Corning Incorporated
Low Inclusion TiO2-SiO2 Glass Obtained by Hot Isostatic Pressing

Abstract:

A silica-titania glass substrate comprising: (i) a composition comprising 5 weight percent to 10 weight percent TiO.sub.2; (ii) a coefficient of thermal expansion (CTE) at 20.degree. C. in a range from -45 ppb/K to +20 ppb/K; (iii) a crossover temperature (Tzc) in a range from 10.degree. C. to 50.degree. C.; (iv) a slope of CTE at 20.degree. C. in a range from 1.20 ppb/K.sup.2 to 1.75 ppb/K.sup.2; (v) a refractive index variation of less than 140 ppm; and (vi) 600 ppm OH group concentration or greater. The substrate can have a mass of 1 kg or greater and less than 0.05 gas inclusions per cubic inch via a method comprising (i) forming the substrate from soot particles comprising SiO.sub.2 and TiO.sub.2, and (ii) subjecting the substrate to an environment having an elevated temperature and an elevated pressure for a period of time until the substrate comprises less than 0.05 gas inclusions per cubic inch.