Abstract
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.
Highlights
No peak of β-Zn4Sb3 can be found in the X-ray diffraction (XRD) patterns, indicating that all the β-Zn4Sb3 nanopowders have been decomposed during the process of spark plasma sintering (SPS) as consistent with the reported work,[14] the decomposition reaction is as follows β-Zn4Sb3 → Zn + 3 ZnSb
There are two peaks in the differential thermal analysis (DTA) curve of the SnTe + β-Zn4Sb3 powder mixture before SPS, the first endothermic peak around ≈680 K corresponds to the decomposition temperature of β-Zn4Sb3, and the second wide exothermic peak around 770 K indicates that another reaction was happened between the decomposition products and the SnTe matrix at elevated temperature, which should be ascribed to the formation of ZnTe phase, as depicted by the following equation
By means of the in situ chemical reactions between the β-Zn4Sb3 additives and SnTe matrix, a typical “core–shell” microstructure of Sb@ZnTe has been introduced to the matrix for the first time, the composition of SnTe matrix has been tuned, and Sn vacancies have been compensated effectively
Summary
Our previous work demonstrated that it could remarkably reduce the phonon thermal conductivity and enhance the thermoelectric performance of p-type (Bi,Sb)2Te3-based materials by decomposing into Zn and ZnSb nanoinclusions.[13]. Single doping and co-doping with Zn and Sb have been studied for comparison, and the results illustrated that only the β-Zn4Sb3 containing samples show special “core–shell” microstructures and achieved higher TE performance. This work presents an effective method to enhance the TE performance of SnTe, which offers a new insight to other related thermoelectric materials
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