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Effect of Vacancies on the Thermoelectric Properties of Mg2Si Containing Sb and Bi Substitution

Published online by Cambridge University Press:  01 February 2011

Titas Dasgupta ,
Christian Stiewe ,
Ralf Hassdorf ,
Lothar Boettcher  and
Eckhard Mueller
Titas Dasgupta
Affiliation:
[email protected], German Aerospace Center (DLR), Institute of Materials Research, Cologne, Germany
Christian Stiewe
Affiliation:
[email protected], German Aerospace Center (DLR), Institute of Materials Research, Cologne, Germany
Ralf Hassdorf
Affiliation:
[email protected], German Aerospace Center (DLR), Institute of Materials Research, Cologne, Germany
Lothar Boettcher
Affiliation:
[email protected], German Aerospace Center (DLR), Institute of Materials Research, Cologne, Germany
Eckhard Mueller
Affiliation:
[email protected], German Aerospace Center (DLR), Institute of Materials Research, Cologne, Germany
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Abstract

Mg2Si1-xRx (R-Sb,Bi) compositions with x=0.025, 0.05 for Sb and x=0.01,0.025, 0.05 for Bi were synthesized by induction melting of the constituent elements followed by compaction by hot pressing. Phase identification by x-ray diffraction (XRD) indicate a biphasic nature for Bi substituted compositions for x≥.025 while solid solubility for the different Sb substitutions. Abundance distribution plots of the Seebeck (S) coefficient show asymmetry in the Sb compositions and is not observed in the Bi substituted samples. This indicates presence of vacancies only in the Sb substituted compositions. Electrical conductivity (σ), Seebeck coefficient (S) and thermal conductivity (κ) values were measured from 300K to 773 K. The observed trends in the absolute values of α and S can be explained based on doping/second phase influence in Bi substitutions and due to effect of vacancies for Sb substitutions. The (κL) (phonon component) values show a significant decrease for the Sb substitutions due to the presence of vacancies. Calculation of the thermoelectric figure of merit (ZT) show a ZTmax of 0.56 for x=0.025 Bi composition compared to a ZTmax of ∼ 0.05 for Mg2Si.

Keywords

thermoelectricthermal conductivityx-ray diffraction (XRD)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1267: Symposium DD – Thermoelectric Materials 2010-Growth, Properties, Novel Characterization Methods and Applications , 2010 , 1267-DD10-23
Copyright
Copyright © Materials Research Society 2010

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References

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