Crystal structures of two alkaline earth ( = Ba and Sr) dimanganese(II) iron(III) tris-(orthophosphates).

Two new orthophosphates, BaMnFe(PO) [barium dimanganese(II) iron(III) tris-(orthophosphate)] and SrMnFe(PO) [strontium dimanganese(II) iron(III) tris-(orthophosphate)], were synthesized by solid-state reactions. They are isotypic and crystallize in the ortho-rhom-bic system with space group type . Their crystal structures comprise infinite zigzag chains of edge-sharing FeO octa-hedra (point group symmetry .2.) and MnO double octa-hedra running parallel to [001], linked by two types of PO tetra-hedra. The so-formed three-dimensional framework delineates channels running along [001], in which the alkaline earth cations (site symmetry .2.) are located within a neighbourhood of eight O atoms.