Coated conductors textured by ion-beam assisted deposition

Abstract

We review the progress on ion-beam assisted deposition (IBAD) textured superconducting tapes. Over the past 15 years there has been much work worldwide on Y2O3-stabilized ZrO2 (YSZ) textured templates for deposition of HTS. More recently Gd2Zr2O7 textured templates have replaced YSZ in Japan. At Los Alamos National Laboratory in the USA we have developed a process for continuous texturing of MgO on metal tapes, with subsequent buffer layer deposition, and REBaCuO pulsed-laser deposition (PLD). We discuss the critical issues being researched in our coated conductor architecture. IBAD-MgO is an extremely fast process, but requires smooth surfaces over long lengths, which is achieved in our laboratory by electropolishing of metal alloy tapes. The progress to date has demonstrated that IBAD-MgO texture can develop in less than 1s. Under optimized processing conditions the in-plane texture full-width half-maximum for the MgO is less than 5° and less than 2° for out-of-plane texture. In the YBCO layer this improves to an in-plane texture of less than 2° and 1° out-of-plane. At this level of alignment critical currents are no longer limited by the film grain boundaries. Critical currents for YBCO layers deposited continuously by PLD on the IBAD-MgO templates have been steadily increasing over the last five years, and have been demonstrated to exceed 500A/cm-width. An important remaining issue for coated conductors is the decrease in Jc with thickness of the HTS film.