Measurement of thermal conductivity and specific heat by impedance spectroscopy of Bi2Te3 thermoelectric element

The thermal conductivity (κ) and specific heat (Cp) of a thermoelectric element consisting of Bi2Te3 (SRM 3451) were obtained by impedance spectroscopy and using only electrometric measurements. The dimensionless figure of merit (zT) was successfully estimated by the four-probe method from the frequency dependence of the impedance, and the result was compared with that obtained using the two-probe method. The calculated values of zT and resistivity were 0.577 and 13.4 µΩ m, respectively, at 300 K, which allowed us to obtain κ = 2.11 W/(m K) and Cp = 165 J/(kg K) by using a Seebeck coefficient of −233 µV/K, a thermal diffusivity of 1.68 mm2/s, and a mass density of 7.60 g/cm3 from our earlier electrometric measurements. The calculated κ and Cp are quite reasonable when compared to reported values. We thus conclude that, without relying on calorimetric measurements, impedance spectroscopy is a powerful technique for determining not only zT but also the thermal properties of thermoelectric materials via the Peltier effect.