Charge disproportionation in (X0.6Sr0.4)0.99Fe0.8Co0.2O3 perovskites (X = La, Pr, Sm, Gd)

Thomas Pedersen, Souheil Saadi, K.H. Nielsen, Steen Mørup, Kent Kammer Hansen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The change in crystal structure and the oxidation state in iron of iron-cobalt-based perovskites with different A-site cations is investigated by the use of powder XRD and Mossbauer spectroscopy. The perovskites investigated are (X0.6Sr0.4)(0.99)Fe0.8Co0.2O3-delta, where X is La, Pr, Sm or Gd. It is shown that the crystal structure changes from hexagonal to orthorhombic when the size of the A-site cation is lowered. At room temperature, the oxidation state of iron increases when the size of the A-site cation is lowered. This is explained by a crystal packing effect. At lower temperatures, charge disproportionation of Fe(IV) occurs to Fe(III) and Fe(V). The transition temperature depends on the type of the A-site cation. Some of the Fe is reduced to Fe(III) by transference of electrons from Co upon cooling below room temperature.
Original languageEnglish
JournalSolid State Ionics
Volume176
Issue number17-18
Pages (from-to)1555-1561
ISSN0167-2738
DOIs
Publication statusPublished - 2005

Keywords

  • Perovskites
  • Charge disproportionation
  • Mossbauer spectroscopy

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