Complex manganese oxides with the brownmillerite structure: synthesis, crystal chemistry and properties

Abstract

Structural features and methods for the synthesis of Structural features and methods for the synthesis of complex manganese oxides with the brownmillerite structure complex manganese oxides with the brownmillerite structure) and of their derivatives = Ga, Al) and of their derivatives are surveyed. Modern approaches to the description of crystal are surveyed. Modern approaches to the description of crystal structures containing various types of chains of tetrahedra are structures containing various types of chains of tetrahedra are considered and possible ordering patterns of these chains are considered and possible ordering patterns of these chains are discussed. The effects of the electronic structure and crystal discussed. The effects of the electronic structure and crystal chemical properties of the B chemical properties of the B H cations on the possibility of for-cations on the possibility of formation of a layered ordered structure is noted. The emphasis is mation of a layered ordered structure is noted. The emphasis is placed on the anion non-stoichiometry of the brownmillerite placed on the anion non-stoichiometry of the brownmillerite phases and the influence of the excess oxygen (fluorine) on the phases and the influence of the excess oxygen (fluorine) on the structure of the compounds. A comparative analysis of properties structure of the compounds. A comparative analysis of properties of oxygen-and fluorine-doped brownmillerites is given. The data of oxygen-and fluorine-doped brownmillerites is given. The data on the magnetic structures, transport and magnetoresistive prop-on the magnetic structures, transport and magnetoresistive properties of Mn-containing brownmillerites are generalised. The erties of Mn-containing brownmillerites are generalised. The bibliography includes 74 references bibliography includes 74 references. .

The Formation of Performance Enhancing Pseudo‐Composites in the Highly Active La1–xCaxFe0.8Ni0.2O3 System for IT‐SOFC Application

“…Peaks from this phase are highlighted in the inset in Figure 1. The appearance of this brownmillerite phase is also reported by other authors28, 29 and the lattice parameters of a = 5.24 Å, b = 15.10 Å and c = 5.52 Å (in LCFN0.7 sample) agree well with those in literature 30, 31. Nominal compositions with a high level of Ca content ( x ≥ 0.8) feature an additional lanthanum oxide (La 2 O 3 ) phase.…”

Structure and magnetic properties of Ca2Fe1−xMnxAlO5+δ

“…This fact is essentially related to the major role of the oxidation of some Mn 3+ to Mn 4+ ions. The performed oxidation treatments led to a consequent oxygen insertion, resulting in an oxygen overstoichiometry (d) between 0.03 and 0.04, in accordance to previous works on Ca 2 MnGaO 5+d compounds (d ¼ 0.045, 0.09 and 0.39) [3,18].…”

“…For all the obtained compounds, as usually observed in the brownmillerite structure, the MnO 6 octahedron is characterized by four short equatorial M-O1 distances and two long apical M-O2 ones oriented along the b-axis, while oxygen tetrahedra are slightly compressed along this axis. Axial distortions of the BO 6 octahedra of the brownmillerite structure A 2 BB 0 O 5 are observed not only for cations exhibiting the Jahn-Teller effect, but also for cations Table 3 Selected bond lengths (Å ) and bond angles (deg) for the as-prepared Ca 2 Fe 1Àx Mn x AlO 5 compounds (strain parameter: devoid of this property, such as in Ca 2 FeAlO 5 [18]. Increasing the manganese content, a more pronounced elongation of the axial M oct -O bonds and a systematic increase of the strain parameter (s JT ) were observed (Table 3).…”

Magnetic Structure and Electronic Study of Complex Oxygen‐Deficient Manganites

“…Actually, there are very few examples of brownmillerite-related compounds with FM interactions and in most cases they comprise an A 2 MBO 5 composition, M being a magnetic cation, such as Mn or Co, and B a non-magnetic cation. [11] In any case, the ND studies only reveal, again, AFM ordering, whereas additional FM behaviour is detected by magnetization measurements. This is the situation for Ca 2 MnAlO 5 and Sr 2 MnGaO 5 , [9] SrCaMnGaO 5 , [10] and even Ca 2 Fe 2 O 5 , [25,27] with only Fe at the B sublattice.…”