Effects of nano-SiO<sub>2</sub> on thermoelectric properties of Mg<sub>3</sub>Sb<sub>2</sub>-based materials

Abstract

Recently, Mg<sub>3</sub>(Sb,Bi)<sub>2</sub>-based thermoelectric materials have received extensive attention owing to excellent thermoelectric properties and the low cost. This study investigates the change and mechanism of thermoelectric transport properties of Mg<sub>3.275</sub>Mn<sub>0.025</sub>Sb<sub>1.49</sub>Bi<sub>0.5</sub>Te<sub>0.01</sub>/SiO<sub>2</sub> nanocomposite. The results show that nano-SiO<sub>2</sub> can effectively scatter phonons, promote the reduction of lattice thermal conductivity, and optimize the heat transport performance owing to the introduction of a large number of tiny grain boundaries. For example, when SiO<sub>2</sub> content is 0.54%, the thermal conductivity decreases by 15% from 1.24 W/(m·K) to 1.04 W/(m·K) compared with that of 0% SiO<sub>2</sub> sample at room temperature. At the same time, the material system also has a strong scattering effect on electrons. This leads to a sharp attenuation of power factor and electrical transport performance with decline of mobility and conductivity in the room temperature area. Nano SiO<sub>2</sub> is an effective candidate for regulating thermoelectric properties of Mg<sub>3</sub>Sb<sub>2</sub> based thermoelectric material. The thermoelectric transport performance of the material will be improved by combining with other methods, such as appropriate grain boundary modification to reduce the potential barrier of charge carrier transport.