Synergetic Approach for Superior Thermoelectric Performance in PbTe-PbSe-PbS Quaternary Alloys and Composites

Thermoelectric power generation is an energy conversion technology from heat to electric energy, which can be applied to waste heat power conversion. Among thermoelectric materials (TE), PbTe-PbSe-PbS quaternary alloys and composites are promising candidates for thermoelectric power generation applications in the mid-temperature operating range from 500 to 850 K. Besides, the thermoelectric performance of quaternary alloys and composites is not fully optimized regarding its composition and synthesis process. In the quaternary system, PbTe-PbSe-PbS, it was found that PbS will form nanoprecipitation in the matrix of quaternary alloy for a small content of PbS (<= 0.07), which reduces the lattice thermal conductivity. The power factor of PbTe-PbSe-PbS quaternary alloys can be significantly enhanced by using a band convergence in PbTe1-xSex. The band structure modifications, with the result of simultaneous PbS nanoprecipitation, give rise to a high ZT value of 2.3 at 800 K for (PbTe)(0.95-x)(PbSe)(x)(PbS)(0.05). The chemical potential tuning by effective K-doping (x = 0.02) and PbS substitution reveals a high power factor and low thermal conductivity, resulting in a comparatively high ZT value of 1.72 at 800 K. The combination of a high Seebeck coefficient and low thermal conductivity results in a very high ZT value of 1.52 at 700 K as n-type materials for low Cl-doped (x = 0.0005) (PbTe0.93-xSe0.07Clx)(0.93)(PbS)(0.07) composites. Therefore, this review presents the simultaneous emergence of effective chemical potential tuning, band convergence, and nanoprecipitation, giving rise to a significant enhancement of the thermoelectric performance of both p- and n-type PbTe-PbSe-PbS quaternary alloy and composite TE materials.