Patent ID: 7476633

Claim:
A glass-ceramic material having β-spodumene solid solution as the predominant crystalline phase, a CTE from about 25 to about 700° C. of about 10-30×10 −7 /° C., and a composition, by weight of the total composition, comprising: 55-68% SiO 2 ; 18-24% Al 2 O 3 ; 3.3-4.1% Li 2 O; 1.5-4.0% ZnO; 1.5-5.0% MgO; 2-5% TiO 2 ; 0-2% ZrO 2 ; 0-5% B 2 O 3 ; 0-8% P 2 O 5 ; 0-2% Na 2 O, 0-2% K 2 O; 0-0.1% As 2 O 3 ; 0-0.1% Sb 2 O 3 ; and components resulting from effective amount of at least one fining agent, wherein: the total of B 2 O 3 and P 2 O 5 is at least 1.5% by weight, the total of MgO and ZnO is at least about 3.5% by weight, the total of Na 2 O and K 2 O is less than about 3.0% by weight, the total of P 2 O 5 , B 2 O 3 , Na 2 O and K 2 O is less than about 11% by weight, the weight ratio of the sum total of Na 2 O+K 2 O to the sum total of P 2 O 5 +B 2 O 3 ( Na 2 ⁢ O + K 2 ⁢ O B 2 ⁢ O 3 + P 2 ⁢ O 5 ) is less than about 0.5.