Constructing Coated Grain Nanocomposites and Intracrystalline Precipitates to Simultaneously Improve the Thermoelectric and Mechanical Properties of SnTe by MgB2 and Sb Co‐Doping

Abstract Thermoelectric materials should be highly efficient and mechanically robust to satisfy the requirements of engineering applications. Herein, an integrated optimization strategy to improve both the thermoelectric performance and mechanical strength of SnTe is proposed. First, grain boundary engineering is applied to SnTe via MgB 2 doping. The decomposition of MgB 2 results in the Mg‐substituted SnTe solid solution and a special “core–shell” structure of Mg‐B compounds coated SnTe grain remarkably reducing the lattice thermal conductivity. Subsequently, trivalent Sb atoms are introduced to tune the carrier concentration and optimize the electrical performance of the MgB 2 ‐doped sample. Sb‐rich Sn‐Te precipitates inside the grains further diminish the lattice's thermal conductivity. Consequently, a prominent improvement in average ZT of ≈117% is achieved for Sn 0.78 Sb 0.16 Te(MgB 2 ) 0.09 compared to pristine Sn 1.03 Te. Moreover, the compressive yield strength and Vickers hardness of Sn 0.78 Sb 0.16 Te(MgB 2 ) 0.09 are significantly increased by ≈168% and 176% relative to pristine Sn 1.03 Te, respectively. The quantitative strengthening models including grain boundary, dislocation, solid solution, intergranular, and precipitation strengthening in MgB 2 ‐ and MgB 2 ‐Sb‐doped Sn 1.03 Te samples are proposed, showing that the dominant strengthening mechanism is precipitation strengthening. This work provides an avenue for designing efficient and robust thermoelectric materials toward commercial application.