Correlation Between Microstructure and In-Field Performance of Zr-Added REBCO Coated Conductors Made by Advanced MOCVD

In this paper, we present correlation features between critical current density (J
_c
) and microstructural characteristics of Zr-added (0, 5, and 15 mol.%) REBa
₂
Cu
₃
O
_7-x
(REBCO and RE = rare earth) coated conductors fabricated by the novel advanced metal organic chemical vapor deposition technique. The J
_c
along the tape normal (~ B || c-axis) measured by a vibrating sample magnetometer at 30 and 65 K and magnetic flux density range of 0-14 T was used for qualitative comparison of different Zr-added REBCO tapes. It is found that tapes with enhanced in-field J
_c
exhibit a rise of critical current (plateau or fishtail effect) at magnetic flux density 1-8 T and temperatures 65 K. The TEM microstructure analysis indicates that the plateau effect is not the intrinsic property of REBCO matrix but depends on size distribution and density of BaZrO
₃
(BZO) self-assembled nanocolumns. Two types of BZO microstructures have been identified: one with uniform BZO diameter 4-7 nm, whereas some films exhibit bottle-shaped BZO nanocolumns with alternating wide and narrow sections, 7-13 and 4-6 nm, respectively. The non-uniform shape and broad size distribution of BZO nanocolumns are correlated to more vortex pinning strength and matching field.