Acoustic Loss of Vitreous Silica at Elevated Temperatures

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Abstract
The resonant sphere technique has been used to measure the temperature variation of the acoustic shear loss of vitreous silica up to 1100°C. The acoustic loss near room temperature, which is on the high temperature end of the 50°K loss peak, was found to be dependent upon fictive temperature, the state of oxidation, and, through the state of oxidation, may be dependent upon the OH or Cl content. A minimum loss occurs above room temperature and for synthesized silicas the loss level is comparable to single‐crystal materials. Above the minimum loss, the loss process appears to be thermally activated with an approximate activation energy of 0.5 eV. This low activation energy suggests the diffusion of a network modifier such as hydrogen as a possible cause of the high temperature loss.