Suppressing monovalent metal ion migration using aluminum-containing barrier layer

摘要

Disclosed is a process for suppressing monovalent metal ion migration between inorganic materials by placing a barrier layer containing Al2O3 and SiO2 between the inorganic materials. Also disclosed is a process for making silica-containing body comprising a step of forming a barrier layer containing Al2O3 and SiO2 over the soot-receiving substrate before the laydown of the fused silica boule. The barrier layer is effective in suppressing monovalent metal ion, especially alkali metal ion, particularly sodium migration at elevated temperature. The processes are particularly useful in the production and working of HPFS(R) materials required of a very low alkali metal, especially sodium, concentration.