Glass ceramics
A group of glass-ceramic compositions nucleated with ZrO 2 and P 2 O 5 can develop a microstructure composed of spherulite grains, which produce a high fracture toughness (about 1.5 MPa·m 0.5 or higher). Also, the glass-ceramic articles can be cerammed to have a CTE value of 30×10 −7 /° C. or lower.
1. A glass ceramic composition comprising, by weight percent:
60-75% SiO 2
10-20% Al 2 O 3
0-4% B 2 O 3
>6-9% Li 2 O
>0 to 5% Na 2 O
0-4% K 2 O
0-8% MgO
0-8% ZnO
>0 to 8% ZrO 2
0-4% TiO 2 , and
>0 to 5% P 2 O 5 , and optionally,
>0 to 0.5% SnO 2
wherein a primary phase of the glass ceramic comprises β-spodumene or β-quartz.
2. The glass ceramic composition according to claim 1 , comprising one or more of a) 0-1 wt % TiO 2 , b) 0.1-5 wt % Na 2 O, c) 0.5-8 wt % ZrO 2 , d) 0.5-5 wt % P 2 O 5 or e) 0.2 wt % or less K 2 O.
3. The glass ceramic of claim 1 , comprising:
60-70% SiO 2
12-16% Al 2 O 3
>6-9% Li 2 O
0.5-2% Na 2 O
0.5-8% ZrO 2
1-3% P 2 O 5
0-4% B 2 O 3
1-3% MgO
2-4% ZnO, and optionally
0.05-0.5% SnO 2
and comprising less than 2% by weight of total oxides other than those recited above.
4. The glass ceramic composition according to claim 1 , wherein the glass ceramic is greater than 60% crystalline and comprises spherulite grains having an average grain size of from 5-10 μm.
5. An article comprising the glass ceramic composition of claim 1 .
6. A glass ceramic composition of claim 1 , further comprising:
from about 0-3 wt %, one or more of Nb 2 O 5 , MoO 3 , Ta 2 O 5 , WO 3 , La 2 O 3 , HfO 2 , CdO, Fe 2 O 3 , CeO 2 , or a halogen.
7. A glass ceramic composition of claim 1 , wherein the glass ceramic composition has an average ring-on-ring strength from 70 MPa to 500 MPa.
8. A glass ceramic composition of claim 1 , wherein the glass ceramic composition has a fracture toughness of 1.5 MPa·m 0.5 or higher.
9. A glass ceramic composition of claim 1 , wherein the glass ceramic has a coefficient of thermal expansion of 30×10 −7 /° C. or lower.
10. A glass ceramic composition comprising, by weight percent:
60-75% SiO 2
10-20% Al 2 O 3
0-4% B 2 O 3
>6-9% Li 2 O
>0 to 5% Na 2 O
0-4% K 2 O
0-8% MgO
0-8% ZnO
>0 to 8% ZrO 2
0-4% TiO 2
>0 to 5% P 2 O 5 ,
comprising less than 2% by weight of total oxides other than those recited above.
11. A glass ceramic composition of claim 10 , further comprising, from about 0-2 wt %, one or more of Nb 2 O 5 , MoO 3 , Ta 2 O 5 , WO 3 , La 2 O 3 , HfO 2 , CdO, Fe 2 O 3 , CeO 2 , or a halogen.
12. The glass ceramic composition of claim 10 , comprising one or more of a) 0-1 wt % TiO 2 , b) 0.1-5 wt % Na 2 O, c) 0.5-8 wt % ZrO 2 , d) 0.5-5 wt % P 2 O 5 , or e) 0.2 wt % or less K 2 O.
13. A method of making the glass ceramic composition of claim 1 , comprising:
providing a glass composition comprising, by weight percent:
60-75% SiO 2
10-20% Al 2 O 3
0-4% B 2 O 3
>6-9% Li 2 O
>0 to 5% Na 2 O
0-4% K 2 O
0-8% MgO
0-8% ZnO
>0 to 8% ZrO 2
0-4% TiO 2
>0 to 5% P 2 O 5 , and optionally,
>0 to 0.5% SnO 2 ;
optionally, forming the glass composition into a shape;
subjecting the glass composition to heat treating conditions; and
forming a β-spodumene or β-quartz crystal phase.
14. The method of claim 13 , comprising one or more of a) 0-1 wt % TiO 2 , b) 0.1-5 wt % Na 2 O, c) 0.5-8 wt % ZrO 2 , d) 0.5-5 wt % P 2 O 5 , or e) 0.2 wt % or less K 2 O.
15. The method of claim 13 , wherein the heat-treating conditions comprise a two-step heat treatment, wherein the first step comprises heating the glass to a temperature from 600-700° C. for 0.1 to 10 hours, and the second step comprises heating the glass to a temperature from 725-1000° C. for 0.1 to 8 hours.
16. The method of claim 13 , wherein the temperature for the first step is from 650-690° C. and the temperature for the second step is from 750-850° C.
17. The method of claim 13 , wherein the time for the first step is from 2-8 hours and the time for the second step is from 2-4 hours.
18. The method of claim 13 , wherein the glass ceramic is greater than 60% crystalline and comprises spherulite grains having an average grain size of from 5-10 μm.
19. The method of claim 13 , wherein the glass ceramic has a coefficient of thermal expansion of 30×10 −7 /° C. or lower.
20. The method of claim 13 , wherein the glass ceramic has a fracture toughness of 1.5 MPa·m 0.5 or higher.