UC Davis

The relaxation behavior of different properties such as stress, volume and structure are known to be strongly coupled in silicate glasses and liquids. However, recent studies have raised the question as to whether the relaxation behavior of these properties are truly equivalent. In this study, density, Raman spectroscopy and viscosity measurements are utilized to probe, respectively, the volume, structural and shear relaxation behavior of a soda lime silicate glass of standard float composition at temperatures below its calorimetric glass transition. The results, when taken together, indicate that the lowering of fictive temperature of the glass during aging results in a Q-species disproportionation of the type Q^2+Q^4 → 2Q^3, and all three relaxation processes are characterized by similar average timescales. Although these processes appear to be causally related, the non-exponential nature of Q-speciation and volume relaxation is found to be significantly different, which is hypothesized to be a manifestation of the corresponding differences in their associated length scales.