High-performance thermoelectrics of p-type PbTe via synergistic regulation of band and microstructure engineering

The strong correlation between Seebeck coefficient and electrical conductivity is a main bottleneck in enhancing the performance of thermoelectric materials. It indicates that optimal carrier concentration and optimized band structure obtained by high level alloying are effective avenue to improve the thermoelectric properties. Therefore, maximizing optimization urgently requires alloying low-cost and high doping efficiency elements. Here, we report an insight that in Te-rich environment, PbTe doped with 4%Na and 2%Sn achieve the maximum zTmax of ∼2.0 at 773 K and the average zTavg between 323 K and 773 K of ∼1.21. The experimental results and two-band model verify that the trace amounts of Sn in Pb0.95Na0.04Te changes the band structure (L and Σ bands), leading to optimized carrier concentration and enhanced effective mass. Simultaneously, the phase and composition characterization indicate that the Sn promotes the partial dissolution of Na at room temperature, adjusted the distribution of multi-dimensional microstructure to reduce the lattice thermal conductivity. Ultimately, the trace Sn and excess Na in this work enables the synergistic optimization of band structure and microscopic structure for maximizing the power factor and minimizing thermal conductivity, resulting in high thermoelectric performance. This inspires us to use low-cost element doping, which is conducive in manufacturing high efficiently PbTe-based devices.