Ab Initio Structure Solution of BaFeO2.8−δ, a New Polytype in the System BaFeOy (2.5≤y≤3.0) Prepared from the Oxidative Thermal Decomposition of BaFe[(CN)5NO]·3H2O

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

“…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.…”

“…In fact, BaFeO 2.80 [9] adopts the same 10H structural type as the anionic vacancies lo- cated in the hexagonal layers on the dimer structural units, changing its anionic composition from BaO 3 to BaO 2 (Figure 3b). The remaining two oxygen atoms rearrange in such a way that only one of them is bonded to the two Fe atoms adjacent to the layer, thus leading to a dimer of cornersharing tetrahedra.…”

“…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.…”

“…A structural study by X-ray profile refinement has been performed by taking as starting model the structural parameters of the hexagonal 10H-BaFeO 2.80-y in the space group P6 3 /mmc. [9] www.eurjic.orgBecause of their similar scattering factors, Mn and Fe are indistinguishable by XRD; therefore, both metals were randomly distributed over the two crystallographically different octahedral sites, the tetrahedral one is fully occupied by Fe, since neither Mn III nor Mn IV are stable in this oxygen coordination. In addition, the determined anionic stoichiometry indicates the presence of oxygen vacancies in the structure, which, according to the above considerations, have been located into the hexagonal hЈ-BaO 2 up to a BaO 1.65 anionic composition; the nonbonding oxygen position (2c) being 65 % occupied.…”

SYNTHESIS OF Pb2Fe2O5 BY THERMAL DECOMPOSITION OF Pb2[Fe(CN)6].4H2O

“…In these compounds, in which iron is in 4+ oxidation state, many oxygen vacancies are usually generated [8][9][10][11][12] due to the high instability of Fe (IV). When d=0.5 all the iron is in oxidation state 3+ and a brownmillerite type compound is formed 9 . ABO 3-δ perovskites containing an easily polarizable A cation with a sterically active lone electron pair (Bi…”