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Lanthanum Telluride: Mechanochemical Synthesis of a Refractory Thermoelectric Material

May, Andrew and Snyder, Jeff and Fleurial, Jean-Pierre (2008) Lanthanum Telluride: Mechanochemical Synthesis of a Refractory Thermoelectric Material. In: SPACE TECHNOLOGY AND APPLICATIONS INTERNATIONAL FORUM - STAIF 2008, Albuquerque, NM, 10–14 February 2008. AIP Conference Proceedings. No.969. American Institute of Physics , Melville, NY, pp. 672-678. ISBN 978-0-7354-0486-1.

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Recent experimental work on lanthanum telluride has confirmed its significant potential as an n-type material for high temperature thermoelectric (TE) power generation application. The phase of interest, La3−xTe4, has a Th3P4 defect structure where x is the lanthanum vacancy with values ranging between 0 and 1/3. Thermoelectric properties change rapidly with x since the carrier concentration, n, is proportional to the (1−3x) parameter. Controlling the Te to La stoichiometry in lanthanum telluride is thus vital to achieving the optimum self-doping level for the highest dimensionless figure of merit ZT value. We report on a significant improvement in reproducibly preparing this refractory compound over prior lengthy and unwieldy high temperature experimental techniques developed in the 1980's. Mechanochemical processes are utilized to synthesize precise stoichiometries of lanthanum telluride at room temperature, enabling improved characterization, analysis and modeling of its transport properties as a function of the number of La vacancies. We report TE properties for a large range of the allowed compositions, with ZT values greater than 1.0 obtained at 1275 K for several compositions. In addition to stoichiometric optimization within the pure compound, chemical substitutions can enhance performance by decreasing the lattice thermal conductivity and tuning the electrical properties for maximum ZT values at lower temperatures; preliminary studies indicate that the addition of ytterbium increases ZT. Some properties pertaining to device development are discussed. Specifically, lanthanum telluride has a low sublimation rate, and a coefficient of thermal expansion that closely matches a p-type rare earth compound analog (the Yb14MnSb11 Zintl compound).

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May, Andrew0000-0003-0777-8539
Snyder, Jeff0000-0003-1414-8682
Additional Information:©2008 American Institute of Physics. Issue Date: January 21, 2008. The work described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. The authors would like to thank T. Ikeda for performing the electron microprobe measurements, S. Firdosy and V.A. Ravi for thermal expansion measurements, J. Paik for sublimation rate measurements and L.D. Zoltan and T. McCarm for help with TE property measurements.
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Subject Keywords:thermoelectric, mechanochemical, mechanical alloying, refractory materials
Series Name:AIP Conference Proceedings
Issue or Number:969
Record Number:CaltechAUTHORS:MAYaipcp08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9630
Deposited By: Archive Administrator
Deposited On:19 Feb 2008
Last Modified:09 Mar 2020 13:19

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