日本金属学会誌

J. Japan Inst. Metals, Vol. 71, No. 11 (2007),
pp. 999-1005

The Mechanism for the Formation of a-Axis Phase in High-Jc Sm1+xBa2-xCu3Oy Thick Films Prepared by Low Temperature Growth Technique

Masashi Miura1,6, Yutaka Yoshida1,6, Toshinori Ozaki1,6, Yusuke Ichino1,6, Yoshiaki Takai1, Kaname Matsumoto2,6, Ataru Ichinose3,6, Shigeru Horii4,6 and Masashi Mukaida5,6

1Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya 464-8603
2Department of Materials Science, Kyoto University, Kyoto 606-8501
3Electroc Power Enginnering Research Lab., Central Research Central Resaerch Institute of Electric Power Industry, Yokosuka 240-0196
4Department of Applied chemistry, University of Tokyo, Tokyo 113-8586
5Department of Materials Science and Engineering, Kyushu University, Fukuoka 812-8581
6CREST-Japan Science and Technology Agency, Saitama 332-0012

Abstract:

REBa2Cu3Oy (REBCO) film is required for high-critical current (Ic) at 77 K, when using in power applications such as superconducting magnetic energy storage (SMES) and nuclear fusion. Generally, critical current density (Jc) of REBCO thick film decreases with increasing thickness of superconductor, because the amount of dead layer such as a-axis oriented phase increases with increasing the thickness. We speculated that the formation of a-axis oriented phase in REBCO thick films is owing to reduction of surface temperature. In this study, we fabricated low temperature growth (LTG)-multi Sm1.04Ba1.96Cu3Oy (SmBCO) thick films using a (Sm1.04Ba1.96Cu3Oy/Sm-rich layer)×N (N=1, 2·s) multilayer system, to suppress the formation of a-axis oriented phases. The LTG-multi thick films retained a large terrace, as a result, supressing the reduction of surface temperature, even if the thickness of the films becomes thick. Therefore, LTG-multi thick films suppressed the formation of a-axis oriented phases and the films showed Ic=630 A/cm-width with a thickness of 1.35 μm at 77 K. From these results, we suggest that LTG-multilayer system is an effective technique for improving the critical current of coated conductor.


(Received 2007/3/16)

Keywords:

Sm1+xBa2-xCu3Oy, crystal growth, thick film, critical current, a-axis oriented phase, multilayer system


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