Application of x-ray absorption fine structure (XAFS) to local-order analysis in Fe-Cr maghemite-like materials

Journal Article · Thu Jul 23 00:00:00 EDT 2015 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4927185· OSTI ID:22488685

Fuentes-Cobas, L. E.; Macías-Ríos, E. ^[1]; Fuentes-Montero, M. E. ^[2]

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1. Centro de Investigación en Materiales Avanzados, Chihuahua, 31136, México (Mexico)
2. Universidad Autónoma de Chihuahua, Chihuahua, 31000, México (Mexico)

The maghemite-like oxide system γ-Fe{sub 2-x}Cr{sub x}O{sub 3} (x=0.75, 1 and 1.25) was studied by X-ray absorption fine structure (XAFS) and by synchrotron radiation X-ray diffraction (XRD). Measurements were performed at the Stanford Synchrotron Radiation Lightsource at room temperature, at beamlines 2-1, 2-3 and 4-3. High-resolution XRD patterns were processed by means of the Rietveld method. In cases of atoms being neighbors in the Periodic Table, the order/disorder degree of the considered solutions is indiscernible by “normal” (absence of “anomalous scattering”) diffraction experiments. Thus, maghemite-like materials were investigated by XAFS in both Fe and Cr K-edges to clarify, via short-range structure characterization, the local ordering of the investigated system. Athena and Artemis graphic user interfaces for IFEFFIT and FEFF8.4 codes were employed for XAFS spectra interpretation. Pre-edge decomposition and theoretical modeling of X-ray absorption near edge structure (XANES) transitions were performed. By analysis of the Cr K-edge XANES, it has been confirmed that Cr is located in an octahedral environment. Fitting of the extended X-ray absorption fine structure (EXAFS) spectra was performed under the consideration that the central atom of Fe is allowed to occupy octa- and tetrahedral positions, while Cr occupies only octahedral ones. Coordination number of neighboring atoms, interatomic distances and their quadratic deviation average were determined for x=1, by fitting simultaneously the EXAFS spectra of both Fe and Cr K-edges. The results of fitting the experimental spectra with theoretical standards showed that the cation vacancies tend to follow a regular pattern within the structure of the iron-chromium maghemite (FeCrO{sub 3})

• OSTI ID: 22488685
• Journal Information: AIP Conference Proceedings, Vol. 1671, Issue 1; Conference: 11. international symposium on radiation physics, Ciudad Juarez (Mexico), 4-6 Mar 2015; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
ATOMS
CATIONS
CHROMATES
CONCENTRATION RATIO
COORDINATION NUMBER
FINE STRUCTURE
INTERATOMIC DISTANCES
INTERFACES
IRON COMPOUNDS
RESOLUTION
SYNCHROTRON RADIATION
TEMPERATURE RANGE 0273-0400 K
VACANCIES
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY