Infrared reflectance studies of ionic conductive glasses. Network structure and cation dynamics

The results of our infrared reflectance studies of single and mixed alkali borate glasses are reviewed and discussed in the context of the network structure and the interactions between alkali cations and their sites in the glass. In particular, we focus on the strong influence of the alkali cation type, content, and alkali subsitution on the structure of the network building units. The dominant role of alkali ions also emerges from the analysis of their motion bands active in the far-infrared. Thus, the presence of two different distributions of anionic site environments was found to characterise the single alkali borate glasses. The corresponding analysis of the mixed alkali glass spectra revealed the existence of interactions between the dissimilar alkalis, which strongly affect their bonding characteristics. The new bonding requirements drive the glass network to perform suitable rearrangements, leading eventually to non-linear variations of the network structure with alkali substitution.