Transport Properties of Bulk Thermoelectrics: An International Round-Robin Study, Part II: Thermal Diffusivity, Specific Heat, and Thermal Conductivity
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For bulk thermoelectrics, improvement of the figure of merit ZT to above 2 from the current values of 1.0 to 1.5 would enhance their competitiveness with alternative technologies. In recent years, the most significant improvements in ZT have mainly been due to successful reduction of thermal conductivity. However, thermal conductivity is difficult to measure directly at high temperatures. Combined measurements of thermal diffusivity, specific heat, and mass density are a widely used alternative to direct measurement of thermal conductivity. In this work, thermal conductivity is shown to be the factor in the calculation of ZT with the greatest measurement uncertainty. The International Energy Agency (IEA) group, under the implementing agreement for Advanced Materials for Transportation (AMT), has conducted two international round-robins since 2009. This paper, part II of our report on the international round-robin testing of transport properties of bulk bismuth telluride, focuses on thermal diffusivity, specific heat, and thermal conductivity measurements.
KeywordsThermoelectric thermal conductivity thermal diffusivity specific heat power factor figure of merit
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The authors would like to thank the International Energy Agency under the Implementing Agreement for Advanced Materials for Transportation for supporting this work and the assistant secretary for Energy Efficiency and Renewable Energy of the Department of Energy and the Propulsion Materials Program under the Vehicle Technologies Program. We would like to acknowledge support from all participating institutions and Oak Ridge National Laboratory managed by UT-Battelle LLC under contract DE-AC05000OR22725.
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