Improvement in structure and superconductivity of bulk FeSe0.5Te0.5 superconductors by optimizing sintering temperature

Sintering temperature plays a vital role in the evolution of phase structure and microstructure in polycrystalline FeSe0.5Te0.5 bulks fabricated by the two-step sintering method, and thus significantly influences their superconducting properties. Elevated sintering temperature (600-700°C) at second step facilitates the substitution of Te into the superconducting phase, which leads to the increased lattice distortion and thus contributes to the enhancement of superconductivity (the value of Tc reaches 15.6K). At the same time, the accelerated growth of the superconducting grains and the improved homogeneity motivated by elevated sintering temperature serve as the main reason for the sharp superconducting transition.