High-purity fluorine-doped silica glass prepared by sol-gel processing

High-purl fluorine-doped silica glass bodies in the form of tubes, rods, an d plates for fiber optics and IR applications were fabricated by an alkoxid e-colloidal sol-gel process using Aerosil with a specific surface area of 2 00 m(2)/g and tetraethyl orthosilicate as starting materials. By fluorinati ng porous xerogels in a C2Cl3F3 + O-2 gas mixture, silica glass containing 10(-2) to 10(-3) ppm transition metals, 0.45-0.6 wt % F, 17 ppm Cl, and 0.1 to 1.0 ppm hydroxyl groups was prepared. Preforms for optical fibers were fabricated from sol-gel-prepared silica-glass tubes by the outdiffusion tec hnique.