Non-linear impedance spectroscopy for complete thermoelectric characterization: Beyond the zT estimation

Thermoelectric measurement of the dimensionless z T = α 2 T σ / κ parameter requires multiple physical quantities to be measured; therefore, there is great interest to find an experimental setup capable of measuring all these properties at once. Previous works on impedance spectroscopy have shown promising results in this direction; however, this technique does not lead to a complete characterization of the thermoelectric system without additional measurement. In order to extend impedance spectroscopy, we have investigated the measurement of the non-linear harmonic response of a Peltier device. The experiments are analyzed using an analytic model obtained by solving the heat equation in the frequency regime. Our work shows that fitting the experimental response of the system in the harmonic regime can lead to a complete characterization of the thermoelectric properties without the need of additional measurement.