Using condensed chemicals to precondition lithium niobate and lithium tantalate crystals

• US 7,381,397 B2
• Filed: 12/02/2005
• Issued: 06/03/2008
• Est. Priority Date: 05/25/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Crystal Technology, Incorporated (Gooch & Housego PLC)
• Inventors: Jundt, Dieter Hans, Kajiyama, Maria Claudia Custodio
• Primary Examiner(s): Vanoy; Timothy C
• Application Number:
  US11/293,010
• Publication Number:
  US 20060107888A1
• Time in Patent Office: 914 Days
• Field of Search: 423/594.8, 423/594.15, 252/62.9 R, 117/3, 117/95, 117/900, 427/372.2, 427/374.1, 427/398.1, 427/240, 427/430.1, 204/192.1
• US Class Current: 423/594.8
• CPC Class Codes: C01G 33/00 Compounds of niobium
• CPC Class Codes: C01G 35/00 Compounds of tantalum
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: Y10S 117/90 Apparatus characterized by composition or treatment thereof, e.g. surface finish, surface coating

Abstract

Methods and apparatus for preconditioning a lithium niobate or lithium tantalate crystal. At least a portion of a surface of the crystal is covered with a condensed material including one or more active chemicals. The crystal is heated in a non-oxidizing environment above an activating temperature at which the active chemicals contribute to reducing the crystal beneath the covered surface portion. The crystal is cooled from above the activating temperature to below a quenching temperature at which the active chemicals become essentially inactive for reducing the crystal.

Claims

1. A method for preconditioning a crystal, the method comprising:

selecting a crystal from the group consisting of lithium niobate and lithium tantalate crystals;

covering at least a portion of a surface of the crystal with a condensed material including one or more active chemicals selected from the group consisting of the oxalates of lithium, sodium, potassium, magnesium, and calcium;

heating the crystal in a non-oxidizing environment above an activating temperature at which the active chemicals contribute to reducing the crystal beneath the covered surface portion; and

cooling the crystal from above the activating temperature to below a quenching temperature at which the active chemicals become inactive for reducing the crystal.

2. The method of claim 1, wherein the active chemicals include lithium oxalate.

3. The method of claim 1, wherein:

covering the surface portion with a condensed material includes covering the surface portion with a condensed material including an inactive component that does not contribute to reducing the crystal at the activating temperature.

4. The method of claim 1, wherein:

covering the surface portion with a condensed material includes depositing a thin film of the condensed material onto the surface portion.

5. The method of claim 4, wherein:

covering the surface portion with a condensed material includes depositing the condensed iiiaterial by condensation onto the surface portion.

6. The method of claim 5, wherein:

depositing the condensed material by condensation onto the surface portion includes depositing the condensed material during the heating of the crystal in the non-oxidizing environment.

7. The method of claim 5, wherein:

depositing the thin film includes physical vapor deposition of the condensed material onto the surface portion.

8. The method of claim 4, wherein:

depositing the thin film includes spin coating the surface portion with the condensed material.

9. The method of claim 4, wherein:

depositing the thin film includes dip coating the surface portion with the condensed material.

10. The method of claim 1, wherein:

covering the surface portion with a condensed material includes covering the surface portion with a nowder of the condensed material.

11. The method of claim 1, wherein:

covering the surface portion with a condensed material includes preparing a solution or dispersion by dissolving or dispersing the active chemicals in a liquid matrix, respectively, and spinning the solution or dispersion onto the surface portion.

12. The method of claim 1, wherein:

heating the crystal above an activating temperature includes heating the crystal to a temperature that is below a ferroelectric phase transition temperature of the crystal.

13. The method of claim 1, wherein:

heating the crystal above an activating temperature includes heating the crystal above about 250 Celsius.

14. The method of claim 1, wherein:

heating the crystal in a non-oxidizing environment includes heating the crystal in a reducing atmosphere.

15. The method of claim 1, wherein:

heating the crystal in a non-oxidizing environment includes heating the crystal in an inert atmosphere.

16. The method of claim 1, wherein:

heating the crystal above an activating temperature includes keeping the crystal above the activating temperature for a predetermined activating time.

17. The method of claim 16, further comprising

determining the activating time based on the active chemicals in the condensed material.

18. The method of claim 16, wherein:

cooling the crystal from above the activating temperature below a quenching temperature includes cooling the crystal from above the activating temperature below a quenching temperature within a quenching time that is substantially smaller than the activating time.

19. The method of claim 1, wherein the crystal is a crystal wafer.

21. The method of claim 1, wherein the crystal is lithum tantalate.

22. The method of claim 2, wherein the crystal is lithum tantalate.

23. The method of claim 3, wherein the crystal is lithum tantalate.

24. The method of claim 4, wherein the crystal is lithum tantalate.

25. The method of claim 11, wherein the crystal is lithum tantalate.

20. A method for preconditioning a crystal, the method comprising:

selecting a crystal from the group consisting of lithium niobate and lithium tantalate crystals;

covering at least a portion of a surface of the crystal with a condensed material including one or more active chemicals selected from the group consisting of oxalate salts;

heating the crystal in a non-oxidizing environment above an activating temperature at which the active chemicals contribute to reducing the crystal beneath the covered surface portion; and

cooling the crystal from above the activating temperature to below a quenching temperature at which the active chemicals become inactive for reducing the crystal.

26. The method of claim 20, wherein the crystal is lithum tantalate.