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Microstructures and nanostructures in long-term annealed AgPb18SbTe20 (LAST-18) compounds and their influence on the thermoelectric properties

Published online by Cambridge University Press:  05 August 2011

Jayaram Dadda ,
Eckhard Müller ,
Susanne Perlt ,
Thomas Höche ,
Paula Bauer Pereira  and
Raphaël P. Hermann
Jayaram Dadda*
Affiliation:
Institute of Materials Research, German Aerospace Center (DLR), D-51170 Köln, Germany
Eckhard Müller
Affiliation:
Institute of Materials Research, German Aerospace Center (DLR), D-51170 Köln, Germany
Susanne Perlt
Affiliation:
Leibniz Institute of Surface Modification (IOM), D-04318 Leipzig, Germany
Thomas Höche
Affiliation:
Leibniz Institute of Surface Modification (IOM), D-04318 Leipzig, Germany
Paula Bauer Pereira
Affiliation:
Forschungszentrum Jülich GmbH, IFF, JNCS and JARA-FIT, D-52425 Jülich, GermanyFaculty of Sciences, University of Liège, B-4000 Liège, Belgium
Raphaël P. Hermann
Affiliation:
Forschungszentrum Jülich GmbH, IFF, JNCS and JARA-FIT, D-52425 Jülich, GermanyFaculty of Sciences, University of Liège, B-4000 Liège, Belgium
*
a)Address all correspondence to this author. e-mail: jayaram.dadda@dlr.de
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Abstract

This article reports on the role of annealing on the development of microstructure and its concomitant effects on the thermoelectric properties of polycrystalline AgPbmSbTe2+m (m = 18, lead–antimony–silver–tellurium, LAST-18) compounds. The annealing temperature was varied by applying a gradient annealing method, where a 40-mm-long sample rod was heat treated in an axial temperature gradient spanning between 200 and 600 °C for 7 days. Transmission electron microscopy investigations revealed Ag2Te nanoparticles at a size of 20–250 nm in the matrix. A remarkable reduction in the thermal conductivity to as low as 0.8 W/mK was also recorded. The low thermal conductivity coupled with a large Seebeck coefficient of ∼320 μV/K led to high ZT of about 1.05 at 425 °C for the sample annealed at 505 °C. These results also demonstrate that samples annealed above 450 °C for long term are more thermally stable than those treated at lower temperatures.

Keywords

ThermoelectricityAnnealingSecond phases
Type
Articles
Information
Journal of Materials Research , Volume 26 , Issue 15: Focus Issue: Advances in Thermoelectric Materials , 14 August 2011 , pp. 1800 - 1812
Copyright
Copyright © Materials Research Society 2011

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