Glasses and glass ceramics including a metal oxide concentration gradient
Embodiments of a glass-based article including a first surface and a second surface opposing the first surface defining a thickness (t) of about 3 millimeters or less (e.g., about 1 millimeter or less), and a stress profile, wherein all points of the stress profile between a thickness range from about 0·t up to 0.3·t and from greater than 0.7·t, comprise a tangent that is less than about −0.1 MPa/micrometers or greater than about 0.1 MPa/micrometers, are disclosed. In some embodiments, the glass-based article includes a non-zero metal oxide concentration that varies along at least a portion of the thickness (e.g., 0·t to about 0.3·t). In some embodiments, the concentration of metal oxide or alkali metal oxide decreases from the first surface to a point between the first surface and the second surface and increases from the point to the second surface. The concentration of the metal oxide may be about 0.05 mol % or greater or about 0.5 mol % or greater throughout the thickness. Methods for forming such glass-based articles are also disclosed.
1. A glass substrate comprising a composition including, in mol %,
SiO 2 in an amount from 60 to 72;
Al 2 O 3 in an amount from 6 to 14;
a non-zero amount of alkaline earth metal oxides up to 15, the alkaline earth metal oxides comprising MgO in an amount from 2 to 4 and a non-zero amount of CaO;
Li 2 O in an amount from 6 to 10;
Na 2 O in an amount from 0.5 to 10;
less than 4 mol. % B 2 O 3 ; and
K 2 O in an amount of less than 2, wherein:
the composition is substantially free of ZnO;
a ratio of MgO (mol %) to RO (mol %) is greater than 0 to 1 where RO is the sum (mol %) of BaO, CaO, MgO, PbO, SrO, and ZnO in the glass;
a total amount of Li 2 O+Na 2 O+K 2 O is from 5 to 15; and
the glass substrate has a transmittance of greater than or equal to 88% over a wavelength range from 380 nm to 780 nm at a thickness of 1 mm.
2. The glass substrate of claim 1 , wherein the composition comprises a non-zero amount of CaO less than 2 mol %.
3. The glass substrate of claim 1 , wherein the total amount of alkaline earth metal oxides is a non-zero amount up to 14 mol %.
4. The glass substrate of claim 1 , wherein the total amount of alkaline earth metal oxides is a non-zero amount up to 12 mol %.
5. The glass substrate of claim 1 , wherein the total amount of alkaline earth metal oxides is from 2.5 mol % to 8 mol %.
6. The glass substrate of claim 1 , wherein Li 2 O+Na 2 O+K 2 O is from 5 mol % to about 14 mol %.
7. The glass substrate of claim 1 , wherein the composition comprises from 0 mol % to 10 mol % P 2 O 5 .
8. The glass substrate of claim 1 , wherein the composition comprises less than 1 mol % Fe 2 O 3 .
9. The glass substrate of claim 1 , wherein the composition comprises less than 0.1 mol % Fe 2 O 3 .
10. The glass substrate of claim 1 , wherein the composition comprises less than 0.1001 mol % As 2 O 3 .
11. The glass substrate of claim 1 , wherein the Na 2 O concentration varies.
12. The glass substrate of claim 1 , wherein the glass substrate is ion-exchangeable and is amorphous.