Thermoelectric properties and electronic structure of p-type Mg2Si and Mg2Si0.6Ge0.4 compounds doped with Ga |
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Authors: | H. Ihou-Mouko C. MercierJ. Tobola G. PontH. Scherrer |
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Affiliation: | a Institut Jean Lamour (I.J.L.) - UMR 7198 - Nancy-Université, Ecole Nationale des Mines de Nancy, Parc de Saurupt, F 54042 Nancy, France b Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Cracow, Poland c Centre National d’Etudes Spatiales (CNES), 18 avenue Edouard Belin, 31401 Toulouse Cedex 09, France |
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Abstract: | Mg2Si:Gax and Mg2Si0.6Ge0.4:Gax (x = 0.4% and 0.8%) solid solutions have been synthesized by direct melting in tantalum crucibles and hot pressing. The effect of Ga doping on the thermoelectric properties has also been investigated by measurements of thermopower, electrical resistivity, Hall coefficient and thermal conductivity in temperature range from 300 to 850 K. All samples exhibit a p-type conductivity evidenced by positive sign of both thermopower and Hall coefficient in the investigated temperatures. The maximum value of the dimensionless figure of merit ZT was reached for the Mg2Si0.6Ge0.4:Ga(0.8%) compound at 625 K (ZT ∼ 0.36). The p-type character of thermoelectric behaviours of Ga-doped Mg2Si and Mg2Si0.6Ge0.4 compounds well corroborates with the results of electronic structure calculations performed by the Korringa-Kohn-Rostoker method and the coherent potential approximation (KKR-CPA), since Ga diluted in Mg2Si and Mg2Si0.6Ge0.4 (on Si/Ge site) behaves as hole donor due to the Fermi level shifted to the valence band edge. The onset of large peak of DOS from Ga impurity at the valence band edge, well corroborates with high Seebeck coefficient measured in Ga-doped samples. |
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Keywords: | Magnesium silicide Electronic structure Thermoelectric properties |
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