Enhanced thermoelectric performance of PbTe bulk materials with figure of merit zT >2 by multi-functional alloying

Forming solid solutions in PbTe based materials can simultaneously reduce lattice thermal conductivity and engineer the band structure to enhance the electrical properties. In this paper, quaternary alloys of Pb_1−xMg_xTe_0.8Se_0.2 were designed to improve the figure of merit zT. The significant roles of MgTe in enhancing electrical properties and reducing thermal conductivity of PbTe_0.8Se_0.2 were investigated. A maximum zT of ∼2.2 at 820 K was achieved in PbTe_0.8Se_0.2 with 8% MgTe. Subsequently, a large dimension bulk (∼200 g, Φ42 mm × 18 mm) was fabricated and its homogeneity and the repeatability of high zT values were determined. The results show that high zT ∼2.0 can also be achieved even in such a large sample. These results highlight the multi-functional roles of quaternary alloying with Mg and Se, and demonstrate the realistic prospect of large-scale commercial fabrication in high performance PbTe-based thermoelectric materials.