| Abstract
| - The crystal structure of K4Co7O14 consists of a P2-type stacking of edge-shared CoO6 octahedron slabs between which K+ ions occupy ordered positions giving rise to a a0√7 × a0√7 supercell. Geometry optimization by means of ab-initio calculations shows that K+−K+ electrostatic repulsions are the driving force for the ground state ordering. The physical properties (thermopower, electrical resistivity, and magnetism) are discussed and compared to the related NaxCoO2 oxides.
- The layered P2−K4Co7O14 oxide has been prepared and characterized by means of X-ray diffraction, electricalconductivity, thermopower, and magnetic measurements. The crystal structure of K4Co7O14 (P63/m space group, Z= 2, a = 7.5171(1) Å, and c = 12.371(1) Å) consists of a stacking of slabs of edge-shared CoO6 octahedra withK+ ions occupying ordered positions in the interslab space, leading to a a0√7 × a0√7 supercell. Potential energycalculations at 0 K are in good agreement with the ordered distribution of potassium ions in the (ab) plane. Thisoxide is metallic, and the magnetic susceptibility is of Pauli-type, which contrasts with the Curie−Weiss behaviorof the homologous NaxCoO2 (x ≈ 0.6) oxide with close alkali content. The thermopower at room temperature isabout one-third that of polycrystalline Na0.6CoO2.
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