Investigation on the microstructure of self-reinforced Nd-α-sialon ceramics

α-Sialon ceramics doped with Nd2O3 were prepared by hot-pressing sintering at 1900 °C holding for 1 h with a heat preservation for 1 h at 1500 °C. Microscopic observations indicate that elongated α-sialon grains appear and are embedded in the fine equiaxed-grain matrix. A small amount of β-sialon phases and secondary crystallized phases M′ (Nd2Si3−xAlxO3+xN4−x) also exist in the Nd-α-sialon ceramic. A core/shell structure can be found in the elongated α-sialon and β-sialon grains with a high aspect ratio, in which some misfit dislocations surround the core. The 21R AlN-polytype was observed by transmission electron microscopy (TEM), which could not be detected by X-ray diffraction (XRD) due to its trace amount. Different nucleation and growth modes of sialon grains were also discussed.