Crystal and magnetic structures of new layered oxides A 2 GaMnO 5+y (A=Ca, Sr)

Sheptyakov, Denis; Abakumov, Artem M.; Antipov, Evgeny V.; Балагуров, А. М.; Billinge, Simon J. L.; Fischer, Peter; Keller, L.; Lobanov, Maxim V.; Pavlyuk, B.Ph.; Pomjakushin, Vladimir; Rozova, Marina G.

doi:10.1007/s003390201842

Cited by 10 publications

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“…This type of structure has been previously reported in the Mn-rich compound, Sr 2 Al 0.78 Mn 1.22 O 5.2 . The other type of structure has been reported for Sr 2 GaMnO 5.52 (oxygen storage phase), in which MnO 6 octahedral layers and GaO 6 octahedral layers are alternately laminated and oxygen defects exist in the GaO 2 plane of the GaO 6 octahedra . In the oxygen release phase, the DP structure is Mn-rich owing to the presence of the SrAl 2 O 4 impurity.…”

Section: Resultssupporting

confidence: 67%

“…29 The other type of structure has been reported for Sr 2 GaMnO 5.52 (oxygen storage phase), in which MnO 6 octahedral layers and GaO 6 octahedral layers are alternately laminated and oxygen defects exist in the GaO 2 plane of the GaO 6 octahedra. 30 In the oxygen release phase, the DP structure is Mn-rich owing to the presence of the SrAl 2 O 4 impurity. Therefore, it is presumed to have the same structure as Sr 2 Al 0.78 Mn 1.22 O 5.2 .…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Sr-Doped Ca₂AlMnO_5 + δ for Energy-Saving Oxygen Separation Process

Tanahashi

Omura

Naya

et al. 2021

ACS Sustainable Chem. Eng.

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Pressure swing adsorption (PSA) is expected to replace the currently used energy-intensive cryogenic distillation process for oxygen separation. For realizing an energy-saving PSA, an oxygen storage material (OSM) with a high oxygen storage capacity and narrow pressure swing gap during reversible oxygen storage and release is necessary. While Ca 2 AlMnO 5 is a promising candidate for PSA, it exhibits a large pressure hysteresis loop during oxygen storage and release. In this study, we investigated the effect of Sr doping of the Ca sites of Ca 2 AlMnO 5 (Ca 2−x Sr x AlMnO 5 ) on the phase compositions and oxygen storage/release performance with the aim of realizing an optimum OSM for the PSA process. From the results of structural refinement, while the oxygen release phase has a Brownmillerite (BM) structure (n = 1) at 0 ≤ x ≤ 1.0, BM (n = 3) and oxygen-defective perovskite were found to be the main structures in the oxygen storage phase at 0 ≤ x < 0.50 and 0.50 ≤ x ≤ 1.0, respectively. The oxygen storage/release temperature obtained from the thermogravimetry curves decreased in the 0 ≤ x < 0.50 range and increased in the 0.50 ≤ x ≤ 1.0 range with increasing x. This difference may be attributed to the structural differences in the storage phase. The pressure− composition−temperature (PCT) analysis by Sieberts' method was applied to the OSM. Although PCT curves exhibited a remarkable decrease in hysteresis in the PSA process as x increased, the difference between onset and offset temperatures for each oxygen storage/release reaction broadened. A new evaluation method to optimize x of Ca 2−x Sr x AlMnO 5 and operating condition in the PSA process using the OSM was also examined. Plots of the pressure change required to release oxygen versus the amount of oxygen extracted allow for the efficient determination of optimal composition and working temperature. Ca 1.2 Sr 0.8 AlMnO 5 (x = 0.80), which exhibited excellent repetition durability, was found to be optimal in this evaluation. The ideal PSA oxygen separation process using Ca 1.2 Sr 0.8 AlMnO 5 has the potential for producing pure oxygen with an energy input of 109.6 kWh/kNm 3 -O 2 , which is a significant energy saving compared to conventional processes.

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Section: Resultssupporting

confidence: 67%

Section: ■ Results and Discussionmentioning

confidence: 99%

Sr-Doped Ca₂AlMnO_5 + δ for Energy-Saving Oxygen Separation Process

Tanahashi

Omura

Naya

et al. 2021

ACS Sustainable Chem. Eng.

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“…This spin axis is determined from the data of Mo¨ssbauer spectroscopy for the tetrahedral site occupied by the Fe 3þ ions. Since in the Mn-based brownmillerites, containing a single magnetic ion, the same spin axis was observed in the octahedral site [8][9][10][11][12][13], a coupling between Fe and Mn is evidenced. In agreement with the previous data of Rietveld analysis [1], we show the wholly unmixed Fe, Mn cationic distribution over the tetrahedral and octahedral sites.…”

Section: Introductionmentioning

confidence: 89%

“…Similarly, a good number of brownmillerites show the random distribution of cations between chains and planes. However, recently a number of site-unmixed (Mn,Al) and (Mn,Ga)-based brownmillerites were synthesized, showing the strongest single-ion magnetocrystalline anisotropy axis oriented perpendicular to the planes [8][9][10][11][12][13]. In all these Mn-based brownmillerites containing no other magnetic ions, such as Sr 2 GaMnO 5 [8][9][10][11], Sr 2 Al 1þd Mn 1Àd O 5 [12], Ca 2 AlMnO 5 [8], SrCaGaMnO 5 [13], the Mn 3þ spins were reported to align normally to layers.…”

Section: Introductionmentioning

confidence: 99%

An Ising ferrimagnet with layered and chained magnetic sublattices:

Rykov¹,

Nomura

Ueda

et al. 2008

Journal of Magnetism and Magnetic Materials

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“…This value is lower than the average theoretical moment expected for a 1:1 ratio of Mn 3+ (d 4 ) and Mn 4+ (d 3 ) cations in Ca 3 GaMn 2 O 8 , which is 4.39 μB. However, low moments have been observed for Mn in other Ga-containing oxides such as Ca 2 GaMnO 5.045 (3.6 μB), SrCaMnGaO 5+δ (3.3 μB), and Sr 2 GaMnO 5.0 (3.2 μB). ,− …”

Section: Resultsmentioning

confidence: 70%

Pseudocapacitive Energy Storage and Electrocatalytic Hydrogen-Evolution Activity of Defect-Ordered Perovskites Sr_xCa_3–xGaMn₂O₈ (x = 0 and 1)

Karki

Ramezanipour

2020

ACS Appl. Energy Mater.

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The diverse range of possible arrangements of oxygen vacancies in oxygen-deficient perovskites results in a variety of structure types and fascinating electrochemical properties. Here, we report Ca 3 GaMn 2 O 8 and SrCa 2 GaMn 2 O 8 , where the ordering of oxygen vacancies leads to cation and polyhedral order, resulting in a remarkable array of electrochemical properties coexisting in the same compound. Neutron and X-ray diffraction have been utilized to study the structure of these materials that feature simultaneous defect order and cation order. Remarkably, both materials show very high electrocatalytic activity for hydrogen-evolution reaction (HER) of water splitting in bulk form, without the need for composite formation or nanofabrication. The HER overpotential required to achieve a current density of 10 mA/cm 2 is as low as η 10 ≈ −315 mV. In addition, detailed pseudocapacitive studies show that both compounds are capable of energy storage as anion-based pseudocapacitors, arising from oxygen ion intercalation. The symmetric pseudocapacitor cells fabricated based on these materials show a combination of high energy density and power density. These pseudocapacitor cells are also extremely stable, maintaining their high activity over 1000 cycles of charge−discharge. Electrical charge-transport studies indicate that these compounds have semiconducting properties in a wide temperature range, 25− 800 °C. Magnetic studies using both magnetometry and neutron scattering indicate a transition to an antiferromagnetic state, with a G-type arrangement of spins, where the moment on each Mn is aligned antiparallel to all nearest neighbors. This combination of properties indicates the great potential of this class of defect-ordered systems and their importance to energy research.

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Crystal and magnetic structures of new layered oxides A 2 GaMnO 5+y (A=Ca, Sr)

Cited by 10 publications

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Sr-Doped Ca₂AlMnO_5 + δ for Energy-Saving Oxygen Separation Process

Sr-Doped Ca₂AlMnO_5 + δ for Energy-Saving Oxygen Separation Process

An Ising ferrimagnet with layered and chained magnetic sublattices:

Pseudocapacitive Energy Storage and Electrocatalytic Hydrogen-Evolution Activity of Defect-Ordered Perovskites Sr_xCa_3–xGaMn₂O₈ (x = 0 and 1)

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Crystal and magnetic structures of new layered oxides A 2 GaMnO 5+y (A=Ca, Sr)

Cited by 10 publications

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Sr-Doped Ca2AlMnO5 + δ for Energy-Saving Oxygen Separation Process

Sr-Doped Ca2AlMnO5 + δ for Energy-Saving Oxygen Separation Process

An Ising ferrimagnet with layered and chained magnetic sublattices:

Pseudocapacitive Energy Storage and Electrocatalytic Hydrogen-Evolution Activity of Defect-Ordered Perovskites SrxCa3–xGaMn2O8 (x = 0 and 1)

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Product

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Sr-Doped Ca₂AlMnO_5 + δ for Energy-Saving Oxygen Separation Process

Sr-Doped Ca₂AlMnO_5 + δ for Energy-Saving Oxygen Separation Process

Pseudocapacitive Energy Storage and Electrocatalytic Hydrogen-Evolution Activity of Defect-Ordered Perovskites Sr_xCa_3–xGaMn₂O₈ (x = 0 and 1)