High dielectric capacitor materials and method of their production

• US 20080218940A1
• Filed: 03/05/2007
• Published: 09/11/2008
• Est. Priority Date: 03/05/2007
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Inventors: Knuteson, David J., Kahler, David, Wagner, Brian, Berghmans, Andre, Singh, Narsingh B., Sherwin, Marc, Adam, John D., Talvacchio, John J.
• Granted Patent: US 7,830,644 B2
• Time in Patent Office: Days
• US Class Current: 361/524
• CPC Class Codes: C01G 23/003 Titanates C01G23/001 takes precedence
• CPC Class Codes: C01P 2002/34 perovskite-type (ABO3)
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3227 Lanthanum oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3281 Copper oxides, cuprates or oxide-forming salts thereof, e.g. CuO or Cu2O
• CPC Class Codes: C04B 35/462 based on titanates
• CPC Class Codes: H01G 4/105 Glass dielectric
• CPC Class Codes: H01G 4/1209 characterised by the ceramic dielectric material H01G4/1272, H01G4/1281 take precedence
• CPC Class Codes: H01G 4/1218 based on titanium oxides or titanates H01G4/1245 takes precedence
• CPC Class Codes: H01G 4/306 made by thin film techniques

Abstract

Methods of producing polycrystalline and single crystal dielectrics are disclosed, including dielectrics comprising CaCu₃Ti₄O₁₂ or La₃Ga₅SiO₄. Superior single crystals are manufactured with improved crystallinity by atomic lattice constant adjustments to the dielectric and to the substrate on which it is grown. Dielectric materials made according to the disclosed methods are useful for manufacture of energy storage devices, e.g. capacitors.

Claims

1. A method of making a crystalline composition selected from the group consisting of CaCu₃Ti₄O₁₂ or La₃Ga₅SiO₄, which comprises:

(a) mixing together, in stoichiometric amounts, powdered materials comprising the Ca, Cu and Ti or La, Ga and Si components of said composition;

(b) subjecting said mixed powders to heat to substantially react the powdered components to form said polycrystalline composition; and

(c) pressing said reacted mixture to form a stoichiometric pellet.

2. The method of claim 1 wherein said pressing is performed using the solid-solid or the solid-liquid sintering method.

3. The method of claim 1 wherein said heat is about 1100°

C. to about 1200°

C.

4. The method of claim 1 wherein said pressing is performed at a temperature below 1200°

C.

5. The method of claim 1 which further comprises interrupting said subjecting the mixed powders to heat, re-mixing said powdered materials, pressing said re-mixed materials and resuming said subjecting the mixed powders to heat.

6. The method of claim 1 wherein said polycrystalline composition is CaCu₃Ti₄O₁₂.

7. The method of claim 1 wherein said powdered materials are selected from the group consisting of calcium oxide, calcium carbonate, calcium oxalate, calcium formate, copper oxide, copper carbonate, copper oxalate, titanium dioxide, titanyl carbonate, titanyl oxalate and a combination thereof.

8. The method of claim 1 wherein said mixed powders are subjected to heat for about 50 to about 100 hours.

9. The method of claim 1 wherein said mixed powders are subjected to heat for about 50 to about 100 hours based on sample size.

10. The method of claim 1 wherein said mixed powders are subjected to heat at about 1000°

C. to about 1100°

C.

11. The method of claim 1 wherein said mixed powders are subjected to heat at about 1000°

C. to about 1100°

C. based on sample size.

12. The method of claim 1 wherein said mixed powders are subjected to heat for 120 hours.

13. The polycrystalline composition made according to the method of claim 1.

14. A method of adjusting the lattice constant mismatch of a film crystal CaCu₃Ti₄O₁₂ dielectric and a deposition substrate, which comprises substituting at least a portion of an ion of the crystal structure of said CaCu₃Ti₄O₁₂ dielectric with an ion having a different ionic radius during liquid phase epitaxial growth of said crystal, wherein the lattice constant of said crystal is changed.

17. A method of claim 14 wherein calcium is substituted with an ion selected from the group consisting of a strontium ion, a bismuth ion, a sodium ion, a lanthanum ion, an ion of a lanthanide element, and a combination of any thereof.

18. The method of claim 14 wherein titanium is substituted with an ion selected from the group consisting of an iron ion, a ruthenium ion, a chromium ion, a germanium ion, a manganese ion and a combination of any thereof.

19. The method of claim 17 wherein about 0% to about 100% of the calcium is substituted with strontium.

20. The method of claim 17 wherein about 0% to about 50% of the calcium is substituted with strontium.

21. The method of claim 17 wherein up to about 50% of the calcium is substituted with strontium.

23. A capacitor which comprises the dielectric of claim 19.

15. A method of adjusting the lattice constant mismatch of a film crystal CaCu₃Ti₄O₁₂ dielectric and a deposition substrate, which comprises substituting at least a portion of an ion of the deposition substrate with an ion having a different ionic radius, wherein said deposition substrate is a conductive oxide electrode and wherein the lattice constant of said conductive oxide electrode is changed.

24. The method of claim 15 wherein said conductive oxide electrode comprises LSCuO and LSCoO.

25. The method of claim 24 wherein the lattice constant of said conductive oxide electrode is changed by partial chemical substitution of said LSCuO, LSCoO, or both.

26. The method of claim 24 wherein said partial chemical substitution is 0-100% substitution.

27. The method of claim 15 wherein said seed layer is about 5 nm thick.

16. A method of adjusting the lattice constant mismatch of a film crystal CaCu₃Ti₄O₁₂ dielectric and a deposition substrate, which comprises depositing a seed layer of CaCu₃Ti₄O₁₂ onto said deposition substrate.

22. A dielectric which comprises Ca_0.8Sr_0.2Cu₃Ti₄O₁₂.

28. A capacitor which comprises a conductive oxide electrode which comprises LSCuO and LSCoO, where the lattice constant of said conductive oxide electrode is changed by partial chemical substitution of said LSCuO, LSCoO, or both.