Activation enthalpies of ionic conductivities in Na–Rb alumino-germanate and borate glasses were reviewed. Correlations between the activation enthalpy and the ratio of average distances between like alkali ions, <dion>, to the average distances between network–former atoms, <dnetwork>, were elucidated for single- and mixed-alkali glasses. The Haven ratio was shown to decrease with decreasing <dion>/<dnetwork>. Interstitial-like and substitutional-like sub-networks of ion sites were suggested. The experimentally observed dependence of the Haven ratio on <dion>/<dnetwork> was consistently reproduced by a Monte Carlo simulation of ion dynamics on this random network including single and collective ion jumps.

Towards a Universal Behaviour of Ion Dynamics in Na- and Rb-Oxide Glasses. S.Voss, S.V.Divinski, Á.W.Imre, H.Mehrer, J.N.Mundy: Solid State Ionics, 2005, 176[15-16], 1383-91