Influences of powder characteristic and compacting condition on solid-state synthesis of Mg₂Si

The influence of the raw powder characteristics and compacting condition on the solid-state synthesis of Mg₂Si from elemental Mg-Si mixture powder has been examined by thermal analysis using DSC thermogram. The Mg₂Si synthesis progresses at the lower temperature range when employing the fine Mg powder, because of the increase in the contacting area between the Mg and Si particles. In employing fine Si powder, the endothermic heat due to the appearance of liquid phase of Mg at 920 K decreases remarkably. MgO film, covering the Mg powder surface, prevents the Mg₂Si synthesis due to its thermal stability, however SiO₂ surface film is not so effective because of the deoxidization by Mg during heating. Concerning the effect of the compaction pressure, when the hard Si particles are embedded in the Mg powder after compacting the mixture powder, the mechanical breakage of the thermally stable MgO surface film occurs. Therefore, the enlargement of the contacting clean area between Mg and Si particles causes the progress of the Mg₂Si synthesis at the lower temperature.