Annealing induced superconductivity in perovskite-related iron-based mixed anion compounds Sr₂VFeAsO_3-δ

Polycrystalline samples of Sr₂VFeAsO_3-δ with perovskite-type carrier blocking layers were prepared by a solid state reaction using an alumina tube in a sealed silica tube. Sr₂VFeAsO _3-δ samples which were prepared as nominally δ 0 were not synthesized as a single phase, suggesting that finite oxygen deficiency is inevitable for the compound. Although a sample, which exhibits relatively larger lattice volume, does not exhibit bulk superconductivity at temperatures 5 K, finite superconducting transition temperatures appear in the sample which exhibits smaller lattice volumes. These results support making the electronic and magnetic phase diagram of Sr₂VFeAsO_3-δ.