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 glass-ceramic article comprising:
a composition, in mole %, comprising:
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 in the range from about 0 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; and
a Vickers crack initiation threshold of about 12 kgf or greater.
2. The glass-ceramic article 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.
3. The glass-ceramic article of claim 2 , wherein the Ti-containing crystalline phase comprises at least one of rutile, anatase, magnesium titanate and aluminum titanate.
4. The glass-ceramic article of claim 2 , wherein the crystalline phase comprises β-spodumene.
5. The glass-ceramic article of claim 4 , wherein the β-spodumene crystalline phase comprises a predominant crystalline phase.
6. The glass-ceramic article of claim 1 , further comprising:
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; and
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.
7. The glass-ceramic article of claim 1 , wherein the crystalline phase comprises at least 70 wt % of the glass-ceramic article.
8. The glass-ceramic article of claim 1 , wherein the crystalline phase and the amorphous phase are generated by ceramming a precursor glass article, and wherein ceramming includes cooling at an average cooling rate in the range from about 300 ° C./minute to about 500 ° C./minute, for a duration of less than about 2 minutes.
9. The glass-ceramic article of claim 1 , further comprising one or more β-spodumene solid solutions and an amorphous phase generated by ceramming a precursor glass article having a thickness of less than about 5 mm, and wherein ceramming in includes cooling the glass-ceramic at an average cooling rate in the range from about 10 ° C./minute to about 25° C./minute.
10. The glass-ceramic article of claim 9 , wherein the glass-ceramic is cooled at the average cooling rate, for a duration of less than 1.5 hours.
11. The glass-ceramic article of claim 1 , further comprising a compressive stress layer extending from a surface of the glass-ceramic article into the glass-ceramic article of at least about 300 MPa, and a depth of compressive stress layer of at least about 1% of an overall thickness of the glass-ceramic article.
12. The glass-ceramic article of claim 1 , wherein the crystalline phase comprises at least 20 wt % of the glass-ceramic article.
13. The glass-ceramic article of claim 1 , further comprising a Vickers crack initiation threshold of about 15 kgf or greater.
14. The glass-ceramic article of claim 1 , further comprising a Vickers crack initiation threshold of about 20 kgf or greater.
15. The glass-ceramic article of claim 1 , wherein the glass-ceramic article is ion-exchange strengthened.