Effect of multiwalled carbon nanotubes on the thermoelectric properties of a bismuth telluride matrix

Carbon nanotubes (CNTs) have been not attractive for thermal energy conversion applications because of their high thermal conductivities and low Seebeck coefficient. In other words, traditional thermoelectric materials are basically low bandgap semiconductors such as bismuth telluride and antimony telluride, which have shown outstanding performance. In this report, we studied the effect of a network consisting of CNTs as an impurity in a matrix of bismuth telluride (Bi2Te3) particles. We dispersed Bi2Te3 particles and CNTs together in a solvent and fabricated composite samples under vacuum filtration. Seven different CNTs concentration, 0, 10, 20, 50, 70, 90, 100 vol% were used to compare the influence of CNTs on electrical conductivity and thermopower of the composites. At the low contents (10 and 20 vol%) of CNTs, the electrical conductivity and the thermopower were a little increased, which can be attributed to p-typed doping effect of CNTs on Bi2Te3 particles. At the high contents (50, 70 and 90 vol%) of CNTs, the electrical conductivity and the thermopower were decreased, which can be attributed to hindered carrier mobility.