Glass-ceramic articles with improved stress profiles
Glass-ceramic articles are manufactured by an ion exchange process that results in glass-based articles having improved stress profiles. A knee may be located at a depth of 3 microns or deeper. A compressive stress at a surface may be 200 MPa or more and at a knee may be 20 MPa or more. A non-sodium oxide may have a non-zero concentration that varies from the first surface to a depth and a depth of compression (DOC) may be located at 0.10·t, or even at 0.17·t or deeper. A two-step ion exchange (DIOX) includes, for example, a potassium bath in a first treatment to form a spike in a spike region of the stress profile, followed by a second treatment which includes, for example, a potassium and sodium mixed bath to maintain the spike and form a tail region of the stress profile. The glass-ceramic articles may thereby avoid developing a vitreous surface layer, which facilitates repeatable and reliable measurement of waveguide modes and determination of compressive stress in the surface (CS) and depth of the spike.
1. A glass-ceramic article comprising:
a glass-ceramic substrate having opposing first and second surfaces defining a substrate thickness (t);
a central composition at a center of the glass-ceramic article containing an alkali metal and a crystalline phase, wherein the crystalline phase is 20% or more by weight of the central composition; and one or more of:
(a) a stress profile comprising: a knee that is at a depth of 3 micrometers or more;
(b) a stress profile comprising: a first compressive stress at the first surface that is 200 MPa or more; and a second compressive stress at a knee that is 20 MPa or more; or
(c) a non-sodium oxide having a non-zero concentration that varies from the first surface to a depth of layer of the non-sodium oxide; and a stress profile comprising a knee and a depth of compression (DOC) that is located at 0.10·t or deeper; and
wherein a vitreous surface layer is absent from the glass-ceramic article.
2. The glass-ceramic article of claim 1 , wherein the alkali metal of the central composition is lithium.
3. The glass-ceramic article of claim 1 , wherein a surface concentration of the crystalline phase at the first and second surfaces is within about 1% of the crystalline phase in the central composition.
4. The glass-ceramic article of claim 1 , wherein the crystalline phase comprises a petalite crystalline phase and/or a lithium silicate crystalline phase, wherein the lithium silicate crystalline phase is a lithium disilicate crystalline phase.
5. The glass-ceramic article of claim 1 , wherein the glass-ceramic substrate comprises lithium-containing aluminosilicate glass-ceramic with a β-spodumene solid solution crystalline phase.
6. The glass-ceramic article of claim 1 , wherein the central composition comprises by weight: 55 to 80% SiO 2 , 2 to 20% Al 2 O 3 , 0.5 to 6% P 2 O 5 , 5 to 20% Li 2 O, 0 to 5% Na 2 O, 0.2 to 15% ZrO 2 , 0 to 10 B 3 O 3 ; and 0 to 10% ZnO.
7. The glass-ceramic article of claim 1 , wherein the stress profile comprises:
a spike region extending from the first surface to the knee; and
a tail region extending from the knee to the center of the glass-ceramic article;
wherein all points of the stress profile located in the spike region comprise a tangent having a value that is 20 MPa/micrometer or greater, and all points of the stress profile located in the tail region comprise a tangent having a value that is 2 MPa/micrometer or less.
8. The glass-ceramic article of claim 1 , wherein lithium is present at the first and/or second surfaces in a non-zero concentration.
9. The glass-ceramic article of claim 1 , wherein t is in the range of from 50 micrometers to 5 millimeters.
10. The glass-ceramic article of claim 1 , wherein at least one of:
(i) a value of color parameter a* in accordance with CIELAB color coordinate system measured after a wash treatment is within 0.05 units of the color parameter a* prior to exposure to the wash treatment, wherein the wash treatment comprises exposing the glass-ceramic article to a wash solution having a pH from 2 to 12 for 30 minutes;
(ii) a value of color parameter b* in accordance with CIELAB color coordinate system measured after a wash treatment is within 0.5 units of the color parameter b* prior to exposure to the wash treatment, wherein the wash treatment comprises exposing the glass-ceramic article to a wash solution having a pH from 2 to 12 for 30 minutes; or
(iii) a value of color parameter L* in accordance with CIELAB color coordinate system measured after a wash treatment is within 1 unit of the color parameter L* prior to exposure to the wash treatment, wherein the wash treatment comprises exposing the glass-ceramic article to a wash solution having a pH from 2 to 12 for 30 minutes.
11. A consumer electronic product comprising:
a housing having a front surface, a back surface, and side surfaces;
electrical components provided at least partially within the housing, the electrical components including at least a controller, a memory, and a display, the display being provided at or adjacent the front surface of the housing; and
a cover disposed over the display;
wherein a portion of at least one of the housing and the cover comprises the glass-ceramic article of claim 1 .