Theoretical Study of the Harman- Method for Evaluating the Thermoelectric Performance of Materials and Components at High Temperature

Over the past decade IPM did implement various measuring techniques applicable to thin films and massive Materials [1]. The customer-oriented measuring systems combine accuracy, rapidity, and few efforts for the mounting of the sample. Some systems are even fully automated, and some measurements are offered to third parts on a commercial basis. In this paper we want to discuss the Harman method for measuring the thermoelectric properties at high temperatures. The Harman method [2] is known to enable the direct measurement of the Figure of Merit at or below room temperature. Beside the simplicity to put the method in practice, the thermoelectric properties are measured in the same direction. The second advantage is that a technological Figure of Merit, which does account for the electrical contacting of the thermoelectric material, is accessible without being forced to make the entire thermoelectric device. In this paper a correction factor is derived to take account for the heat loss by radiation at higher temperatures, the contact resistances and the effect of the geometry of the sample. The correction factor is evaluated for various experimental conditions and the key features of an experimental setup for measurements at high temperature are discussed.