Conductivity and dielectric relaxation in niobium alkali borate glasses

Abstract

The frequency and temperature dependent conductivity investigations for alkali niobium borate glasses of composition xNb 2O 5·(30− x)M 2O·70B 2O 3 (where M=Li, Na; x=0, 4, 8 mol%) have been carried out using impedance spectroscopy (IS). The complex impedance data have been analyzed by using both the conductivity and the electric modulus formalisms. The conductivity decreases with the decrease in M 2O:Nb 2O 5 ratio. The effect of temperature on the scaling of dielectric modulus indicates that the conductivity relaxation mechanism is temperature independent. The overlapping of the normalized peaks corresponding to impedance and electric modulus and the identical values of thermal activation energy for conduction and relaxation suggest the single mechanism for the dynamic processes occurring in the present glasses. The variation of density, molar volume and glass transition temperature with glass composition has also been reported to supplement the conductivity results.