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Published September 15, 2009 | public
Journal Article

Characterization and analysis of thermoelectric transport in n-type Ba_(8)Ga_(16−x)Ge_(30+x)


The thermoelectric transport properties of polycrystalline, Ba_(8)Ga_(16−x)Ge_(30+x) were characterized from 300 to 1000 K. The carrier density was found to vary precisely with the experimental x as expected from simple electron counting. The experimental data are analyzed within the framework of a single parabolic band model, which is found to accurately describe transport for the compositions of interest for thermoelectric application. The lattice thermal conductivity, calculated with a degeneracy adjusted Lorenz number, does not show a trend with composition and a value of ~1 Wm^(−1) K^(−1) is observed at 300 K. A maximum figure of merit zT = 0.86 is obtained at 950 K, and the optimal doping level for thermoelectric application is predicted to be ~2 × 10^(20) cm^(−3), which corresponds to Ba_(8)Ga_(15.75)Ge_(30.25_ by electron counting. An unexpected transition event is observed near 650 K, which results in a significant increase in the heat capacity.

Additional Information

© 2009 American Physical Society. Received 27 May 2009; revised 17 August 2009; published 18 September 2009. The Jet Propulsion Laboratory, Beckman Foundation, and the Swedish Bengt Lundqvist Minne Foundation are gratefully acknowledged for support. We thank L. MacPherson of NETZSCH for carefully performing TGA and DSC measurements, T. Ikeda for obtaining WDS data, and L. D. Zoltan for Seebeck coefficient measurements. Finally, we thank G. S. Nolas for discussions regarding the event in C_P.

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