Volume relaxation of soda-lime silicate glasses below glass transition temperature

Structural relaxation is a widely known phenomenon that occurs in glassy systems, which still attracts strong industrial and research interest. Although the volume change associated with structural relaxation is well described by the Kohlrausch–Williams–Watts function, its origin, particularly from a glass structural viewpoint, is not clearly defined. To understand the behavior of structural relaxation, in this study, we performed volume relaxation evaluations, Raman spectroscopy assessments, and surface resistivity measurements before and after annealing at 50 K below the glass transition temperature Tg of soda-lime silicate glasses with the same Tg but different fragilities. The combined results indicated that the following changes in the glass structure occurred during the structural relaxation: (1) reorganization of the SiO2 network; (2) transfer of Na ions from the ion channel region into the SiO2 network region; and (3) segmentation of the ion channel region in the modified random network model.