Skutterudite Thermoelectric Unicouples for Generating Power

A report presents some results of continuing efforts to develop advanced thermoelectric devices and, more particularly, thermoelectric unicouples for generating electric power from diverse thermal sources, including automotive exhausts and other waste-heat sources. The basic principles of operation and design of these devices were described in "Highly Efficient Thermoelectric Unicouples" (NPO-20872), NASA Tech Briefs, Vol. 24, No. 10 (October 2000), page 42. The report reiterates the basic principles and then goes on to describe two thermoelectric-unicouple designs, the first of which is theoretically optimal and similar to that of a segmented thermoelectric unicouple described in the cited previous article. The second design — a variant of the first design — is that of an experimental unicouple that was made from skutterudite (only) thermoelectric materials: CeFe4Sb12-based (p-type) and CoSb3-based (n-type) alloys. The report describes the fabrication and the thermal and electrical tests of the experimental unicouple. Among the reported test results are a thermal-to-electrical energy-conversion efficiency of as much as 9.8 percent during operation at hot- and cold-side temperatures of 863 and 363 K, respectively. The report projects that, in the future, more nearly optimal designs could yield efficiencies as large as 15 percent.