Improved figure of merit (z) at low temperatures for superior thermoelectric cooling in Mg3(Bi,Sb)2
Nan Chen, Hangtian Zhu, Guodong Li, Zhen Fan, Xiaofan Zhang, Jiawei Yang, Tianbo Lu, Qiulin Liu, Xiaowei Wu, Yuan Yao, Youguo Shi, Huaizhou Zhao
Abstract
Abstract The low-temperature thermoelectric performance of Bi-rich n-type Mg 3 (Bi,Sb) 2 was limited by the electron transport scattering at grain boundaries, while removing grain boundaries and bulk crystal growth of Mg-based Zintl phases are challenging due to the volatilities of elemental reactants and their severe corrosions to crucibles at elevated temperatures. Herein, for the first time, we reported a facile growth of coarse-grained Mg 3 Bi 2- x Sb x crystals with an average grain size of ~800 μm, leading to a high carrier mobility of 210 cm 2 · V −1 · s −1 and a high z of 2.9 × 10 −3 K −1 at 300 K. A $$\Delta$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Δ</mml:mi> </mml:math> T of 68 K at T h of 300 K, and a power generation efficiency of 5.8% below 450 K have been demonstrated for Mg 3 Bi 1.5 Sb 0.5 - and Mg 3 Bi 1.25 Sb 0.75 -based thermoelectric modules, respectively, which represent the cutting-edge advances in the near-room temperature thermoelectrics. In addition, the developed grain growth approach can be potentially extended to broad Zintl phases and other Mg-based alloys and compounds.