Simultaneous synthesis and densification of nanocrystalline magnesium silicide compound by spark plasma sintering

Magnesium silicide (Mg2Si) is considered as a promising candidate among semiconducting materials for thermo-electric energy harvesting at medium functional temperature range (room temperature – 600°C) due to its light weight, good thermo-physical properties and economically inexpensive. However, synthesis of pure Mg2Si compound through conventional metallurgical processes are found to be a difficult task. The present investigation reports on the simple and robust attempt to fabricate nanocrystalline Mg2Si bulk compound from mechanically milled nanostrutured Mg-Si powder mixture by self-propagating high temperature synthesis (SHS) in spark plasma sintering (SPS). X ray diffraction and trasnsmission electron microscopy (TEM) analysis confirms the phase formation and structural features of Mg2Si compound by SPS. Energy dispersive X-ray absorption spectroscopy (EDAX) mapping reveals the homogenous distribution of constituent elementals and an estimated stochiometry. Differential thermal analysis (DTA) study confirms the lowering of recrystallization and combustion temperatures of milled Mg-Si powder mixture. It is understood that SPS temperature and pressure plays a crucial role in the reaction and densification kinectics in Mg2Si formation of theoretical density. The fabricated nanocrystalline Mg2Si exhibits n type semiconducting behavior and superior power factor (thermo-power) of 11.160μW/cm-K2 at 300°C. [Display omitted] •Rapid synthesis of bulk nanocrystalline Mg2Si by coupling SHS and SPS techniques•SPS temperature provide crucial in rapid SHS and densification of Mg2Si.•Alternative method against synthesis of Mg2Si powders and further consolidation•Superior thermo-electric power factor of 11.160μW/cm-K2