| Autor: |
Wu, E., Campbell, S. J., Kaczmarek, W. A., Hofmann, M., Kennedy, S. J. |
| Zdroj: |
International Journal of Materials Research: Zeitschrift fuer Metallkunde; February 2022, Vol. 94 Issue: 10 p1127-1133, 7p |
| Abstrakt: |
The effects of wet-milling mixtures of α-Fe2O3and cobalt hydroxide Co(OH)2over a range of Co/Fe ratios for 215 h have been investigated by neutron diffraction and Mössbauer spectroscopy. The starting materials were mixed according to the stoichiometric formula (CoxFe1 –x)3O4for values of x= 0.037, 0.071, 0.133, 0.234 and 0.380 (i. e., from ≈ Co0.1Fe2.9O4to the cobalt spinel CoFe2O4). These studies reveal the formation of a nanostructured, mixed Co–Fe spinel phase with non-stoichiometric composition (CoxFe1– x)3 –yO4; the defect spinels have refined values xc= 0.04, 0.08 and 0.14 for the mixtures with the lowest Co content (x= 0.037, 0.071 and 0.133) and defect concentrations in the range y ≈ 0.1 –0.2. Both the spinel phase and un-reacted α-Fe2O3are found to occur in the neutron diffraction patterns and Mössbauer spectra for the high Co content mixtures x= 0.234 and x= 0.380. Rietveld refinements of the neutron data indicate that the Co atoms predominantly occupy the octahedral B sites with vacancies also found to be located on the octahedral B sites. Analyses of the Mössbauer spectra of the milled samples confirm the existence of vacancy defects in the B sites and reveal that the vacancies cause similar effects to those of the Co ions, leading to a higher average charge state per iron atom. |
| Databáze: |
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