First experimental evidence of potassium ordering in layered k4co7o14.
The layered P2-K4Co7O14 oxide has been prepared and characterized by means of X-ray diffraction, electrical conductivity, thermopower, and magnetic measurements. The crystal structure of K4Co7O14 (P6(3)/m space group, Z=2, a=7.5171(1) A, and c=12.371(1) A) consists of a stacking of slabs of edge-shared CoO6 octahedra with K+ ions occupying ordered positions in the interslab space, leading to a a0 radical7xa0 radical7 supercell. Potential energy calculations at 0 K are in good agreement with the ordered distribution of potassium ions in the (ab) plane. This oxide is metallic, and the magnetic susceptibility is of Pauli-type, which contrasts with the Curie-Weiss behavior of the homologous NaxCoO2 (x approximately 0.6) oxide with close alkali content. The thermopower at room temperature is about one-third that of polycrystalline Na0.6CoO2.
Blangero
Maxime
M
Institut de Chimie de la Matière Condensée de Bordeaux, ICMCB-CNRS, 87, avenue du Dr. Schweitzer, 33608 Pessac Cedex, France.
Decourt
Rodolphe
R
Carlier
Dany
D
Ceder
Gerbrand
G
Pollet
Michael
M
Doumerc
Jean-Pierre
JP
Darriet
Jacques
J
Delmas
Claude
C