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

Quantitative analytical electron microscopy study of dopant
distribution in the rnicrostructure of selected Nd-alpha-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-alpha-sialon
composition from the expected values, which shifts the
alpha-beta-sialon phase boundary. Only extra Nd2O3 additives enable a
monolithic alpha-sialon microstructure. The absence of similar glass in
Yb-alpha-sialon materials keeps the phase relations from such
deviations.