Enhanced and uniform in-field performance in long (Gd, Y)–Ba–Cu–O tapes with zirconium doping fabricated by metal–organic chemical vapor deposition

The influence of Zr doping in (Gd, Y)--Ba--Cu--O ((Gd, Y)BCO) tapes made by metal--organic chemical vapor deposition has been studied with a specific objective of uniform and reproducible enhancement in in-field critical current (Ic) over long lengths. 50 m long tapes with 7.5 and 10 at.% Zr doping in 1 mu m thick (Gd, Y)BCO films have been found to exhibit a sharply enhanced peak in Ic in the orientation of field parallel to the c-axis and retain 28% of their self-field Ic value at 77 K and 1 T. BaZrO3 (BZO) nanocolumn density in the cross-sectional microstructure was found to increase with increasing Zr addition. The end segments of the 50 m long tapes were found to display nearly identical angular dependence of critical current at 77 K and 1 T, indicative of the uniformity in in-field performance over this length. A 610 m long tape was fabricated with 10% Zr doping and a 130 m segment showed a 3.2% uniformity in critical current measured every meter in the orientation of -axis. A retention factor of 36% of the zero-field Ic value measured at 0.52 T over the 130 m is consistent with that obtained in short samples.