Effects of nano-TiO2 dispersion on the thermoelectric properties offilled-skutterudite Ba0.22Co4Sb12

Homogeneously dispersed nano-TiO₂ was introduced into the matrix of n-type barium-filled cobalt antimony (Ba_0.22Co₄Sb₁₂) via sol–gel method successfully. The Seebeck coefficients are improved and the lattice thermal conductivities are depressed with a proper addition of nano-TiO₂ not more than 0.8 vol.%, while the electrical conductivities nearly remain unchanged. The effects of n-type semiconductive nanoscale inclusions on the electrical and thermal transport characteristics are discussed. Microstructure analyses indicate that the fine nanoinclusions locate on the grain boundaries as well as inside grains, which serve as extra phonon scattering mode and new type energy filtering. As a result, the optimal ZT value was achieved for the sample of 0.4 vol.% TiO₂ composition.