Structural and electrical properties of β-FeSi2 bulk materials for thermoelectric applications

β-FeSi2 bulk materials for thermoelectric applications were prepared from high-purity (99.99%) β-FeSi2 powders or mixed Si and Fe powders. First, FeSi2 powders were milled to reduce the particle size, which can improve the thermoelectric figure of merit by reducing lattice thermal conductivity. Second, they were cold pressed and then sintered by two different sintering methods: a conventional electrical furnace and a Plasma Activated Sintering (PAS) system. The bulk densities and grain sizes were decreased by ball milling of the powders starting materials. The comparison of the two sintering methods showed that, the sample density of the PAS samples was 11%- 23% higher than that of the samples sintered in the conventional electrical furnace. Moreover, the comparison of the two types of powders, β-FeSi2 and the mixture of Fe and Si, indicated that, β-FeSi2 bulk crystals were formed only when β-FeSi2 powders were used.