Thermoelectric properties and extremely low lattice thermal conductivity in p-type Bismuth Tellurides by Pb-doping and PbTe precipitation

We investigated the thermoelectric properties of Pb-doped compounds (Bi_0.2 Sb_0.8-x Pb_x)₂ Te₃ and pseudo-binary PbTe composites of [(Bi_0.2 Sb_0.8)₂ Te₃]_1-2x(PbTe)_2x (x = 0.0, 0.01, 0.02, 0.05, and 0.10). The Pb-doping and PbTe-precipitation enhanced their metallic properties, as confirmed by the increase in electrical conductivity and carrier density, and the decrease in Seebeck coefficient and Hall mobility. We obtained the exceptionally low lattice thermal conductivity of 0.2 W m^-1 K^-1 from the single parabolic band model, which can be justified by the good fitting with the Pisarenko plot. Because of the high electrical conductivity at room temperature and high Seebeck coefficient at high temperature, with the decrease in thermal conductivity with increasing temperature, the thermoelectric figure-of-merits ZT were enhanced in the mild temperature range, which can be advantageous in energy harvesting technologies.