Thermoelectric property measurements by the improved Harman method

Abstract

The Harman method, which is generally utilized in the evaluation of the figure of merit, Z, has been improved to measure several thermoelectric properties. We fabricated equipment for simultaneous measurement of not only the resistivity /spl rho/ and Z but also the Seebeck coefficient /spl alpha/. The thermal conductivity can also be obtained by the calculation of /spl kappa/=/spl alpha//sup 2/ /(/spl rho/ZT). It is pointed out that the evaluation of ZT by the Harman method is equivalent to the determination of the temperature distribution induced in thermoelectric materials when dc current is applied. Furthermore, the equipment is improved to measure thermal heat-flow induced by low frequency ac current. The thermal heat-flow is characterized by the amplitude and the phase delay against the applied current. Fabrication of the equipment is described in detail, where it is emphasized that sufficient thermally isolated conditions are quite important. The experimental results, using the equipment, are shown.