Corning Incorporated
Transparent hexagonal stuffed .beta.-quartz glass-ceramic articles having large grain size

Abstract:

A glass-ceramic article includes 50 mol. % to 80 mol. % SiO.sub.2; 10 mol. % to 25 mol. % Al.sub.2O.sub.3; 5 mol. % to 20 mol. % MgO; 0 mol. % to 10 mol. % Li.sub.2O; and 1 mol. % to 3 mol. % of a nucleating agent. The nucleating agent is selected from the group consisting of ZrO.sub.2, TiO.sub.2, SnO.sub.2, HfO.sub.2, Ta.sub.2O.sub.5, Nb.sub.2O.sub.5, Y.sub.2O.sub.3, and combinations thereof. The nucleating agent may comprise greater than or equal to 50% ZrO.sub.2 and less than 50% of at least one compound selected from the group consisting of TiO.sub.2, SnO.sub.2, HfO.sub.2, Ta.sub.2O.sub.5, Nb.sub.2O.sub.5, Y.sub.2O.sub.3, and combinations thereof. The glass-ceramic article may have a molar ratio of MgO to Li.sub.2O of greater than or equal to 1:1. The glass-ceramic article may satisfy the relationship 0.85.ltoreq.(MgO (mol %)+Li.sub.2O (mol %))/Al.sub.2O.sub.3 (mol %).ltoreq.1.2. The glass-ceramic article may comprise a crystalline phase comprising hexagonal stuffed .beta.-quartz and glass.