Synthesis and high temperature thermoelectric properties of calcium and cerium double-filled skutterudites Ca0.1CexCo4Sb12

The thermoelectric properties of double-filled skutterudites Ca0.1CexCo4Sb12 (x = 0.05, 0.10 and 0.15) were investigated at temperatures ranging from 300 to 775 K. The results showed that the addition of Ca and Ce as filler atoms into CoSb3 led to a substantial decrease in lattice thermal conductivity. The minimum lattice thermal conductivity of 2.76 WK-1 m(-1) was observed in the sample Ca0.1Ce0.15Co4Sb12 at 323 K. This is a 69% reduction as compared with pristine CoSb3. Moreover, filling the voids of the skutterudite crystal lattice with Ca and Ce atoms led to a transition from semiconducting-like behaviour (i. e. d rho/dT < 0) to metallic behaviour (i. e. d rho/dT > 0) as well as a change in the sign of the Seebeck coefficient. The highest dimensionless figure of merit, ZT, was obtained for the sample Ca0.1Ce0.15Co4Sb12. Specifically, it reached ZT of 0.83 at 677 K, which is double that of single-filled Ca0.2Co4Sb12 reported in the literature.