The high thermoelectric performance of slightly Sb doped PbTe alloys

Simple chemical compositions are more suitable for practical applications of thermoelectric materials due to the high success rates of their syntheses and their higher stabilities. Here, n-type PbTe alloys doped with a small amount of Sb were synthesized, and the effects of slight doping on the thermoelectric properties were investigated. All samples have single-phase microstructures, uniform composition distributions, and non-uniform grain sizes on the micro- and nano-scales. A higher power factor of 22.5 μW K−2 cm−1 has been obtained for the composition Pb0.995Sb0.005Te, which was attributed to a reduction in resistivity and to the preservation of a relatively high Seebeck coefficient though tuning the carrier concentrations. In addition, the highly heterogeneous grain size distribution strengthens the grain boundary scattering, and the Sb doped and Te vacancies result in an enhancement in point defect scattering. These two main factors lead to a lower lattice thermal conductivity of 0.68 W m−1 K−1 for the Pb0.988Sb0.012Te alloy at 723 K. In the end, a maximum zT value of about 1.1 has been achieved for the Pb0.995Sb0.005Te alloy, which is comparable to that of Sb doped PbTe alloys with a high doping concentration.