Abstract
Much attention has been focused recently on the apparent differences between ion dynamics in ion-containing glasses as probed by electrical conductivity relaxation (ECR) and by nuclear spin relaxation (NSR) techniques. In both relaxation processes, a power law frequency dependence is observed. Based upon fluctuation–dissipation arguments, the power law exponents should be equivalent. However, experimentally, it appears that the conductivity exponent is generally smaller than the NSR exponent. While an explanation for this discrepancy based upon fundamental differences in the correlation functions probed by the two techniques has been proffered, we show how this discrepancy may simply arise from differing analyses of the ac conductivity. We review several cases taken from the literature in which the conductivity exponent was obtained from analysis of the electrical modulus. We demonstrate how this analysis approach generally underestimates the conductivity exponent. When we instead determine the exponent directly from the ac conductivity, we find near equivalence between the NSR and ECR exponents.