YBCO coated conductor by multiple-stage CVD

A high speed deposition technique for YBCO coated conductors has been required from the viewpoint of cost reduction for second generation wire. The multiple-stage chemical vapor deposition technique was employed for making YBCO coated conductors with a high deposition rate. In our earlier research, over 2.0 MA/cm2 of Jc was confirmed on IBAD (PLD-CeO2/IBAD-Gd2Zr2O7/Hastelloy) substrates with a maximum deposition rate of 25 m/h using the six-stage CVD system. To evaluate the availability of the multiple-stage CVD technique for making a longer YBCO tape, we have fabricated a 200 m-long YBCO tape on a non-textured silver substrate. Deposition rate was 10 m/h, and number of passing was two times. Total deposition time was 40 h (20 h × 2). During the deposition of a YBCO layer, the CVD system was quite stable. Jc was measured at a voltage tap interval of 10 m with criterion of 1 μV/cm. Jc of the YBCO tape remained in the order of 104 A/cm2 due to the non-textured microstructure. However, Jc distribution of the tape showed a good uniformity. A 210 m-long YBCO/(Ag + IBAD) tape was also prepared. A 210 m-long substrate combined with IBAD and Ag was used. Ic of 60-78 A was obtained on the IBAD substrates part. This result suggested that the multiple-stage CVD technique was very useful to making a long YBCO tape.