Development of ion-beam-assisted-deposition method using pyrochlore type oxide buffer layers for Y-123 coated conductors

In recent years, worldwide research efforts have been made to develop Y-123 coated conductors. Ion-Beam-Assisted Deposition (IBAD) is the method that presents quite reliable superconducting properties, by using highly aligned buffer layers on non-textured substrate tapes. In this work biaxially aligned growth was studied for ZrO2-RE2O3 oxide films on polycrystalline Ni-based alloy substrates. Several pyrochlore type oxides (RE2Zr2O7) were found to have sharp textures and RE element was optimized to be Gd, or Eu. The origin of texture enhancement was discussed based on the variation of radiation damage come from lattice bonding energies including the stability of ordered structure for pyrochlore. The time constant of texture evolution for Gd2Zr2O7 was about half compared to YSZ. The growth structures were observed by transmission electron microscope, (TEM), which have columnar-like colony of small size crystallites nearly equal to YSZ. Continuous depositions were performed on 10-mm width Ni-alloy tapes by a large-area reel-to-reel IBAD system with the production speed of 1.0 m/h. A uniform Gd2Zr2O7 film Of 60-m length was obtained with the in-plane mosaic spread (Deltaphi) of 16-18 degrees. Y-123 films were deposited by Pulsed Laser Deposition (PLD) with tape speed of 1.0 m/h. I-c of 50.0 A and J(c) of 4.2 x 10(9) A/m(2) were obtained at the length of 9.6 in, with Deltaphi for the Y-123 film were 9-12 degrees. I-c of 150.0 A and J(c) of 1.0 x 10(10) A/m(2) were obtained on a shorter sample at the length of 8 cm.