Synthesis and Structural Characterization of La1−xAxMnO2.5 (A = Ba, Sr, Ca) Phases: Mapping the Variants of the Brownmillerite Structure

Parsons, Thomas G.; D’Hondt, Hans; Hadermann, Joke; Hayward, Michael A.

doi:10.1021/cm902535m

Cited by 101 publications

(147 citation statements)

References 45 publications

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“…These arguments were then used to construct a "structure map" relating the observed phase of different brownmillerites to these factors, followed by a classification of several known compounds into this scheme. 36 Although these observations have been key in building an understanding of structural trends in brownmillerite oxides, and are corroborated by some recently synthesized brownmillerite phases (such as Ca 2 Cr 2 O 5 ), 37 discrepancies in this structure map show there are additional effects which should be considered. Ca 2 FeCoO 5 and Ca 2 Co 2 O 5 , for example, both display the P bcm rather than the structure-map predicted P nma geometry.…”

Section: A Polyhedral Rotation Definitionsmentioning

confidence: 81%

Crystal structure and electronic properties of bulk and thin film brownmillerite oxides

Young¹,

Rondinelli²

2015

Phys. Rev. B

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The equilibrium structure and functional properties exhibited by brownmillerite oxides, a family of perovskite-derived structures with alternating layers of BO6 octahedra and BO4 tetrahedra, viz., ordered arrangements of oxygen vacancies, is dependent on a variety of competing crystal-chemistry factors. We use electronic structure calculations to disentangle the complex interactions in two ferrates, Sr2Fe2O5 and Ca2Fe2O5, relating the stability of the equilibrium (strain-free) and thin film structures to both previously identified and newly herein proposed descriptors. We show that cation size and intralayer separation of the tetrahedral chains provide key contributions to the preferred ground state. We show the bulk ground state structure is retained in the ferrates over a range of strain values; however, a change in the orientation of the tetrahedral chains, i.e., a perpendicular orientation of the vacancies relative to the substrate, is stabilized in the compressive region. The structure stability under strain is largely governed by maximizing the intraplane separation of the 'dipoles' generated from rotations of the FeO4 tetrahedra. Lastly, we find that the electronic band gap is strongly influenced by strain, manifesting as an unanticipated asymmetric-vacancy alignment dependent response. This atomistic understanding establishes a practical route for the design of functional electronic materials in thin film geometries.

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Section: A Polyhedral Rotation Definitionsmentioning

confidence: 81%

Crystal structure and electronic properties of bulk and thin film brownmillerite oxides

Young¹,

Rondinelli²

2015

Phys. Rev. B

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“…Two molar equivalents of citric acid and 5 mL of ethylene glycol were added and the solutions heated with constant stirring. 59 The resulting gel was dried and ground to fine powder, placed in a crucible and heated in air to 1000…”

Section: Methods Sample Preparation and Characterisationmentioning

confidence: 99%

Local structure study of the orbital order/disorder transition inLaMnO3

et al. 2017

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We use a combination of neutron and X-ray total scattering measurements together with pair distribution function (PDF) analysis to characterise the variation in local structure across the orbital order-disorder transition in LaMnO3. Our experimental data are inconsistent with a conventional order-disorder description of the transition, and reflect instead the existence of a discontinuous change in local structure between ordered and disordered states. Within the orbital-ordered regime, the neutron and X-ray PDFs are best described by a local structure model with the same local orbital arrangements as those observed in the average (long-range) crystal structure. We show that a variety of meaningfully-different local orbital arrangement models can give fits of comparable quality to the experimental PDFs collected within the disordered regime; nevertheless, our data show a subtle but consistent preference for the anisotropic Potts model proposed in Phys Rev. B 79, 174106 (2009). The key implications of this model are electronic and magnetic isotropy together with the loss of local inversion symmetry at the Mn site. We conclude with a critical assessment of the interpretation of PDF measurements when characterising local symmetry breaking in functional materials.

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“…18,19 In the case of strontium-doped lanthanum manganite, this phase has been observed only upon reduction with hydrides or upon exposure to 50% hydrogen gas. 20,21 Such extreme reducing conditions are not encountered under typical thermochemical cycling conditions and accordingly the Brownmillerite phase is not anticipated to form as part of the fuel generation process.…”

Section: Background: Structural Thermodynamic and Kinetic Propertiesmentioning

confidence: 99%

Thermodynamic and kinetic assessments of strontium-doped lanthanum manganite perovskites for two-step thermochemical water splitting

et al. 2014

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Solar-driven thermochemical water splitting using non-stoichiometric oxides has emerged as an attractive technology for solar fuel production. The most widely considered oxide for this purpose is ceria, but the extreme temperatures required to achieve suitable levels of reduction introduce challenges in reactor design and operation, leading to efficiency penalties. Here, we provide a quantitative assessment of the thermodynamic and kinetic properties of La 1Àx Sr x MnO 3Àd perovskites, targeted for a reduced temperature operation of thermochemical water splitting. Sr-doping into lanthanum manganite increases the thermodynamic fuel production capacity, which reaches 9 ml g À1 for 0.

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Synthesis and Structural Characterization of La_1−xA_xMnO_2.5 (A = Ba, Sr, Ca) Phases: Mapping the Variants of the Brownmillerite Structure

Cited by 101 publications

References 45 publications

Crystal structure and electronic properties of bulk and thin film brownmillerite oxides

Crystal structure and electronic properties of bulk and thin film brownmillerite oxides

Local structure study of the orbital order/disorder transition inLaMnO3

Thermodynamic and kinetic assessments of strontium-doped lanthanum manganite perovskites for two-step thermochemical water splitting

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