Superconducting YBa 2 Cu 3 O x films prepared on YSZ polycrystalline substrates by rf thermal plasma evaporation
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As-grown YBa 2 Cu 3 0 x films prepared on single crystal (100)MgO substrates by rf thermal plasma evaporation have the advantages of a high deposition rate of 730 nm/min, a large area deposition over 300 cm2, and a high Jc of 6.8 X 105 A/cm 2 (77 K, 0 T), as reported in previous papers.1'2 We report in this paper about the preparation of YBa2Cu3Ox films on yttria-stabilized zirconia (YSZ) polycrystalline substrates for a practical application using this technique to synthesize these films on flexible (metal or flexible polycrystal) substrates. Films prepared on YSZ polycrystalline substrates grew with a c-axis orientation at a relatively high deposition rate and exhibited a zero resistance temperature (Tc0) of 88 K and a critical current density Jc of 3500 A/cm 2 (77 K, 0 T). Films prepared on flexible YSZ polycrystalline tapes with a length of 100 mm were also grown with a c-axis orientation and exhibited Tc0 over 77 K.
I. INTRODUCTION Recently, high temperature superconducting wire and tape for engineering power applications have been fabricated by several methods. The YBa 2 Cu 3 0^ system is one of the superconductors with a high critical temperature (Tc) over liquid nitrogen temperature (77 K), and high-quality YBa 2 Cu 3 0^ films with a critical current density (Jc) of more than 106 A/cm 2 (77 K, 0 T) have been prepared by vapor phase processes such as chemical vapor deposition,3 rf sputtering,4 reactive evaporation,5 laser ablation,6 and so on. However, these high-quality films are almost always prepared on single crystal substrates. Moreover, deposition is limited to small areas and low growth rates. Therefore, for engineering power applications, it is important to develop a practical process that synthesizes YBa 2 Cu 3 0 x films on flexible (metal or flexible polycrystal) and large area substrates with a high deposition rate. The rf thermal plasma evaporation technique is a vapor phase process using thermal O 2 plasma with an extremely high temperature of several thousands degrees and active atmosphere.7"9 As reported in previous papers,1'2 as-grown YBa 2 Cu 3 0^ films prepared on single crystal (100)MgO substrate by rf thermal plasma evaporation have the advantages of a high deposition rate of 730 nm/min, a large area deposition over 300 cm 2 , and a high Jc of 6.8 X 105 A/cm 2 (77 K, 0 T). Accordingly, this technique is considered to be one of the practical processes to synthesize superconducting tape, wire, and shields for engineering power applications. We report in this paper on the preparation of asgrown YBa 2 Cu 3 0 x films by rf thermal plasma evaporation on YSZ polycrystalline substrates, in order to J. Mater. Res., Vol. 9, No. 5, May 1994
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investigate (i) the characteristics as a buffer layer for deposition on metal substrates10'11 and (ii) the preparation of YBa 2 Cu 3 0 A: films on flexible YSZ polycrystalline tapes using an Inconel holder rotating around the horizontal axis.12 II. EXPERIMENTAL PROCEDURES The schematic diagram of the exper
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