High thermoelectric performance of triple-filled n-type skutterudites (Sr,Ba,Yb)yCo4Sb12

The influences of single, double and triple filling of Yb, Ba and Sr in CoSb3 on thermoelectric performance were evaluated. A significant suppression of lattice thermal conductivity κl is achieved by the increase in the number of filler elements. The highest power factor appears in triple-filled (Ba0.1Yb0.1)0.25(Sr0.1Yb0.1)0.75Co4Sb12, whereas single-filled Ba0.23Co4Sb12 has higher S2/ρ than double-filled (Ba,Yb)0.2Co4Sb12 forming a sequence S2/ρ(triplefilling) > S2/ρ(singlefilling) > S2/ρ(doublefilling). However, the respective figures of merit follow a sequence ZT(triplefilling) > ZT(doublefilling) > ZT(singlefilling) proving a strong correlation with κl that appears to be a predominant factor in the efficiency of filled skutterudites. Thus, κ and ZT increase with increasing lattice thermal resistivity (1/κl) and maximum efficiencies may be obtained for 1/κl > 0.2 cm K mW-1.