Combined effect of Sn addition and post-rolling sintering on the superconducting properties of SmFeAsO1−xFx tapes fabricated by an ex-situ powder-in-tube process

Abstract

Polycrystalline Sn-added SmFeAsO1−xFx tapes were prepared by an ex-situ powder-in-tube method. It is found that the transport critical current density (Jc) of the SmFeAsO1−xFx tapes can be significantly improved with 10-30 wt. % Sn addition. A transport Jc of 2.11 × 104 A cm−2 at 4.2 K in self-field was obtained in SmFeAsO1−xFx + 30 wt. % Sn sample. Most interestingly, Sn-added SmFeAsO1−xFx tapes without any sintering also showed substantial transport Jc of 9.81 × 103 A cm−2, which is reported for the first time. X-ray diffraction and scanning electron microscopy characterization revealed that the elemental Sn dispersed in the sample transformed into FeSn2 during the post-rolling sintering (PRS). The reaction between Sn and FeAs helps to eliminate the detrimental FeAs wetting phase, which blocks the supercurrent path between SmFeAsO1−xFx grains. The combined impact of fluorine loss and Sn reaction was discussed in this work by varying the Sn addition quantity and PRS condition.