Improved figure of merit (z) at low temperatures for superior thermoelectric cooling in Mg3(Bi,Sb)2

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 Mg3Bi2-xSbx crystals with an average grain size of similar to 800 mu m, leading to a high carrier mobility of 210 cm(2) . V-1 . s(-1) and a high z of 2.9 x 10(-3)K(-1) at 300 K. A Delta 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 Mg3Bi1.5Sb0.5- and Mg3Bi1.25Sb0.75-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.