MOCVD and spray pyrolysis for coated conductor synthesis

A reel-to-reel MOCVD system has been optimized to get high quality YBCO coated conductor tapes. The buffer layer architectures, the superconducting film as well as the silver shunt layer were deposited in this reactor. Reported stacking are YSZ/CeO₂/YBCO and CeO₂/YBCO, respectively, on Ni/CeO₂ alloys (5%W) and on SS/YSZ (IBAD) tapes. Epitaxial growth was depicted with a strong in-plane and out-of-plane texture: FWHM of YBCO phi-scans were 6.6° on Ni tapes and 8.3° on IBAD hastelloy ones. High performance was obtained with Jc values reaching 0.6 MA/cm² at 77 K (sf) on Ni tape and larger than 1.3 MA/cm² on IBAD substrates. Critical currents over 80 A/cm were attained on samples prepared with a tape velocity set at 4.6 m/h. Beside MOCVD, spray pyrolysis has been developed as an alternative method to decrease significantly the equipment and the production costs. This technique works at atmospheric pressure and uses an aqueous solution of nitrates as precursors. First transport measurements gave Ic values close to 20 A/cm (77 K, sf) on single crystals. Textured YBCO was also deposited on metallic tapes.