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Anharmonic vs. relaxational sound damping in glasses: II. Vitreous silica

R. Vacher·E. Courtens·M. Foret
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Abstract

The temperature dependence of the frequency dispersion in the sound velocity and damping of vitreous silica is reanalyzed. Thermally activated relaxation accounts for the sound attenuation observed above 10 K at sonic and ultrasonic frequencies. Its extrapolation to the hypersonic regime reveals that the anharmonic coupling to the thermal bath becomes important in Brillouin-scattering measurements. At 35 GHz and room temperature, the damping due to this anharmonicity is found to be nearly twice that produced by thermally activated relaxation. The analysis also reveals a sizeable velocity increase with temperature which is not related with sound dispersion. This suggests that silica experiences a gradual structural change that already starts well below room temperature.

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R. Vacher, E. Courtens, M. Foret. 2005-11-22. Anharmonic vs. relaxational sound damping in glasses: II. Vitreous silica. https://doi.org/10.1103/physrevb.72.214205

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