Development of Long Length IBAD-MgO and PLD Coated Conductors

For high speed and low cost production of coated conductors, a simplified 4-layered buffer architecture consisting of Gd₂Zr₂O₇ (GZO)/Ion Beam Assisted Deposition (IBAD)-MgO/LaMnO₃/CeO₂ was realized, which is compared with the conventional 5-layered IBAD-MgO buffer layers. A new cation diffusion barrier and nucleation GZO layer was first reported. The fourth layer of Pulsed Laser Deposition (PLD)-CeO₂ showing the self-epitaxial growth effect resulted in the in-plane texturing (Deltaphi) of about 3 to 4 degrees. Consequently, high critical current, I_c, values above 600 A/cm-width were attained for PLD-GdBa₂Cu₃O_7-X (GdBCO) short samples. Using this result, a 41 m long GdBCO coated conductors was successfully fabricated at the production rate of 24 m/h for IBAD-MgO. This conductor exhibited superior Deltaphi values of 3.7 to 3.8 degrees and high I_c values of 500 to 600 A/cm-width at 77 K and self -field (s.f.) along almost the entire length. The highest I_c recorded 608 A/cm-width with the J_c value of 2.43 Ma/hboxcm². Furthermore, a new IBAD-MgO deposition method was developed, using DC-reactive sputtering which is expected to be inexpensive and easy to scale up. This system brought about a high production rate of 150 m/h in spite of the small deposition area (6 times 20 cm²). The GdBCO on this buffered substrate also showed a high I_c value of 286 A/cm-width at 77 K and s.f., corresponding to the J_c value of 1.43 Ma/hboxcm².