Skutterudite Unicouple Characterization for Energy Harvesting Applications

Skutterudites are promising thermoelectric materials because of their high figure of merit, ZT, and good thermomechanical properties. This work reports the effective figure of merit, ZTeff, and the efficiency of skutterudite legs and a unicouple working under a large temperature difference. The p- and n-type legs are fabricated with electrodes sintered directly to the skutterudite during a hot pressing process. CoSi2 is used as the electrode for the n-type skutterudite (Yb0.35Co4Sb12) and Co2Si for the p-type skutterudite (NdFe3.5Co0.5Sb12). A technique is developed to measure the ZTeff of individual legs and the efficiency of a unicouple. An ZTeff of 0.74 is determined for the n-type legs operating between 52 and 595 °C, and an ZTeff of 0.51 for the p-type legs operating between 77 and 600 °C. The efficiency of the p–n unicouple is determined to be 9.1% operating between ∼70 and 550 °C.