Conductivity studies of lithium zinc silicate glasses with varying lithium contents

The electrical conductivity of lithium zinc silicate (LZS) glasses with composition, (SiO2)0.527 (Na2O)0.054(B2O3)0.05(P2O5)0.029(ZnO)0.34−x(Li2O)x (x = 0.05, 0.08, 0.11, 0.18, 0.21, 0.24 and 0.27), was studied as a function of frequency in the range 100 Hz–15 MHz, over a temperature range from 546–637 K. The a.c. conductivity is found to obey Jonscher’s relation. The d.c. conductivity (σd.c.) and the hopping frequency (ωh), inferred from the a.c. conductivity data, exhibit Arrhenius-type behaviour with temperature. The electrical modulus spectra show a single peak, indicating a single electrical relaxation time, τ, which also exhibits Arrhenius-type behaviour. Values of activation energy derived from σd.c., ωh and τ are almost equal within the experimental error. It is seen that σd.c. and ωh increase systematically with Li2O content up to 21 mol% and then decrease for higher Li2O content, indicating a mixed alkali effect caused by mobile Li+ and Na+ ions. The scaling behaviour of the modulus suggests that the relaxation process is independent of temperature but depends upon Li+ concentration.