Patent ID: 8664130

Claim:
An IX, β-spodumene glass-ceramic comprising: a. a nominal composition, in mole percent (mole %), comprises: i. 67-74 SiO 2 ; ii. 11-15 Al 2 O 3 ; iii. 5.5-9 Li 2 O; iv. 0.5-2 ZnO; v. 2-4.5 MgO; vi. 3-4.5 TiO 2 ; vii. 0-2.2 B 2 O 3 ; viii. 0-1 Na 2 O; ix. 0-1K 2 O; x. 0-1 ZrO 2 ; xi. 0-4% P2O5 xii. 0-0.1 Fe 2 O 3 ; xiii. 0-1.5 MnOx; and xiv. 0.08-0.16 SnO 2 ; b. a ratio: [ Li 2 ⁢ O + Na 2 ⁢ O + K 2 ⁢ O + MgO + ZnO ] [ Al 2 ⁢ O 3 + B 2 ⁢ O 3 ] between 0.7 to 1.5; c. a ratio: [ TiO 2 + SnO 2 ] [ SiO 2 + B 2 ⁢ O 3 ] greater than about 0.04; d. one or more β-spodumene solid solutions comprising: i. at least about 70 wt % of the crystalline phases of the glass-ceramic and ii. one or more Li 2 O:Al 2 O 3 :SiO 2 ratios between about 1:1:4.5-1:1:8; e. at least one Ti-containing crystalline phase comprising: i. about 2.5-8 wt % of the crystalline phases of the glass-ceramic, ii. an acicular morphology exhibiting a length≧about 50 nm, and iii. rutile; f. an opacity comprising ≧about 85% over the wavelength range of 400-700 nm for an about 0.8 mm thickness; g. a depth of layer (DOL)≧about 2% of an overall thickness of an article of the IX, β-spodumene glass-ceramic and a compressive stress (σ s ) in at least a portion of a surface of the article of at least about 300 MPa; and h. optionally, one or more crystalline phase comprising: i. up to about 10 wt % of the crystalline phases of the glass-ceramic and ii. a spinel structure.