The synthesis and complex anion-vacancy ordered structure of La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42}

Journal Article · Fri Jul 15 04:00:00 EDT 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.05.026· OSTI ID:21580152

Dixon, Edward ^[1]; Hadermann, Joke ^[2]

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1. Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom)
2. EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium)

The low-temperature topotactic reduction of La{sub 0.33}Sr{sub 0.67}MnO{sub 3} with NaH results in the formation of La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42}. A combination of neutron powder and electron diffraction data show that La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42} adopts a novel anion-vacancy ordered structure with a 6-layer OOTOOT' stacking sequence of the 'octahedral' and tetrahedral layers (Pcmb, a=5.5804(1) A, b=23.4104(7) A, c=11.2441(3) A). A significant concentration of anion vacancies at the anion site, which links neighbouring 'octahedral' layers means that only 25% of the 'octahedral' manganese coordination sites actually have 6-fold MnO{sub 6} coordination, the remainder being MnO{sub 5} square-based pyramidal sites. The chains of cooperatively twisted apex-linked MnO{sub 4} tetrahedra adopt an ordered -L-R-L-R- arrangement within each tetrahedral layer. This is the first published example of a fully refined structure of this type which exhibits such intralayer ordering of the twisted tetrahedral chains. The rationale behind the contrasting structures of La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42} and other previously reported reduced La{sub 1-x}Sr{sub x}MnO{sub 3-y} phases is discussed. - Graphical Abstract: The topotactic reduction of the perovskite phase La{sub 0.33}Sr{sub 0.67}MnO{sub 3} with NaH yields La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42(3)}, which adopts a novel anion vacancy ordered structure with a 6-layer OOTOOT' stacking sequence of the 'octahedral' and tetrahedral layers. The anion site that links the neighbouring octahedral layers is partially occupied so only 25% of the 'octahedral' manganese sites actually have 6-fold MnO{sub 6} coordination. Highlights: > Topotactic reduction with NaH to form a mixed valent Mn{sup 2+}/Mn{sup 3+} phase. > Novel layered anion-vacancy ordered structure. > Comparison to related brownmillerite structure types.

• OSTI ID: 21580152
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 7 Vol. 184; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ANIONS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
COMPARATIVE EVALUATIONS
COMPLEXES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DIFFRACTION
ELECTRON DIFFRACTION
ELEMENTS
EVALUATION
IONS
LAYERS
MANGANESE
MANGANESE COMPOUNDS
MANGANESE IONS
MANGANESE OXIDES
METALS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PERMANGANATES
PEROVSKITE
PEROVSKITES
POINT DEFECTS
SCATTERING
SYNTHESIS
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VACANCIES