Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from solid or gel state
Reexamination Certificate
1999-07-20
2001-05-15
Utech, Benjamin L. (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from solid or gel state
C117S068000, C117S070000
Reexamination Certificate
active
06231666
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
This invention relates to methods for forming epitaxial thin films of perovskite materials via chemical solution deposition. More particularly this invention relates to methods for forming such films through the use of halide precursors. This invention also relates to methods for forming buffer layers to lie between YBCO superconductor layers and metallic or single crystal oxide substrates.
Tremendous interest exists for use of high temperatures superconducting cables for AC power transmission, as roughly half the electric power produced in the U.S. is lost over power lines before reaching the end customer. Production of flexible, kilometer lengths of superconducting wire or tape would enable zero-resistance current transport, recovering this lost power. A major challenge to attaining this goal is achieving a low-cost, high throughput method of producing flexible, epitaxial superconducting films on such length scales. This invention teaches a major advance in production of epitaxial films on flexible, inexpensive base-metal tapes, which enable low-cost, continuous processing of such wires, and other products.
To achieve a needed superconducting power handling capability of about 10
6
A/cm
2
, epitaxial or single crystal-like superconducting films of YBa
2
CuO
7−x
(YBCO) or similar materials are required. Production of such films likely requires use of a substrate with a similar atomic lattice structure to template crystalline growth. Through cold-rolling of nickel wire, long lengths of (200) oriented nickel tape have been demonstrated by Oak Ridge National Laboratory and others, enabling the required length scales of lattice-matched, oriented, and relatively inexpensive substrates. Superconducting materials such as YBCO would react chemically if deposited directly on nickel. Therefore, some sort of buffer layer is necessary between the YBCO and the nickel substrate.
BRIEF SUMMARY OF THE INVENTION
This unmet need, as well as others, can be satisfied by the method of the present invention which is a chemical solution deposition (CSD) technique that enables production of epitaxial buffer layers atop oriented oxide or nickel substrates, and subsequent CSD of epitaxial YBCO atop these buffer layers. This method enables inexpensive production of epitaxial superconductor/buffer layer/oriented nickel tape structures at low processing temperatures. This CSD method enables continuous processing of kilometer lengths of superconducting wire at much smaller expense than competing vapor phase deposition processes including chemical vapor deposition, sputtering, electron beam evaporation, or pulsed laser deposition. In addition, the ability to integrate such oxide buffer layers, as BaTiO
3
on Ni is a major advance for production of multilayer ceramic capacitors. Ni electrodes are much less costly than the silver, silver/palladium, or platinum electrodes normally used for these applications. As electrode costs in half the expense for such capacitors, such an advance is significant.
REFERENCES:
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Ronald H. Baney, Debora F. Bergstrom, and Bruce H. Justice,Metal Iodides: Novel Solution Precursors to Cuprate Superconductors, American Chemical Society, 0897-4756/92/2804-0984, 1992.
Paul C. McIntyre, Michael J. Cima, and Man Fai Ng,Metalorganic Deposition of high JcBa2Ycu3O7-xThin Films from Trifluoroaecetate Precursors onto(100)SrTiO3, Journal of Applied Physics, 68(8), Oct. 15, 1990.
Paul C. McIntyre, Michael J. Cima, John A. Smith, Jr., Robert B. Hallock, Michael P. Siegal and Julia M. Phillips,Effect of Growth Conditions on the Properties and Morphology of Chemically Derived Epitaxial Thin Films of Ba2Ycu3O7-xon(001)LaAIO3, Journal of Applied Physics 71(4), Feb. 15, 1992.
Paul C. McIntyre and Michael J. Cima,Heteroepitaxial Growth of Chemically Derived ex situ Ba2Ycu3O7-xThin Films, J. Mater Res., vol. 9, No. 9, Sep. 1994.
P. C. McIntyre, M. J. Cima, A. Roshko,Epitaxial Nucleation and Growth of Chemically Derived Ba2Ycu3O7-xThin Films on(001) )SrTiO3, Journal of Applied Physics 77(10), May 15, 1995.
Ashley Carol S.
Clem Paul G.
Rodriguez Mark A.
Voigt James A.
Anderson Matthew
Cone Gregory A.
Sandia Corporation
Utech Benjamin L.
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