Patent ID: 6248678
Filing Date: 2001-06-19
Classification: C03C

Abstract:
A transparent glass-ceramic containing solid solution spinel as a predominant crystal phase and exhibiting a linear coefficient of thermal expansion (CTE) over the temperature range 25-300.degree. C. between 22-32.times.10.sup.-7 /.degree. C., the glass-ceramic comprising the following composition as calculated in weight percent on an oxide basis: 60-75 SiO.sub.2, 8-20 Al.sub.2 O.sub.3, 2-10 ZnO, 1-6 MgO, 1-10 TiO.sub.2, 0-6 ZrO.sub.2, 0-3 BaO, ZnO+MgO in combination being greater than or equal to about 5.5, TiO.sub.2 +ZrO.sub.2 in combination being greater than or equal to about 4, and the molar ratio of (R.sub.2 O+RO)Al.sub.2 O.sub.3 being between about 0.5 and 1.5, where R.sub.2 O is the sum of the moles of alkali oxides and RO is the sum of the moles of alkaline earth oxides plus ZnO.