Patent ID: 7107793

Claim:
A method for the manufacture of a lithium-aluminosilicate glass ceramic comprising at least 70 vol.-% of keatite mixed crystals, the method comprising the following steps: casting a lithium-aluminosilicate base glass comprising (in wt.-%): SiO 2 : 50–75 Al 2 O 3 : 17–30 Li 2 O: 2–8 B 2 O 3 : 0–5 P 2 O 5 : 3–15 at least one of SnO 2 , ZrO 2 , and TiOa 2 : 0.1–7 at least one of Na 2 O, K 2 O, and Cs 2 O: 0–6 at least one of CaO, MgO, SrO, BaO, and ZnO: 0–8 at least one of refining agents: 0–3 at least one of coloring oxides and other oxides: 0–5 into a mold; annealing the base glass for nucleation at a nucleation temperature of about 600 to 900° C.; annealing for keatite formation at a temperature of 800 to 1300° C., wherein the temperature and the duration of annealing for keatite formation is selected so as to yield a glass ceramic comprising at least 70 vol.-% of keatite mixed crystals and having a coefficient of thermal expansion between 1.5×10 −6 /K and 3×10 −6 /K in the range between 20° C. and 700° C.; and cooling to room temperature.