Transparent lithium glass-ceramic material, production and use thereof
A lithium-containing, transparent glass-ceramic material is provided. The material has low thermal expansion and has an amorphous, lithium-depleted, vitreous surface zone. The zone is at least 50 nm thick on all sides and encloses a crystalline interior, which has high transmission. The material includes a transition region connecting the zone and the interior.
1. A lithium-containing, transparent glass-ceramic material comprising an amorphous, lithium depleted, predominantly vitreous surface zone that is at least 50 nm thick on all sides and surrounds a crystalline interior, wherein the vitreous surface zone is connected to the crystalline interior by a transition region, and wherein the vitreous surface zone has a consistent thickness on all sides.
2. The glass-ceramic material of claim 1 , wherein the vitreous surface zone has a thickness of 50 to 5000 nm.
3. The glass-ceramic material of claim 1 , wherein the thickness is not more than 200 nm.
4. The glass-ceramic material of claim 1 , comprising a principal crystal phase of more than 50% by weight of beta-quartz solid solutions.
5. The glass-ceramic material of claim 4 , wherein the beta-quartz solid solutions have a lattice constant from 5.18 A to 5.19 A.
6. The glass-ceramic material of claim 1 , wherein the vitreous surface zone comprises not more than 10% by weight of crystals and the crystalline interior comprises at least 50% by weight of crystals.
7. The glass-ceramic material of claim 4 , further comprising a refractive index difference between a glass phase and the principal crystal phase, in a range between 0.001 and 0.05.
8. The glass-ceramic material of claim 1 , wherein the vitreous surface zone has a lower refractive index than the crystalline interior.
9. The glass-ceramic material of claim 1 , further comprising a difference in refractive indices between a residual glass phase of the vitreous surface zone and a crystal phase of the interior that is between +/−0.3.
10. The glass-ceramic material of claim 1 , wherein the high transmission is greater than 0.75 at 400 nm in the visible wavelength range based on a wall thickness of 4 mm.
11. The glass-ceramic material of claim 1 , wherein the glass-ceramic comprises nucleating agents selected from the group consisting of Ti0 2 , Zr0 2 , SnO, and combinations of Ti0 2 and Zr0 2 .
12. The glass-ceramic material of claim 1 , further comprising crystals having a uniform distribution in the interior and particle sizes that deviate between +/−5%.
13. The glass-ceramic material of claims 1 , wherein the glass-ceramic material comprises a ceramicized lithium aluminosilicate (LAS) glass.
14. The glass-ceramic material of claim 1 , further comprising a compositional range, in % by mass, of:
50-75.0 SiO 2 ,
15-28.0 Al 2 O 2 ,
0-2.0 B 2 0 3 ,
0-1.0 F,
2.0-6.0 Li 2 O,
0-6.5 CaO +SrO +BaO,
0-7.0 TiO 2 ,
0-5.0 ZrO 2 ,
0-4.0 ZnO,
0-3.0 Sb 2 O 3 ,
0-3.0 MgO,
0-3.0 SnO 2 ,
2.0-7.0 TiO 2 +ZrO 2 +Sn0 2 ,
0-8.0 P 2 O 5 ,
0-1.5 AS 2 0 3 ,
0-1.0 Nd 2 O 3 ,
0-4.0 Na 2 0 +K 2 0, the respective fractions being situated within the ranges indicated hereinafter,
0-4.0 Na 2 O,
0-4.0 K 2 0, and
a water content of 0.01%-0.08% by mass.
15. The glass-ceramic material of claim 14 , further comprising an Fe 2 0 3 content of 0.007% to 1.00% by weight.
16. The glass-ceramic material of claim 1 , wherein the vitreous surface zone is formed in a kiln atmosphere having a controlled OH and/or hydrogen content of between 1% to 20% by volume.
17. The glass-ceramic material of claim 16 , wherein the controlled OH and/or hydrogen content comprises H 2 0.
18. The glass-ceramic material of claim 1 , wherein the vitreous surface zone is formed in a kiln atmosphere having a controlled OH and/or hydrogen content of between 0.1% to 1% by volume.
19. The glass-ceramic material of claim 18 , wherein the controlled OH and/or hydrogen content comprises H 2 0.
20. A lithium-containing, transparent glass-ceramic material comprising an amorphous, lithium depleted, predominantly vitreous surface zone having a consistent thickness on all sides that is more than 1500 nm and less than 5000 nm thick and surrounds a crystalline interior, wherein the vitreous surface zone is connected to the crystalline interior by a transition region.