Bulk SrMnOx samples with O contents 2.5 ≤ x < 2.7 were studied using a combination of neutron time-of-flight and high-energy high-resolution synchrotron X-ray diffraction measurements along with thermogravimetric analysis. The identification and characterization was reported of 2 new O-vacancy ordered phases: Sr5Mn5O13 (SrMnO2.6-tetragonal P4/m a = 8.6127Å, c = 3.8102Å) and Sr7Mn7O19 (SrMnO2.714-monoclinic P2/m a = 8.6076Å, b = 12.1284Å, c = 3.8076Å, γ = 98.203°). The nuclear and magnetic structures of Sr2Mn2O5 were also reported (SrMnO2.5 nuclear: orthorhombic Pbam, magnetic: Orthorhombic Ay type Pcbam with cM=2c). In the 3 phases, O-vacancies were ordered in lines running along one of the (100) directions of the parent cubic perovskite system. Oxygen-vacancy ordering permitted charge and orbital ordering of the Mn3+ and Mn4+ cations in the new phases.

Crystal Structures, Charge and Oxygen-Vacancy Ordering in Oxygen Deficient Perovskites SrMnOx (x<2.7). L.Suescun, O.Chmaissem, J.Mais, B.Dabrowski, J.D.Jorgensen: Journal of Solid State Chemistry, 2007, 180[5], 1698-707