Vol.7 No.4 2015

Research paper : Preparation of superconducting films by metal organic deposition (T. MANABE et al.)−247−Synthesiology - English edition Vol.7 No.4 (2015) a.Manufacture of microwave filter on a 2 cm × 2 cm LaAlO3 substrate and verification of filter performance[40]b.Achievements of YBCO deposition on a 5 cm diameter LaAlO3 substrate and low surface resistance[41]c.Achievements of double-sided YBCO deposition on a 5 cm diameter CeO2/sapphire substrate and low surface resistance[42]d.Possibilities of YBCO deposition by excimer-laser-assisted MOD (ELAMOD) and concurrent patterning[43](2) Application to wire rods and tapesThe YBCO superconducting wires and tapes with long length and thickness were achieved by chemical vapor deposition (CVD) and TFA-MOD using trifluoroacetate (TFA) as the raw material . The MOD method discussed in this research is called the fluorine free (FF) MOD method since it does not include harmful fluorine in the raw material, and is expected to become a manufacturing method for superconducting wire rods and tapes at low cost and low environmental load. The authors have been conducting research with the goal of developing high critical current (Ic) films (high Jc and thick film) on oriented metal substrates that can be made long (Goal II-5), and the following results have been obtained to present.a.Development of a thick coating solution: 0.8 m was achieved by a single coat and firing[44]b.Manufacture of a thick film by repetition of the whole MOD process that includes coating, prefiring, and final heat treatment: manufactured a 4-m-thick epitaxial filmc.Achievement of high Ic (>200 A/cm) by introducing pinning: highest for a FF-MOD film[45]7 SummaryThis paper introduced the following two scenarios and elemental technologies that were employed to achieve the goals to meet the product requirements for the technology for a high-quality, large-area superconducting film by the MOD method for the purpose of FCL application.I.Verification of YBCO thin film manufacturing and achievement of high JcII.Deposition of a high-Jc, large-area YBCO filmIn Scenario I, the main topic was the preparation of a homogeneous coating solution based on solution chemistry and the development of a low-temperature process using low oxygen pressure that is based on solid physical chemistry. Even though we started from the solution, we obtained a high-Jc film that grew epitaxially on the substrate.On the other hand, in Scenario II, the approach taken was first contemplating the enlargement of the YBCO film on the lattice-matched substrate, II-1, and, concurrently, conducting the manufacture of the buffer layer on lattice-mismatched sapphire and the tuning of YBCO deposition, II-2. Afterwards, a large surface area was achieved for the superconducting/buffer/sapphire multilayers, II-3. In executing this approach according to the development plan, there were researchers who were specialists of gas phase deposition and those who specialized in liquid phase deposition within the group, and the two sets of researchers collaborated and offered good feedback. It was also crucial that we were able to procure manufacturing and evaluation devices that could handle large substrates at the appropriate time.These approaches are utilized in the applications to microwave devices and wire rods and tapes.AcknowledgementsWe are deeply thankful to the Power and System Laboratory of the Furukawa Electric Co., Ltd. that provided us with the photographs of the FCL test. We also thank all the people of the R&D Joint Research Committee of the R&D for Practical Superconducting FCL.References[1]New Energy and Industrial Technology Development Organization: R&D of the Core Technology for Superconducting AC Equipment, Fact Sheet, I-2-I-6 (2005) (in Japanese).http://www.nedo.go.jp/content/100091370.pdf[2]T. Okuma and Y. Iwata: Superconducting fault current limiter, J. Inst. Elect. Engnr. Jpn., 117 (4), 222-226 (1997) (in Japanese).[3]S. Mizuta, T. Kumagai and T. Manabe: Preparation of superconducting films by dipping-pyrolysis process, J. Chem. Soc. Jpn. 1, 11-23 (1997) (in Japanese).[4]I. Yamaguchi, T. Manabe, T. Kumagai and S. Mizuta: Preparation of epitaxial oxide films by the coating-pyrolysis process, J. Magn. Soc. Jpn., 24 (8), 1173-1180 (2000) (in Japanese).[5]T. Araki, K. Yamagiwa and I. Hirabayashi: Fabrication of YBCO films by metalorganic deposition using trifluoroacetates and its process conditions, Journal of Cryogenics and Superconductivity Society of Japan, 35 (11), 516-522 (2000) (in Japanese).[6]K. Ueda, K. Yasuda, K. Inoue, A. Kikuchi and K. Iwadate: R&D of HTS power cable and fault current limiter in Super-ACE project, Physica C, 392-396, 1171-1179 (2003).[7]New Energy and Industrial Technology Development Organization: R&D of the Core Technology for Superconducting AC Equipment, Fact Sheet, Basic Plan 1 (2005) (in Japanese). http://www.nedo.go.jp/content/100091370.pdf[8]G. Kästner, D. Hesse, M. Lorenz, R. Scholz, N.D. Zakharov and P. Kopperschmidt: Microcracks observed in epitaxial thin films of YBa2Cu3O7- and GdBa2Cu3O7-, Phys. Stat. Sol. (a), 150 (1), 381-394 (1995).[9]M. Kawasaki: Thin-film technology for high- Tc superconducting devices, J. Cryo. Soc. Jpn., 31 (11), 563-571


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