7芯复合包套Ba_(1-x)KxFe_(2)As_(2)线带材的显微结构与超导性能研究

Microstructure and Superconducting Properties of 7-Filament Ba_(1-x)KxFe_(2)As_(2)Composite Conductors

传统Ag包套与铁基超导材料具有良好的化学相容性以及塑性加工特性,但是其机械强度低;而采用复合包套来制备高强度Ba_(1-x)KxFe_(2)As_(2)铁基多芯线带材是一种直接高效且成本低廉的方法。本研究选取高强度高延展性的Ag/Nb/Cu3层复合包套,从线带材包套尺寸、冷加工工艺和中间退火等方面进行优化,获得了结构稳定且易于加工的Ba_(1-x)KxFe_(2)As_(2)多芯线带材。Ag/Nb/Cu复合包套Ba_(1-x)KxFe_(2)As_(2)线带材的多芯孔型完整并且分布均匀,超导填充因子约为25.3%~28.0%,并且具有较好的力学性能。Ba1-xKxFe_(2)As_(2)多芯带材的转变Tc为37.5K,M-H曲线表明样品具有较强的内在磁通钉扎能力。在4.2 K和2 T下其传输Jc约为1.7×10^(4)A/cm^(2),在10 T时传输Jc仍然保持为8.7×10^(3)A/cm^(2)。

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 Ba_(1-x)KxFe_(2)As_(2)conductors.In this study,the Ba_(1-x)KxFe_(2)As_(2)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 Ba_(1-x)KxFe_(2)As_(2)tape is about 1.7×10^(4)A/cm^(2)at 4.2 K and 2 T,and it still holds 8.7×10^(3)A/cm^(2)at 4.2 K and 10 T.