TlBaCaCuO and YBaCuO superconductor thin films via an electrodeposition process
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TIBaCaCuO and YBaCuO superconductor thin films via an electrodeposition process R. N. Bhattacharya, P. A. Parilla, A. Mason, L. L. Roybal, R. K. Ahrenkiel, and R. Noufi Solar Energy Research Institute, Golden, Colorado 80401
R. P. Hellmer, J. F. Kwak, and D. S. Ginley Sandia National Laboratories, Albuquerque, New Mexico 87185 (Received 2 January 1991; accepted 20 March 1991)
Thin-film superconductors of TIBaCaCuO (TBCCO) and YBaCuO (YBCO) were fabricated via an electrodeposition process. The precursors of the superconducting TBCCO films were codeposited at a constant potential of —4 V onto a silver-coated SrTiO3 substrate. The YBCO precursors also were codeposited but under pulsed-potential conditions (in order to improve the film morphology) and onto a silver-coated MgO substrate. The pulsed-potential cycle consisted of 1 s at —4 V followed by 1 s at —1 V. The post-annealed TBCCO film showed zero resistance at about 102 K and critical current density at 76 K of 20 000 A/cm 2 in zero magnetic field and 5000 A/cm 2 in a 10 kOe field parallel to the film plane. The post-annealed YBCO film showed zero resistance at approximately 80 K and critical current density of 5160 A/cm 2 at 4 K in zero magnetic field.
The electrodeposition of thin-film superconductors has considerable practical potential, particularly in the fabrication of large nonplanar devices as well as other electronic device applications. Electrodeposition has recently been used to fabricate high temperature thinfilm superconductors.1"5 In principle, electrodeposition from both aqueous and nonaqueous solutions is possible, although aqueous solutions apparently are unsuitable because the reduction of water (—1.23 V vs NHE) is kinetically more favorable on most electrode materials (except Hg) than the alkaline metals ( < - 2 . 0 V vs NHE). Information on the characteristics (structural, morphological, compositional, and electronic) of electrodeposited TBCCO and YBCO, and electrochemistry involved in the deposition process, however, is limited in the literature; therefore, we have undertaken a systematic study of these aspects in our laboratory. A summary of our findings to date is presented in this paper. Only one report of electrodeposited TBCCO by Maxfield et al? is available in the literature, and this describes the preparation of Tl-based superconductor films by sequential electrodeposition of the constituent metals. This method resulted in films with critical currents of 3000 A/cm 2 at 77 K in zero magnetic field. We report on the fabrication and properties J. Mater. Res., Vol. 6, No. 7, Jul 1991
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of TBCCO and YBCO thin-film superconductors deposited from a single bath solution under constant potential and pulsed-potential conditions, respectively. The precursors of superconducting TBCCO and YBCO films are obtained by codeposition of constituent metals. We find a significant improvement in the critical current density (20 000 A/cm 2 at 76 K, zero field) of electrodeposited TBCCO superconductor
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