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.