Fabrication and Properties of PIT Processed Iron-Based Ba-122 Superconducting Tapes Using Double Sheath of Stainless Steel and Ag-Sn Alloy

The fabrication of Fe-based Ba-122 superconducting tapes was studied by ex-situ powder-in tube (PIT) process using double sheathing technique of stainless steel (SS) and Ag-Sn alloy. We found that the double sheathed SS/Ag-Sn/Ba-122 tapes show much more improved critical current density (Jc) compared to the previously reported single sheathed Ag/Ba-122 tapes. By optimizing the Sn content, heat treatment temperature, and tape thickness, we have achieved high Jc of well over 105 A/cm2 at 4.2 K and 10 T, which is the target value for practical application. Taking into account coil winding in the future, we fabricated a ～1 m long SS/Ag-Sn/Ba-122 tape and evaluated the uniformity of Jc along tape length and the Jc degradation by bending. The Jc distributed within 5.5-7.2 × 104 A/cm2 (4.2 K, 10 T) over the entire length and showed no degradation until 3 cm diameter bending.