Advances in surface-oxidation epitaxy processed substrates for YBa 2Cu 3O 7- δ film

The preparation of long oxide template using surface-oxidation epitaxy (SOE) method and the deposition of oxide cap layer and YBa ₂Cu ₃O _{7- δ} (YBCO) film on it have been studied for the fabrication of coated conductors. In SOE process, Cr-oxide behaves as a barrier against Cr contamination with SOE-NiO layer in high strength and low magnetism Ni-clad Ni-20wt.%Cr (Ni/NiCr) tape. MgO cap layer makes SOE-processed tape surface smooth with the average roughness of a few nm. The critical current ( I_c) of 8 A (the critical current density ( J_c) of 0.2 MA/cm ²) was obtained for the YBCO film deposited on a 10 cm long×5 mm width SOE-processed tape with MgO cap layer in a short sample cut from a 10 cm long specimen. J_c exceeding 0.1 MA/cm ² was obtained for YBCO film on SrTiO ₃ cap layer and CeO ₂ one of SOE-processed tape.