A new way of synthesis and characterization of superconducting oxyfluoride Sr2Cu(O, F)4 + δ

Abstract Superconducting Cu mixed oxyfluoride, Sr2Cu(O, F)4 + δ, was obtained via fluorination of Sr2CuO3 by XeF2 in the 100–250°C temperature range in a closed Ni container. The prepared samples exhibited a lower Tc in comparison with earlier reported values. Different samples in the SrCuOF system were prepared by a solid-state reaction at 220–400°C, but no formation of the oxyfluoride was detected even with an addition of xenon difluoride. These data allow one to draw conclusions on the metastability of the oxyfluoride under the conditions used. Electron microscopy and X-ray powder diffraction studies revealed large amounts of badly crystallized SrF2; this could be a reason for the small superconducting volume fraction as well as for the inhomogeneous distribution of the anions.