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 glass-ceramic article comprising:
a major nepheline crystalline phase; and
a minor phosphate crystalline phase,
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.
2. The glass-ceramic article of claim 1 , further comprising a lithium aluminosilicate phase.
3. The glass-ceramic article of claim 1 , wherein at least one of the nepheline phase and the phosphate phase comprises a plurality of nanocrystals having a major cross-sectional dimension of about 100 nm or less.
4. The glass-ceramic article of claim 3 , wherein the plurality of nanocrystals form at least one of the nepheline phase, the phosphate phase and the lithium aluminosilicate phase, and the plurality of nanocrystals have a major cross-sectional dimension of about 100 nm or less.
5. The glass-ceramic article of claim 4 , wherein the plurality of nanocrystals form the nepheline phase, the phosphate phase and the lithium aluminosilicate phase.
6. The glass-ceramic article of claim 1 , comprising 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 about 0 to about 20,
Li 2 O in the range from about 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 about 0 to about 6.
7. The glass-ceramic article of claim 6 , wherein the 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 .
8. The glass-ceramic article of claim 1 , wherein the 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 about 0 to about 10,
P 2 O5 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 about 0 to about 4.
9. The glass-ceramic article of claim 6 , wherein the composition comprises less than about 1 mol % TiO 2 .
10. The glass-ceramic article of claim 1 , wherein the nepheline phase comprises a solid solution.
11. The glass-ceramic article of claim 1 , further comprising a compressive stress layer, the compressive stress layer optionally comprising kalsilite.
12. The glass-ceramic article of claim 1 , comprising an average surface compressive stress of about 400 MPa or greater.