ANALYSIS OF ELECTRICAL RELAXATION IN GLASSES AND MELTS WITH LARGE CONCENTRATIONS OF MOBILE IONS

Various analyses of or fits to electrical relaxation data for a model Li2O-Al2O3-2SiO(2) glass were tried. These included three-parameter fits using Kohlrausch-Williams-Watts (KWW) and Cole-Davidson (CD) distributions of electric field relaxation times, along with a four-parameter sigma'(omega(n)) fit using the distribution implicit in the Jonscher expression for the frequency dependence of the real part of the complex conductivity, sigma' = sigma + A omega(n). In the frequency range 10(-2) less than or equal to omega<tau> less than or equal to 10(2), where <tau> is the mean electric field relaxation time, the KWW fit was best, the sigma'(omega(n)) fit second best and the CD fit the worst. Because the sigma'(omega(n)) fit predicts qualitatively incorrect relaxational behavior at low frequencies, it is suggested that this method of data analysis not be used. It was noted that the dependence of sigma' on omega(1) observed for ionically conducting solids at very high frequencies or very low temperatures makes a nearly negligible contribution to the relaxation of the electric field.