Hierarchically structured TiO2 for Ba-filled skutterudite with enhanced thermoelectric performance

Abstract

The influence of hierarchical TiO₂ inclusions on electrical and thermal transport properties has been investigated in the Ba-filled skutterudite compound Ba_0.3Co₄Sb₁₂ synthesized by ball milling followed by hot pressing. The hierarchical TiO₂, with the morphology of nanocrystallite aggregates, was prepared using a carbon sphere-templated method. It was found that TiO₂ inclusions strongly enhance the Seebeck coefficient while they weakly degrade the electric conductivity. In addition, TiO₂ inclusions reduce significantly the lattice thermal conductivity through all-scale length phonon scattering due to the hierarchically-structured TiO₂ particles. ZT values up to 1.2 were obtained for Ba_0.3Co₄Sb₁₂ with an optimal amount and dispersion of TiO₂ inclusions. These observations demonstrate an exciting scientific opportunity to raise the figure-of-merit of filled skutterudites via hierarchical dispersion.