Enhancement of Thermoelectric Figure of Merit by the Insertion of MgTe Nanostructures in p-type PbTe Doped with Na2Te

Abstract

The thermoelectric properties of crystalline melt-grown ingots of p-type PbTe–xMgTe (x = 1–3 mol%) doped with Na2Te (1–2 mol%) were investigated over the temperature range of 300 K to 810 K. While the powder X-ray diffraction patterns show that all samples crystallize in the NaCl-type structure with no MgTe or other phases present, transmission electron microscopy reveals ubiquitous MgTe nanoprecipitates in the PbTe. The very small amounts of MgTe in PbTe have only a small effect on the electrical transport properties of the system, while they have a large effect on thermal transport significantly reducing the lattice thermal conductivity. A ZT of 1.6 at 780 K is achieved for the PbTe containing 2% MgTe doped with 2% Na2Te.