ICT2014 Abstracts

The enhanced scattering of long-wavelength phonons induced by porous structures has been thought to be a new approach to remarkably decrease lattice thermal conductivity k_L of thermoelectric materials. The work aims at introducing micron-sized porous structure in filled skutterudites bulk materials to lower the k_L through the pore-edge boundary scattering of long-wavelength phonons induced by porous structures and resonance scattering of short- and middle-wavelength phonons by the rattling of fillers. A novel preparation method has been developed to fabricate the porous (Ba,In) double-filled skutterudite bulk materials with pore diameter about 1-4 μm by the decomposition of metastable ZnSb inclusions induced by the Zn sublimation. It is discovered that the ZT values of the porous (Ba, In) double-filled skutterudite bulk materials can be significantly improved due to the increased Seebeck coefficient α and decreased k_L as well as unchanged electrical conductivity σ. The increase in α is attributed to the electron energy filtering induced by nanostructures in the internal surfaces of pores. The almost identical σ is related to the percolation effect of conducted network of filled skutterudites. The dramatic decrease in k_L originates from the pore-edge boundary scattering of the long-wavelength phonons. This work confirmed experimentally that by introducing micropores in bulk thermoelectric materials is an efficient strategy to improve TE properties.