Preparation of high purity, low water content fused silica glass

High purity, low water content silica glasses were prepared by melting crystallized, sol–gel-derived powders. Sol–gel-derived amorphous powders have been used to produce high purity silica glass, but a small quantity of water (hydroxyl) tends to remain in the resulting silica glass. High purity crystalline silica powders were prepared by heat-treating the sol–gel-derived amorphous powders in a silica crucible. Both amorphous silica powders and crystallized silica powders were melted in vacuum at 1800 °C for 1 h. The water content of the glass from amorphous silica powders was 44 ppm while that of the glass from the crystallized silica powder was less than 0.1 ppm.