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

High-purity fluorine-doped silica glass bodies in the form of tubes, rods, and plates for fiber optics and IR applications were fabricated by an alkoxide-colloidal sol-gel process with Aerosil with a specific surface area of 200 m 2 /g and tetraethyl orthosilicate as starting materials. By fluorinating porous xerogels in a C 2 Cl 3 F 3 +O 2 gas mixture, silica glass containing 10 -2 to 10 -3 ppm transition metals, 0.45-0.6 wt%, 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 technique.