First-Principles Analysis of Cation Diffusion in Mixed Metal Ferrite Spinels

Christopher Muhich, Victoria J. Aston, Ryan M. Trottier, Alan W. Weimer, Charles B. Musgrave

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Ferrite spinels are metal oxides used in a wide variety of applications, many of which are controlled by the diffusion of metal cations through the metal oxide lattice. In this work, we used density functional theory (DFT) to examine the diffusion of Fe, Co, and Ni cations through the Fe3O4, CoFe2O4, and NiFe2O4 ferrite spinels. We apply DFT and crystal field theory to uncover the principles that govern cation diffusion in ferrite spinels. We found that a migrating cation hops from its initial octahedral site to a neighboring octahedral vacancy via a tetrahedral metastable intermediate separated from octahedral sites by a trigonal planar transition state (TS). The cations hop with relative activation energies of Co ≈ < Fe < Ni; the ordering of the diffusion barriers is controlled by the crystal field splitting of the diffusing cation. Specifically, the barriers depend on the orbital splitting and number of electrons which must be promoted into the higher energy t2g orbitals of the tetrahedral metastable intermediate as the cations move along the minimum energy pathway of hopping. Additionally, for each diffusing cation, the barriers are inversely proportional to the spinel lattice parameter, leading to relative barriers for cation diffusion of Fe3O4 < CoFe2O4 < NiFe2O4. This results from the shorter cation-O bonds at the TS for spinels with smaller lattices, which inherently possess shorter bond lengths, and consequently higher system energies at their more constricted TS geometries.

Original languageEnglish (US)
Pages (from-to)214-226
Number of pages13
JournalChemistry of Materials
Volume28
Issue number1
DOIs
StatePublished - Jan 12 2016
Externally publishedYes

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Ferrite
Cations
Positive ions
Metals
Oxides
Density functional theory
Crystals
Diffusion barriers
Bond length
Lattice constants
Vacancies
Activation energy
Geometry
Electrons

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

Cite this

First-Principles Analysis of Cation Diffusion in Mixed Metal Ferrite Spinels. / Muhich, Christopher; Aston, Victoria J.; Trottier, Ryan M.; Weimer, Alan W.; Musgrave, Charles B.

In: Chemistry of Materials, Vol. 28, No. 1, 12.01.2016, p. 214-226.

Research output: Contribution to journalArticle

Muhich, Christopher ; Aston, Victoria J. ; Trottier, Ryan M. ; Weimer, Alan W. ; Musgrave, Charles B. / First-Principles Analysis of Cation Diffusion in Mixed Metal Ferrite Spinels. In: Chemistry of Materials. 2016 ; Vol. 28, No. 1. pp. 214-226.
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