YBCO films on buffered Haynes® 230 substrate

Abstract

The use of buffer as intermediate layer between Ba₂Cu3O_7−δ film and Nickel-based alloy substrate for tape conductor applications is necessary to prevent decomposition of YBCO due to the interdiffusion of metallic species. Electrophoretic deposition and post heat treatments were employed to deposit CeO₂ and Yttrium-stabilized Zirconia (YSZ) buffer layers on Haynes® 230 substrates, and to subsequently deposit YBCO films on top of these buffer layers. The resulting surface morphology and phase composition of the films were analyzed using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). While XRD analysis reveals peaks of both films correspond to the superconducting YBCO phase and orthorhombic structure, notable presence of non-superconducting Y211 phases are also observed specially with YSZ-buffered film. YBCO film deposited on CeO_2-buffered substrate show signs of partial melting, indicated by formation of necks between grains, whereas YBCO deposited on YSZ-buffered substrate melted and grew into isolated rectangular crystals. Introduction of flux to lower the melting temperature of the film and prevent formation of the non-superconducting Y211 phase is recommended.