Microstructure and Superconducting Properties of 7-Filament Ba1-xKxFe2As2 Composite Conductors
The traditional Ag sheath has both good chemical compatibility and plastic processing characteristic with iron-based superconductors(IBS),but it possesses too low mechanical strength.Employing composite sheathes is a direct,efficient and low-cost method to prepare high strength Ba1-xKxFe2As2 conductors.In this study,the Ba1-xKxFe2As2 multifilamentary wires/tapes with stable structure and large ductility were obtained through optimizing the sheath size,cold deformation and intermediate annealing.It is found that the shape distribution of multi-cores is uniform,and the superconducting filling factor is 25.3％-28.0％for this Ag/Nb/Cu composite sheathed Ba1-xKxFe2As2 superconductors.The magnetic critical transition temperature Tc of Ba1-xKxFe2As2 tape is up to 37.5 K,and the magnetization of hysteresis loops(M-H)shows a strong flux pinning ability.The transport critical current density Jc of Ba1-xKxFe2As2 tape is about 1.7× 104 A/cm2at 4.2 K and 2 T,and it still holds 8.7×103 A/cm2 at 4.2 K and 10 T.
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