glasses at different temperature ranges (120-240 degrees C). Equivalent circuit analysis was adopted to study the glass materials further. The introduction of a constant phase element (Q) in a modified RQ circuit describes the Cole-Cole plot well, which accounts for the frequency dependence of dielectric response. The electrical conductivity analysis is performed using Jonscher's law and Arrhenius plots. The exponent "n" was found to be a decreasing function of temperature. The DC part of the electrical conductivity is analyzed on the basis of alkali ion distance and alkali-oxygen distance. The activation energy estimated by the Arrhenius equation is found to decrease from 0.54 to 0.39 eV as lithium content increases. The estimated mobility of lithium ions was found to decrease as the lithium content increases in both doped and undoped cases.