IONIC AND POLARONIC HOPPING IN GLASS

In this paper we present conductivity spectra of the ion conducting gl asses B2O3 . 0.56Li(2)O . 0.45LiBr and Ag2S . GeS2 and of the polaron conducting glass 0.2P(2)O(5) . 0.8 (0.89V(2)O(5) . 0.11V(2)O(4)), cove ring a frequency range of more than 13 decades. At frequencies below t he onset of the vibrational motion the spectra of both ion conducting glasses clearly differ from those of the polaronic glass. The dispersi ve conductivity of 0.2P(2)O(5) . 0.8 (0.89V(2)O(5) . 0.11V(2)O(4)) fol lows a simple power-law behavior, the exponent being smaller than one. In contrast, the conductivities of both ion conducting glasses show t he existence of two power-law exponents; one is the Jonscher exponent, the other is larger than unity. The data are interpreted in terms of the 'unified site relaxation model'.