Iron valence in double-perovskite (Ba,Sr,Ca) 2FeMoO 6: Isovalent substitution effect

Y. Yasukawa, J. Lindén, T. S. Chan, R. S. Liu, H. Yamauchi, M. Karppinen*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

40 Citations (Scopus)

Abstract

In the Fe-Mo based B-site ordered double-perovskite, A 2FeMoO 6.0, with iron in the mixed-valence II/III state, the valence value of Fe is not precisely fixed at 2.5 but may be fine-tuned by means of applying chemical pressure at the A-cation site. This is shown through a systematic 57Fe Mössbauer spectroscopy study using a series of A 2FeMoO 6.0 [A=(Ba,Sr) or (Sr,Ca)] samples with high degree of Fe/Mo order, the same stoichiometric oxygen content and also almost the same grain size. The isomer shift values and other hyperfine parameters obtained from the Mössbauer spectra confirm that Fe remains in the mixed-valence state within the whole range of A constituents. However, upon increasing the average cation size at the A site the precise valence of Fe is found to decrease such that within the A=(Ba,Sr) regime the valence of Fe is closer to II, while within the A=(Sr,Ca) regime it is closer to the actual mixed-valence II/III state. As the valence of Fe approaches II, the difference in charges between Fe and Mo increases, and parallel with this the degree of Fe/Mo order increases. Additionally, for the less-ordered samples an increased tendency of clustering of the antisite Fe atoms is deduced from the Mössbauer data.

Original languageEnglish
Pages (from-to)2655-2662
Number of pages8
JournalJournal of Solid State Chemistry
Volume177
Issue number8
DOIs
Publication statusPublished - Aug 2004
MoE publication typeA1 Journal article-refereed

Keywords

  • Fe Mössbauer spectroscopy
  • Double perovskite
  • Halfmetal
  • Isovalent substitution
  • Valence mixing

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