Deposition Properties of High-Silica Particles in the Flame Hydrolysis Reaction for Optical Fiber Fabrication

Abstract

The deposition properties of SiO2-GeO2, SiO2-B2O3 and SiO2-TiO2 particles produced by the flame hydrolysis reaction of SiCl4-GeCl4 (10 mol%), SiCl4-BBr3 (8 mol%) and SiCl4-TiCl4 (4 mol%) were investigated with emphasis on the effect of substrate temperature Ts (200-800°C). The GeO2 and B2O3 components were found to be deposited with crystalline structure for Ts<400°C, but with noncrystalline form dissolved in SiO2 glass networks for Ts higher than 400°C; the dissolved GeO2 and B2O3 concentrations increased with increasing Ts. The TiO2 component had noncrystalline form, irrespective of Ts, and no significant dependence of the dissolved TiO2 concentration on Ts was observed. An interpretation of the experimental results and possible structural models for the SiO2-GeO2 system (the most important system for optical fiber fabrication) are presented, taking account of the saturated vapor pressure of each component at high temperature in the oxy-hydrogen flame.