Synthesis and superconductivity of MgB2/Fe–Se–Te composites

MgB2/FeSe0.75Te0.25 composites were synthesized to see the effect of the co-existence of superconducting phases on the superconductivity. MgB2 powders were mixed with pre-alloyed FeSe0.75Te0.25 or elemental powder mixture, followed by sintering at 400 °C. The resulting materials were superconducting MgB2/FeSe0.75Te0.25 composites without impurity phase when using pre-alloyed FeSe0.75Te0.25 as a starting powder. When FeSe0.75Te0.25 was prepared by in situ reaction from the elemental powder mixture of Fe–Se–Te, on the other hand, non-superconducting impurity phases partly formed after sintering. No double superconducting transition was observed in MgB2/FeSe0.75Te0.25 composites in spite of coexistence of two superconducting phases.