White, opaque, βspodumene glass-ceramic articles with tunable color and methods for making the same

1. A glass-ceramic article comprising:

a composition, in mole %, comprising:

i) SiO 2 in a range from about 62 to about 75,

ii) Al 2 O 3 in a range from about 10 to about 18,

iii) Li 2 O in a range from about 5 to about 14,

iv) B 2 O 3 in a range from about 2 to about 12,

v) Fe 2 O 3 in a range from about 0.4 to about 2,

vi) MgO in a range from 0 to about 8,

vii) ZnO in a range from 0 to about 4,

viii) TiO 2 in a range from about 2 to about 5,

ix) Na 2 O in a range from 0 to about 5,

x) K 2 O in a range from 0 to about 4,

wherein a ratio of the mole sum total [Li 2 O+Na 2 O+K 2 O+MgO+ZnO]/moles of [Al 2 O 3 ] in a range from about 0.8 to about 1.5, and

wherein β-spodumene is the predominant crystalline phase.

2. The glass-ceramic article of claim 1 , wherein the glass-ceramic article comprises 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 comprising:

a) CIE a* in a range from about −0.5 to about 0.5;

b) CIE b* in a range from about −2.5 to about 2; and

c) CIE L* in a range from about 90 to about 93.

3. The glass-ceramic article of claim 1 , wherein the composition comprises Fe 2 O 3 in a range from about 0.5 to about 2 mole %.

4. The glass-ceramic article of claim 1 , further comprising a compressive stress layer formed by ion-exchange.

5. The glass-ceramic article of claim 4 , wherein the compressive stress layer has a compressive stress of at least 300 MPa and a depth of layer (DOL) of at least about 2% of an overall thickness of the article.

6. The glass-ceramic article of claim 1 , wherein the composition further comprises:

xi) SnO 2 in a range from about 0.05 to about 0.5.

7. A process for making a glass-ceramic comprising:

a) heating a crystallizable glass at a rate in a range from about 1° C./min to about 10° C./min to a nucleation temperature in a range from about 700° C. and 810° C., wherein, in mole %, the crystallizable glass comprises:

i) SiO 2 in a range from about 62 to about 75,

ii) Al 2 O 3 in a range from about 10 to about 18,

iii) Li 2 O in a range from about 5 to about 14,

iv) B 2 O 3 in a range from about 2 to about 12, and

v) Fe 2 O 3 in a range from about 0.4 to about 2, and

b) maintaining the crystallizable glass at the nucleation temperature to produce a nucleated crystallizable glass;

c) heating the nucleated crystallizable glass at a rate in a range from about 1° C./min to about 10° C./min to a crystallization temperature of in a range from about 850° C. to about 1200° C.; and

d) maintaining the nucleated crystallizable glass at the crystallization temperature to produce a glass-ceramic having β-spodumene as a predominant crystalline phase.

8. The process of claim 7 , wherein the glass-ceramic article comprises 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 comprising:

a) CIE a* in a range from about −0.5 to about 0.5;

b) CIE b* in a range from about −2.5 to about 2; and

c) CIE L* in a range from about 90 to about 93.

9. The process of claim 8 , wherein a correlation between a* and b* exists, as a function of crystallization temperature, wherein a plot of a* vs. b* has a slope of delta b*/delta a* between about 8 and about 22.

10. The process of claim 9 , wherein a correlation between b* and L* exists, as a function of crystallization temperature, wherein a plot of b* vs. L* has a slope of delta L*/delta b* of between about 0.75 and about 1.25.

11. The process of claim 9 , further comprising selecting the crystallization temperature to tune the color based on the correlation between a* and b*.

12. The process of claim 10 , further comprising selecting the crystallization temperature to tune the color based on the correlation between a* and b* and the correlation between b* and L*.

13. The process of claim 7 , wherein the crystallizable glass further comprises:

vi) MgO in a range from 0 to about 8,

vii) ZnO in a range from 0 to about 4,

viii) TiO 2 in a range from about 2 to about 5,

ix) Na 2 O in a range from 0 to about 5,

x) K 2 O in a range from 0 to about 4, and

xi) SnO 2 in a range from about 0.05 to about 0.5, and

xii) a ratio of the mole sum total [Li 2 O+Na 2 O+K 2 O+MgO+ZnO]/moles of [Al 2 O 3 ] in a range from about 0.8 to about 1.5.

14. A process for making a glass-ceramic comprising:

a) heating a nucleated crystallizable glass at a rate in a range from about 1° C./min to about 10° C./min to a crystallization temperature of in a range from about 850° C. to about 1200° C., wherein, in mole %, the nucleated crystallizable glass comprises:

i) SiO 2 in a range from about 62 to about 75,

ii) Al 2 O 3 in a range from about 10 to about 18,

iii) Li 2 O in a range from about 5 to about 14,

iv) B 2 O 3 in a range from about 2 to about 12,

v) Fe 2 O 3 in a range from about 0.4 to about 2, and

b) selecting the crystallization temperature to tune the color based on a correlation between a* and b*, wherein:

i) the color is 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 comprising:

(1) CIE a* in a range from about −0.5 to about 0.5;

(2) CIE b* in a range from about −2.5 to about 2; and

(3) CIE L* in a range from about 90 to about 93; and

ii) based on the correlation between a* and b*, as a function of crystallization temperature, a plot of a* vs. b* has a slope of delta b*/delta a* of between about 8 and about 22; and

 maintaining the nucleated crystallizable glass at the crystallization temperature to produce a glass-ceramic having β-spodumene as a predominant crystalline phase.

15. The process of claim 14 , wherein based on a correlation between b* and L*, as a function of crystallization temperature, a plot of b* vs. L* has a slope delta L*/delta b* of between about 0.75 and about 1.25.

16. The process of claim 15 , further comprising selecting the crystallization temperature to tune the color based on the correlation between a* and b* and the correlation between b* and L*.

17. The process of claim 14 , further comprising ion exchanging the glass ceramic to form a compressive stress layer.

18. The process of claim 17 , wherein the compressive stress layer has a compressive stress of at least 300 MPa and a depth of layer (DOL) of at least about 2% of an overall thickness of the glass-ceramic.

19. The process of claim 14 , wherein the crystallizable glass further comprises:

vi) MgO in a range from 0 to about 8,

vii) ZnO in a range from 0 to about 4,

viii) TiO 2 in a range from about 2 to about 5,

ix) Na 2 O in a range from 0 to about 5,

x) K 2 O in a range from 0 to about 4, and

xi) SnO 2 in a range from about 0.05 to about 0.5, and

xii) a ratio of the mole sum total [Li 2 O+Na 2 O+K 2 O+MgO+ZnO]/moles of [Al 2 O 3 ] in a range from about 0.8 to about 1.5.

20. A glass-ceramic article comprising:

a) a composition, in mole %, comprising:

i) SiO 2 in a range from about 62 to about 75,

ii) Al 2 O 3 in a range from about 10 to about 18,

iii) Li 2 O in a range from about 5 to about 14,

iv) B 2 O 3 in a range from about 2 to about 12,

v) a metal oxide selected from group consisting of CoO, Cr 2 O 3 , Cu 2 O, MnO 2 , Sb 2 O 3 , In 2 O 3 , Bi 2 O 3 , NiO, V 2 O 3 , Ta 2 O 5 , and combinations thereof in a range from about 0.01 to about 2,

vi) MgO in a range from 0 to about 8,

vii) ZnO in a range from 0 to about 4,

viii) TiO 2 in a range from about 2 to about 5,

ix) Na 2 O in a range from 0 to about 5,

x) K 2 O in a range from 0 to about 4, and

wherein a ratio of the mole sum total [Li 2 O+Na 2 O+K 2 O+MgO+ZnO]/moles of [Al 2 O 3 ] in a range from about 0.8 to about 1.5, and

wherein β-spodumene is the predominant crystalline phase.

21. The glass-ceramic article of claim 20 , wherein the glass-ceramic article comprises 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 comprising:

a) CIE a* in a range from about −0.5 to about 0.5;

b) CIE b* in a range from about −2.5 to about 2; and

c) CIE L* in a range from about 90 to about 93.

22. The glass-ceramic article of claim 20 , further comprising a compressive stress layer formed by ion-exchange.

23. The glass-ceramic article of claim 22 , wherein the compressive stress layer has a compressive stress of at least 300 MPa and a depth of layer (DOL) of at least about 2% of an overall thickness of the article.

24. The glass-ceramic article of claim 20 , wherein the composition further comprises:

xi) SnO 2 in a range from about 0.05 to about 0.5.

25. An electronic device comprising the glass-ceramic article of claim 1 .

26. An electronic device comprising the glass-ceramic article of claim 20 .

27. The glass-ceramic article of claim 1 , wherein the composition further comprises up to 2 mol% ZrO 2 .

28. The glass-ceramic article of claim 20 , wherein the composition further comprises up to 2 mol% ZrO 2 .