Method for the preparation of glasses and glass ceramics with SiO2 as main crystal phase
The invention relates to a method for the preparation of a glass ceramic or a glass, which comprise cerium ions and are suitable in particular for the preparation of dental restorations, the fluorescence properties of which largely correspond to those of natural teeth. The invention also relates to a glass ceramic and a glass which can be obtained using the method according to the invention, the use thereof as dental material and in particular for the preparation of dental restorations, as well as a glass-forming composition which is suitable for use in the method according to the invention.
1. Method for the preparation of a glass ceramic with SiO 2 as main crystal phase or a glass which comprises nuclei for the crystallization of SiO 2 , which comprises a step in which a melt of a starting glass is formed from a glass-forming composition which comprises SiO 2 , Li 2 O, a cerium compound and at least one reducing agent.
2. Method according to claim 1 , in which the at least one reducing agent is a compound which comprises at least one oxidizable carbon atom.
3. Method according to claim 1 , in which the at least one reducing agent is an acetylacetonate.
4. Method according to claim 1 , in which the starting glass comprises 0.1 to 7.0 wt.-% cerium ions, calculated as CeO 2 .
5. Method according to claim 1 , in which the starting glass comprises 0 to 11.0 wt.-% alkaline earth metal oxide.
6. Method according to claim 1 , in which the starting glass comprises at least one of the following components in the given quantities:
Component
wt. %
SiO 2
58.0 to 92.0
Li 2 O
2.0 to 10.0
CeO 2
0.1 to 7.0
Tb 4 O 7
0 to 2.0
Me I 2 O
0 to 13.0
Me II O
0 to 11.0
Me III 2 O 3
0 to 10.0
Me IV O 2
0 to 21.0
P 2 O 5
0 to 7.0
Me V 2 O 5
0 to 6.0
Me VI O 3
0 to 6.0
fluorine
0 to 5.0,
wherein
Me I 2 O is selected from Na 2 O, K 2 O, Rb 2 O and/or Cs 2 O,
Me II O is selected from MgO, CaO, SrO and/or ZnO,
Me III 2 O 3 is selected from Al 2 O 3 , B 2 O 3 , Y 2 O 3 , La 2 O 3 , Ga 2 O 3 and/or In 2 O 3 ,
Me IV O 2 is selected from ZrO 2 , GeO 2 , TiO 2 and/or SnO 2 ,
Me V 2 O 5 is selected from V 2 O 3 , Ta 2 O 5 and/or Nb 2 O 5 and
Me VI O 3 is selected from WO 3 and/or MoO 3 .
7. Method according to claim 1 for the preparation of a glass with nuclei which are suitable for forming low quartz, cristobalite or a mixture thereof.
8. Method according to claim 1 for the preparation of a glass ceramic which has low quartz, cristobalite or a mixture thereof as main crystal phase.
9. Method according to claim 1 for the preparation of a glass ceramic which comprises 5.0 to 50.0 wt.-% SiO 2 as crystal phase.
10. Method according to claim 1 , in which the starting glass is subjected to at least one heat treatment in the range of from 700° to 950° C.
11. Method according to claim 1 , in which the glass ceramic or the glass are present in the form of a powder, a blank or a dental restoration.
12. Method according to claim 2 , in which the at least one reducing agent is selected from the group consisting of organic salts, carbohydrates and cereal flours.
13. Method according to claim 4 , in which the starting glass comprises 1.0 to 4.0 wt.-% cerium ions, calculated as CeO 2 .
14. Method according to claim 9 for the preparation of a glass ceramic which comprises 10.0 to 30.0 wt.-% SiO 2 as crystal phase.
15. Method for the preparation of a glass ceramic with SiO 2 as main crystal phase or a glass which comprises nuclei for the crystallization of SiO 2 , which comprises a step in which a melt of a starting glass which comprises cerium ions and terbium ions is exposed to reducing conditions.
16. Method according to claim 15 , in which the starting glass comprises 0.05 to 2.0 wt.-% terbium ions, calculated as Tb 4 O 7 .
17. Method according to claim 15 , in which the starting glass comprises 0.3 to 0.7 wt.-% terbium ions, calculated as Tb 4 O 7 .
18. Method according to claim 5 , in which the starting glass comprises 1.0 to 7.0 wt.-% alkaline earth metal oxide.