Reaction Synthesis of Magnesium Silicon Nitride Powder

The synthesis of magnesium silicon nitride (MgSiN 2 ) by direct nitridation of a Si/Mg 2 Si/Mg/Si 3 N 4 powder mixture is described. A nucleation period at 550°C and stepwise heat‐treatment schedule up to 1350°C was adopted for the synthesis of MgSiN 2 powder, based on TG‐DTA measurements. The influence of the ratio of constituents on the final phase composition also has been studied. The content of magnesium and silicon in the starting powder should fulfill the conditions Mg 2 Si/Mg ≥ 3 and Si 3 N 4 /Si tot ≥ 0.5 to obtain single‐phase MgSiN 2 . The silicon particle size of <0.5 μm is preferable to decrease the time of nitridation. The oxygen content of as‐synthesized powders is in the range 0.9–1.2 wt%. However, the oxygen content of MgSiN 2 powder decreases further by the addition of 2 wt% CaF 2 or 0.75 wt% carbon and reaching the lowest value of 0.45 wt% oxygen after carbothermal reduction in an alumina‐tube furnace.