Fabrication of Fe_1.1Se_0.5Te_0.5 bulk by a high energy ball milling technique

Fe_1.1Se_0.5Te_0.5 superconducting bulks were successfully synthesized by a high energy ball milling (HEBM) aided sintering technique. Two advantages of this new technique have been revealed compared with traditional solid state sintering method. One is greatly increased the density of sintered bulks. It is because the precursor powders with β-Fe(Se, Te) and δ-Fe(Se, Te) were obtained directly by the HEBM process and without formation of liquid Se (and Te), which could avoid the huge volume expansion. The other is the obvious decrease of sintering temperature and dwell time due to the effective shortened length of diffusion paths. The superconducting critical temperature T_c of 14.2 K in our sample is comparable with those in previous reports, and further optimization of chemical composition is on the way.