NON-EXPONENTIALITY OF THE IONIC MIGRATION RELAXATION IN GLASSES

Superionic glasses are characterized by mobile ionic species, which have a high mobility compared with those of the rigid host matrix below the glass transition temperature T(g). The diffusion of the mobile ions on pathways built within the glassy network gives rise to relaxational losses and dispersions in the mechanical spectra, which are usually broader than a Debye behaviour. The anelastic behaviour supplies useful information on the characteristics of the ionic motion and show a decreasing non-exponentiality with increasing cation concentration in silver borate glasses. An analysis of the observed peculiarities in glassy and crystalline ionic conductors reveals that, among the possible sources for the non-exponentiality, the topological and the positional disorder present in the diffusion pathways plays a relevant role.