Phase Relationship of MgSi at High Pressures and High Temperatures and Thermoelectric Properties of MgSi.

Magnesium silicide (MgSi) is a promising eco-friendly thermoelectric material, which has been extensively studied in recent times. However, its phase behavior at high pressures and temperatures remains unclear. To this end, in this study, X-ray diffraction analysis was conducted at high pressures ranging from 0 to 11.3 GPa and high temperatures ranging from 296 to 1524 K, followed by quenching. The antifluorite-phase MgSi decomposed to MgSi and Mg at pressures above 3 GPa and temperatures above 970 K. The antifluorite-phase MgSi underwent a structural phase transition to yield a high-pressure room-temperature (HPRT) phase at pressures above 10.5 GPa and at room temperature. This HPRT phase also decomposed to MgSi and Mg when heated at ∼11 GPa. When 5MgSi decomposed to MgSi and Mg, the volume reduced by ∼6%. MgSi synthesized at high pressures and high temperatures was quenchable under ambient conditions. Thermoelectric property measurements of MgSi at temperatures ranging from 10 to 390 K revealed that it was a p-type semiconductor having a dimensionless thermoelectric figure of merit () of 3.4 × 10 at 283 K.