Structure of ten-layer orthorhombic Ba5Fe5O14 (BaFeO2.8) determined from single crystal X-ray diffraction

Structural Chemistry of a New 10H Hexagonal Perovskite: BaMn0.4Fe0.6O2.73

“…As a consequence, with respect to the ideal structure, the M3···M1 distance increases, reducing the electrostatic repulsion between cations in adjacent face-sharing polyhedra. This feature is shown by other polytypes with structural lengths range from 1.94 to 2.14 Å, whereas the Fe-O bond lengths in 10H-BaFeO 2.8-y [9,10] range from 1.94 to 1.859 Å; both are in octahedral coordination. The Fe2O 4 tetrahedra are quite distorted with three long Fe2-O1 bonds (1.860 Å) and one short Fe2-O3 bond (1.71 Å).…”

“…For lower oxygen content, this nonbonding oxygen is partially removed, and this results in a hexagonal BaO 2-y layer. [10] On the basis of the crystallochemical analysis of this phase, we propose that, in a similar way, the anionic range of the stability of the 10H-BaMn 0.4 Fe 0.6 O 3-y phase varies from 2.80 to 2.60, which corresponds to the range from an h-BaO 2 down to an h-BaO layer from one to zero nonbonding oxygen atoms, respectively. According to this assumption, the anionic composition of BaMn 0.4 Fe 0.6 O 3-y can be obtained from a reduction and re-oxidation cycle of the sample.…”

“…In this structure (Figure 3a), blocks of three face-sharing octahedra are linked by their terminal corners to blocks of two face-sharing octahedra. It is worth mentioning that this hexagonal polytype is stable in both the Ba-Mn-O and the Ba-Fe-O systems for the compositions BaMnO 2.90 [2] and BaFeO 2.80 , [9,10] respectively. 80 (according to ref.…”

“…This value is in excellent agreement with Mn-O bond lengths observed for Mn IV in the same environment as 2H-BaMnO 3 (1.9044 Å), [15] and it is also close to that found in 10H-BaFeO 2.8-y for Fe III in octahedral coordination (d average = 2.01 Å). [9,10] In contrast, the M1O 6 octahedron is quite distorted, with three long and three short M-O bonds (see Table 2), indicating that metals in this position are displaced from the center toward the oxygen atoms in the cubic layer (O1), i.e., to the neighboring tetrahedra sharing a corner, and hence away from the shared face. As a consequence, with respect to the ideal structure, the M3···M1 distance increases, reducing the electrostatic repulsion between cations in adjacent face-sharing polyhedra.…”

“…[2][3][4][5] This behavior is also observed in the BaFeO 3-y system, which has been extensively studied in the 0 Ͻ y Յ 0.5 compositional range. [6][7][8][9][10] This system is characterized by a large structural variety; in particular, three different hexagonal polytypes are stabilized for the more oxidized samples. Unlike in the Ba-Mn-O system, stoichiometric BaFeO 3 has not been stabilized up to now, but the closest anionic composition, BaFeO 2.95 , adopts the 6H hexagonal polytype with a (hcc) 2 stacking arrangement containing only 33 % hexagonal layers, [11] that is, much less than BaMnO 3 .…”