In Situ Reaction Induced Core–Shell Structure to Ultralow κlat and High Thermoelectric Performance of SnTe

Lead‐free chalcogenide SnTe has been demonstrated to be an efficient medium temperature thermoelectric (TE) material. However, high intrinsic Sn vacancies as well as high thermal conductivity devalue its performance. Here, β‐Zn4Sb3 is incorporated into the SnTe matrix to regulate the thermoelectric performance of SnTe. Sequential in situ reactions take place between the β‐Zn4Sb3 additive and SnTe matrix, and an interesting “core–shell” microstructure (Sb@ZnTe) is obtained; the composition of SnTe matrix is also tuned and thus Sn vacancies are compensated effectively. Benefitting from the synergistic effect of the in situ reactions, an ultralow κlat ≈0.48 W m−1 K−1 at 873 K is obtained and the carrier concentrations and electrical properties are also improved successfully. Finally, a maximum ZT ≈1.32, which increases by ≈220% over the pristine SnTe, is achieved in the SnTe‐1.5% β‐Zn4Sb3 sample at 873 K. This work provides a new strategy to regulate the TE performance of SnTe and also offers a new insight to other related thermoelectric materials. In situ chemical reactions occur between the β‐Zn4Sb3 additive and SnTe matrix, and the resultant interesting “core–shell” structure is obtained in this work. The composition, microstructure, and transport properties of SnTe thermoelectric materials are synergistically tuned, so an ultralow lattice thermal conductivity (≈0.48 Wm−1 K−1 at 873 K) and relatively high ZT (≈1.32 at 873 K) are achieved, which present an effective method to enhance the thermoelectric performance of SnTe, and are also of referential values for other thermoelectric materials.