Characterization of thermoelectric elements and devices by impedance spectroscopy

This article describes a new measurement technique that utilizes impedance spectroscopy for the characterization of thermoelectric materials and devices. Two circuit models were developed and used to help explain the impedance spectroscopy data using transmission line theory and a coupled electrothermal model. Two testing configurations have been investigated including one based on a sinusoidal source (ac lock-in technique) and one based on a pulsed wave source. Methods for reducing the measurement times for this technique are discussed. In addition, the influence of radiation losses on this measurement technique has also been analyzed to further understand the limitations of this technique at higher temperatures.