Development of Long REBCO Coated Conductors by PLD-REBCO/Sputter-CeO2/IBAD-MgO at SJTU and SSTC

Through collaboration with SJTU, a pilot REBCO coated conductor fabrication line has been set up at the Shanghai Superconductor Technology Corporation Ltd., in 2013. To reduce the cost of coated conductor tapes, simplified tape architecture was developed, i.e., PLD-REBCO/Sputter-CeO₂/IBAD-MgO on metal tapes with amorphous oxide barrier layer. High-quality long REBCO coated conductors have been successfully fabricated by pulsed laser deposition (PLD) plus magnetron sputter and ion-beam-assisted deposition (IBAD) processes. Under optimized conditions, the IBAD-MgO layers showed pure (001) orientation and excellent in-plane texture. AFM observation showed MgO layer had very smooth surface. The RMS is less than 1 nm. On the textured MgO layer, sputter deposited single CeO₂ cap layer showed pure (001) orientation and excellent in-plane texture of 47-6°. A reel-to-reel PLD process with high deposition rate was already scaled up to 100-m/h tape speed. One-micrometer-thick REBCO films had a high critical current density of over 3.0 MA/cm² (at 77 K, self-field). The critical current density of 2 μm thick films is still more than 2.5 MA/cm². Hundred-meterlong coated conductor tapes with over 500 A/cm performance have been routinely fabricated. Currently, the process optimization for kilometer-long coated conductor tapes is underway.