SrMn^II₂Mn^III(PO₄)₃

Abstract

The title compound, barium trimanganese tris-(ortho-phosphate), was synthesized hydro-thermally. Its structure is isotypic with the lead and strontium analogues AMn(II) 2Mn(III)(PO4)3 (A = Pb, Sr). Except for two O atoms on general positions, all atoms are located on special positions. The Ba and one P atom exhibit mm2 symmetry, the Mn(II) atom 2/m symmetry, the Mn(III) atom and the other P atom .2. symmetry and two O atoms are located on mirror planes. The crystal structure contains two types of chains running parallel to [010]. One chain is linear and is composed of alternating Mn(III)O6 octa-hedra and PO4 tetra-hedra sharing vertices; the other chain has a zigzag arrangement and is built up from two edge-sharing Mn(II)O6 octa-hedra connected to PO4 tetra-hedra by edges and vertices. The two types of chains are linked through PO4 tetra-hedra into an open three-dimensional framework which contains channels parallel to [100] and [010] in which the Ba(II) ions are located. The alkaline earth cation is surrounded by eight O atoms in the form of a slightly distorted bicapped trigonal prism.