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_1.1Se_0.5Te_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 T_c value could demonstrate a good superconducting phase obtained by the HEBM aided sintering method.