Evolution of tetragonal phase in the FeSe wire fabricated by a novel   chemical-transformation PIT process
  We fabricated superconducting FeSe wires by the chemical-transformation PIT process. The obvious correlation between annealing temperature and phase transformation was observed. Annealing above 500^{\circ}C produced wire-core transformation from hexagonal to tetragonal phase. Furthermore the hexagonal phase completely transformed into the tetragonal phase by annealing at 1000^{\circ}C. With increasing annealing temperature, the superconducting property was dramatically improved, associated with the evolution of the tetragonal phase. 
Hiroki Izawa, Yoshikazu Mizuguchi, Toshinori Ozaki, Yoshihiko Takano,   Osuke Miura
cond-mat.supr-con