ac conductivity spectra of alkali tellurite glasses: composition-dependent deviations from the Summerfield scaling

We report, for the first time, deviations from the Summerfield scaling in the ac conductivity spectra of single ion conducting glasses. In contrast to the extensively studied borate and germanate glasses, the conductivity isotherms of alkali tellurite glasses do not superimpose upon application of the Summerfield scaling. The deviations depend on the alkali oxide content as well as on the type of the alkali ion. Remarkably, our experimental findings differ considerably from theoretical results describing the hopping dynamics of charge carriers in random barrier landscapes.