Ionic transport in glasses

Glasses with good ionic conduction have always a high concentration of monovalent ions that are acting as charge carriers. Because of this high concentration, ionic transport is determined not only by interactions between the ions and the glass network but also by correlations between the moving ions themselves. Starting with considerations on chemical bonding and structure, local motions and long range transitions of mobile ions are distinguished. Ion motions are considered in the light of general aspects of transport processes in solids such as interactions of moving ions with the surrounding network or with other mobile ions and the influence of structure on the geometry of transport pathways. Various types of correlated motions and their importance for ionic transport and related phenomena such as tracer diffusion, conductivity and frequency response and its dependence on glass composition and temperature are discussed.