Microstructure and thermoelectric properties of p-type Fe0.9Mn0.1Si2 compounds prepared by pressureless sintering

The microstructure and thermoelectric properties of porous p-type Fe0.9Mn0.1Si2 compounds fabricated by pressureless sintering were investigated. A small amount of metallic phases, α-Fe2Si5 and ε-FeSi, remained after annealing at 800°C for 100 h. As the sintering temperature increased from 1150 to 1175°C, the phase transition to β-FeSi2 during annealing occurred more rapidly. The figure of merit at room temperature increased with the porosity because although the electrical conductivity decreased, the Seebeck coefficient increased and the thermal conductivity decreased. The porous specimen, sintered at 1150°C for 2 h with coarse powders (<45 μm) and annealed at 800°C for 100 h, showed the highest Seebeck coefficient of 380 μV K−1 at 400°C, and the highest power factor of 1.7×10−3 W m−1 K−2 at 500°C.