Fabrication of YBCO Superconducting Tape by Metal Organic Chemical Vapor Deposition Method

Abstract

YBCO films for coated conductors (CC) were fabricated by a metal organic chemical vapor deposition (MOCVD) system of hot-wall type using a single source. The deposition condition was optimized using (100) SrTiO/sub 3/ single crystal substrates in a steady state, and then the substrate was replaced by moving IBAD template (CeO/sub 2//IBAD-YSZ/stainless steel) of 40 cm/hr. Two different types of IBAD templates with thin CeO/sub 2/ and thick CeO/sub 2/ layers were used. The mole ratio of MO source was Y(tmhd)/sub 3/:Ba(tmhd)/sub 2/:Cu(tmhd)/sub 2/=1:2.1:2.9, and the YBCO films were prepared at the deposition temperatures of 780/spl sim/890/spl deg/C. The a-axis growth was observed together with the c-axis growth up to 830/spl deg/C, while the c-axis growth became dominant above 830/spl deg/C. The top surface of the c-axis film was fairly dense and crack-free. In case of the YBCO film with a 2.2 /spl mu/m thickness deposited on the SrTiO/sub 3/ substrate at 860/spl deg/C, the deposition rate was as high as 0.37 /spl mu/m/min. The critical current and critical current density of the film was 104 A/cm-width and 0.47 MA/cm/sup 2/, respectively. The YBCO film deposited on the IBAD template with a thin CeO/sub 2/ layer showed a low critical current of 2.5 A/cm-width, while the YBCO film deposited on the IBAD template with a thick CeO/sub 2/ layer showed a higher critical current of 50 A/cm-width. It indicates that the stable buffer layer at high deposition temperature is needed for the MOCVD process.