Intergranular amorphous films at grain boundaries (GB) in Si3N4
ceramics doped with 0, 80, 220 and 450 ppm of calcia were investigated
by high resolution transmission electron microscopy (HRTEM) and
spatially-resolved electron energy-loss spectroscopy (EELS). The
observed film thicknesses are consistent with previous observations
. Ca additives segregated at GB films, but not at the large triple
pockets. EELS revealed the presence of N in the GB films. It is
suggested that N is introduced into the GB films by Ca segregation.
Electron energy-loss near-edge structure (ELNES) analysis indicates the
presence of Si-(O,N)(4) tetrahedra in the GB films.