Cation occupancies in Mg, Co, Ni, Zn, Al ferrite spinels: A multi-element EXAFS study

John Charnock, C. M B Henderson, J. M. Charnock, D. A. Plant

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The distribution of cations between tetrahedral (A) sites and octahedral (B) sites in ferrite spinels has been studied using K-edge x-ray absorption spectroscopy. The samples include natural and synthetic end-member magnetites (Fe3O4), a natural Mn-and Zn-rich magnetite (franklinite) and synthetic binary, ternary and quaternary ferrites of stoichiometry M 2+M23+O4, where M2+ ≤ Mg, Co, Ni, Zn and M3+ ≤ Fe, Al. XAS data were obtained for all metals. Complete, unfiltered, EXAFS spectra were refined to determine the percentage distribution of each element over the Aand Bsites and these data were combined with microprobe analyses to quantify the tetrahedral occupancy for each element in each sample. Measured site occupancies and an internally consistent set of (M-O)A and (M-O)B bond lengths were used to calculate unit-cell parameters, which show excellent agreement with measured values, pointing to the reliability of the measured occupancy factors. The average occupancies determined for the tetrahedral sites in ferrites are (atoms per formula unit) Mg0.44, Co0.24, Ni0.11, Zn0.76, Al0.11 and Fe3+ 0.92-0.19. The wide range found for Fe3+ is consistent with it playing a relatively passive role by making good any A-site deficit left by the other competing cations. © IOP Publishing Ltd.
    Original languageEnglish
    Article number076214
    JournalJournal of Physics: Condensed Matter
    Volume19
    Issue number7
    DOIs
    Publication statusPublished - 14 Feb 2007

    Keywords

    • X-RAY-DIFFRACTION
    • MAGNETIC CIRCULAR-DICHROISM
    • XRD STRUCTURAL
    • REFINEMENTS
    • NEUTRON POWDER DIFFRACTION
    • CURVED-WAVE THEORY
    • ABSORPTION
    • FINE-STRUCTURE
    • TEMPERATURE-DEPENDENCE
    • MGAL2O4 SPINEL
    • ORDER-DISORDER
    • MAGNESIOFERRITE MGFE2O4

    Fingerprint

    Dive into the research topics of 'Cation occupancies in Mg, Co, Ni, Zn, Al ferrite spinels: A multi-element EXAFS study'. Together they form a unique fingerprint.

    Cite this