Thermal to Electrical Energy Conversion of Skutterudite-Based Thermoelectric Modules

The performance of thermoelectric (TE) materials has improved tremendously over the past decade. The intrinsic thermal and electrical properties of state-of-the-art TE materials demonstrate that the potential for widespread practical TE applications is very large and includes TE generators (TEGs) for automotive waste heat recovery. TE materials for automotive TEG applications must have good intrinsic performance, be thermomechanically compatible, and be chemically stable in the 400 K to 850 K temperature range. Both n-type and p-type varieties must be available at low cost, easily fabricated, and durable. They must also form robust junctions and develop good interfaces with other materials to permit efficient flows of electrical and thermal energy. Among the TE materials of interest for automotive waste heat recovery systems are the skutterudite compounds, which are the antimony-based transition-metal compounds RTE4Sb12, where R can be an alkali metal (e.g., Na, K), alkaline earth (e.g., Ba), or rare earth (e.g., La, Ce, Yb), and TE can be a transition metal (e.g., Co, Fe). We synthesized a considerable quantity of n-type and p-type skutterudites, fabricated TE modules, incorporated these modules into a prototype TEG, and tested the TEG on a production General Motors (GM) vehicle. We discuss our progress on skutterudite TE module fabrication and present module performance data for electrical power output under simulated operating conditions for automotive waste heat recovery systems. We also present preliminary durability results on our skutterudite modules.