Recent advances in characterization of thermoelectric materials
Dimitri Vasilevskiy, Ph.D., Dr. Sc.
Polytechnique Montréal, Temte Inc.
Friday, January 12, 2018
C2-361 (Reading Room)
Host: Parisa Jafarzadeh (graduate student with Holger Kleinke)
Abstract: The dimensionless thermoelectric (TE) figure of merit ZT (Z=α2/ρλ where α, ρ and λ are, respectively, the Seebeck coefficient, the electrical resistivity and the thermal conductivity) is the main parameter which allows a comparison of the overall performance of different thermoelectric materials at different temperatures. Despite its extreme importance there are very limited possibilities to provide an accurate measurement of its value. In fact, presently, the most widely used approach separately measures each one of the components of ZT. This approach led to a total uncertainty in ZT as high as 40-50% which is unacceptable in most scientific and industrial applications. The best accuracy of the ZT value can potentially be obtained using the Harman method. However, from the very first publications and up to the most recent, the impact of parasitic heat exchange between the sample and its environment has been identified as critical for measurement accuracy. This fact has seriously reduced the application of Harman based measurements, specifically at elevated temperatures where radiation losses rapidly increase.
We will discuss a novel calibration procedure, which radically solves the problem related to the parasitic thermal phenomena. This novel two-sample system calibration (2SSC) is successfully implemented on a system (ZT-Scanner, by TEMTE Inc) developed for the simultaneous Harman based measurement of all thermoelectric parameters from 240 K to 720 K. We will show how successfully the developed system works with different materials and sample sizes.
The general questions related to the thermoelectric materials and their application will be also discussed.