Improving effects of mechanical alloying (MA) and grinding (MG) on the preparation processes as well as on the thermoelectric properties of semiconducting β-FeSi₂ were reviewed.
MA and MG strongly accelerates the preparation reaction to form β-phase from elemental powders and from the mixture of α-Fe₂Si₅ and ε-FeSi. The electrical resistivity significantly decreased due to the dispersion of fine particles of metallic phase, e.g. ε-FeSi phase. As a result, the power factor Q²⁄ρ was significantly improved. Figure of merit Z=Q²⁄ρκ was also improved by MA and MG due to the decrease in the thermal conductivity κ. This is due to a decrease in grain size of the β-phase which causes an increase in phonon scattering at the grain boundaries.
MA and MG are promissing techniques for the acceleration of β-FeSi₂ formation as well as the improvement of the thermoelectric properties of β-FeSi₂.