Ionic conductivity and glass structure

Abstract

The characteristic properties of vitreous electrolytes are summarised for convenience under the three headings of ‘continuity’, ‘variability’ and ‘vulnerability’. These cover respectively the temperature and compositional dependences of conductivity, and non-additive behaviour such as the mixed alkali effect. Some aspects of glass behaviour are apparently ‘universal’ in the sense that they show little sensitivity to changes in short-range structural order. It is argued here that a recently proposed cluster bypass model (in which pathways for ion migration are located within ‘connective tissue’ surrounding ordered microdomains or clusters) provides a straightforward explanation for all these characteristics of vitreous electrolytes. It also provides a framework for more detailed discussions of conduction mechanisms in the context of percolation theory.