Effect of High BZO Dopant Levels on Performance of 2G-HTS MOCVD Wire at Intermediate and Low Temperatures

Flux pinning in REBCO (rare-earth Ba-Cu-O) by self-assembly of BZO (barium zirconate) nanorods has emerged as one of the most prominent techniques for improving the in-field performance of 2G-HTS wire in terms of I_c and angular I_c anisotropy. In our previous study on metalorganic chemical vapor deposition REBCO wire, an optimum performance was found for 7.5% Zr at 1 T, 77 K, while further increase in Zr content resulted in I_c and T_c degradation. However, recent results indicate that the pinning performance at high Zr content actually surpasses that of the 7.5% Zr wire at intermediate and low temperatures. In-depth understanding of the effect of high Zr levels on REBCO provides a strong potential for further substantial increase in pinning performance at high Zr content if the unwanted effects can be minimized by process modification. In this study, we analyze the effect of high Zr doping levels on REBCO properties with emphasis on microstructure analysis. Structural properties as a function of BZO dopant level have been analyzed using X-ray reciprocal space maps and transmission electron microscopy, while the performance has been characterized using angular in-field I_c characterization up to 9T at temperatures of 20-77 K.