NONEXPONENTIAL RELAXATION IN IONICALLY CONDUCTING GLASSES - THE DIFFUSION-CONTROLLED RELAXATION MODEL

A model is described which can account for the non-exponential relaxation behaviour usually found in ionically conducting glasses. The microscopic transport mechanism is assumed to involve the motion of interstitialcies; ionic relaxation is presumed to be triggered by the arrival of a diffusing ion at a site, thereby forming an interstitialcy centre. This process of 'target diffusion' naturally leads to a stretched exponential behaviour of the time-dependent dielectric relaxation decay. This model can also account for the behaviour of NMR relaxation in ionically conducting glasses.