Analysis of mechanical losses due to ion-transport processes in silicate glasses

Ion-transport processes in silicate glasses containing alkali and alkaline-earth ions are studied using dynamic mechanical thermal analysis. The mechanical loss spectra are analyzed with respect to the frequency response, the height, and the activation energy of the loss peaks. It is found that the frequency response of all loss peaks is very similar, independent of the glass composition and the nature of the transport process. In the spectra of many mixed alkali-alkaline earth glasses, the low-temperature loss peak seems to be ''suppressed'' by intense high-temperature losses. This feature is well known from the mechanical loss spectra of mixed alkali glasses. We show that there is a correlation between this "suppression" effect and the difference between the activation energies of the low-temperature and the high-temperature peak. Furthermore, the "suppression" of the low-temperature losses seems to;be accompanied by the occurrence of additional intermediate-temperature losses originating from the interaction of monovalent and divalent cations.