THE EFFECT OF OH CONCENTRATION ON THE LOW-TEMPERATURE HEAT-CAPACITY AND RAMAN-SCATTERING OF VITREOUS SILICA

Heat capacity of three different samples of vitreous silica namely, Spectrosil-B containing 1200 ppm OH, Heralux containing 130 to 180 ppm OH and Spectrosil-WF containing 20 ppm OH has been measured in the temperature range of 1.5 to 20 K using heat pulse technique to determine the effect of OH concentration on heat capacity. Our results indicate that the specific heats of spectrosil-B and Spectrosil-WF are almost identical and are 20% higher than those of Heralux. We, therefore, conclude that the variations in the specific heats, of commercially available vitreous silica sold under different trade names, are not due the variation in the amount of OH present in them. The Raman scattering from Spectrosils are almost identical in the frequency range from 10cm-1 to 140 cm-1. The Raman coupling constant has been determined and its form is different from that predicted by Martin-Brenig theory. © 1990.