IBAD–MgO buffer layers for coated conductors in the large-scale system

Abstract

For practical applications of high-temperature superconductor tape, the high production rate of tapes is needed to reduce its cost. Recently, the long-length coated conductor with high performance has been fabricated by an ion beam assisted deposition/pulsed laser deposition (IBAD/PLD) method in Fujikura. In IBAD process, we adopted IBAD–Gd 2Zr 2O 7 (GZO) film. The process speed of IBAD–GZO film was increased up to 5 m/h using a polished metal substrate tape. To fabricate biaxially-textured buffer layers at a higher rate, we have started to develop another structures such as (a) IBAD–GZO/IBAD–MgO (3-fold symmetry) and (b) IBAD–MgO (4-fold symmetry). In the case (a), we fabricated GdBCO/CeO 2/IBAD–GZO/IBAD–MgO tape and the critical current was I c = 550 A/cm (2.46 MA/cm 2) and throughput of IBAD processes were 20 m/h. In the case (b), IBAD–MgO short samples with Δ Φ of 9°–11° were obtained at 500 m/h. The 500 m/h (10 mm width) is extremely high rate in IBAD process in the world. As long-length IBAD layer 10 m, 50 m and 100 m IBAD–MgO films were fabricated at the speed of 100 m/h. After CeO 2 deposition, in-plane textures of these samples were Δ Φ of 3.7°–3.7°, 4.1°–4.9° and 4.2°–4.8°. Using some of these buffer layers, we have obtained GdBCO film with I c = 400 A/cm (2 MA/cm 2, 10 m) and I c = 550 A/cm (2.7 MA/cm 2, short sample).