Thermoelectric Properties (Resistivity and Thermopower) in (Bi1.5Pb0.5Ca2−xMxCo2O8−δ (M=Sc3+, Y3+, or La3+)

✍ Scribed by E. Iguchi; S. Katoh; H. Nakatsugawa; F. Munakata

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 226 KB
• Volume: 167
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2002.9664

✦ Synopsis

In order to understand the origin of good thermoelectric (TE) properties in the transition metal oxides with the lattice structure isomorphous to the 232-structure, the bond nature between Co and O ions in Bi 1:5 Pb 0:5 Ca 2Àx M x Co 2 O 8Àd -system has been tried to vary by replacing M with Sc 3þ ; Y 3þ or La 3þ and by changing x from 0 to 0.3. The resistivity is minimum at x = 0.1 in Sc-and Y-systems, but very high in La-system. The large thermopower is obtained in every compound. The experimental TE properties have been discussed mainly within the framework of the chargetransfer scheme in which the ionic radii of Sc 3þ and Y 3þ smaller than Ca 2þ reduce the energy between O 2p levels and Co e g parentages but the large ionic radius of La 3þ expands it. The oxygen solubility in the compounds and the lattice distortion peculiar to the 232-structure are also likely to contribute somewhat to the experimental results.