β-FeSi2の熱電特性に及ぼすMGの効果

概要

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The thermoelectric properties of β-FeSi2 consolidated by hot pressing of the mechanical grinded (MG) powders were investigated. Mixture of Fe and Si powders was arc-melted in an argon atmosphere to form a button composed of a -Fe2Si5 and ε-FeSi phases. The botton was grinded in a conventional ball-mill for 20-650 hr. The ball-milled powders were hot pressed at 900°C for 30 min under 25 MPa. X-ray diffraction and EPMA analysis showed that mechanical grinding strongly accelerated the formation of β-FeSi2 during hot pressing and small size particles of ε-phase were dispersed in β-FeSi2 matrix. The amount of ε-phase increased with increasing MG time. The electrical resistivity ρ significantly decreased with increasing MG time, on the other hand the thermoelectric power Q increased with increasing MG time and reached at a maximum at 100 hr MG time, and thereafter decreased with increasing MG time. As the result, the power factor Q2/ρ was at maximum at 250 hr MG time. Thermal conductivity decreased by about 35% with increasing MG time up to 500 hr, but increased again by annealing at 900°C.
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