Phase Transition and Thermoelectric Property of Ultra-Fine Structured β-FeSi2 Compounds

Abstract

FeSi2 compounds were fabricated by rapid solidification and hot pressing, which is considered to be a mass production technique for this alloy. Structural behavior of melt-spun ribbon during heat-treatment and Seebeck coefficient of the hot pressed bulk were systemically investigated and compared with conventionally fabricated alloys. The melt-spun ribbon consists of α-Fe2Si5 and ε-FeSi phase. With increasing annealing time, the phase transition to β-FeSi2 phase occurred more rapidly. 20 min of annealing is sufficient for a homogeneous formation of β-FeSi2 phase in melt-spun ribbon, while it is 100 h in as-cast alloy. In this research, the formation mechanism of β-FeSi2 phase during annealing is a transition of α+ε→β. The microstructure of sintered bulk generally consist of a randomly distributed β-FeSi2 phase with an average grain size of 0.9 μm. The increase of Seebeck coefficient in melt-spun and sintered specimen is due to fine grain size formed by rapid solidification.