Structural Chemistry of a New 10H Hexagonal Perovskite: BaMn_0.4Fe_0.6O_2.73

Abstract

A new 10H polytype has been stabilized in the BaMn1–xFexO3–y system with the composition BaMn0.4Fe0.6O2.73. The anionic composition has been established by a reduction and re‐oxidation cycle in the stability range of this phase. The structural characterization was carried out by high‐resolution electron microscopy (HREM), electron diffraction, and X‐ray diffraction. The structure is closely related to the ideal (hch′ch)2 10H polytype with two oxygen‐deficient hexagonal (h′) BaO2–y layers per unit formula. This framework gives rise to blocks of three octahedra sharing faces linked by corners to two corner‐sharing tetrahedra.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Anion-Vacancy-Induced Magneto−Crystalline Anisotropy in Fluorine-Doped Hexagonal Cobaltites

“…The h-type layer yields XBa 5 trigonal pyramids. As reported for 10H-BaFeO 2.8 and 10H-BaMn 0.4 Fe 0.6 O 2.73 , there are examples in which the “[BaO 2 ]” layers appear to be h-type layers. However, the oxygen atoms associated with the OBa 5 trigonal bipyramids have the bond valence sum (BVS) of approximately −0.5 instead of −2 expected for O 2− , and the structure optimization for the hypothetical 6H-Ba 6 Co 6 O 17 by density functional calculations leads to a severely distorted structure .…”

“…In PND refinements, the difference between the O and F Fermi lengths is relatively small so that a mixed O/F occupancy might result for O and F positions. In two 10H-BaFeO 3-x polytypes ( x = 0.2, 0.35) and 10H-BaMn 0.4 Fe 0.6 O 2.73 , the oxygen atoms were allowed to occupy the halogen-sites. In such a case, the trigonal bipyramidal OBa 5 associated with this site leads to a highly unreasonable BVS of the oxygen (i.e., ∼−0.5 instead of ∼−2).…”

Microstructure and magnetic properties of a novel 10-H hexagonal perovskite nanosheet in a Bi–Fe–Cr–O system

“…The lattice constants of the 10-H hexagonal BFCO perovskite were determined as a = 0.517 nm and c = 2.47 nm with the electron diffraction pattern of single crystalline Si as an internal standard. Similar 10-H hexagonal perovskites have also been observed in BaRuO 3 , 29 BaFe 0.6 Mn 0.4 O 2.73 , 30 and Cs(Ni 0.75 Cd 0.25 )O 3 31 systems.…”

Synthesis, structure, and magnetic property of hexagonal perovskite Ba5Sn1.1Mn3.9O15

“…New hexagonal perovskite polytypes are generated when Mn is substituted by different cations. Several doped BaMnO 3 systems including Ba 1−x Sr x MnO 3−ı [5,8], BaTi x Mn 1−x O 3 [9], BaCa x Mn 1−x O 3−ı [10,11], BaIr x Mn 1−x O 3−ı [12], BaLn x Mn 1−x O 3−ı (Ln = rare earth element) [13][14][15][16][17], BaIn x Mn 1−x O 3−ı [18,19], BaCo x Mn 1−x O 3−ı [20,21], BaRu x Mn 1−x O 3 [22] and BaFe x Mn 1−x O 3−ı [23] have been explored. Among them, two B-cation ordered hexagonal perovskite structure are found with a formula Ba n+1 XMn n O 3n−ı (n = 2, 3), which contains one layer of corner-sharing XO 6 octahedron and n layers of face-sharing MnO 6 octahedra [13][14][15][16]19].…”