Enhanced strength and plasticity with high thermoelectric performance in Mg₃(Sb, Bi)₂ by microstructure design

The intrinsic trade-off between strength and plasticity is a major obstacle to improving the mechanical performance of materials, particularly brittle thermoelectric compounds. Developing intrinsically plastic thermoelectric materials with improved machinability and functionality has received increasing attention. Yet, the existing plastic thermoelectrics often show low strength and poor thermoelectric performance at elevated temperatures. Here, we introduce a microstructure-engineering strategy that integrates nanopore architectonics with heterointerface design to achieve a synergistic enhancement of strength, plasticity, and thermoelectric performance in Mg₃(Sb, Bi)₂. Dispersed nanopores improve both strength and plasticity by promoting dislocation-surface interactions. In parallel, TiB₂ hetero-particles strengthen the material via pinning dislocations at phase interfaces while preserving plasticity via interfacial complexions that facilitate dislocation slip. These heteroparticles also enhance phonon scattering and provide charge compensation, thereby significantly improving the thermoelectric figure of merit ( zT ). As a consequence, polycrystalline Mg_3.2Sb_1.5Bi_0.49Te_0.01–0.03 TiB₂ achieves an exceptional strength of ∼ 730 MPa and a superior strain of ∼ 45%, alongside zT above 1 across 400–723 K and a peak zT of ∼ 1.55 at 723 K. This work demonstrates an effective strategy for simultaneously optimizing mechanical robustness and thermoelectric performance through microstructure manipulation, offering a pathway toward the design of next-generation high-performance plastic thermoelectrics.