Enhanced thermoelectric performance of n-type PbTe doped with Na2Te

The n-type PbTe doped with Na2Te (0.5-1.5 mol%) powders was prepared via planetary ball milling and then compacted via hot-pressed sintering at 773 K and 50 MPa. The effect of Na2Te on the thermoelectric performance of PbTe was investigated. The results demonstrated that Na2Te doping not only increased the lattice parameter, but also transformed the conduction type from p- to n-type. Moreover, Na+ was located at the interstitial sites of PbTe and generated excess electrons, increasing carrier concentration and electrical conductivity. The enhancement in the power factor of PbTe doped with Na2Te samples was due to the higher Seebeck coefficient and electrical conductivity at a high measurement temperature. A maximum ZT value of 0.81 at 700 K was obtained for n-type PbTe doped with 1 mol% Na2Te due primarily to a significant increase in the power factor and a reduction in thermal conductivity.