Structure and properties of NaxM2SbO6 · yH2O, M = Co(III), Ni(III) honeycomb oxyhydrates

J. H. Roudebush, R. J. Cava

Research output: Contribution to journalArticle

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Abstract

The oxyhydrates Na0.85Co2SbO6 · 1.7H2O and Na0.95Ni2SbO6 · 1.5H2O were prepared by Br2 oxidation of Na 3Co2SbO6 and Na3Ni 2SbO6 and exposure to ambient air. Their composition and structure are characterized by thermogravimetric analysis, elemental analysis and powder X-ray diffraction. Both form monolayer hydrates with metal cations (Co or Ni) near the 3+ oxidation state. In the parent materials, MO6 octahedra surround SbO6 units, forming a honeycomb geometry; Rietveld refinement of the hydrate phases indicate that this motif is retained. Magnetic susceptibility plots display paramagnetic behavior and Curie-Weiss fits support the 3+ oxidation state (low spin d6 s=0 for Co and low spin d 7 s = 1/2 for Ni). Close inspection of the Ni hydrate's susceptibility reveals a feature at 6.2 K and a nonlinear magnetization at 2 K with no saturation up to 9 T. Heat capacity measurements show a large amount of excess entropy in the Ni hydrate in the 2-20 K temperature range, while the heat capacity of the Co hydrate can be described by a simple lattice contribution. The Ni hydrate sample is easily dehydrated by heating above 100 °C and forms a new Na-deficient phase, Na0.95Ni2SbO6, which is stable at room temperature. Magnetic susceptibility of this phase is consistent with the Ni atom remaining in the 3+ oxidation state after dehydration.

Original languageEnglish (US)
Pages (from-to)178-185
Number of pages8
JournalJournal of Solid State Chemistry
Volume204
DOIs
StatePublished - Jan 1 2013

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

  • Heat capacity
  • Honeycomb
  • Hydrate
  • Magnetism

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