Corning Incorporated
PHASE SEPARABLE GLASS COMPOSITIONS HAVING IMPROVED MECHANICAL DURABILITY

Abstract:

A glass composition includes: greater than or equal to 53 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 9 mol % and less than or equal to 20 mol % Al.sub.2O.sub.3; greater than or equal to 10 mol % and less than or equal to 17.5 mol % B.sub.2O.sub.3; greater than or equal to 0 mol % Li.sub.2O; greater than or equal to 0 mol % Na.sub.2O; and greater than 0.1 mol % of a nucleating agent. The sum of Li.sub.2O and Na.sub.2O in the glass composition may be greater than or equal to 8 mol % and less than or equal to 30 mol %. The amount of Al.sub.2O.sub.3 minus the sum of R.sub.2O and RO in the glass composition may be greater than or equal to -3 mol %. The glass composition may be phase separable and may have an improved K.sub.Ic fracture toughness.