Structural relaxation in silicate glasses and melts: High-temperature Raman spectroscopy

By combining both isothermal and rate heating experiments, structural relaxation times were determined in the glass transition range with in situ, high-temperature Raman spectroscopy. The obtained relaxation times agree well with the shear relaxation times obtained from viscosity data. Thus, the time scale for viscous flow is the same as the time scale of the rearrangement of the silicate network structure toward chemical equilibrium. This demonstrates that Si-O bond breaking is the primary control on silicate melt viscosity.