The Mixed Alkali Effect Revisited - An New Look At An Old Problem

Progress is reported in resolving the long-standing problem of the mixed alkali effect. Previously, theories have failed to encompass all aspects of this phenomenon which involves both a loosening up of glass structure and the reduction of ionic diffusivities. The recently proposed "dynamic structural model", however, reconciles the electrical and structural anomalies by recoupling ion hopping processes to localized site relaxations in glass. The appearance of a mismatch energy and site memory effects leads to successful prediction of the diffusivity "crossover".