Fabrication of Y-Ba-Cu-O films on surface-oxidation epitaxy (SOE) processed substrates

The surface-oxidation-epitaxy (SOE) method promotes simple and cost-effective process to form a biaxially textured NiO template for epitaxial growth of YBa₂Cu₃O_x (Y-Ba-Cu-O) film. SOE tapes of 100 m in length were prepared by the reel-to-reel oxidation system with the tape moving speed of 10 m/h. A highly biaxially textured NiO layer, which had Δφ (full width at half maximum from X-ray φ-scan) of less than 23° throughout the whole length, was successfully formed under appropriate conditions of temperature and atmosphere. In order to improve surface conditions for obtaining high critical current density (J_c) for Y-Ba-Cu-O film on the SOE-tapes, we have investigated the effect of thin oxide cap layers such as MgO, SrTiO₃, CeO₂, and so on. When BaZrO₃ was used as a cap layer, J_c and critical current (I_c) of Y-Ba-Cu-O films grown by the pulsed laser deposition (PLD) at 77 K were measured to be 1.3 MA/cm² and 137 A, respectively. These values were for a 10 mm-width short tape. A continuous deposition of YBCO on 10-cm long ×10-mm wide SOE tape with SrTiO₃ or BaZrO₃ cap layer was also investigated. The end-to-end I_c was 1 A (J_c of 1.6 ×10⁴ A/cm²) for SrTiO₃ cap layer and 4 A (J_c of 5.6 ×10⁴ A/cm²) for BaZrO₃ one.