Improved transport critical currents in Ag and Pb co-doped BaxK1-xFe2As2   superconducting tapes
  Fe-clad BaxK1-xFe2As2 superconducting tapes were fabricated by the ex situ powder-in-tube method combined with a short high-temperature annealing technique. The effect of annealing time and different dopants on the transport properties of the BaxK1-xFe2As2 tapes were systematically studied. By co-doping with Ag and Pb, the transport critical current density Jc of BaxK1-xFe2As2 tapes was significantly improved in whole field region and the highest transport Jc was up to 1.4x10^4 A/cm^2 (Ic=100 A) at 4.2K in self field. It is proposed that the superior Jc in the co-doped samples are due to the combine effect of Pb doping at low fields and Ag doping at high fields. 
Chao Yao, Chunlei Wang, Xianping Zhang, Lei Wang, Zhaoshun Gao,   Dongliang Wang, Chengduo Wang, Yanpeng Qi, Yanwei Ma, Sato...
cond-mat.supr-con