Anionic Isoelectronic Substitution Effects on Thermal Stability and Thermoelectric Performance of PbTe-PbSe Compounds

Here, we report that a combination of vacuum melting and spark plasma sintering efficiently enhances the thermoelectric properties of the PbTe-PbSe compounds. Thermal analysis results show that all the PbTe 1− x Se x samples have excellent thermal stability. Positron annihilation spectroscopy results indicate improvement of the crystal quality in all obtained PbTe 1− x Se x samples. X-ray photoelectron spectroscopy studies revealed the presence of Pb 2+ , Pb 4+ , Te 2− , Te 4+ , Se 2− states of Pb, Te, and Se. Meanwhile, replacing the isoelectronic cations with those of different electronegativity will lead to a variation in carrier concentration. All samples exhibit p -type conduction with carrier concentrations varying from 0.07 × 10 19 to 7.34 × 10 19  cm −3 , since carrier mobility changes from 4.7 to 727.7 cm 2 V −1 s −1 at room temperature. Therefore, the maximum figure of merit ( ZT ) value reaches 0.6 at 773 K for the PbSe 0.95 Te 0.05 sample benefiting from the greatly reduced thermal conductivity, which is three times more than the intrinsic PbSe. The peak ZT value of 0.70 at 773 K is obtained in PbTe 0.98 Se 0.02 due to the excellent power factor. Valuable insight can be obtained from a quantitative analysis of the thermoelectric transport in PbTe-PbSe compounds with the anion vacancies (Se 2− and Te 2− ). Graphical