Uniform and polycrystalline tellurium nanoplates with a thickness of 100–300 nm can be rapidly synthesized by a simple solvothermal method in mixtures of water and ethanediamine at 180 °C with the assistance of glucose. By adjusting the concentration of glucose, tellurium microrods and nanoplates can be prepared. Based on the electron microscope observations, a possible mechanism involved the self-assembly process and dissolution–recrystallization mechanism is proposed for explaining the formation of polycrystalline tellurium nanoplates and their transformation into single crystalline nanorods. Furthermore, the Raman scattering measurement for the different morphologies is conducted, and the polycrystalline nanoplates present the stronger Raman scattering spectrum.
The single crystal growth of Mg 3 Bi 2 -based thermoelectric materials is of great significance for their applications near room temperature. So far, it is still a big challenge to grow such bulk single crystals and attempts are primarily focused on the metal flux methods. For the first time, bulk single crystals of n-type Mg 3 Bi 1.49 Sb 0.5 Te 0.01 are directly grown by applying an In-situ Loading Bridgman method. The as-grown single crystal features an excellent carrier mobility of 220 cm 2 V −1 s −1 , which is among the best compared to other Mg 3 Bi 2 -based bulk materials. Besides, this method is successfully developed to fast grow uniform polycrystalline materials with high thermoelectric and mechanic performance. As demonstrated by the single-leg device, a large temperature difference of 10.5 K is achieved at the supplied electric current of 0.6 A, much superior to other room temperature state-of-the-art thermoelectric materials. With the single crystalline and polycrystalline materials prepared reliably and conveniently, in-depth investigations on the Mg 3 Bi 2 thermoelectric system can be greatly benefited, which should as well significantly facilitate their practical applications at room temperature.
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