Enhanced thermoelectric figure of merit in indium and ytterbium double-filled skutterudite bulk materials through simultaneously optimising power factor and reducing thermal conductivity

Abstract

In this study, YbxCo4Sb12 and InxYb0.3Co4Sb12 bulk materials were fabricated via microwave synthesis combined with spark plasma sintering. Based on ytterbium single filling, indium was further filled into the voids of CoSb3. Carrier concentration and mobility were regulated as 1.6–1.8 × 1020 cm-³ and ∼30 cm2V−1S−1, respectively, resulting in an improved power factor of ∼4900 μWm−1K−2. The phonon-resonant scattering, caused by indium and ytterbium double filling, was combined with other phonon scattering mechanisms such as nano-inclusion, dislocation, and grain boundary segregation, which resulted in a significantly decreased lattice thermal conductivity of 0.72–2.08 Wm−1K−1. Owing to the improvements in carrier concentration and phonon transport, excellent thermoelectric performance, reflected by ZT = 1.38 at 773 K, was achieved in In0.4Yb0.3Co4Sb12.