Scratch resistant glass and method of making

1. A glass-based article comprising:

a lithium aluminosilicate composition;

a molar ratio of sodium oxide (Na 2 O) to lithium oxide (Li 2 O) that is less than or equal to 0.9 at the center of the glass-based article;

a thickness t; and

a stress profile comprising:

a spike region extending from the first surface to a knee at a spike depth of layer (DOL spike ); and

a tail region extending from the knee to a center of the glass-based article, wherein within the tail region there is a post-spike near region;

wherein a molar ratio of sodium dioxide (Na 2 O) to lithium dioxide (Li 2 O) in the post-spike near region is greater than or equal to 0.9.

2. The glass-based article of claim 1 , wherein the post-spike near region is located over a distance that is deeper than the knee by from 20 to 100% of the DOL spike .

3. The glass-based article of claim 1 , wherein the molar ratio of sodium dioxide (Na 2 O) to lithium dioxide (Li 2 O) in the post-spike near region is averaged over the distance that is deeper than the knee by from 20 to 100% of the DOL spike .

4. The glass-based article of claim 1 , wherein the molar ratio of sodium dioxide (Na 2 O) to lithium dioxide (Li 2 O) in the post-spike near region is averaged over a depth of from 6 micrometers to 10 micrometers.

5. The glass-based article of claim 1 , wherein in the post-spike near region the molar ratio of sodium dioxide (Na 2 O) to lithium dioxide (Li 2 O) is less than 1.5.

6. The glass-based article of claim 1 further comprising a stress profile comprising:

a maximum compressive stress (CS max ) greater than or equal to 650 MPa;

a depth of compression (DOC) that is greater than or equal to 0.19·t; and

a peak central tension (CT) in a tensile region.

7. The glass-based article of claim 6 , wherein the stress profile further comprises:

a spike region extending from the first surface to a knee at a spike depth of layer (DOL k ); and

wherein a compressive stress at the knee (CS k ) is greater than or equal to 100 MPa.

8. The glass-based article of claim 6 , wherein the stress profile further comprises: a negative curvature region, wherein a second derivative of stress as a function of depth is negative.

9. The glass-based article of claim 8 , wherein a maximum absolute value of an average of the second derivative in the range of 0.03·t to 0.175·t is greater than or equal to 0.0001 MPa/μm 2 .

10. The glass-based article of claim 1 , comprising a Knoop scratch initiation threshold of greater than or equal to 5 N.

11. The glass-based article of claim 10 , wherein an average width at a center of scratches at 8 N of scratch testing with a Knoop geometry diamond tip and a rate of 9.34 mm/min is less than or equal to 600 micrometers after 10 scratches.

12. 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 at least a portion of at least one of the housing or the cover comprises the glass-based article of claim 1 .

13. A method of manufacturing a glass-based article comprising:

exposing a glass-based substrate having opposing first and second surfaces defining a substrate thickness (t) and having a lithium aluminosilicate composition to an ion exchange treatment to form the glass-based article having a lithium aluminosilicate composition and a stress profile comprising: a spike region extending from the first surface to a knee at a spike depth of layer(DOL spike ); and a tail region extending from the knee to a center of the glass-based article, wherein within the tail region there is a post-spike near region, the ion exchange treatment comprising:

a first molten salt bath comprising a potassium salt, a sodium salt, and a lithium salt, wherein a concentration of the lithium salt is in the range of greater than or equal to 15 weight % to less than or equal to 50 weight %; and

a second molten salt bath comprising a potassium salt, a sodium salt, and a lithium salt, wherein a concentration of the lithium salt is in the range of greater than or equal to 0 weight % to less than or equal to 1 weight %;

wherein the glass-based article comprises a molar ratio of sodium oxide (Na 2 O) to lithium oxide (Li 2 O) that is less than or equal to 0.9 at the center of the glass-based article; and

wherein the glass-based article comprises a molar ratio of sodium dioxide (Na 2 O) to lithium dioxide (Li 2 O) in the post-spike near region that is greater than or equal to 0.9.

14. The method of claim 13 , wherein the post-spike near region is located over a distance that is deeper than the knee by from 20 to 100% of the DOL spike .

15. The method of claim 13 , wherein the molar ratio of sodium dioxide (Na 2 O) to lithium dioxide (Li 2 O) in the post-spike near region is averaged over the distance that is deeper than the knee by from 20 to 100% of the DOL spike .

16. The method of claim 13 , wherein the molar ratio of sodium dioxide (Na 2 O) to lithium dioxide (Li 2 O) in the post-spike near region is averaged over a depth of from 6 micrometers to 10 micrometers.

17. The method of claim 13 , wherein in the post-spike near region the molar ratio of sodium dioxide (Na 2 O) to lithium dioxide (Li 2 O) is less than 1.5.

18. The method of claim 13 , wherein:

the first molten salt bath comprises a concentration of the potassium salt in the range of greater than or equal to 30 weight % to less than or equal to 40 weight %, a concentration of the sodium salt in the range of greater than or equal to 30 weight % to less than or equal to 40 weight %, and the concentration of the lithium salt is in the range of greater than or equal to 25 weight % to less than or equal to 35 weight %, with the proviso that the concentrations of the potassium salt, the sodium salt, and the lithium salt in the first molten bath total 100%, and

the second molten salt bath comprises a concentration of the potassium salt in the range of greater than or equal to 95 weight % to less than or equal to 99 weight %, a concentration of the sodium salt in the range of greater than or equal to 0 weight % to less than or equal to 5 weight %, and the concentration of the lithium salt is in the range of greater than or equal to 0.1 weight % to less than or equal to 1 weight %, with the proviso that the concentrations of the potassium salt, the sodium salt, and the lithium salt in the second molten bath total 100%.

19. The method of claim 13 , wherein the stress profile further comprises:

a maximum compressive stress (CS max ) greater than or equal to 650 MPa,

a depth of compression (DOC) that is greater than or equal to 0.19·t, and

a peak central tension (CT) in a tensile region.