Preparation of High Purity Low Hydroxyl Synthetic Fused Silica Glass

Abstract

High purity low hydroxyl synthetic fused silica glass was prepared by electric melting synthetic crystallized silica powders which were made by the process of hydrolysis, dehydration and calcination of high purity silicon tetrachloride obtained from the by-product of polysilicon production. The structure morphology and hydroxyl content of synthetic silica powders were characterized by XRD and IR, respectively. The experimental results suggest that the silica powders dried at 120°C are amorphous, and the amorphous silica powders are gradually transformed to alpha-cristobalite after sintered in 1250°C, but the crystallization peaks are very strong and sharp until the temperature reaches at 1400°C. The hydroxyl content of silica powders can be effectively reduced by heat-treatment at high temperature.the crystallized silica powders calcined at 1500°C have much lower hydroxyl content than the amorphous silica powders. The hydroxyl group content in the silica glass products melted synthetic pre-crystallized silica powders is 7.3ppm, which meets the requirements for full-spectrum (wavelength from 190nm to 3200nm) transmittance.