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Synthesis and thermoelectric properties of Bi2.5Ca2.5Co2Ox layered cobaltites

Published online by Cambridge University Press:  01 April 2005

Emmanuel Guilmeau ,
Masashi Mikami ,
Ryoji Funahashi  and
Daniel Chateigner
Emmanuel Guilmeau
Affiliation:
National Institute of Advanced Industrial Science and Technology, Osaka 563-8577, Japan
Masashi Mikami
Affiliation:
National Institute of Advanced Industrial Science and Technology, Midorigaoka, Ikeda, Osaka 563-8577, Japan; and CREST, Japan Science and Technology Agency, Ikeda, Osaka 563-8577, Japan
Ryoji Funahashi*
Affiliation:
National Institute of Advanced Industrial Science and Technology, Midorigaoka, Ikeda, Osaka 563-8577, Japan; and CREST, Japan Science and Technology Agency, Ikeda, Osaka 563-8577, Japan
Daniel Chateigner
Affiliation:
CRISMAT-ENSICAEN Laboratory, UMR CNRS 6508, 14050 Caen Cedex, France
*
a) Address all correspondence to this author. e-mail: funahashi-r@aist.go.jp
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Abstract

Bi–Ca–Co–O polycrystalline materials with a layered structure were prepared. The synthesis of the sintered specimens from two starting compositions, Bi1.8Ca2Co2Oxand Bi2.5Ca2.5Co2Ox, revealed the latter is preferentially formed at high temperature(850 °C). The increase in sintering time was shown by growth of large platelike grains (up to 50 μm in diameter and several micrometers in thickness). The reaction mechanisms during the heat treatment and the preferential formation of the Bi2.5Ca2.5Co2Ox phase were observed by x-ray diffraction, thermogravimetry–differential thermal analysis, and scanning electron microscopy. These techniques supposed the presence of a liquid phase at high temperature, origin of a highly kinetic phase formation, and the growth of large grains. Interestingly the liquid phase reaction promotes an efficient stacking and sliding of grains during hot-forging treatment, and highly (00l) oriented materials were prepared. A relationship between thermoelectric performance, texture strength, and microstructure is clarified.

Keywords

LayeredTextureThermoelectricity
Type
Research Article
Information
Journal of Materials Research , Volume 20 , Issue 4 , April 2005 , pp. 1002 - 1008
Copyright
Copyright © Materials Research Society 2005

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