Effects of metallic elements on thermoelectric properties of silicon borides

Silicon borides have excellent potential as high-temperature thermoelectric materials because of their high melting point and relatively large Seebeck coefficient. In the present work, effects of metallic elements on thermoelectric properties of the silicon borides were examined. The silicon borides containing some metallic elements were prepared by a plasma melting method. Silicon, boron and metallic elements powder were melted in a high-frequency induction plasma flame, and the silicon borides including metallic elements were formed. The crystal structures of the samples were characterized by X-ray diffraction (XRD), and the morphologies were observed by scanning electron microscope (SEM). Electrical properties such as Seebeck coefficient, electrical conductivity and Hall effect of the samples were measured. Seebeck coefficient of the boride reached about 400μVK^-1, the electrical conductivity was above 100Sm^-1. Because carrier mobility of the sample was less than about 1cm^-2V^-1 s^-1 and increased with an increase of temperature, the conduction mechanism of silicon borides seems to be a polaron hopping. The effect of metallic elements was increasing Seebeck coefficient, and the carrier mobility of silicon borides decreased by adding metallic elements.