Limiting behavior of ac conductivity in ionically conducting crystals and glasses: A new universality

Abstract

The ac conductivity \ensuremath{\sigma}(\ensuremath{\omega}) of three ionically conducting crystalline materials (${\mathrm{NaClZn}}^{2+}$, ${\mathrm{KTaO}}_{3}$:${\mathrm{Co}}^{3+}$,${\mathrm{H}}^{+}$, and ${\mathrm{CeO}}_{2}$:${\mathrm{Gd}}^{3+}$) and two glasses have been studied over an unusually wide temperature range. In all cases, limiting power-law behavior [exponent s=1 in \ensuremath{\sigma}(\ensuremath{\omega})=${\mathrm{\ensuremath{\sigma}}}_{0}$+A${\mathrm{\ensuremath{\omega}}}^{\mathit{s}}$] is observed at relatively low temperatures. It is concluded that this limiting behavior is a universal phenomenon. Available theoretical explanations have been examined and found to be unsatisfactory.