Characterization of multiple-filled skutterudites with high thermoelectric performance

High performance multiple-filled X–CoSb₃ skutterudites (X = Yb、Ca、Ba、Al、Ga、In、La、Eu) was prepared by the long term annealing and hot-pressing approaches. Compared with the one-element filling method, multi-elements filling in CoSb₃ can improve their thermoelectric values. The lattice constant of skutterudite filled with multiple types of atoms was increased to 9.076 Å, higher than 9.036 Å of the un-filled one. The electrical conductivity, thermal conductivity and Seebeck coefficient were analyzed from 300K to 823K. The filling fraction of Yb increase with the increasing Fe content in both the Fe-rich phase and the Fe-poor phase. For Ca atoms, a significant phase separation occurs in the Fe-rich phase and the Fe-poor phase, and the Ca filling fraction in the Fe-poor phase is much higher. With the increase of Fe contents, the Al atoms gradually increase in the Fe-poor phase and decrease in the Fe-rich phase. On the contrary, the filled Ga and In atoms have no obvious regularity in this statistical analysis. Compared with the referred Yb_0.5Co₄Sb₁₂ sample, the lattice thermal conductivity is effectively reduced by multi-filling, the multi-filled skutterudite obtained the 47% reduce of the lattice thermal conductivity and the maximum ZT value was reached 1.22 at 823K.