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Modulated Structure of Misfit Layered Cobalt Oxide [(Ca 0.90 Bi 0.10 ) 2 (Co 0.95 Bi 0.05 )O 3 ] p CoO 2

2004; Institute of Physics; Volume: 43; Issue: 9R Linguagem: Inglês

10.1143/jjap.43.6252

1347-4065

Yuzuru Miyazaki, Yousuke Suzuki, Mitsuko Onoda, Yoshinobu Ishii, Yukio Morii, Tsuyoshi Kajitani,

Magnetic and transport properties of perovskites and related materials

We have determined the crystal structure of Bi-substituted and Bi-free misfit layered cobalt oxides [Ca 2 CoO 3 ] 0.62 CoO 2 , by a (3+1)-dimensional superspace group approach. Structural parameters have been refined with a superspace group of C 2/ m (1 p 0) s 0 using powder neutron diffraction data. Bismuth atoms are found to substitute for both Ca and Co atoms in the rock salt-type [Ca 2 CoO 3 ] subsystem. The resulting structural formula is expressed as [(Ca 0.90 Bi 0.10 ) 2 (Co 0.95 Bi 0.05 )O 3 ] p CoO 2 with a refined b -axis ratio of p =0.6183. By Bi substitution, the modulation of the Co–O distances in the [Ca 2 CoO 3 ] subsystem is markedly decreased relative to the Bi-free counterpart, whereas such a modulation in the [CoO 2 ] 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.