Crystalline Alignment and In-plane Texture Improvement of Buffer Layers Deposited on NiW Tapes
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Crystalline Alignment and In-plane Texture Improvement of Buffer Layers Deposited on NiW Tapes Linfei Liu1, Yijie Li1, Huaran Liu1, Xiaokun Song1, Dan Hong1, Ying Wang1 and Da Xu1 1 Department of Physics, Shanghai Jiao Tong University, Shanghai, Shanghai, China ABSTRACT In order to deposit YBCO coated conductor with high critical current densities on rolling assisted biaxially textured Ni-W tapes, this paper has systematically studied the influence of deposition conditions on the orientation, in-plane texture and surface morphology of buffers and superconducting layers. It was found that the crystalline alignment and the in-plane texture of cerium oxide cap-layers were well improved by optimizing deposition parameters. The full width at half maximum of phi-scan x-ray diffraction peaks were reduced from original values of 7-8 degrees to 5-6 degrees. A high critical current density of 4.6×106 A/cm2 has been achieved on optimized buffer layers. This value is comparable with the critical current density of YBCO thin films deposited on single crystalline substrates. INTRODUCTION Recently, tremendous efforts have been made towards scaling up superconducting YBa2Cu3O7-X(YBCO) coated conductors to commercial length and further developing various applications, such as generators, motors and transmission cables [1-2]. Several methods have been reported for achieving YBCO texture on long metal substrates [3-5]. In all these techniques, at least one buffer layer is needed to grow high quality YBCO films on the metal substrate. CeO2 film is the most widely used cap layer for YBCO films because it has a comparatively small lattice mismatch, similar thermal expansion coefficient and good chemical compatibility with YBCO at its high deposition temperature [6-8]. When used as a cap layer, CeO2 film should have an appropriate orientation, high crystallinity and a smooth surface. Research on CeO2 buffer films has commonly focused on the relationship between orientation and deposition conditions [9-11]. In this paper, we report the deposition of pinhole-free, crack-free and textured CeO2 thin films on textured Ni tapes using a reel-to-reel pulsed laser deposition method (PLD) for YBCO coated conductors. We have extensively analyzed the texture of the CeO2 cap layers. EXPERIMENT Biaxially textured Ni-5at.%W(NiW) rolling assisted biaxially textured substrates (RABiTS) obtained from EVICO GmbH in Germany were used as templates for epitaxial growth for all samples. RABiTS-Ni-5W has a sharp {100} cube texture with typical X-ray ω- and Φscans having full-width half-maximum (FWHM) of 5° and 7°, respectively. 50 nm thick CeO2 and 100 nm thick yttria-stabilized zirconia (YSZ) films were deposited sequentially on the substrate using a reel-to-reel PLD system with a high vacuum chamber up to 5×10-7 Torr. The details of these experiments were described in a previous paper [12].
The CeO2 cap layer was deposited and grown epitaxially on the CeO2/YSZ buffered RABiTS tapes by a reel-to-reel PLD system using a KrF (λ = 248 nm) excimer laser. The lase
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