Enhanced low-temperature critical current by reduction of stacking faults in REBCO coated conductors

The effect of stacking faults (SF) on flux pinning and critical current (I _c) in rare earth based coated conductors was investigated. The SF density in YBa₂Cu₃O_7−δ (YBCO) films with and without Dy addition, produced by metal organic deposition, was modified by altering the oxygenation temperature. A detailed microstructural analysis of the coated conductors was performed by x-ray diffraction, scanning and transmission electron microscopy and energy dispersive spectroscopy, and the observed defect population was correlated with both the self-field and in-field I_c. We report that the best self-field I_c was obtained for samples having a low SF density, in spite of the SF being effective flux pinning defects at 77 K for magnetic fields applied within the ab plane. We also show that the SF have no observable flux pinning effect at low temperatures. This study demonstrates that for devices operated at low temperatures, the elimination of SF in the conductor wires is essential to attain higher I_c. (paper)