GZO/MgO IBAD-buffer layers for coated conductors

Abstract

Long-length and low-cost coated conductors are necessary for practical use such as motor, generator, transformer, fault current limiter, SMES and so on. For fabricating low-cost coated conductors, production speeds at each process should be faster. The structure of coated conductor we adopted, is GdBa 2Cu 3O y (GdBCO)/CeO 2/Gd 2Zr 2O 7 (GZO)/metal. To make processes faster without changing such beneficial structures, we adopted another buffer layer under GZO film. At the IBAD (ion-beam-assisted deposition) process, MgO is known as one of the suitable materials to achieve high alignment with thin film thickness. We fabricated IBAD-MgO film with changing deposition rates and ion-current densities, and got two types of IBAD-MgO film. One is the film with its crystal orientation aligned to the MgO(1 1 1) parallel to the tape surface, and the other is with MgO(1 0 0). And each film has in-plane texture such that 3-fold symmetry, and 4-fold symmetry respectively in the pole figure of MgO<1 1 0>. We performed IBAD-GZO on the 3-fold IBAD-MgO film, and got 4-fold IBAD-GZO film. In-plane textures of GZO were not so different from the ordinary IBAD-GZO film, but the thickness of the films became from 1.2 μm to 0.3 μm (1/4). And a critical current of the GdBCO film on the buffer layer was over 210 A/cm ( J c > 1.5 MA/cm 2) at 77 K.