Elasticity & Anelasticity Of Oxide Glasses

The current understanding of sound properties in glasses is reviewed & compared to that in crystals. Sound damping in oxide glasses is controlled mainly by three processes which in increasing order of the frequency at which they dominate are: The thermal relaxation of defects; Relaxation via anharmonic interactions with the thermal bath; & Hybridization with optic- like vibrations. The former two also affect distinctly on the velocity of sound. The latter relates to the boson peak & the low temperature plateau generally observed in the thermal conductivity. In addition, in silica & other tetrahedrally co-ordinated glasses, the sound velocity tends to increase with temperature, presumably owing to a progressive structural change.