Local structure and electrical response of Rb and (Rb, Ag) germanate glasses: electrical conductivity relaxation

Abstract

Correlation between local structure (interatomic distances and structural disorder around the cations) and electrical conductivity relaxation was examined for two glass series: xRb 2O · (1 − x)GeO 2 with x = 0.01 − 0.20 and 0.2( yAg ·(1 − y)Rb) 2O · 0.8GeO 2 with y = 0.0−1.0. The Kohlrausch parameter, β, which represents electrical relaxation in the vicinity of dc (Maxwell) relaxation time, decreases with increasing mobile ion concentration but does not correlate well with the activation energy of dc conductivity, nominal mobile ion-ion distance, local structural disorder or the ‘unoccupied volume’. The non-ideal electrical relaxation does not arise from the distribution of relaxation time alone. Instead, it appears to follow the trend of Coulomb interaction between mobile ions and their charge compensation centers. For the (Rb, Ag) germanate glass series β is greater for the mixed than for the single mobile ion glasses. It correlates rather well with the high frequency dielectric constant, again indicating its primary origin in the Coulomb interaction between mobile ions and their charge compensation centers.