Factors Influencing the Acoustic Properties of Vitreous Silica

• Published in: Journal of applied physics 1968-12, Vol.39 (13), p.5868-5878
• Main Author: Fraser, David B.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1656080

The acoustic properties of various types of commercial vitreous silica have been studied as functions of thermal treatment and impurity-ion concentrations. The properties studied include density, shear-wave attenuation, shear and dilatational wave velocities, and elastic constants. The measurements of acoustic properties are made on small sphere-shaped samples using primarily a technique that sets the sphere into a resonant mode of vibration and then allows the vibration to decay freely. Both frequency and the decrement of the decay are measured. Use of this resonant sphere technique is particularly appropriate to the present study because it permits precise measurements on samples small enough to conveniently undergo laboratory modification, and it permits the study of velocity variations in a single block of material by measurements on many localized samples. The major findings of this study are the following: (1) An increase of one degree in fictive temperature (a parameter assumed to be related to the equilibrium internal configuration of the glass) causes a decrease in the shear velocity of 13–16 ppm. (2) Gross differences of OH content result in differences in shear velocity. Although shear velocity differences could be induced by changing fictive temperature and the gross OH content, shear velocity fluctuations (of the order ± 125 ppm) observed in single large pieces of commercial vitreous silica were not correlated with variation of either fictive temperature or OH content. Attempts to relate fluctuations of shear velocity to differences of Na content were inconclusive.