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 (I_c) over long lengths. 50m long tapes with 7.5 and 10at.% Zr doping in 1 νm thick (Gd, Y)BCO films have been found to exhibit a sharply enhanced peak in I_c in the orientation of field parallel to the c-axis and retain 28% of their self-field I_c value at 77K and 1T. BaZrO ₃ (BZO) nanocolumn density in the cross-sectional microstructure was found to increase with increasing Zr addition. The end segments of the 50m long tapes were found to display nearly identical angular dependence of critical current at 77K and 1T, indicative of the uniformity in in-field performance over this length. A 610m long tape was fabricated with 10% Zr doping and a 130m 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 I_c value measured at 0.52T over the 130m is consistent with that obtained in short samples.