Synthesis of single-phase polycrystalline Ca 2 Si powder and sintered compacts

Orthorhombic polycrystalline Ca 2 Si sintered compact bulk crystals were synthesized via a two-step treatment, and the experimental evaluation of the electrical and thermoelectric properties of Ca 2 Si is reported for the first time. First, single-phase Ca 2 Si powders were synthesized by the heat treatment of Mg 2 Si powders under a Ca vapor. Then Ca 2 Si sintered compacts were synthesized by the spark plasma sintering technique using the Ca 2 Si powders. It was found that single-phase Ca 2 Si sintered compacts were obtained when the sintering was carried out at temperatures lower than 673 K with high pressure of 300 MPa. The structural, electrical and thermoelectric properties of the Ca-silicide sintered compacts and their dependence on process conditions are discussed.