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 language | English (US) |
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Pages (from-to) | 178-185 |
Number of pages | 8 |
Journal | Journal of Solid State Chemistry |
Volume | 204 |
DOIs | |
State | Published - 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