Entropy‐Enabled Hierarchical Defect Architecture for Dual Enhancement of Thermoelectric and Mechanical Performance in SnTe Alloys

ABSTRACT Designing thermoelectric materials that combine high conversion efficiency with mechanical robustness remains challenging—especially in metavalent‐bonded chalcogenides, where weak bonds yield intrinsically low lattice thermal conductivity yet compromise mechanical integrity. Here we present an entropy‐enabled defect architecture in SnTe‐based alloys that steers hierarchical defect evolution—from 0D substitutional clusters to 1D dislocations and 3D coherent nanoprecipitates—enabling multiscale regulation of phonon transport and strengthening mechanisms. Broadband phonon scattering depresses lattice thermal conductivity to 0.26 W·m −1 ·K −1 at 873 K, while coherent (Cd,Ge)Se nanoprecipitates and dislocation networks establish effective load‐transfer and pinning pathways, elevating the yield strength to 220 MPa, an improvement of ∼100 MPa (≈83%) relative to pristine SnTe (120 MPa), while retaining reasonable plasticity. In parallel, modest band‐structure optimization through compositionally complex alloying within the entropy‐stabilized matrix improves the power factor. Benefiting from these synergies, the optimized composition Sn 0.91 Cd 0.03 Sb 0.09 Te(GeSe) 0.25 delivers a peak figure of merit of 1.7 and device efficiencies of 7.2% (single‐leg) and 5.7% (multi‐leg). This work establishes a generalizable pathway to strong, efficient thermoelectric materials, particularly applicable to metavalent bonding systems.