Superconducting Properties of 100-m Class Sr0.6K0.4Fe2As2 Tape and Pancake Coils

Iron-pnictides are hotly studied since 2008 in the superconducting materials research area, due to their special properties and unclear mechanism. Big achievement has been made in the pnictide research during the past years. For practical uses, pnictide superconductor should be fabricated in a form that can be used for different devices. In this paper, 100-m class 7-core Sr_0.6K_0.4Fe₂As₂ (Sr122) tapes have been made by using the powder-in-tube technique, which is reported for the first time. Clearly, an average J_c of 1.3 × 10⁴ A/cm² at 10 T was reached over the 115-m length, showing a high property and good uniformity of 100-m level Sr122 tapes. Using the 10-m long Sr122 tapes, two double-pancake coils were fabricated by a wind and reaction technique. No transport current could be measured for the coil made from the monofilamentary tape. However, transport I_c was obtained in the coil made from the 7-filamentary tape. The factors that affect the superconducting property of the coil were discussed in this paper.