Direct Contact Resistance Evaluation of Thermoelectric Legs

Abstract

In developing intermediate temperature (300-700 A degrees C) thermoelectric modules with high conversion efficiencies exceeding 10 %, the evaluation of the electrical contact resistance between the thermoelectric material and metallic electrode is a critical issue. In this work, a novel direct contact resistance measurement apparatus is proposed that enhances the previously reported extrapolation based erroneous contact resistance evaluation methods. The accuracy and resolution of this apparatus are investigated in detail, and the proposed novel contact resistance measurement exhibits sufficient performance to evaluate high efficiency thermoelectric modules. The presence of the Peltier effect in the direct current-induced contact resistance measurements is verified experimentally using the proposed apparatus. Two modified measurement parameters, i.e., the pulse shape input current and heat dissipating metallic block, are proposed and their effects in suppressing the unintended Peltier effect are discussed in detail.