Enhanced thermoelectric properties of the Lu-doped and CNT-dispersed Bi2Te3 alloy

Bi2Te3 and Lutetium-doped Lu0.1Bi1.9Te3 nanopowders were prepared by the hydrothermal method. Different amounts of carbon nanotubes (CNTs) were dispersed into Lu0.1Bi1.9Te3 nanopowders and hot pressed into bulk samples with nominal chemical formula of Lu0.1Bi1.9Te3 + xwt% CNT (x=0, 0.05, 0.1, 0.5, 1) to assess the effects of lutetium doping and CNT dispersing on the thermoelectric properties. The electrical resistivity decreased because of the increase of the carrier concentration and carrier mobility at a low CNTs content. Herein, a small amount of CNTs were used as conducting filler to provide a free path of carriers which would lead to an increase of carrier mobility, though a large number of CNTs mainly played an energy-filtering effect. The thermal conductivity of Lu0.1Bi1.9Te3 + xwt% CNT nanocomposite showed an evident decrease, which resulted from the enhanced phonon scattering by the point defects caused by Lu doping and the interfaces between Lu0.1Bi1.9Te3 and CNTs. Due to the decrease in the electrical resistivity and thermal conductivity, the figure of merit (ZT) of Lu0.1Bi1.9Te3 + 0.05wt% CNT nanocomposite was higher than that of Bi2Te3 and Lu0.1Bi1.9Te3 when the temperature was below 473K.