Low‐Temperature Synthesis of Nanocrystalline α‐Si 3 N 4 Powders by the Reaction of Mg 2 Si with NH 4 Cl

Nanocrystalline α‐Si 3 N 4 powders have been prepared with a yield of 93% by the reaction of Mg 2 Si with NH 4 Cl in the temperature range of 450° to 600°C in an autoclave. X‐ray diffraction patterns of the products can be indexed as the α‐Si 3 N 4 with the lattice constants a = 7.770 and c = 5.627 Å. X‐ray photoelectron spectroscopy analysis indicates that the composition of the α‐Si 3 N 4 samples has a Si:N ratio of 0.756. Transmission electron microscopy images show that the α‐Si 3 N 4 crystallites prepared at 450°, 500°, and 550°C are particles of about 20, 40, and 70 nm in average, respectively.