ION-TRANSPORT IN SUPERIONIC CONDUCTING GLASSES

Models of the dependence of conductivity with modifier content in glas ses are reviewed in this paper. It is shown that the recent 'site memo ry effect' model provides very good fits of experimental data by predi cting a power law dependence of dc conductivity or a logarithmic depen dence of activation energy of conductivity on modifier content. The co nsequence of the mixed alkali effect (MAE) on frequency-dependent prop erties is emphasized. The coupling factors (for nuclear magnetic reson ance-spin lattice relaxation, n(s), and for electrical conductivity re laxation, n(sigma)) are shown to be constant and independent of compos ition. This may indicate that the mobile ion concentration remains pra ctically constant when one cation is replaced by another. The MAE woul d then be caused by a change in the mobility of mobile ions.