We have determined the crystal structure of Bi-substituted and Bi-free misfit layered cobalt oxides [Ca2CoO3] 0.62CoO2, by a (3+1)-dimensional superspace group approach. Structural parameters have been refined with a superspace group of C2/m(1p0)s0 using powder neutron diffraction data. Bismuth atoms are found to substitute for both Ca and Co atoms in the rock salt-type [Ca 2CoO3] subsystem. The resulting structural formula is expressed as [(Ca0.90Bi0.10)2(Co 0.95Bi0.05)O3]pCoO2 with a refined b-axis ratio of p = 0.6183. By Bi substitution, the modulation of the Co-O distances in the [Ca2CoO3] subsystem is markedly decreased relative to the Bi-free counterpart, whereas such a modulation in the [CoO2] subsystem is slightly increased. The observed increase in the Seebeck coefficient and electrical resistivity of the Bi-substituted phase can be explained in terms of the decrease in hole concentration in the CoO 2 sheets.
|ジャーナル||Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers|
|出版ステータス||Published - 2004 9|
ASJC Scopus subject areas
- Physics and Astronomy(all)