ANALYSIS OF AC CONDUCTIVITY DATA FOR NA2O-CENTER-DOT-3SIO2 GLASS BY STRETCHED EXPONENTIAL AND JONSCHER POWER-LAW METHODS

A comparison is made between two widely used empirical methods of ac conductivity data analysis, namely, the Kohlrausch-Williams-Watts (KWW) approach, which starts from a stretched exponential in the time domain and transforms to the electric modulus function in the frequency domain, and the Jonscher approach, which deals directly with the ac conductivity and looks for a power-law dependence on frequency. By taking one set of data for the sodium trisilicate glass in the temperature range 300-400 K and analyzing it in both ways, the differences between these two methods can be examined. It is found that the KWW approach does not properly fit the data at the higher frequencies, and thus requires an excessively high constant-loss contribution. It is concluded that the Jonscher approach is a more meaningful way to explore the high-frequency range of ac conductivity behavior.