Phase Stability of Thermoelectric Alkaline Earth Metal Borides and Silicides

摘要

Group (Ⅱ) metal borides and silicides have been studied as high temperature thermoelectric materials because of their good thermal stabilities and high melting points. In the present study, an investigation was carried out on thermoelectric and thermodynamic properties of group (Ⅱ) metal borides (CaB_6 and SrB_6) and silicides (Mg_2Si and CaSi) at high temperatures (up to 1050 K). Experimental data on thermoelectric properties (Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit) of the borides and silicides was collected and evaluated as a function of temperature. Thermodynamic properties such as Gibbs energy and activities of B and Si in the binary alloys and corresponding binary phase diagrams were evaluated. Phase equilibria and crystal structure of the alloys were determined from the available binary alloy data. Mg_2Si exhibited better thermoelectric figure of merit and has greater potential for power generation at high temperatures.