Fine-grained glass-ceramics

• US 5,491,116 A
• Filed: 04/03/1995
• Issued: 02/13/1996
• Est. Priority Date: 04/03/1995
• Status: Expired due to Term

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Beall, George H., Pinckney, Linda R.
• Primary Examiner(s): GROUP, KARL E
• Application Number:
  US08/415,791
• Time in Patent Office: 316 Days
• Field of Search: 501/5, 501/10, 65/33.1, 428/694 ST
• US Class Current: 501/5
• CPC Class Codes: C03C 10/0045 containing SiO2, Al2O3 and MgO as main constituents

Abstract

A glass-ceramic article, such as an information disk substrate, and a method of making the article. The glass-ceramic has Mg-rich pyroxene and spinel-type predominate crystal phases and a composition at least 92% of which consists essentially of 35-60% SiO₂, 10-30% Al₂ O₃, 12-30% MgO, 0-10% ZnO, 5-20% TiO₂, and 0-8% NiO.

Claims

1. A glass-ceramic article exhibiting an MOR of at least about 15,000 psi, a Knoop hardness value of greater than at least about 760 KHN, a Young'"'"'s modulus about 20×

10⁶ psi and a fracture toughness in excess of 1.0 MPa.m^1/2, wherein the crystal phase assemblage is comprised predominately of magnesium containing crystals having a pyroxene structure represented by the formula (M₂)(M₁)Si₂ O₆ where M₂ has a coordination of 6-8 oxygen atoms and M₁ is octahedrally coordinated and spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase, the article having an overall composition at least 92 % of which consists essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO₂, 10-30% Al₂ O₃, 12-30% MgO, 0-10% ZnO, 5-20% TiO₂, and 0-8% NiO.

2. The glass-ceramic article according to claim 1 wherein the composition additionally contains a transition metal oxide selected from the group consisting of the oxides of Cu, Co, Fe, Mn, Cr, Sn and V, the oxide of Cr not exceeding about 1%.

3. A glass-ceramic article according to claim 1 wherein the pyroxene crystals exhibit dimensions less than about 1500 Å

.

4. A glass-ceramic article according to claim 1 wherein the spinel crystals exhibit dimensions less than about 500 Å

.

5. A glass-ceramic article according to claim 1 wherein the pyroxene crystal phase in the crystal phase assemblage is enstatite or an enstatite solid solution.

6. A glass-ceramic article according to claim 1 wherein the spinel crystals are primarily MgAl₂ O₄.

7. A glass-ceramic article according to claim 1 wherein the composition consists essentially, expressed in terms of weight percent on the oxide basis, of 44-53% SiO₂, 15-24% Al₂ O₃, 15-22% MgO, 0-5% ZnO, 9-14% TiO₂, and 0-3% NiO.

8. A glass-ceramic article according to claim 1 wherein the crystal phase assemblage further contains up to about 15% by weight titanate crystals.

9. A glass-ceramic article according to claim 1 wherein the Al₂ O₃ content in the composition does not exceed 25% unless NiO is present in an amount greater than 2%.

10. A method for making a glass-ceramic article which comprises the steps of

a. melting a batch for a glass composition at least 92% of which consists essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO₂, 10-30% Al₂ O₃, 12-30% MgO, 0-10% ZnO, 5-20% TiO₂, and 0-8% NiO,

b. heating the glass article to a temperature range of about 750°

-850°

C.,

c. maintaining the temperature for a time sufficient to cause the article to obtain a high degree of nucleation,

d. heating the glass article to a temperature range about 900°

-1100°

C. and,

e. maintaining the temperature for a time sufficient to cause the article to crystallize in situ forming a crystallized glass article which exhibits crystal phase assemblage comprised predominately of generally uniformly-sized magnesium containing crystals having a pyroxene structure represented by the formula (M₂)(M₁)Si₂ O₆ where M₂ has a coordination of 6-8 oxygen atoms and M₁ is octahedrally coordinated and spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase.

11. The method according to claim 10 wherein the glass composition additionally contains a transition metal oxide selected from the group consisting of the oxides of Cu, Co, Fe, Mn, Cr, Sn and V, the oxide Cr not exceeding about 1%.

12. The method according to claim 10 wherein the pyroxene crystals exhibit dimensions less than about 1500 Å

in diameter.

13. The method according to claim 10 wherein the spinel crystals exhibit dimensions less than about 500 Å

in diameter.

14. The method according to claim 10 wherein the period of time sufficient to cause the article to obtain a high degree of nucleation is at least 1 hour and the period of time sufficient to cause the article crystallize in situ ranges between about 1-4 hours.

15. The method according to claim 10 wherein the crystal phase assemblage contains primary crystal phases of enstatite or enstatite solid solution and MgAl₂ O₄, and additionally contains a titanate crystal phase.

16. A rigid information disk for use in a magnetic memory storage device consisting essentially of a substrate with a coating of magnetic media on a surface thereof, wherein the substrate is comprised of a glass-ceramic material exhibiting an MOR of at least about 15,000 psi, a Knoop hardness value of greater than at least about 760 KHN, a Young'"'"'s modulus about 20×

10⁶ psi and a fracture toughness in excess of 1.0 MPa.m^1/2, wherein the crystal phase assemblage is comprised predominately of magnesium containing crystals having a pyroxene structure represented by the formula (M₂)(M₁)Si₂ O₆ where M₂ has a coordination of 6-8 oxygen atoms and M₁ is octahedrally coordinated and spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase, the substrate having an overall composition at least 92 % of which consists essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO₂, 10-30% Al₂ O₃, 12-30% MgO, 0-10% ZnO, 5-20% TiO₂, and 0-8% NiO.

17. A rigid information disk according to claim 16 wherein the substrate composition additionally contains a transition metal oxide selected from the group consisting of the oxides of Cu, Co, Fe, Mn, Cr, Sn and V, the oxide Cr not exceeding about 1%.

18. A rigid information disk according to claim 16 wherein the pyroxene crystals exhibit dimensions less than about 1500 Å

.

19. A rigid information disk according to claim 16 wherein the spinel crystals exhibit dimensions less than about 500 Å

.

20. A rigid information disk according to claim 16 wherein the pyroxene crystal phase in the crystal phase assemblage is enstatite or an enstatite solid solution.

21. A rigid information disk according to claim 16 wherein the spinel crystals are primarily MgAl₂ O₄.

22. A rigid information disk according to claim 16 wherein the composition consists essentially, expressed in terms of weight percent on the oxide basis, of 44-53% SiO₂, 15-24% Al₂ O₃, 15-22% MgO, 0-5% ZnO, 9-14% TiO₂, and 0-3% NiO.

23. A rigid information disk according to claim 16 wherein the crystal phase assemblage further contains up to about 15% by weight titanate crystals.

24. A rigid intimation disk according to claim 16 wherein the Al₂ O₃ content in the composition does not exceed 25% unless NiO is present in an amount greater than 2%.