Integrating Band Structure Engineering with All-Scale Hierarchical Structuring for High Thermoelectric Performance in PbTe System

PbTe_{1− x}Se_x-2%Na-y%SrTe system is investigated and a high maximum ZT of 2.3 at 923 K for PbTe_0.85Se_0.15-2%Na-4%SrTe is reported. This is achieved by performing electronic band structures modifications as well as all-scale hierarchical structuring and combining the two effects. It is found that high ZTs in PbTe_0.85Se_0.15-2%Na-4%SrTe are possible at all temperature from 300 to 873 K with an average ZT_ave of 1.23. The high performance in PbTe_{1− x}Se_x-2%Na-y%SrTe can be achieved by either choosing PbTe-2Na-4SrTe or PbTe_0.85Se_0.15-2Na as a matrix. At room temperature the carrier mobility shows negligible variations as SrTe fraction is increased, however the lattice thermal conductivity is significantly reduced from ≈1.1 to ≈0.82 W m⁻¹ K⁻¹ when 5.0% SrTe is added, correspondingly, the lattice thermal conductivity at 923 K decreases from ≈0.59 to ≈0.43 W m−¹ K⁻¹. The power factor maxima of PbTe_{1− x}Se_x-2Na-4SrTe shift systematically to higher temperature with rising Se fractions due to bands divergence. The maximum power factors reach ≈27, ≈30, ≈31 μW cm⁻¹ K⁻² for the x = 0, 0.05, and 0.15 samples peak at 473, 573, and 623 K, respectively. The results indicate that ZT can be increased by synergistic integration of band structure engineering and all-scale hierarchical architectures.