Specific Volume of Fluorine-Doped Silica Glass with Various Fictive Temperatures

Abstract

The specific volume of silica glass was measured as a function of fictive temperature and the concentration of fluorine dopant up to 1550°C and 7.2 mol%, respectively. It was found that the relationship between volume and fictive temperature is strongly influenced by the fluorine dopant. The rate of change in volume to change in fictive temperature, which is negative for pure silica glass, increases linearly with increasing fluorine concentration and then becomes positive at the concentration higher than 3.3 mol%. On the other hand, the relationship between fictive temperature and spatially averaged structure, observed by infrared absorption and Raman spectra, is negligibly affected by the dopant. Such a difference between behaviors in the density and in the vibrational spectra indicates the possibility that with varying fictive temperature, a structural change in the local volume around the doped fluorine is much larger than the average structural change over the whole volume in the bulk.