Ionic and polaronic hopping in glass

In this paper we present conductivity spectra of the ion conducting glasses 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)), covering a frequency range of more than 13 decades. At frequencies below the onset of the vibrational motion the spectra of both ion conducting glasses clearly differ from those of the polaronic glass. The dispersive conductivity of 0.2P(2)O(5) . 0.8 (0.89V(2)O(5) . 0.11V(2)O(4)) follows a simple power-law behavior, the exponent being smaller than one. In contrast, the conductivities of both ion conducting glasses show the 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'.