Structural investigation of oxygen-deficient perovskite CaMnO2.75

Abstract Perovskite CaMnO3 and its oxygen-deficient derivatives have been prepared from solid solution precursor with a calcite-type structure. CaMnO3−x phases are constructed from MnO6 octahedra and MnO5 square pyramids. From X-ray powder data CaMnO2.75 75 was indexed on an orthorhombic cell with a = 5.35(1) A , b = 20.96(2) A and c = 7.47(1) A . Rietveld refinement of time-of-flight neutron diffraction data was attempted for several models containing 50 mol% MnO5 and 50 mol% MnO6 based on MnO6 octahedra and MnO5 square pyramids, but the results were inconclusive. Simulation patterns illustrate the intrinsic difficulty for structural comprehension.