Electrical Resistivity and Seebeck Coefficient of Segmented Thermoelements

To enhance efficiency while maintaining device simplicity, wafers of different thermoelectric materials are sometimes joined to form segmented thermoelements. Properly designed segmented thermoelements provide a high average ZT by matching materials to the temperature profile along the thermoelement length. One possible penalty of segmentation is reduction of ZT by interfacial effects, such as contact resistance or reaction zones. Interfacial effects will become increasingly important as the wafers are made thinner, but thinner wafers are more economical. We are making segmented thermoelements for an U.S. Department of Energy waste heat recovery program. The thermoelements contain one to three segments of common power generation materials, and they are 0.5 to 2 mm thick. Here we present measurements of the electrical resistivity and Seebeck coefficient of PbTe and n-type Bi₂Te₃ alloy samples designed to highlight interfacial effects. For 1 mm thick wafers, we do not see significant contact resistance. There is insufficient data at this point to assess if the effective Seebeck coefficient is thickness-dependent