Yang-Wei Wang,Yu Wang,Hao Liang,Yi-Xin Zhang,Jing Feng,Zhen-Hua Ge
Bismuth telluride-based materials has been applied in thermoelectric cooling wildly, but the properties still can be further enhanced by doping, microstructure controlling and compositing strategies. Herein, we demonstrate an anomalous doping strategy in (Bi, Sb) 2 Te 3 (BST) materials, where the strong n type dopant of PbBr 2 acts as p-type dopant, introducing holes in BST materials. The anomalous doping is attributed to the dissolution of Pb and Br elements into the matrix in a non-stoichiometric ratio, with Pb predominantly occupying Sb vacancies and Br enriching the in-situ generated Sb 2 O 3 , resulting in the increased hole concentration and improved electrical conductivity. The maximum power factor (PF) ultimately increases to 3972 μW m −1 K −2 for the 0.3 mol% PbBr 2 doped BST sample. Moreover, the enhanced multi-scale wavelength phonon scattering centers cause the lattice thermal conductivity fall to 0.52 W m −1 K −1 . Finally, the peak ZT is effectively enhanced to 1.3 at 323 K, which is 22 % higher than that of pristine sample. Furthermore, a direct conversion efficiency of 4.6 % is achieved in a single 0.3 mol% PbBr 2 -doped BST leg at a temperature gradient of ΔT = 200 K. Thus, this study underscores the anomalous PbBr 2 doping in Bi 0.42 Sb 1.58 Te 3 , promoting the wider application of BST-based materials.
Enhancing phonon scattering has emerged as an effective strategy for suppressing lattice thermal conductivity (κL), thereby improving the performance of bulk thermoelectric materials. Compared with other strategies, the primary purpose of introducing more grain boundaries is to enhance the scattering of mid to low-frequency phonons, consequently reducing the κL at the near-room temperature, which proves advantageous for enhancing the thermoelectric properties of Bismuth telluride-based materials. In this study, MnS/MoS2 as a heterojunction compound was incorporated into a Bi2Te2.7Se0.3 matrix, resulting in the formation of a unique (Bi2Te2.7Se0.3 → MnS → MoS2) three grain boundary interface structure, which significantly enhanced phonon scattering. Additionally, the MnSe secondary phase was observed and confirmed through both X-ray diffraction (XRD) and transmission electron microscopy (TEM). The introduction of 0.3% MnS/MoS2 leads to a reduction in the κL from 0.58 W m−1 K−1 to 0.41 W m−1 K−1 at 300 K. Simultaneously, the synergistic optimization of electrical properties results in a PF of 33 µW cm−1 K−2 at 300 K. Finally, a high ZT value ∼1.17 (375 K) and an average ZTave ∼ 1.08 (300–500 K) were achieved for Bi2Te2.7Se0.3–0.3% MnS/MoS2, which was enhanced 54% and 57% compared with those of the Bi2Te2.7Se0.3 alloy, respectively.
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