Hierarchically structured TiO2 for Ba-filled skutterudite with enhanced thermoelectric performance
The influence of hierarchical TiO2 inclusions on electrical and thermal transport properties has been investigated in the Ba-filled skutterudite compound Ba0.3Co4Sb12 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 Ba0.3Co4Sb12 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.