Thermoelectric properties of calcium silicides

We investigated the thermoelectric properties of CaSi, Ca₅ Si₃ and Ca₂Si. Polycrystalline CaSi and Ca ₅Si₃ 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 times 10^-3 at 950 K and 0.11 at 50 K, respectively