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

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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 Pb1−xMgxTe0.8Se0.2 were designed to improve the figure of merit zT. The significant roles of MgTe in enhancing electrical properties and reducing thermal conductivity of PbTe0.8Se0.2 were investigated. A maximum zT of ∼2.2 at 820 K was achieved in PbTe0.8Se0.2 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.