DISTRIBUTION OF IONIC CHARGE-CARRIERS AND MIGRATION BARRIERS IN BINARY ALKALI SILICATE-GLASSES

Likely spatial distributions of network-modifying (and mobile) cations in (oxide) glasses are discussed here. At very low modifier concentra tions, the ions form dipoles with non-bridging oxygen centres while, a t higher levels of modification, the cations tend to order as a result of Coulombic interactions. Activation energies for cation migration a re calculated, assuming that the ions occupy (face-sharing) octahedral sites. It is found that conductivity activation energy decreases mark edly with increasing modifier content, in agreement with experiment.