Thermoelectric Properties of Indium-Added Skutterudites In x Co4Sb12

The high-temperature thermoelectric properties of In (x) Co4Sb12 (0.05 a parts per thousand currency sign x a parts per thousand currency sign 0.40) skutterudite compounds were investigated in this study. The phase states of the samples were identified by x-ray diffraction analysis and field-emission scanning electron microscopy at room temperature. InSb and CoSb2 were found as secondary phases in samples with x = 0.10 to 0.40. The filling limit of In into the CoSb3 cages of In (x) Co4Sb12 was in the range 0.05 < x < 0.10. The electrical resistivity, Seebeck coefficient, and thermal conductivity of the In (x) Co4Sb12 samples were measured from room temperature to 773 K. The Seebeck coefficient of all samples was negative. Reduction of the thermal conductivity by In addition resulted in a high thermoelectric figure of merit (ZT) of 0.67 for In0.35Co4Sb12 at 600 K.