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.
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 Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); USDOD; OGA
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 942713
- Report Number(s):
- ANL/MSD/JA-33919; JSSCBI; TRN: US200922%%575
- Journal Information:
- J. Solid State Chem., Vol. 151, Issue 2 ; May 2000; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- ENGLISH
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