Multistep synthesis of the SrFeO2F perovskite oxyfluoride via the SrFeO2 infinite-layer intermediate

•Novel multi-step synthetic method to access metastable oxyfluorides.•Control of local coordination in FeO4F2 polyhedra possible.•DFT calculations used to investigate structure of ordered SrFeO2F.

The SrFeO2F oxyfluoride was prepared through a low temperature, multistep synthetic route starting with the SrFeO3−x perovskite via the SrFeO2 infinite layer intermediate phase. In the final step SrFeO2F was formed by reacting SrFeO2 with XeF2 at 150 °C. In spite of utilizing an intermediate with layered ordering of oxygen vacancies, disordered SrFeO2F was synthesized. Rietveld refinement of synchrotron powder diffraction data did not reveal any signs of tetragonal distortion predicted by DFT calculations for SrFeO2F with layered O/F ordering. Significantly, the magnetic properties observed are drastically different from those reported earlier in the literature indicating that the properties of O/F disordered phases depend on the degree of short range ordering. Mössbauer spectroscopy measurements revealed the predominance of cis fluorine configuration in FeO4F2 polyhedra, confirming a difference in local Fe coordination in comparison with O/F disordered SrFeO2F.

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