Figure 3: Lattice thermal conductivity and model prediction.

Temperature- (a) and composition- (b) dependent lattice thermal conductivity (symbols) for Pb_1−xSb_2x/3Se solid solution. Taking into account the frequency (ω)-dependent terms for phonon relaxation time including ω⁻² for phonon–phonon (black line in Fig. 3a), ω⁻⁴ for point defect (solid blue line) and ω⁻¹+ω⁻³ for dislocation scattering (olive line), a model based on the Debye approximation (curves) predicts the experimental results. The dashed blue line shows the model prediction, assuming all the Pb vacancies stabilize as random point defects rather than dislocations. The comparison of the dislocations between the x=0.05 (Fig. 1a) and the x=0.03 (Fig. 1b) samples indicates a nearly linear increase in dislocation density with increasing x, further enabling a reliable model prediction on κ_L versus x.