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

The deposition properties of SiO 2 -GeO 2 , SiO 2 -B 2 O 3 and SiO 2 -TiO 2 particles produced by the flame hydrolysis reaction of SiCl 4 -GeCl 4 (10 mol%), SiCl 4 -BBr 3 (8 mol%) and SiCl 4 -TiCl 4 (4 mol%) were investigated with emphasis on the effect of substrate temperature T s (200-800°C). The GeO 2 and B 2 O 3 components were found to be deposited with crystalline structure for T s <400°C, but with noncrystalline form dissolved in SiO 2 glass networks for T s higher than 400°C; the dissolved GeO 2 and B 2 O 3 concentrations increased with increasing T s . The TiO 2 component had noncrystalline form, irrespective of T s , and no significant dependence of the dissolved TiO 2 concentration on T s was observed. An interpretation of the experimental results and possible structural models for the SiO 2 -GeO 2 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.