Measuring temperature dependence of dimensionless figure of merit of a thermoelectric module using time-domain impedance spectroscopy.

This paper introduces transient Harman (TH), impedance spectroscopy (IS), and time-domain impedance spectroscopy (TDIS) methods as feasible techniques for determining the temperature dependence shown by the dimensionless figure of merit (zT) of a BiTe-based thermoelectric module from 50 to 320 K. An optimum current was selected to deduce the proper zT under a dominant Peltier heat. The comparison results indicated that the TH method enables a rapid estimation of zT, typically within several minutes. Although the measurement times for the IS (several minutes to hours) and TDIS (several minutes) methods were different, both the methods yielded comparable zT values, and the TDIS method was found to be more reliable for the module with zT > 0.02 and a resolution of 0.001. Furthermore, temperature stabilization of the measurement specimen using the TDIS method also emerged as one of the key factors that determined the accuracy and resolution of the zT estimation.