Glass and glass-ceramic materials, articles and method of preparing the same
The present invention relates to novel glass and glass-ceramic materials, articles made from said novel glass-ceramics and to methods of preparing said novel glass-ceramics and articles. Said novel, transparent, translucent or opaque glass-ceramics, which contain, as main crystalline phase, a solid solution of β-quartz or of β-spodumene, essentially have the following composition, expressed as percentages by weight of oxides: 65 to 70% of SiO 2 ; 18 to 23% of Al 2 O 3 ; >4 to 5% of Li 2 O; 0 to <1% of MgO; 1 to 3% of ZnO; 0 to 2% of BaO; 1.8 to 4% of TiO 2 ; 1 to 2.5% of ZrO 2 ; 0.4 to 1% of K 2 O and/or Na 2 O; with, advantageously, an effective and non-excess amount of at least one fining agent. The glass-ceramic material is also characterized by a water content of β-OH higher than 0.2 mm −1 , preferably higher than 0.4 mm −1 .
1. A transparent, translucent or opaque glass-ceramic material containing, as main crystalline phase, solid solution of β-quartz or β-spodumene, consisting essentially of the following composition, expressed as percentages by weight of oxides:
65 to 70% of SiO 2
18 to 23% of Al 2 O 3
>4 to 5% of Li 2 O
0 to <1% of MgO
1 to 3% of ZnO
0 to 2% of BaO
1.8 to 4% of TiO 2
1 to 2.5% of ZrO 2
0.4 to 1% of K 2 O and/or Na 2 O;
with an effective and non-excess amount of at least one fining agent; and (ii) it has a β-OH value of higher than 0.2 mm −1 .
2. The glass-ceramic material according to claim 1 , having β-OH value of higher than 0.4 mm −1 .
3. The glass-ceramic material according to claim 1 , the composition of which contains As 2 O 3 and/or Sb 2 O 3 , as fining agent, in the following percentages by weight:
As 2 O 3 0–1.5
Sb 2 O 3 0–1.5
with As 2 O 3 +Sb 2 O 3 0.5–1.5.
4. The glass-ceramic material according to claim 1 , the composition of which further contains an effective amount of at least one colorant.
5. The glass-ceramic material according to claim 4 , wherein the at least one colorant is selected from the group consisting of CoO, Cr 2 O 3 , Fe 2 O 3 , MnO 2 , NiO, V 2 O 5 , CeO 2 and their mixtures.
6. The glass-ceramic material according to claim 1 , which contains, as main crystalline phase, a solid solution of β-spodumene.
7. An article made from a glass-ceramic material according to claim 1 .
8. An article according to claim 7 , which is selected from the group consisting of a cook-top, a cooking utensil, a microwave oven plate, a fireplace window, a fire-door or fire-window, a pyrolysis oven window and a catalysis oven window.