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/cm(2) of J(c) was confirmed on MAD (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 x 2). During the deposition of a YBCO layer, the CVD system was quite stable. J(c) was measured at a voltage tap interval of 10 in with criterion of 1 mu V/cm. J(c) of the YBCO tape remained in the order of 10(4) A/cm(2) due to the non-textured microstructure. However, J(c) distribution of the tape showed a good uniformity. A 2 10 m-long YBCO/(Ag +BAD) tape was also prepared. A 210 m-long substrate combined with MAD and Ag was used. I-c 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. (c) 2005 Elsevier B.V. All rights reserved.