Comprehensive Investigation on the Thermoelectric Properties of p-Type PbTe-PbSe-PbS Alloys

Solid solution alloying is one of the quite powerful approaches to enhance thermoelectric performance because it can simultaneously optimize electrical and thermal transport properties. Herein, a comprehensive investigation on p-type PbTe-PbSe-PbS alloys is reported, in which the carrier concentration is fixed with 2 mol% Na doping. High thermoelectric performance is achieved via synergistically tuning carrier concentration, manipulating electronic band structure, introducing nanostructures, and separating phases. Thus, a high ZT value ≈1.9 is obtained in (PbTe)_{1− x}(PbSe)_x alloys, which show both higher Seebeck coefficients and lower lattice thermal conductivities contributed from enlarging band effective mass and scattering phonons, respectively. The obtained results are well confirmed by microstructure characterizations and theoretical calculations based on the single parabolic band (SPB) model and Callaway model. Besides, ZT values ≈1.8 and 1.2 are achieved in (PbTe)_{1− x}(PbS)_x and (PbSe)_{1− x}(PbS)_x alloys, respectively. Based on the obtained thermoelectric performance from the selected compositions between two or three end-members (PbTe, PbSe, and PbS), the thermoelectric performance distribution maps for the PbTe-PbSe-PbS alloys are established. This comprehensive investigation can provide the performance prediction on any composition within the performance maps of (PbTe)_{1− x − y}(PbSe)_x(PbS)_y alloys.