Effective Ex-situ Fabrication of F-Doped SmFeAsO Wire for High Transport Critical Current Density

We demonstrate the fabrication of superconducting SmFeAsO 1-x F x (Sm-1111) wires by using the ex-situ powder-in-tube technique. Sm-1111 powder and a binder composed of SmF 3 , samarium arsenide, and iron arsenide were used to synthesize the superconducting core. Although the F content of Sm-1111 is reduced in the process of ex-situ fabrication, the binder compensates by sufficiently supplementing the F content, thereby preventing a decrease in the superconducting transition temperature and a shrinkage of the superconducting volume fraction. Thus, in the superconducting Sm-1111 wire with the binder, the transport critical current density reaches the highest value of ${\sim}4$ kA/cm 2 at 4.2 K.