High critical current density YBa 2Cu 3O 7− δ tapes prepared by the surface-oxidation epitaxy method

Abstract

YBa 2Cu 3O 7− δ (YBCO) films with high critical current density ( J c) were successfully fabricated on nickel tapes buffered with epitaxial NiO. NiO was prepared on the textured nickel tape by the surface-oxidation epitaxy (SOE) method. We have reported so far a critical temperature ( T c) of 87 K and J c=4–6×10 4 A/cm 2 (77 K, 0 T) for the YBCO films on NiO/Ni tapes. To enhance the superconducting properties of the YBCO films on the SOE-grown NiO, depositions of thin oxide cap layers such as YSZ, CeO 2, and MgO on NiO were investigated. These oxide cap layers were epitaxially grown on NiO and provided the template for the epitaxial growth of YBCO films. Substantially improved data of T c=88 K and J c=3×10 5 A/cm 2 (77 K, 0 T) and 1×10 4 A/cm 2 (77 K, H∥ c, 4 T) were obtained for YBCO film on NiO, by using a MgO cap layer with a thickness of 50 nm. The method described in this paper is a simple way to produce long YBCO tape conductors with high- J c values.