Point-Defect Populations As Induced by Cation/Anion Substitution in β-Si3N4Lattice. A Cathodoluminescence Study

Point-defect characterizations in bulk β-silicon nitride polycrystalline ceramics were performed by means of cathodoluminescence (CL) spectroscopy. Three kinds of samples were compared: undoped Si 3 N 4, SiO 2 -doped Si 3 N 4, and Si 3 N 4 doped with Al 2 O 3 and Y 2 O 3 . Intrinsic defects and the effect of anion and cation substitutions (i.e., O for N and Al(Y) for Si) on the spectroscopic behavior of defect emissions were investigated with the aim of assigning the physical origin of the observed CL spectra. Upon deconvoluting the retrieved CL spectra into individual sub-bands, emissions originating from different defects stored in the neighborhood of the surface of these materials could be classified. A clear dependence of defect type and content on the presence of dopants could be found, despite the well-known notion that most of the dopant ions reside at grain boundaries rather than being assimilated into the hexagonal structure of β-silicon nitride.