Structures and magnetic ordering in the brownmillerite phases, Sr2MnGaO5 and Ca2MnAlO5

Abstract

The crystal and magnetic structures of the two related phases, Sr 2 MnGaO 5 and Ca 2 MnAlO 5 are reported. Rietveld analysis of neutron powder diffraction has revealed that both phases adopt the brownmillerite structure. Subtle differences in structure lead to the structure of Sr 2 MnGaO 5 being best described by the space group Icmm (a ~5.4888(2) A ˚, b ~16.2256(6) A ˚, c ~5.35450(2) A ˚at 2 K) while that of Ca 2 MnAlO 5 is best described by Ibm2 (a ~5.46258(9) A ˚, b ~14.9532(3) A ˚, c ~5.23135(8) A ˚at 2 K). Low temperature neutron powder diffraction data show that both phases have a simple antiferromagnetic structure. However, magnetisation data suggest a more complex picture of the magnetic order within these phases.

Redox characteristics variations in the cation-ordered perovskite oxides BaLnMn2O5+δ(Ln = Y, Gd, Nd, and La) and Ca2Al1−xGaxMnO5+δ(0 ≤ x ≤ 1)

“…5 BaYMn 2 O 5+δ may be used as reducing catalysts and oxygen getter, owing to its great affinity to oxygen. layers with a preferential formation of AlO 4 and MnO 6 polyhedra, [11][12][13] as illustrated in Fig. 1.…”

Solution combustion synthesis of Brownmillerite-type Ca2AlMnO5 as an oxygen storage material

“…However, both methods require a heat-treatment period, the former needing 48 h at 1250 ˚C [13] and the latter needing 36 h at 1250 ˚C [11] and also producing an impurity. In addition, there has been no comprehensive study of the optimal conditions for Ca 2 AlMnO 5 production, even though it is a promising material for energy efficient air separation.…”

“…Motohashi et al synthesized Ca 2 AlMnO 5 by coprecipitation from nitrate salts and employed a heat-treatment period of 36 h at 1250 C [11]. Wright et al and Palmer et al synthesized Ca 2 AlMnO 5 from carbonate and oxide powders by solid state reaction at 1250 C for 48 h[12,13]. Therefore, SCS affords the energy saving advantage of rapid synthesis of high-purity Ca 2 AlMnO 5 .…”

Local structure study of the orbital order/disorder transition inLaMnO3

“…55. Though unexpected for LaMnO 3 , this model is actually related to the ordered JT distortion known to occur in some Mn 3+ brownmillerites, [56][57][58] and so could not be dismissed out of hand.…”

“…And, second, of the two models with different orbital arrangements to that of the ordered phase, it is the 3SP-type arrangement that contains the more conventional local JT distortion of MnO 6 octahedra. While the off-centered distortion of the L-type model is not without precedent in the structural chemistry of manganites, [56][57][58] the 180…”