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Synthesis of In2−xGexO3 nanopowders for thermoelectric applications

Published online by Cambridge University Press:  20 December 2011

Emmanuel Combe ,
Shekhar D. Bhame ,
Emmanuel Guilmeau ,
Frédéric Boschini  and
Rudi Cloots
Emmanuel Combe
Affiliation:
Laboratoire CRISMAT, UMR 6508 CNRS-ENSICAEN, 14050 Caen Cedex, France; and Laboratoire LCIS-GREENMAT, University of Liège, Chemistry Institute B6, 4000 Liège (Sart-Tilman), Belgium
Shekhar D. Bhame
Affiliation:
Laboratoire CRISMAT, UMR 6508 CNRS-ENSICAEN, 14050 Caen Cedex, France
Emmanuel Guilmeau*
Affiliation:
Laboratoire CRISMAT, UMR 6508 CNRS-ENSICAEN, 14050 Caen Cedex, France
Frédéric Boschini
Affiliation:
Laboratoire LCIS-GREENMAT, University of Liège, Chemistry Institute B6, 4000 Liège (Sart-Tilman), Belgium
Rudi Cloots
Affiliation:
Laboratoire LCIS-GREENMAT, University of Liège, Chemistry Institute B6, 4000 Liège (Sart-Tilman), Belgium
*
a)Address all correspondence to this author. e-mail: emmanuel.guilmeau@ensicaen.fr
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Abstract

Bulk ceramics In2−xGexO3 have been synthesized in air by using citrate gel process. Nanoparticles of less than 20 nm have been synthesized through an accurate control of the processing parameters. X-ray diffraction and scanning electron microscopy studies confirmed that the solubility limit of Ge in In2O3 (xℓ) is very small and that additions of more than about 0.5 at.% Ge lead to the presence of In2Ge2O7 inclusions. Thanks to a high interdispersion of metal ions and homogeneity in elemental composition of the nanopowders obtained by citrate gel process, well-dispersed In2Ge2O7 secondary phases can be formed in the Ge-doped In2O3 matrix. An abrupt increase in the electrical conductivity and in the carrier concentration with x is observed in the monophasic region (x < xℓ), whereas in the biphasic region (x > xℓ), these values do not vary significantly. Similarly, the thermopower |S| value is correlated to this variation decreasing as x increases for x < xℓ. Above the solubility limit, the decrease in the lattice thermal conductivity is shown to be dependent on the presence of well-dispersed In2Ge207 secondary phases. The dimensionless figure of merit value is increased up to 0.3, thanks to electron doping and phonon scattering.

Keywords

ThermoelectricMicrostructureElectrical properties
Type
Articles
Information
Journal of Materials Research , Volume 27 , Issue 2 , 28 January 2012 , pp. 500 - 505
Copyright
Copyright © Materials Research Society 2011

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