High thermoelectric figure of merit in heavy hole dominated PbTe

Thermoelectric transport properties of p-type PbTe:Na, with high hole concentrations of approximately 10(20) cm(-3), are reinvestigated from room temperature to 750 K. The greatly enhanced Seebeck coefficient at these doping levels can be understood by the presence of a sharp increase in the density of states around the Fermi level. As a result, the thermoelectric figure of merit, zT, reaches similar to 1.4 at 750 K. The influence of these heavy hole carriers may contribute to a similarly high zT observed in related p-type PbTe-based systems such as Tl-doped PbTe and nanostructured composite materials.