ABSTRACT
Segmented thermoelectric unicouples (STUs) could be optimized for conversion efficiency or electric
power density, depending on the application. Those are not only more efficient than nonsegmented
unicouples, but also facilitate operation at a relatively large temperature difference in addition, high-
source and low-sink temperatures. The lengths of the segments of different materials in the p-legs and n-
legs are based on the temperatures in which each material has the highest figure-of-merit (FOM).
Changing either the cold or the hot junction temperature affects the number of segments in the n-legs and
p-legs and the performance of the STU. Results are presented for hot junction temperatures of 350 to 973 K
and cold junction temperatures of 300 to 850 K. These combinations of temperatures cover awide range of
potential terrestrial and space nuclear power systems applications of segmented thermoelectric converters.
Thermoelectric (TE) energy conversion and cooling devices are used in recreational, industrial,
military, waste heat recovery, and space nuclear power systems. In the last four decades, PbTe/TAGS-85
and SiGe unicouples have been used on board of more than 44 spacecrafts, mostly for planetary
exploration missions, with the thermal power supplied by radioisotope heat sources. These
radioisotope thermoelectric generators (RTGs) generated 2.7 to 290 W
