Investigation of a repeatable and widely applicable method to reduce the turn-to-turn contact resistivity of REBCO tapes

In this study, a repeatable and widely applicable method for decreasing the turn-to-turn contact resistivity of REBa₂Cu₃O₇-x (RE=rare earth, REBCO) tapes was demonstrated. By applying a solder without further connections, the contact resistivity can be significantly and consistently decreased to low values. Four solders and five REBCO tapes from various manufacturers were tested to demonstrate the wide applicability of this method. The lowest value achieved by using a combination of solder and surface cleaning procedure was around 3 μΩ cm². Furthermore, a possible governing mechanism for the repeatable decrease method using solder is discussed. The Mikic elastic correlation was considered the most probable candidate. After carefully discussing the three factors of contact resistivity, namely surface roughness, surface conductance, and surface Young's modulus, surface Young's modulus was considered to have a much higher weight index than the surface roughness, and the surface conductance was negligible. This research can help us better understand the contact resistivity of REBCO and develop a method that can controllably adjust the contact resistivity.