The Effect of Mechanical Slitting on 1 mm-Width REBCO Coated Conductors

In recent years, to reduce AC loss and ensure flexibility, narrow REBa
₂
Cu
₃
O
_y
(REBCO, RE = Gd, Y, Sm, etc.) coated conductors (CCs) have been developed. A standard method common of CC narrowing is mechanical slitting with a slitting blad. However, cracks may occur near the slit edge due to the impact during slitting, which may affect the critical current density (
J
_c
). In particular, for 1 and 2 mm-width CCs, the effect of this damage becomes more significant than that for 4 mm-width CCs. In this study, we have investigated the effect of mechanical slitting on 1 mm-width REBCO CC by
J
_c
distribution measurement, microstructural observation, and in-field
J
_c
measurement. Also, comparisons with 2 and 4 mm-width CCs fabricated by a similar process were conducted. From the
J
_c
distribution analysis,
J
_c
along the slit edges for 1 mm-width CC fluctuated more than those for 2 and 4 mm-width CCs. Microcracks and delamination were observed at the slit edges of the 1 to 4 mm-width CCs. These were longitudinally continuous and may occur during slitting. The density or relative portion of cracked area induced in the REBCO layer by slitting was increased as the width of the CC narrowed. Furthermore, it is confirmed that large microcracks of up to about 200 μm corresponded to the region of fluctuating
J
_c
. In-field
J
_c
, 1 mm-width CC had a lower
J
_c
than 2 and 4 mm-width CCs. These results indicate that microcrack propagation increases with narrower CCs and has a more pronounced effect on the critical current. Microcracks and delamination are predicted to be more significant when the CC is slit into narrow CCs, such as 0.5 mm-width.