We investigated the thermoelectric properties of CaSi, Ca5Si3 and Ca2Si. Polycrystalline CaSi and Ca5Si3 were prepared by spark plasma sintering (SPS) technique. Polycrystalline Ca2Si was prepared by an interdiffusion process. The electrical resistivity, Seebeck coefficient, and thermal conductivity for CaSi and Ca5Si3 were measured from room temperature to approximately 1000 K. Then, the figure of merit was evaluated by using these values. The temperature dependence of the electrical properties for CaSi and Ca5Si3 showed metallic behavior in all temperature range. CaSi showed n-type conduction and Ca5Si3 showed p-type conduction. The evaluated maximum dimensionless figure of merit for CaSi and Ca5Si3 are 5.1 X 10-3 at 950 K and 0.11 at 950 K, respectively.
IntroductionThermoelectric power generation can directly convert heat into electricity by giving temperature differences to both ends of thermoelectric materials. The efficiency of thermoelectric conversion increases with the dimensionless figure of merit, ZT = S2cT/K, where Z, T, S, CT, and K are the figure of merit, absolute temperature, Seebeck coefficient, electrical conductivity, and thermal conductivity, respectively. A large variety of materials, such as intermetallic compounds, silicides, and borides have been investigated as thermoelectric materials. Particularly, several metal silicides, such as Mg2(Si,