Enhanced thermoelectric performance of Bi₂Te₃ through uniform dispersion of single wall carbon nanotubes

The advancement in nanostructured powder processing has attracted great interest as a cost effective and scalable strategy for high performance thermoelectric bulk materials. However, the level of technical breakthrough realized in quantum dot supperlattices/wires has not yet been demonstrated in these materials. Here, we report the first ever study on the uniform dispersion of single wall carbon nanotubes (SWCNTs) in nanostructured Bi₂Te₃ bulk, and their effect on thermoelectric parameters above room temperature. The Bi₂Te₃ based SWCNT composites were prepared through controlled powder processing, and their thermoelectric properties were finely tuned at the nanoscale by regulating various (0.5, 0.75, 1.0 and 1.5) vol% of SWCNTs in the matrix. The flexible ropes of SWCNT, making an interconnected network through the inter/trans granular positions of Bi₂Te₃, thus substantially change the transport properties of the composites. The perfect one-dimensional (1D) conducting structure of SWCNTs acts as a source of electrical transport through a percolating network, with significantly suppressed lattice thermal conductivity, via intensified boundary scattering. The remarkable increase in power factor is ascribed to energy filtering effects and excellent electrical transport of 1D SWCNTs in the composites. Consequently, with a considerable reduction in thermal conductivity, the figure of merit culminates in a several-fold improvement, at 0.5 vol% of SWCNTs, over pristine bulk Bi₂Te₃.