Non-opaque arsenic-free beta-spodumene glass ceramic exhibiting brown-grey coloration
Methods, compositions, and articles provide for LAS-type glass-ceramics having specific thermo-mechanical, optical and coloration characteristics to yield generally brown-grey products. The glass-ceramic materials may include as colorants iron oxide, vanadium oxide, chromium oxide, cobalt oxide, nickel oxide and/or cerium oxide.
1. A method, comprising:
melting a load of vitrifiable raw materials;
fining the load to obtain molten glass;
cooling the molten glass to a temperature sufficient to shape it into a desired shape; and
ceramming of the glass in the desired shape at a maximum temperature between about 960° C. to about 1060° C., to produce a lithium aluminosilicate glass-ceramic material containing beta-spodumene as a predominant crystalline phase, wherein the glass-ceramic material comprises:
60-72% SiO 2 , 18-23% Al 2 O 3 , and 2.5-4.5% Li 2 O; and
0.05-0.20% V 2 O 5 , 0.15-0.30% Fe 2 O 3 , 0.015-0.030% Cr 2 O 3 , 0-0.05% CoO, 0-0.3% NiO, and 0-0.2% CeO 2 ;
wherein the glass-ceramic material, exhibits a brown-grey color with an optical transmittance for a wavelength of 62.5 nm of greater than 2.0% as measured using an illuminant D65, 2° observer test on 4 mm thick glass-ceramic.
2. The method of claim 1 , wherein at least one of:
a green-red hue (a*) of the glass-ceramic is between about −3 to +4,
a blue-yellow hue (b*) of the glass-ceramic is between about −10 to +4, and
said hue is measured in reflection using an illuminant D65, 10° observer test.
3. The method of claim 1 , wherein a lightness L* of the glass-ceramic is between about 15-40 measured in reflection using an illuminant D65, 10° observer test.
4. The method of claim 1 , wherein an integrated visible transmission (Tl) of the glass-ceramic is between about 0.3% to about 6%, wherein said integrated visible transmission (Tl) is measured using an illuminant D65, 2° observer test on 4 mm thick glass-ceramic.
5. The method of claim 1 , wherein an optical transmission of the glass-ceramic, measured at about 625 nm, is higher than about 3.5%, and wherein said optical transmission is measured using an illuminant D65, 2° Observer test on 4 mm thick glass-ceramic.
6. The method of claim 1 ; wherein an optical transmission of the glass-ceramic, measured at about 950 nm, is between about 35-75%, and, wherein said optical transmission is measured using an illuminant D65, 2° observer test on 4 mm thick glass-ceramic.
7. The method of claim 1 , wherein an infra-red optical transmission of the glass-ceramic, measured at about 1600 nm, is greater than 45%, wherein said optical transmission is measured using an illuminant D65, 2° observer test on 4 mm thick glass-ceramic.
8. The method of claim 1 , wherein the glass-ceramic material is substantially free of As 2 O 3 and Sb 2 O 3 .
9. The method of claim 8 , wherein the glass comprises (in weight %): 0-2.5% ZrO 2 , and 1.5-4% TiO 2 .
10. The method of claim 8 , wherein the glass comprises (in weight %): 0-3% MgO, 0-3% ZnO, BaO, 0-2% CaO, 0-1.5% K 2 O, 0-1.5% Na 2 O.
11. The method of claim 8 , wherein the glass comprises (in weight %): 0-0.6% SnO 2 .