Eu-doping of hematite (alpha-Fe2O3) nanoparticles (NPs) takes place under hydrothermal conditions, and does not at ambient temperature and pressure. Required circumstances have been studied in detail. In the presence of Eu, besides hematite, some goethite and ferrihydrite are formed. Evidence for the occurrence of doping is reported. Chemical composition, as studied by EDS (bulk) and XPS (surface), reveals an enrichment of Eu at NPs core, ascribed to the occurrence of a two-step mechanism of NP formation, comprising nucleation at first, in which Eu3+ ions compete with Fe3+ ions, notwithstanding the large difference in concentration, and a successive growth step. of NPs in a solution comparatively richer in Fe3+ species. The Eu content affects: (i) the morphology of NPs, as shown by TEM and FE-SEM; (ii) lattice parameters, as obtained by Rietveld refinement of XRD patterns; (iii) magnetic properties, due to the presence of Eu3+ ions, characterized by a higher one-ion anisotropy and a lower magnetic moment with respect to iron cations. (C) 2013 Elsevier Inc. All rights reserved.
Eu-doped alpha-Fe2O3 nanoparticles with modified magnetic properties / Freyria, Fs; Barrera, G; Tiberto, PAOLA MARIA; Belluso, E; Levy, D; Saracco, G; Allia, P; Garrone, E; Bonelli, B.. - In: JOURNAL OF SOLID STATE CHEMISTRY. - ISSN 0022-4596. - 201:(2013), pp. 302-311. [10.1016/j.jssc.2013.03.018]
Eu-doped alpha-Fe2O3 nanoparticles with modified magnetic properties
Barrera G;TIBERTO, PAOLA MARIA;
2013
Abstract
Eu-doping of hematite (alpha-Fe2O3) nanoparticles (NPs) takes place under hydrothermal conditions, and does not at ambient temperature and pressure. Required circumstances have been studied in detail. In the presence of Eu, besides hematite, some goethite and ferrihydrite are formed. Evidence for the occurrence of doping is reported. Chemical composition, as studied by EDS (bulk) and XPS (surface), reveals an enrichment of Eu at NPs core, ascribed to the occurrence of a two-step mechanism of NP formation, comprising nucleation at first, in which Eu3+ ions compete with Fe3+ ions, notwithstanding the large difference in concentration, and a successive growth step. of NPs in a solution comparatively richer in Fe3+ species. The Eu content affects: (i) the morphology of NPs, as shown by TEM and FE-SEM; (ii) lattice parameters, as obtained by Rietveld refinement of XRD patterns; (iii) magnetic properties, due to the presence of Eu3+ ions, characterized by a higher one-ion anisotropy and a lower magnetic moment with respect to iron cations. (C) 2013 Elsevier Inc. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
