Determination of thermal diffusivity of thermoelectric materials using a micro four-point probe method

To develop materials with higher thermoelectric efficiency, a comprehensive characterization of material properties on the relevant spatial scales is pertinent. In this study, we develop a new method based on a micro four-point probe (M4PP) to determine the thermal diffusivity of a bulk material using the phase delay of the second harmonic voltage. The method is demonstrated on two relevant thermoelectric materials i.e. skutterudite and bismuth telluride. Individual measurements on skutterudite and bismuth telluride are characterized by a precision better than 9% and 12%, with mean thermal diffusivities of 1.87 +/- 0.17 mm2/s and 1.14 +/- 0.13 mm2/s for 100 measurements, respectively. These values are found to be in good agreement with their independent estimates. M4PP electrical characterization of bismuth telluride shows signs of percolation network behavior, thus we believe that the new M4PP methodology applies even to materials whose electrical resistivity is nonuniform and erratic.