Effect of starting materials on the superconducting properties of   SmFeAsO1-xFx tapes
  SmFeAsO1-xFx tapes were prepared using three kinds of starting materials. It shows that the starting materials have an obvious effect on the impurity phases in final superconducting tapes. Compared with the other samples, the samples fabricated by SmAs, FeO, Fe2As, and SmF3 have the smallest arsenide impurity phase and voids. As a result, these samples possess much denser structure and better grain connectivity. Moreover, among the three kinds of samples fabricated in this work, this kind of sample has the highest zero-resistivity temperature ~40 K and largest critical current density ~4600 A/cm^2 in self-field at 4.2 K. This is the highest Jc values reported so far for SmFeAsO1-xFx wires and tapes. 
Chunlei Wang, Chao Yao, Xianping Zhang, Zhaoshun Gao, Dongliang Wang,   Chengduo Wang, He Lin, Yanwei Ma, Satoshi Awaji, and...
cond-mat.supr-con