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Lattice parameters and site occupancy factors of magnetite–maghemite core–shell nanoparticles. A critical study
Author(s) -
Cervellino Antonio,
Frison Ruggero,
Cernuto Giuseppe,
Guagliardi Antonietta,
Masciocchi Norberto
Publication year - 2014
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576714019840
Subject(s) - maghemite , magnetite , lattice constant , stoichiometry , materials science , scattering , nanoparticle , diffraction , lattice (music) , chemistry , nanotechnology , physics , optics , metallurgy , acoustics
The size‐driven expansion and oxidation‐driven contraction phenomena of nonstoichiometric magnetite–maghemite core–shell nanoparticles have been investigated by the total scattering Debye function approach. Results from a large set of samples are discussed in terms of significant effects on the sample average lattice parameter and on the possibility of deriving the sample average oxidation level from accurate, diffraction‐based, cell values. Controlling subtle experimental effects affecting the measurement of diffraction angles and correcting for extra‐sample scattering contributions to the pattern intensity are crucial issues for accurately estimating lattice parameters and cation vacancies. The average nanoparticle stoichiometry appears to be controlled mainly by iron depletion of octahedral sites. A simple law with a single adjustable parameter, well correlating lattice parameter, stoichiometry and size effects of all the nanoparticles present in the whole set of samples used in this study, is proposed.