Transparent glass-ceramic articles, glass-ceramic precursor glasses and methods for forming the same
Embodiments of glass ceramic articles and precursor glasses are disclosed. In one or more embodiments, the glass-ceramic articles are transparent and include a nepheline phase and a phosphate phase. The glass-ceramic articles are colorless and exhibit a transmittance of about 70% or greater across the visible spectrum. The glass-ceramic articles may optionally include a lithium aluminosilicate phase. The crystals of the glass-ceramic articles may have a major cross-section of about 100 nm or less.
1. A method of forming a glass-ceramic article, comprising:
heat treating a precursor glass article by heating the precursor 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 600° to about 1000° C.;
maintaining the precursor glass article at the Tc to produce a glass-ceramic article having a nepheline crystalline phase and a phosphate phase; and
cooling the glass-ceramic article to about room temperature.
2. The method of claim 1 , further comprising heating the precursor glass article to a nucleating temperature (Tn) in the range from about 700° C. to about 900° C., and maintaining the precursor glass article at the Tn to produce a nucleated precursor glass article prior to maintaining the precursor glass article at the Tc.
3. The method of claim 2 , further comprising heating the nucleated precursor glass article at a rate in the range from about 1° C./minute to about 10° C./minute to the Tc.
4. The method of claim 1 , further comprising ion exchanging the glass-ceramic article.
5. The method of claim 4 , wherein the ion exchanging generates a compressive stress layer comprising a compressive stress of at least 400 MPa.
6. The method of claim 4 , wherein the ion exchanging generates a kalsilite surface layer.
7. The method of claim 4 , wherein the ion exchanging generates a depth of layer in the range from about 50 μm to about 150 μm.
8. The method of claim 1 , wherein the precursor glass article has a composition, in mol %, comprising:
SiO 2 in the range from about 35% to about 60%,
Al 2 O 3 in the range from about 10% to about 30%,
Na 2 O in the range from about 7% to about 31%,
K 2 O in the range from 0% to about 20%,
Li 2 O in the range from 0% to about 20%,
P 2 O 5 in the range from about 1.5% to about 8%, and
a rare earth oxide in the range from 0% to about 6%.
9. The method of claim 8 , wherein the precursor glass article composition further comprises at least one oxide in an amount in the range from 0 mol % to about 8 mol %, wherein the at least one oxide comprises one of B 2 O 3 , MgO, CaO, SrO, BaO, and ZrO 2 .
10. The method of claim 8 , wherein the precursor glass article composition further comprises, in mol %:
SiO 2 in the range from about 40% to about 55%,
Al 2 O 3 in the range from about 14% to about 21%,
Na 2 O in the range from about 13% to about 29%,
K 2 O in the range from about 2% to about 14%,
Li 2 O in the range from 0% to about 10%,
P 2 O 5 in the range from about 2.5% to about 5%, and
at least one of ZrO 2 , Y 2 O 3 and La 2 O 3 in an amount in the range from 0% to about 4%,
wherein the composition comprises less than about 1% TiO 2 .
11. The method of claim 1 , wherein the precursor glass article is a glass sheet having a thickness of less than about 5 mm.
12. The method of claim 1 , wherein the glass-ceramic article is colorless and has transmission or reflection color coordinates under the CIE L*, a*, b* colorimetry system of L* in the range from about 80 to about 100, a* in the range from about −5 to about 5, and b* in the range from about b* in the range from about −5 to about 5, and exhibits a transmittance of about 70% or greater across the visible spectrum, in the range from about 390 nm to about 700 nm.
13. The method of claim 1 , wherein the glass-ceramic article further comprises a lithium aluminosilicate phase.