Local structure of core−shell MnFe2O4+δ-based nanocrystals: cation distribution and valence states of manganese ions
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The Journal of Physical Chemistry C
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We investigate the local structure of nanoparticles
based on a manganese ferrite core surrounded or not by a
maghemite layer obtained after hydrothermal surface treatment.
Results of X-ray powder diffraction (XRD) and neutron powder
diffraction (NPD) measurements are crossed with those of infield
Mössbauer spectroscopy and X-ray absorption spectroscopy
(XANES/EXAFS) to study the valence state of Mn ions and the
cation distribution at interstitial sites of the core−shell nanoparticle
structure. Linear combination fitting of XANES data
clearly indicates the existence of mixed valence states of Mn
cations in the Mn ferrite phase. As a direct consequence, it induces nonequilibrium cation distributions in the nanoparticle core
with the presence of a large amount of Mn cations at octahedral sites. The quantitative results of the inversion degree given by
NPD, Mössbauer spectroscopy measurements, and EXAFS are in good accordance. It is also shown that both the proportions of
each oxidation degree of Mn ions and their location at tetrahedral or octahedral sites of the spinel nanocrystal core can be
modified by increasing the duration of the surface treatment.
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MARTINS, FERNANDO H.; SILVA, FRANCISCARLOS G.; PAULA, FABIO L.O.; GOMES, JULIANO de A.; AQUINO, RENATA; MESTNIK-FILHO, JOSE; BONVILLE, PIERRE; PORCHER, FLORENCE; PERZYNSKI, REGIME; DEPEYROT, JEROME. Local structure of core−shell MnFe2O4+δ-based nanocrystals: cation distribution and valence states of manganese ions. The Journal of Physical Chemistry C, v. 121, n. 16, p. 8982-8991, 2017. DOI: 10.1021/acs.jpcc.6b09274. Disponível em: http://repositorio.ipen.br/handle/123456789/27753. Acesso em: 20 Mar 2026.
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