Atomic structural environment of Y in the residual glass phase of silicon nitride and α-sialon Original Research Article

The atomic structural environments around Y ions in the residual glass phase of Si3N4 and α-sialon densified with Y2O3 and Al2O3 have been investigated using extended X-ray absorption fine structure (EXAFS). In the residual glass phase, on average, the Y–O/N nearest neighbor bond length is determined to be 2.30 Å, which corresponds to the Y–O bond length in cubic Y2O3, indicating that O is the dominant nearest neighbor of Y. The fitted apparent Y–O/N nearest neighbor coordination number is ~4, which is apparently lower than that when Y is dissolved in a bulk glass, indicating that Y occupies substitutional Si sites. It is also further suggested that the Y–O/N polyhedron in the residual glass phase in silicon nitride and α-sialon is more distorted in comparison with that when Y is dissolved in a bulk glass phase.