Evaluation of the Interface Resistance on Heated REBCO Tape

Soldering is one of the most common jointing methods in a tape-to-tape joint of Rare-earth Barium Copper Oxide (REBCO) tapes. In this procedure, heating REBCO tapes is inevitable. In soldered lap joints, it was reported that the joint resistance varies depending on the heating temperature and duration of the soldering process. The joint resistance is composed of several factors. One of the factors is the interface resistance between Cu/Ag and Ag/REBCO interfaces in the REBCO tape. In this study, we investigated how the interface resistance changes due to heating process of REBCO tapes. We prepared REBCO tapes heated at 300 °C for 1, 5, and 10 minutes and evaluated the critical current (
I
_c
) with a four-terminal method as well as the interface resistance of the tapes with the contact-probing current transfer length method in a liquid nitrogen bath, self-field. Also, the temperature dependence of the interface resistivity of non-heated tape was evaluated from 10 K to critical temperature
T
_c
. As a result, the interface resistivity (interface resistance for 1 cm
²
joint area) increased from 12 nΩ⋅cm
²
to 55 nΩ⋅cm
²
at the most and there was a strong correlation between
I
_c
degradation and the increase of the interface resistivity. The interface resistivity of non-heated tape decreased in the temperature range of 10 K to 85 K. However, it changed to increasing from 85 K to
T
_c
.