Influence of Thomson effect on the resultant local Seebeck coefficient in thermoelectric composite materials

The resultant local Seebeck coefficient αR (=αS−αT) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric efficiency, where αS is the local Seebeck coefficient and αT is the one caused by the Thomson effect. It is shown in this paper that αS, αT, and αR of the p- and n-type Cu/Bi–Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of the composite on which the temperature difference ΔT is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position from the local experimental data of R,ΔI,ΔT, and V generated by applying an additional current of ±I to the composite, where R is the electrical resistance and ΔI is a current generated by the composite. As a result, it was found that the absolute values of αS at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite, respectively, while those of αT are less than 8% of αS all over the composite and are so small that the relation αR≈αS can be held. We thus succeeded in measuring αR at the interfaces of the composite.