Enhancement of superconductivity in the sintered FeSe0.5Te0.5 bulks with proper amount of Sn addition

Sn added bulk FeSe0.5Te0.5 samples are synthesized through two-step solid state reaction route. It is found that Sn addition can significantly enhance the transformation from the hexagonal phase to the superconducting tetragonal phase during the sintering process of FeSe0.5Te0.5 samples due to the appearance of liquid Sn at low temperature. With increase of superconducting phase proportion as well as improvement of its crystallinity, 5 wt% Sn addition dramatically enhances the zero resistivity temperature (Tc0) by 3 K accompanying with a bit improvement in the onset temperature of superconducting transition (Tcon). From this view, our work suggests a new prospective that how to search proper dopant to further improving superconductivity in 11 type Fe based superconductors.