Syntheses, powder neutron diffraction structures and Mössbauer studies of some complex iron oxyfluorides: Sr3Fe2O6F0.87, Sr2FeO3F and Ba2InFeO5F0.68

Abstract

Sr₂FeO₃F and the novel phases Sr₃Fe₂O₆F_0.87 and Ba₂InFeO₅F_0.68 have been prepared and their structures investigated by powder neutron diffraction methods. Sr₂FeO₃F crystallises with the T* modification of the K₂NiF₄ structure owing to oxide/fluoride ordering. Sr₃Fe₂O₆F_0.87 and Ba₂InFeO₅F_0.68 are mixed valent phases prepared by reaction of anion deficient iron(III) materials with gaseous fluorine. Sr₃Fe₂O₆F_0.87 is a Ruddlesden–Popper type material which has been shown by Mössbauer spectroscopy to contain iron(III) and iron(V). Ba₂InFeO₅F_0.68 is the first example of an iron oxyfluoride with a perovskite-type structure.