Improvement and Practical Application of FeSi_2 Thermoelectric Materials with Dispersion of Fine Particles by Liquid Phase Sintering.

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The performance of the thermoelectric materials is represented by the figure of merit Z : Z=α^2/ρκ, where α is Seebeck coefficient, ρ is electrical resistivity, and κ is thermal conductivity. In order to obtain a high figure of merit, a large Seebeck coefficient and low electrical resistivity is required, as well as a low thermal conductivity. The effects of liquid phase sintering and dispersion of fine particles on the thermoelectric propeties are investigated in this study. The results obtained are as follows :(1) β-FeSi_2 with dispersion of fine particles are obtained by mechanical alloying (MA) and liquid phase sintering method. (2) β-FeSi_2 with ultra-fine SiC dispersion was obtained by MA of FeSi_2, Si and C powders. The performance was markedly improved by decreasing the thermal conductivity. (3) Electrical resistivity and thermal conductivity of β-FeSi_2 were markedly decreased by the dispersion of metallic phase particles with low resistivity. (4) Cu addition significantly accelerated densification by liquid phase sintering. (5) The figure of merit Z of β-FeSi_2 was markedly improved by the simultaneous addition of SiC and Cu. The figure of merit of FeSi_2-SiC-Cu system was 4 times larger than that of β-FeSi_2 without addition.