Variables Affecting the Acoustic Loss and Velocity of Vitreous Silica from 4 to 300°K

Abstract

The temperature dependence of acoustic loss and velocity together with the effects on these properties of variations in fictive temperature and OH concentration is shown for vitreous silica over the temperature range 4 to 300°K. The results indicate a reversal in dependency of loss upon fictive temperature and OH concentration between low- and high-temperature regions. Room-temperature loss measurements indicate that the lowest loss values are obtained for silica of fairly high OH content and low fictive temperature. Low-temperature velocity measurements show that variations in OH content affect the velocity by −0.8 cm/sec for each ppm increase in OH content. The rate of change apparently is independent of fictive temperature. Fictive temperature influence on velocity is zero at 80°K with the degree of influence increasing with increasing temperature. At temperatures above 140°K the temperature coefficient of velocity is proportional to the OH concentration and inversely proportional to the fictive temperature. Variations between 67 and 84 ppm/°K are attainable.