| CPC C03C 3/089 (2013.01) [C03B 32/00 (2013.01)] | 20 Claims |

|
1. A borosilicate-based composition, comprising:
50-85 mol % SiO2,
>15-30 mol % B2O3,
>0-5 mol % SnO2, and
5.5-20 mol % R2O, where R2O is a total amount of Li2O, Na2O, K2O, Rb2O, and Cs2O,
wherein the composition has a Young's Modulus less than 64 GPa, and the borosilicate-based composition is phase separated into a silicate glass and a borate glass.
|