Low-temperature Synthesis of FeTe0.5Se0.5 Polycrystals with a High   Transport Critical Current Density
  We have prepared high-quality polycrystalline FeTe0.5Se0.5 at temperature as low as 550{\deg}C. The transport critical current density evaluated by the current-voltage characteristics is over 700 A/cm2 at 4.2 K under zero field, which is several times larger than FeTe0.5Se0.5 superconducting wires. The critical current density estimated from magneto-optical images of flux penetration is also similar to this value. The upper critical field of the polycrystalline FeTe0.5Se0.5 at T = 0 K estimated by Werthamer-Helfand-Hohenberg theory is 585 kOe, which is comparable to that of single crystals. This study gives some insight into how to improve the performance of FeTe0.5Se0.5 superconducting wires. 
Qing-Ping Ding, Shyam Mohan, Yuji Tsuchiya, Toshihiro Taen, Yasuyuki   Nakajima, Tsuyoshi Tamegai
cond-mat.supr-con