Evolution of oxygen-vacancy ordered crystal structures in the perovskite series SrnFenO3n-1 (n=2, 4, 8, and {infinity}), and the relationship to electronic and magnetic properties.

Journal Article · Mon May 01 04:00:00 EDT 2000 · J. Solid State Chem.

DOI:https://doi.org/10.1006/jssc.1999.8640· OSTI ID:942713

Hodges, J P; Jorgensen, J D; Xiong, X; Dabrowski, B; Mini, S M; Kimball, C W

Over the oxygen composition range 2.5{<=}x{<=}3.0, the SrFeO{sub x} system exists as four distinct compounds with the nominal composition Sr{sub n}Fe{sub n}O{sub 3n-1} (n=2, 4, 8, and {infinity}). The end member SrFeO{sub 3} (n={infinity}) possesses a simple cubic perovskite crystal structure, whereas the oxygen-deficient (n=2, 4, and 8) members each adopt a different vacancy-ordered perovskite crystal structure. Using time-of-flight neutron powder diffraction, we show that previously proposed structures for the Sr{sub 4}Fe{sub 4}O{sub 11} (n=4) and Sr{sub 8}Fe{sub 8}O{sub 23} (n=8) compounds are incorrect. We determine the correct crystal structures for Sr{sub 4}Fe{sub 4}O{sub 11} (orthorhombic, space group Cmmm, a=10.974(1) {angstrom}, b=7.702(1) {angstrom}, and c=5.473(1) {angstrom}) and Sr{sub 8}Fe{sub 8}O{sub 23} (tetragonal, space group I4/mmm, a=10.929(1) {angstrom} and c=7.698(1) {angstrom}) through comparisons of the goodness of fit for Rietveld refinements of candidate models and bond-length distributions for each model. Using the correct crystal structures, we are able to assign valence states to the Fe crystallographic sites and to achieve consistency with published Moessbauer results for the same compounds.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC; DOD; OGA
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 942713
• Report Number(s): ANL/MSD/JA-33919
• Journal Information: J. Solid State Chem., Journal Name: J. Solid State Chem. Journal Issue: 2 ; May 2000 Vol. 151; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
CRYSTAL STRUCTURE
CUBIC LATTICES
ELECTRICAL PROPERTIES
IRON OXIDES
MAGNETIC PROPERTIES
OXYGEN
PEROVSKITE
STRONTIUM OXIDES
VACANCIES
VALENCE