EFFECTS OF MECHANICAL ALLOYING AND GRINDING ON THE PREPARATION AND THERMOELECTRIC PROPERTIES OF BETA-FESI2

Improving effects of mechanical alloying (MA) and grinding (MG) on the preparation processes as well as on the thermoelectric properties of semiconducting beta-FeSi2 were reviewed. MA and MG strongly accelerates the preparation reaction to form beta-phase from elemental powders and from the mixture of alpha-Fe2Si5 and epsilon-FeSi. The electrical resistivity significantly decreased due to the dispersion of fine particles of metallic phase, e.g. epsilon-FeSi phase. As a result, the power factor Q(2)/rho was significantly improved. Figure of merit Z=Q(2)/rho kappa was also improved by MA and MG due to the decrease in the thermal conductivity kappa. This is due to a decrease in grain size of the beta-phase which causes an increase in phonon scattering at the grain boundaries. MA and MG are promissing techniques for the acceleration of beta-FeSi2 formation as well as the improvement of the thermoelectric properties of beta-FeSi2.