Low Resistance Soldered Joint of REBCO Coated Conductors With Novel Ag-Dispersed Structure

We deposited deeply Ag-doped REBa ₂ Cu ₃ O _7-x (REBCO) films of 0.5–2.0 μm thick by hot-wall pulsed laser deposition (PLD) method on 12 mm wide and 50 μm thick Hastelloy tapes with ion beam assisted deposition (IBAD) templates. Ag protection layer of 2.0 μm thick were deposited on them by sputtering. Lap or bridge joints of those tapes were made just by soldering. The joint resistances were measured by DC four-probe method at 77 K and by the loop current attenuation method at 4.2 K. Microscopic structures were evaluated by the scanning electron microscope (SEM). Metal Ag particles were clearly dispersed at REBCO surface. The joint resistances were measured as 0.9–1.8 × 10 ⁻¹² Ωm ² at 77 K, and 1.6–4.8 × 10 ⁻¹³ Ωm ² at 4.2 K. Double layer structure of a thin Ag-doped REBCO film on a high- I _c 2.5 μm thick REBCO film had also a low joint resistance without spoiling high- I _c properties. The results indicate a possibility to make low joint resistance of 10 ⁻¹² Ω just by soldering of commercial REBCO coated conductors.