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_0.91Cd_0.03Sb_0.09Te(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.