Nanostructured Composites of BiSb Nanoparticles and Carbon Nanotubes and the Characterization of Their Thermoelectric Properties.

The impact of inclusions of carbon nanotubes (CNT) on the thermoelectric properties of nanostructured BiSb alloys with an Sb content between 10 and 20% was investigated for varying amounts of CNT. Three series of BiSb pellets with 0, 0.3, and 0.5 wt % CNT were synthesized by mechanical alloying followed by uniaxial pressing. The resistivity was investigated in the temperature range from 30 to 500 K, revealing an enlargement of the band gap due to nanostructuring of the BiSb alloy, which is even more pronounced for alloys including CNT. This enlargement is attributed to a modification of the interface between the BiSb nanoparticles by a graphene-like coating, which is formed during the fabrication process due to the addition of CNT. Measurements of the Seebeck coefficient and the thermal conductivity were also performed to determine the thermoelectric properties. In total, the CNT-containing samples show a significant improvement of the figure of merit up to 250% for the BiSb composition with 0.3 wt % CNT due to the interface modification between the nanoparticles, demonstrating the beneficial effect of CNT on the thermoelectric properties.