High-Temperature Thermoelectric Properties of Co4Sb12-Based Skutterudites with Multiple Filler Atoms: Ce0.1InxYbyCo4Sb12

Void-filling in the CoSb3 skutterudite lattice with different kinds of heavy elements has proven to be an effective mechanism to enhance thermoelectric performance due primarily to a reduction in lattice thermal conductivity. Specifically, our findings on the series In (x) Yb (y) Co4Sb12 [0 a parts per thousand currency sign (x, y) a parts per thousand currency sign 0.2] have further motivated an attempt to form triple-filled skutterudites Ce0.1In (x) Yb (y) Co4Sb12 with In and Yb concentrations [0 a parts per thousand currency sign (x, y) a parts per thousand currency sign 0.2] and with the Ce concentration held constant (Ce-0.1). All of these samples have been prepared via a simplified melting-annealing-sintering procedure and were first characterized by means of x-ray powder diffraction and scanning electron microscopy, followed by measurements of the Hall coefficient, electrical and thermal conductivities, and Seebeck coefficient. Our aim is to further elucidate the roles of the three elements (Ce, In, and Yb) in these materials. Compared with the addition of just In or Yb, we found that simultaneous addition of both In and Yb reduced the lattice thermal conductivity without significantly degrading the power factor. Further addition of the third element (Ce), along with In and Yb, also produced a similar result. However, we noticed that some of the In and Yb were also observed in the form of secondary phases (InSb and Yb2O3), not entering entirely as filler atoms. As a result of our investigation, several compositions achieved increased sustainability and enhanced thermoelectric performance, with maximum ZT values of about 1.3 to 1.4 obtained at around 800 K.