Phase Transition Mechanism of Fe1.1Se0.5Te0.5 Fabricated by High-Energy Ball Milling Aided Sintering Method

We report the phase transition mechanism of Fe
_1.1
Se
_0.5
Te
_0.5
fabricated by the high-energy ball milling (HEBM) aided sintering method, which was achieved by multistep quenching heat treatment process. The precursor powders, composed of Fe and (Se, Te)ss, were synthesized via an HEBM method for 2 h using Fe, Se, and Te mixture powders. Under the sintering temperature of 400 °C, the two compositions began to diffuse into each other and Fe(Se, Te)2 phase with uniform Se and Te distribution was formed directly. With further increasing temperature to 500 °C, tetragonal β-Fe(Se, Te) phase was obtained owing to the elemental diffusion of Fe into Fe(Se, Te)2. Due to the effective shortened length of diffusion paths, the superconducting phase formation temperature was ~100 °C lower during our HEBM aided sintering method than that in the traditional solid state sintering method. Finally, a critical temperature of 14.2 K was observed in the final treatment sample, which was sintered for 12 h at 700 °C with a slow cooling rate followed by an annealing process under oxygen atmosphere for 24 h. This Tc value could demonstrate a good superconducting phase obtained by the HEBM aided sintering method.