Structures of the reduced niobium oxides Nb12O29 and Nb22O54

T. McQueen, Q. Xu, E. N. Andersen, H. W. Zandbergen, Robert Joseph Cava

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31 Scopus citations

Abstract

The crystal structure of Nb22O54 is reported for the first time, and the structure of orthorhombic Nb12O29 is reexamined, resolving previous ambiguities. Single crystal X-ray and electron diffraction were employed. These compounds were found to crystallize in the space groups P2/m (a = 15.7491 (2) Å, b = 3.8236 (3) Å, c = 17.8521 (2) Å, β = 102.029 (3){ring operator}) and Cmcm (a = 3.8320 (2) Å, b = 20.7400 (9) Å, c = 28.8901 (13) Å), respectively and share a common structural unit, a 4×3 block of corner sharing NbO6 octahedra. Despite different constraints imposed by symmetry these blocks are very similar in both compounds. Within a block, it is found that the niobium atoms are not located in the centers of the oxygen octahedra, but rather are displaced inward toward the center of the block forming an apparent antiferroelectric state. Bond valence sums and bond lengths do not show the presence of charge ordering, suggesting that all 4d electrons are delocalized in these compounds at the temperature studied, T=200 K.

Original languageEnglish (US)
Pages (from-to)2864-2870
Number of pages7
JournalJournal of Solid State Chemistry
Volume180
Issue number10
DOIs
StatePublished - Oct 1 2007

All Science Journal Classification (ASJC) codes

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

Keywords

  • Antiferroelectric
  • NbO
  • NbO
  • Niobium magnetic moment
  • Niobium magnetism
  • Niobium oxide
  • Niobium shear structures
  • Orthorhombic NbO
  • Orthorhombic niobium oxide
  • Reduced niobium oxide

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