Effect of intergranular glass on phase relation of Nd-α-sialon

Quantitative analytical electron microscopy study of dopant distribution in the microstructure of selected Nd-α-sialon samples revealed the presence of relatively large amounts of glassy phase at quadruple pockets, which exhibited a common composition similar to a melilite solution. Al segregants were depleted from adjacent grain boundaries to satisfy the “stoichiometry” of such glass. Existence of this glass results in significant deviation of the Nd-α-sialon composition from the expected values, which shifts the α-β-sialon phase boundary. Only extra Nd2O3 additives enable a monolithic α-sialon microstructure. The absence of similar glass in Yb-α-sialon materials keeps the phase relations from such deviations.