Synthesis of thermoelectric Mg2Si by reactive sintering utilizing directly applied current sintering

Abstract

Synthesis of the thermoelectric Mg2Si sintered body was tried by reactive pulsed current sintering (PCS) using graphite punches and a nonconductive quartz glass die (directly applied current sintering). The mechanically milled powder mixture of Mg and Si was heated by directly applied current sintering, and the densification behaviour, Mg2Si phase formation and the power consumption during sintering, the relative density and the microstructure of the sample were compared to those of a sample sintered by the conventional PCS (using graphite punches and a graphite die). When the mechanically milled powders were heated by directly applied current sintering, the densification of a powder compact became larger during heating and the density of a sintered body was also significantly higher as compared to those of the sample sintered by the conventional PCS. The relative density of a compound sintered in a quartz die at 973 K for 10 min was 99.3%, which is almost the same as that of the sample sintered by the conventional PCS at 1073 K for 60 min, 99.6%. Furthermore, directly applied current sintering is found to accelerate the reaction between Mg and Si to form Mg2Si phase.