Relationship between critical current properties and nanorod morphology in REBa 2 Cu 3 O y thin films
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Relationship between critical current properties and nanorod morphology in REBa2Cu3Oy thin films M. Haruta1, N. Fujita1, Y. Ogura1, T. Nakata1, T. Maeda1, A. Ichinose2, P. Mele3, K. Matsumoto4, and S. Horii1 1 School of Environmental Science and Engineering, Kochi University of Technology, Kami-shi, Kochi 782-8502, Japan 2 Central Research Institute of Electric Power Industry, Yokosuka, Kanagawa 240-0196, Japan 3 Institute for Sustainable Science and Development, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan 4 Department of Materials Science and Engineering, Kyushu Institute of Technology, Tobata-ku, Kitakyushu 804-8550, Japan ABSTRACT Changes in critical current properties depending on growth temperature (Ts) were clarified for Ba-Nb-O-doped YBa2Cu3Oy (Y123) films deposited by YAG- and excimer-PLD. Due to the introduction of Ba-Nb-O-nanorods, a vortex-Bose-glass-like behavior emerged as irreversibility lines and in-field critical current densities (Jcs) were improved. Crossover magnetic fields (Bcr) and in-field Jcs increased with the increase in Ts for the Y123 films with nanorods. These Ts-dependent critical current properties were attributable to the changes in morphology of the nanorods with Ts and were independent of laser source in PLD apparatuses. For the fabrication of RE123 coated conductors containing nanorods, optimization of Ts with taking both materials of RE123 matrix and nanorod into account is necessary to achieve higher in-field Jc. INTRODUCTION Introduction of non-superconducting second phase with the size of nano-meter-order as vortex pinning centers is effective to improve in-field critical current densities (Jcs) for practical applications of high-Tc superconductors based on REBa2Cu3Oy (RE: Y and rare-earth elements, RE123). A practical process to artificially introduce the fine second phase into RE123 films had not been developed until a pioneer work by MacManus-Driscoll et al. [1]. That is, introduction of nanorods of BaZrO3 (BZO), which were self-assembled and elongated along the c-axis of Y123 matrix, was realized only by mixture of BZO into Y123 target in pulsed laser deposition (PLD). This process led to drastic improvement of Jc under the magnetic fields applied parallel to the c-axis (B//c) for Y123 coated conductors. After this work, many nanorod materials were developed such as BZO [1-6], BaNb2O6 (BNO) [7-10] and BaSnO3 (BSO) [11]. Furthermore relationship between doping level of nanorod material and superconducting properties (Tc, Jc) [4, 12] and quantitatively understanding of critical current properties [2, 8, 13] were reported. In order to achieve higher in-field Jc, optimization of doping level of the nanorod material is necessary for nanorod-doped RE123 films. The influences of doping level and type of nanorod material to in-field Jc and Tc were reported [4, 12]. However, the effects of growth conditions on critical current properties for RE123 films with nanorods have not been clarified yet. Recently,
critical current properties of RE123 films with nanoro
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