Abstract: The present invention relates to a boroaluminosilicate glass which exhibits excellent UV transmission. In particular, the present invention is directed at an alkali fluorine-doped boroaluminosilicate glass comprising, in mole percent on the oxide basis, of 30-80% SiO2, 1-20% Al2(O, F2)3, 5-35% B2O3, 5-20% R2O, where R is Li, Na, K, Rb or Cs, and an amount of up to 12% of F. The glass possesses an R/Al molar ratio of between 0.4 to 3 and an F/O molar ratio of no greater than 0.35. The alkali fluorine-doped boroaluminosilicate glass of the present invention exhibits a UV transmission at 300 nm, of greater than 80%/mm.

Abstract: 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 migration, especially alkali metal ion, particular sodium ion, migration at elevated temperature. The processes are particularly useful in the production and working of high purity fused silica material required of a very low sodium concentration. The barrier layer material is prepared by using an aqueous suspension comprising silica soot.