Long-length IBAD-MgO buffer layers for high performance RE-123 coated conductors by a large ion beam source

In Fujikura, a large-scale ion-beam-assisted deposition (IBAD) system with a large ion source has been employed to fabricate biaxially textured MgO films. The large-scale IBAD system has multiple deposition lanes where substrate tapes move, and therefore we have to optimize experimental conditions at each lane. We selected an appropriate deposition area and, finally, we successfully fabricated a 1 km-length IBAD-MgO film at a production rate of 1 km/h. We also studied pulsed-laser-deposited (PLD) CeO₂ films directly on the IBAD-MgO films in spite of a large lattice mismatch between CeO₂ and MgO. From transmission electron microscope (TEM) observations at an interface between MgO and CeO₂ films, it is revealed that there is domain-matching-epitaxy relationship between MgO and CeO₂ films. We also fabricated thin (1.0 μm) and thick (3.7 μm) PLD – GdBa₂Cu₃O_7−x (GdBCO) film on the long-length CeO₂/MgO substrate (over 150 m). Critical currents (I_c) and current density (J_c) were over 300 A and 3 MA/cm² respectively for the thin GdBCO film and were about 645 A and 1.7 MA/cm² for the thick GdBCO film at 77 K in self-field.