Growth of Mg2Si thermoelectric eutectics by unidirectional solidification

Abstract

Mg2Si/Si eutectics are grown from melt by the Vertical Bridgman method using a carbon crucible at three pulling rates. All the Mg2Si/Si eutectics are composed of Mg2Si and Si phases, and the eutectic structure becomes finer with an increase in the pulling rate. Increasing the pulling rate systematically decreases the thermal conductivities of the Mg2Si/Si eutectics, suggesting that a decrease in the thermal conductivity is attributed to an increase in phonon scattering at the boundaries between the two phases. The power factor and figure of merit of the Mg2Si/Si eutectics are larger than those of Mg2Si above 400 °C because of the increase in the Seebeck coefficient. The figure of merit, ZT, of the Mg2Si/Si eutectics solidified at a 103 mm/min pulling rate reached 0.076 at 600 °C.