Nanostructuring as a tool to adjust thermal expansion in high ZT skutterudites

Abstract Although filled skutterudites have a high figure of merit, ZT, it is still an aim to further improve their thermoelectric behavior. One successful route is to homogeneously disperse nanoparticles into the skutterudite matrix and thereby to reduce the lattice thermal conductivity without disturbing the electrical conductivity and the Seebeck coefficient. In this work Ta 0.8 Zr 0.2 B was dispersed into n-type (Mm,Sm) y Co 4 Sb 12 powder by ball-milling or high energy ball-milling prior to hot-pressing. Structural and physical properties, covering also the low temperature range, were studied and compared with the recently investigated impact of nano Ta 0.8 Zr 0.2 B on p-type skutterudites. ZT was enhanced by 16%. As for thermoelectric applications good mechanical properties are important, we investigated the influence of Ta 0.8 Zr 0.2 B nanoparticles, added to (Mm,Sm) y Co 4 Sb 12 , on the hardness, elastic moduli and fracture toughness and found an enhancement of all three mechanical properties. It is well known that p-type skutterudites generally have a higher thermal expansion coefficient than their n-type counterpart. We show that dispersed borides in both n-type (Mm,Sm) y Co 4 Sb 12 and p-type DD 0.7 Fe 3 CoSb 12 can level out this discrepancy.