The solubility and site preference of Fe3+ in Li7-3xFexLa3Zr2O12 garnets

D. Rettenwander*, C. A. Geiger, M. Tribus, P. Tropper, Richard Wagner, G. Tippelt, W. Lottermoser, G. Amthauer

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

A series of Fe3+-bearing Li7La3Zr2O12 (LLZO) garnets was synthesized using solid-state synthesis methods. The synthetic products were characterized compositionally using electron microprobe analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES) and structurally using X-ray powder diffraction and 57Fe Mössbauer spectroscopy. A maximum of about 0.25 Fe3+ pfu could be incorporated in Li7-3xFexLa3Zr2O12 garnet solid solutions. At Fe3+ concentrations lower than about 0.16 pfu, both tetragonal and cubic garnets were obtained in the synthesis experiments. X-ray powder diffraction analysis showed only a garnet phase for syntheses with starting materials having intended Fe3+ contents lower than 0.52 Fe3+ pfu. Back-scattered electron images made with an electron microprobe also showed no phase other than garnet for these compositions. The lattice parameter, a0, for all solid-solution garnets is similar with a value of a0≈12.98 Å regardless of the amount of Fe3+. 57Fe Mössbauer spectroscopic measurements indicate the presence of poorly- or nano-crystalline FeLaO3 in syntheses with Fe3+ contents greater than 0.16 Fe3+ pfu. The composition of different phase pure Li7-3xFexLa3Zr2O12 garnets, as determined by electron microprobe (Fe, La, Zr) and ICP-OES (Li) measurements, give Li6.89Fe0.03La3.05Zr2.01O12, Li6.66Fe0.06La3.06Zr2.01O12, Li6.54Fe0.12La3.01Zr1.98O12, and Li6.19Fe0.19La3.02Zr2.04O12. The 57Fe Mössbauer spectrum of cubic Li6.54Fe0.12La3.01Zr1.98O12 garnet indicates that most Fe3+ occurs at the special crystallographic 24d position, which is the standard tetrahedrally coordinated site in garnet. Fe3+ in smaller amounts occurs at a general 96h site, which is only present for certain Li-oxide garnets, and in Li6.54Fe0.12La3.01Zr1.98O12 this Fe3+ has a distorted 4-fold coordination.

Original languageEnglish
Pages (from-to)266-271
Number of pages6
JournalJournal of solid state chemistry
Volume230
DOIs
Publication statusPublished - 22 Jul 2015
Externally publishedYes

Keywords

  • <sup>57</sup>Fe Mössbauer spectroscopy
  • Chemical composition
  • Ion conductors
  • Li-oxide garnet
  • Synthesis
  • X-ray powder diffraction

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Ceramics and Composites
  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry

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    Rettenwander, D., Geiger, C. A., Tribus, M., Tropper, P., Wagner, R., Tippelt, G., ... Amthauer, G. (2015). The solubility and site preference of Fe3+ in Li7-3xFexLa3Zr2O12 garnets. Journal of solid state chemistry, 230, 266-271. https://doi.org/10.1016/j.jssc.2015.01.016