VITROCERAMIC PLATE

Abstract

A transparent, colorless and non-scattering glass-ceramic plate of lithium aluminosilicate type and containing crystals of β-quartz structure, the chemical composition of which does not contain oxides of arsenic, of antimony and of neodymium, and includes the following constituents within the limits defined below, expressed as weight percentages: SiO.sub.2 55-75%; Al.sub.2O.sub.3 12-25%; Li.sub.2O 2-5%; Na.sub.2O+K.sub.2O 0-<2%; Li.sub.2O+Na.sub.2O+K.sub.2O 0-<7%; CaO 0.3-5%; MgO 0-5%; SrO 0-5%; BaO 0.5-10%; CaO+BaO >1%; ZnO 0-5%; TiO.sub.2 ≦1.9%; ZrO.sub.2 ≦3%;TiO.sub.2+ZrO.sub.2 >3.80%; SnO.sub.2 ≧0.1%; SnO.sub.2/(SnO.sub.2+ZrO.sub.2+TiO.sub.2)<0.1.

Claims

1. A transparent, colorless and non-scattering glass-ceramic plate of lithium aluminosilicate type and containing crystals of β-quartz structure, the chemical composition of which does not contain oxides of arsenic, of antimony and of neodymium, and comprises the following constituents within the limits defined below, expressed as weight percentages: TABLE-US-00004 SiO.sub.2   55-75%, Al.sub.2O.sub.3   12-25%, Li.sub.2O    2-5%, Na.sub.2O + K.sub.2O  0-<2%, Li.sub.2O + Na.sub.2O + K.sub.2O  0-<7%, CaO    0.3-5%, MgO    0-5%, SrO    0-5%, BaO  0.5-10%, CaO + BaO    >1%, ZnO    0-5%, TiO.sub.2  ≦1.9%, ZrO.sub.2    ≦3%, TiO.sub.2 + ZrO.sub.2  >3.80%, SnO.sub.2  ≧0.1%, SnO.sub.2/(SnO.sub.2 + <0.1 ZrO.sub.2 + TiO.sub.2).

2. The glass-ceramic plate as claimed in claim 1, the wherein a light transmission factor of the glass-ceramic plate is at least 75%, and the b* color coordinate of the glass-ceramic plate is at most 20.

3. The glass-ceramic plate as claimed in claim 1, wherein the glass-ceramic has a coefficient of linear thermal expansion of at most 10×10.sup.−7 K.sup.−1 between 20 and 700° C.

4. The glass-ceramic plate as claimed in claim 1, wherein the crystals of β-quartz structure have a size of at most 100 nm.

5. The glass-ceramic plate as claimed in claim 1, wherein a sum of the TiO.sub.2 and ZrO.sub.2 contents is greater than 4%.

6. The glass-ceramic plate as claimed in claim 1, wherein the TiO.sub.2 content is at most 1.8%.

7. The glass-ceramic plate as claimed in claim 1, wherein the SnO.sub.2 content is at least 0.15%.

8. The glass-ceramic plate as claimed in claim 1, wherein the CaO content is at least 0.8%.

9. A glass plate capable of being converted to a glass-ceramic plate as claimed in claim 1 by a ceramization treatment.

10. A cooking device comprising at least one plate as claimed in claim 1.

11. A domestic oven door comprising at least one plate as claimed in claim 1.

12. A fireplace insert comprising at least one plate as claimed in claim 1.

13. A fire-resistant glazing comprising at least one plate as claimed in claim 1.

14. A process for obtaining a glass-ceramic plate as claimed in claim 1, comprising performing a melting step, a forming step, then a ceramization step.

15. The glass-ceramic plate as claimed in claim 1, comprising, expressed as weight percentages: TABLE-US-00005 SiO.sub.2   60-70%, Al.sub.2O.sub.3   19-24%, Li.sub.2O    3-4%, Na.sub.2O + K.sub.2O    0-1%, Li.sub.2O + Na.sub.2O + K.sub.2O    0-5%, CaO   0.3-5%, MgO    0-1%, SrO    0-1%, BaO    1-5%, CaO + BaO    3-5%, ZnO    1-2%, TiO.sub.2  ≦1.9%, ZrO.sub.2    2-3%, TiO.sub.2 + ZrO.sub.2  >3.80%, SnO.sub.2  ≧0.1%, SnO.sub.2/(SnO.sub.2 + <0.06 ZrO.sub.2 + TiO.sub.2).

16. The glass-ceramic plate as claimed in claim 2, wherein the b* color coordinate of the glass-ceramic plate is at most 15.

17. The domestic oven door as claimed in claim 11, wherein the plate is the closest to a chamber of said oven.

Description

[0077] Examples C1 and C2 are comparative examples. Since their contents of titanium and zirconium oxides are too low, the glass-ceramics obtained have an unacceptable haze. Examples 1 to 11 are examples according to the invention.

TABLE-US-00001 TABLE 1 C1 C2 1 2 3 SiO.sub.2 64.9 64.2 63.2 63.1 63.6 Al.sub.2O.sub.3 21.6 21.3 22.0 21.4 21.7 Li.sub.2O 3.70 3.60 3.90 3.70 3.70 Na.sub.2O 0.68 0.68 0.77 0.80 0.71 K.sub.2O 0.25 0.24 0.28 0.25 0.26 MgO 0.29 0.27 0.40 0.37 0.47 CaO 1.31 0.38 1.00 0.49 1.11 BaO 2.04 3.99 2.05 4.27 2.51 ZnO 1.50 1.55 1.60 1.47 1.47 TiO.sub.2 1.41 1.44 1.81 1.53 1.71 ZrO.sub.2 2.00 2.02 2.60 2.29 2.52 TiO.sub.2 + ZrO.sub.2 3.41 3.46 4.41 3.82 4.23 SnO.sub.2 0.31 0.34 0.23 0.33 0.19 SnO.sub.2/(TiO.sub.2 + 0.083 0.089 0.049 0.079 0.043 ZrO.sub.2 + SnO.sub.2) T4 (° C.) 1301 1307 — — — T.sub.c (° C.) 890 890 890 890 880 t.sub.c (min) 35 35 35 35 15 α (10.sup.−7/K) — — — 5.8 5.1 Appearance S S T T T TL (%) — — 78.0 77.7 75.5 b* — — 12.1 13.6 11.9

TABLE-US-00002 TABLE 2 4 5 6 7 8 SiO.sub.2 63.6 64.1 64.4 63.7 64.2 Al.sub.2O.sub.3 21.5 21.1 21.0 21.7 22.0 Li.sub.2O 3.69 3.70 3.69 3.80 3.66 Na.sub.2O 0.84 0.87 0.83 0.65 0.69 K.sub.2O 0.26 0.26 0.27 0.27 0.26 MgO 0.47 0.48 0.48 0.48 0.30 CaO 1.25 1.35 1.33 1.26 1.34 BaO 2.20 2.02 2.01 2.02 2.06 ZnO 1.50 1.50 1.48 1.49 1.41 TiO.sub.2 1.72 1.72 1.72 1.75 1.75 ZrO.sub.2 2.55 2.52 2.40 2.36 2.10 TiO.sub.2 + ZrO.sub.2 4.27 4.27 4.12 4.11 3.85 SnO.sub.2 0.26 0.36 0.41 0.18 0.26 SnO.sub.2/(TiO.sub.2 + 0.057 0.078 0.088 0.042 0.063 ZrO.sub.2 + SnO.sub.2) T4 (° C.) 1280 — 1280 1280 1288 T.sub.c (° C.) 890 870 890 890 890 t.sub.c (min) 35 35 35 35 35 α (10.sup.−7/K) 6.7 7.3 — 5.0 3.1 Appearance T T T T T TL (%) 81.5 — 74.2 81.6 77.3 b* 8.4 — 14.7 8.4 10.4

TABLE-US-00003 TABLE 3 9 10 11 SiO.sub.2 64.0 63.6 64.3 Al.sub.2O.sub.3 21.9 21.9 21.6 Li.sub.2O 3.53 3.51 3.50 Na.sub.2O 0.74 0.72 0.61 K.sub.2O 0.27 0.28 0.27 MgO 0.30 0.40 0.29 CaO 1.35 1.29 1.27 BaO 2.14 2.04 2.02 ZnO 1.49 1.63 1.41 TiO.sub.2 1.75 1.82 1.74 ZrO.sub.2 2.20 2.60 2.36 TiO.sub.2 + ZrO.sub.2 3.95 4.42 4.10 SnO.sub.2 0.30 0.23 0.27 SnO.sub.2/(TiO.sub.2 + 0.071 0.078 0.062 ZrO.sub.2 + SnO.sub.2) T4 (° C.) — — 1300 T.sub.c (° C.) 890 890 890 t.sub.c (min) 35 35 35 α (10.sup.−7/K) 4.4 — 3.1 Appearance T T T TL (%) 82.5 78.0 85.5 b* 7.8 12.1 6.4