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

Abstract

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 ∼10¹⁷ cm⁻³ (∼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 (∼945 cm⁻¹) was in the order of ∼10²⁰–10²¹ cm⁻³.