Structure of Ba₃In₂O₅F₂by combined powder X-ray and neutron diffraction analysis; oxide/fluoride ordering in a Ruddlesden–Popper phase

The structure of a new fluoride oxide Ba3In2O5F2 has been determined from the simultaneous refinement of powder X-ray and powder neutron diffraction data. This Ruddlesden–Popper type phase crystallises in the space group I4/mmm with lattice parameters a= 4.18 and c= 22.82 Å. The structure shows ordering of the oxide and fluoride ions, as evidenced from bond valence considerations, producing sheets of vertex-sharing indium–oxygen square pyramids separated by BaF layers.