Improved thermoelectric performance of n-type PbTe composites via incorporation of high-entropy secondary phases

Simultaneously optimizing electrical and thermal transport properties remains a major challenge for thermoelectric materials. In this work, high-entropy secondary phases (HE2P) were introduced into a Cu-doped PbTe matrix to improve the thermoelectric performance of n-type PbTe. Carbon-coated HE2P particles were incorporated into the PbTe matrix through vacuum melting and fast hot-pressing, resulting in a hierarchical microstructure with refined grains, heterointerfaces, and defect structures. The introduced HE2P effectively suppresses lattice thermal conductivity through enhanced phonon scattering induced by interfaces, lattice distortion, and mass fluctuation. Meanwhile, the heterogeneous interfaces introduced by the carbon-coated HE2P particles may also influence carrier transport behavior. As a result, the composite with 7% HE2P achieves a low lattice thermal conductivity of 0.39 W m −1  K −1 at 838 K and a peak ZT value of 1.38, together with an average ZT of 1.01 over 300–850 K. These results suggest that incorporating high-entropy secondary phases provides a feasible approach for improving the thermoelectric performance of PbTe-based materials.