Promoted Na Solubility and Modified Band Structure for Achieving Exceptional Average ZT by Extra Mn Doping in PbTe

Na doping strategy provides an effective avenue to upgrade the thermoelectric performance of PbTe-based materials by optimizing electrical properties. However, the limited solubility of Na inherently restricts the efficiency of doping, resulting in a relatively low average ZT, which poses challenges for the development and application of subsequent devices. Herein, to address this issue, the introduced spontaneous Pb vacancies and additional Mn doping synergistically promote Na solubility with a further modified valence band structure. Furthermore, the induced massive point defects and multiscale microstructure greatly strengthen the scattering of phonons over a wide frequency range, leading to a remarkable ultralow lattice thermal conductivity of ∼0.42 W m^-1 K^-1. As a result, benefiting from the significantly enhanced Seebeck coefficient and superior thermal transports, a high peak ZT of ∼2.1 at 773 K and an excellent average ZT of ∼1.4 between 303 and 823 K are simultaneously achieved in Pb_0.93Na_0.04Mn_0.02Te. This work proposes a simple and constructive method to obtain high-performance PbTe-based materials and is promising for the development of thermoelectric power generation devices.