Crack-resistant glass-ceramic articles and methods for making the same
Glass-ceramics exhibiting a Vickers indentation crack initiation threshold of at least 15 kgf are disclosed. These glass-ceramics may be ion exchangeable or ion exchanged. The glass-ceramics include a crystalline and amorphous phases generated by subjecting a thin precursor glass article to ceramming cycle having an average cooling rate in the range from about 10° C./minute to about 25° C./minute. In one or more embodiments, the crystalline phase may comprise at least 20 wt % of the glass-ceramics. The glass-ceramics may include β-spodumene ss as the predominant crystalline phase and may exhibit an opacity ≥about 85% over the wavelength range of 400-700 nm for an about 0.8 mm thickness and colors an observer angle of 10° and a CIE illuminant F02 determined with specular reflectance included of a* between −3 and +3, b* between −6 and +6, and L* between 88 and 97.
1. A method of making a glass-ceramic article comprising:
a) heating a precursor glass article at a rate in the range from about 1° C./minute to 10° C./minute to a nucleating temperature (Tn) in the range from about 700° C. to 810° C., the precursor glass article having a thickness of about 2 mm or less and a composition comprising B 2 O 3 ,
b) maintaining the precursor glass article at at least the Tn within the range of from about 700° C. to 810° C. to produce a nucleated glass article,
c) heating the nucleated glass article at a rate in the range from about 1° C./minute to about 10° C./minute to a crystallization temperature (Tc) in the range from about 850° to about 1250° C.,
d) maintaining the nucleated glass article at at least the Tc to produce a glass-ceramic article having a crystalline phase, and
e) cooling the glass-ceramic article from (i) a temperature of within a range from 800° C. to about 1250° C. to (ii) about room temperature at an average rate of 10° C./minute or greater, and less than 6 hours elapsing from beginning step a) through step e);
wherein, the glass-ceramic article exhibits a color presented in CIELAB color space coordinates for an observer angle of 10° and a CIE illuminant F02 determined from reflectance spectra measurements using a spectrophotometer with specular reflectance included, the color space coordinates comprising:
CIE a* between −3 and +3,
CIE b* between −6 and +6, and
CIE L* between 88 and 97.
2. The method of claim 1 , further comprising ion exchanging the glass-ceramic article to generate a compressive stress layer comprising a compressive stress of at least 300 MPa and a depth of compressive stress layer of at least about 1% of the overall thickness of the glass-ceramic article.
3. The method of claim 2 , wherein the glass-ceramic article exhibits a Vickers crack initiation threshold of at least 15 kgf.
4. The method of claim 1 , wherein less than about 4 hours elapses from beginning step a) through step e).
5. The method of claim 1 , wherein the cooling extends for less than 1.5 hours.
6. The method of claim 1 , wherein the glass-ceramic article comprises, in mole %:
SiO 2 in the range from about 62 to about 75;
Al 2 O 3 in the range from about 10.5 to about 17;
Li 2 O in the range from about 5 to about 13;
ZnO in the range from about 0 to about 4;
MgO in the range from about 0 to about 8;
TiO 2 in the range from about 2 to about 5;
B 2 O 3 to about 4;
Na 2 O in the range from about 0 to about 5;
K 2 O in the range from about 0 to about 4;
ZrO 2 in the range from about 0 to about 2;
P 2 O 5 in the range from about 0 to about 7;
Fe 2 O 3 in the range from about 0 to about 0.3;
MnOx in the range from about 0 to about 2;
SnO 2 in the range from about 0.05 to about 0.2;
a ratio
[
Li
2
O
+
Na
2
O
+
K
2
O
+
MgO
+
ZnO
]
[
Al
2
O
3
+
B
2
O
3
]
in the range from about 0.7 to about 1.5; and
a ratio:
[
TiO
2
+
SnO
2
]
[
SiO
2
+
B
2
O
3
]
greater than about 0.04.
7. The method of claim 6 , wherein the glass-ceramic article exhibits a Vickers crack initiation threshold of at least about 15 kgf.
8. The method of claim 7 , wherein the glass-ceramic article exhibits a Vickers crack initiation threshold of at least about 20 kgf.
9. The method of claim 1 , wherein the crystalline phase comprises at least one of a β-spodumene solid solution, a Ti-containing crystalline phase, a spinel structure and cordierite.
10. The method of claim 9 , wherein the Ti-containing crystalline phase comprises at least one of rutile, anatase, magnesium titanate and aluminum titanate.
11. The method of claim 9 , wherein the crystalline phase comprises β-spodumene.
12. The method of claim 11 , wherein the β-spodumene crystalline phase comprises a predominant crystalline phase.
13. The method of claim 1 , wherein the crystalline phase comprises at least 20 wt % of the glass-ceramic article.
14. The method of claim 13 , wherein the crystalline phase comprises at least 70 wt % of the glass-ceramic article.
15. The method of claim 1 , wherein the glass-ceramic article exhibits an average opacity of at least 85% over a wavelength in the range from about 400 nm to about 700 nm for a thickness of about 0.8 mm.
16. The method of claim 1 , wherein the glass-ceramic article exhibits a color presented in CIELAB color space coordinates for an observer angle of 10° and a CIE illuminant F02 determined from reflectance spectra measurements using a spectrophotometer with specular reflectance included, the color space coordinates comprising:
CIE a* between −1 and +1,
CIE b* between −0.5 and +0.5, and
CIE L* between 93 and 96.5.
17. A method of making a glass-ceramic article comprising:
a) subjecting a glass substrate having a thickness of about 2 mm or less to a temperature of 700° C. to 810° C. for a period of time sufficient to form a nucleated glass substrate;
b) subjecting the nucleated glass substrate to a temperature of 850° C. to 1250° C. for a period of time sufficient to form a glass-ceramic article having a crystalline phase; and
c) cooling the glass-ceramic article from (i) a temperature of within a range of 800° C. to about 1250° C. to (ii) room temperature at a rate of 300° C./minute to 500° C./minute.
18. The method of claim 17 , wherein the temperature of step b) is 950° C. to 1250° C., the method further comprising:
after b) but before c), cooling the glass-ceramic article from the temperature of the range of b) to the temperature of c) during a time period of 5 minutes to 35 minutes; and
after c), ion-exchanging the glass-ceramic article to form a compressive layer of compressive stress;
wherein, the glass-ceramic article has a Vickers indentation crack initiation threshold of greater than 20 kgf; and
wherein, the glass substrate has a composition comprising, in mole %: 62 to 75 SiO 2 ; 10.5 to 17 Al 2 O 3 ; 5 to 13 Li 2 O; 0 to 4 ZnO; 0 to 8 MgO; 2 to 5 TiO 2 ; B 2 O 3 ; 0 to 5 Na 2 O; 0 to 4 K 2 O; wherein the ratio of (i) the sum of Li 2 O, Na 2 O, K 2 O, MgO, and ZnO, to (ii) the sum of Al 2 O 3 and B 2 O 3 , is 0.7 to 1.
19. A method of making a glass-ceramic article comprising:
a) reducing a thickness of a glass substrate from a first thickness of greater than 2 mm to a second thickness of about 2 mm or less using rolls, wherein the glass substrate has a composition comprising, in mole %: 62 to 75 SiO 2 ; 10.5 to 17 Al 2 O 3 ; 5 to 13 Li 2 O; 0 to 4 ZnO; 0 to 8 MgO; 2 to 5 TiO 2 ; B 2 O 3 ; 0 to 5 Na 2 O; 0 to 4 K 2 O; wherein the ratio of (i) the sum of Li 2 O, Na 2 O, K 2 O, MgO, and ZnO, to (ii) the sum of Al 2 O 3 and B 2 O 3 , is 0.7 to 1;
b) subjecting the glass substrate to a temperature of 700° C. to 810° C. for a period of time sufficient to form a nucleated glass substrate;
c) subjecting the nucleated glass substrate to a temperature of 850° C. to 1250° C. for a period of time sufficient to form a glass-ceramic article having a crystalline phase; and
d) cooling the glass-ceramic article to room temperature at a rate of 10° C./minute or greater.
20. The method of claim 19 further comprising e) ion-exchanging the glass-ceramic article to form a compressive layer of compressive stress;
wherein, the glass-ceramic article has a Vickers indentation crack initiation threshold of greater than 15 kgf.
21. The method of claim 19 ,
wherein the crystalline phase comprises at least 70 wt % of the glass-ceramic article;
wherein the crystalline phase is predominately β-spodumene crystalline phase; and
wherein the glass-ceramic article exhibits a color presented in CIELAB color space coordinates for an observer angle of 10° and a CIE illuminant F02 determined from reflectance spectra measurements using a spectrophotometer with specular reflectance included, the color space coordinates comprising:
CIE a* between −1 and +1,
CIE b* between −0.5 and +0.5, and
CIE L* between 93 and 96.5.