Electron charge density study of (Na1-xKx)NbO 3 in cubic structure

Chikako Moriyoshi, Jun Ichi Kato, Yoshihiro Terado, Satoshi Wada, Masaki Takata, Yoshihiro Kuroiwa

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14 Citations (Scopus)

Abstract

The electron charge density study by synchrotron-radiation powder diffraction has been performed for the cubic structure of (Na 1-xKx)NbO3 (NKN: 0 ≤ x ≤ 1) at 1000 K to investigate the atomic substitution effect on chemical bonding. Our precise analysis using the maximum entropy method (MEM)/Rietveld method demonstrates that the covalent bonding is formed on the Nb-O bond whereas the Na/K atoms are ionic in the entire composition range. The thermal motion of the Na ion in NaNbO3 is fairly larger than that of the K ion in KNbO3. The charge density distributions around the O atoms in NaNbO3 are extended in the directions perpendicular to the Nb-O bond, which can be related to the rotational mode of the Nb-O6 octahedron driving the antiferroic phase transition. No such anisotropy is clearly observed in KNbO3 around the O atoms. These behaviors are closely related to the change in the tolerance of the perovskite structure caused by the atomic substitution.

Original languageEnglish
Pages (from-to)7745-7748
Number of pages4
JournalJapanese journal of applied physics
Volume47
Issue number9 PART 2
DOIs
Publication statusPublished - 2008 Sep 19
Externally publishedYes

Keywords

  • Charge density
  • KNbO
  • Maximum entropy method
  • NKN
  • NaNbO
  • Perovskite
  • Powder diffraction
  • Synchrotron radiation
  • Thermal motion
  • Tolerance factor

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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