Improved thermoelectric properties in double-filled Cey/2Yby/2Fe4-x(Co/Ni)xSb12 skutterudites -: art. no. 033710

We have investigated the thermal and electrical properties of filled skutterudites belonging to the series Ce1-zYbzFe4Sb12 and Cey/2Yby/2Fe4-x(Co/Ni)(x)Sb-12, as well as their potential for thermoelectric power generation. In the first series, increasing the Yb fraction decreases the resistivity and thermopower. These effects are related to the variations of valence of Yb with the Yb fraction (from 2.2 in Yb0.92Fe4Sb12 to 2.7 in Ce0.85Yb0.05Fe4Sb12). The power factor is increased in Ce0.40Yb0.53Fe4Sb12 while the thermal conductivity is reduced and this leads to an improved figure of merit in this compound when compared to Ce0.85Fe4Sb12. Co or Ni substitution was used to tune the carrier concentration and improve the power factor: we measure a ZT=0.5 at 500 K in Ce0.44Yb0.32Fe3.02Co0.98Sb12 and an extrapolation leads to ZT=0.95 at 800 K, which is close to state-of-the-art Ce0.28Fe1.52Co2.48Sb12 although the composition is far from being optimized. Double filling happens to be a promising path to provide good thermoelectric performances. (c) 2005 American Institute of Physics.