Sol-gel synthesis of fluorine-doped silica glasses with low SiOH concentrations

Fluorine-doped monolithic silica glasses with low SiOH concentrations were prepared by a sol-gel method using hydrofluoric acid as a fluorine source. Without employing dehydration of dried gels using halogen-containing gases, or vacuum sintering, the concentration of SiOH groups was reduced to similar to 10(17) cm(-3) (similar to 1 ppmw), which is comparable to that of synthetic silica glasses mildly dehydrated during their vapor-phase synthesis. The fluorine concentration evaluated from the intensity of the Raman band of SiF groups (similar to 945 cm(-1)) was in the order of similar to 10(20)-10(21) cm(-3). (C) 2011 The Ceramic Society of Japan. All rights reserved.