Transient growth bands in silicon nitride cooled in rare-earth-based glass
Wang, C. M.; Pan, X. Q.; Gu, H.; Duscher, G.; Hoffmann, M. J.; Cannon, R. M.; Ruhle, M.
JOURNAL OF THE AMERICAN CERAMIC SOCIETY 80 (1997), 6, 1397–1404
Transient growth bands in silicon nitride cooled in rare-earth-based glass.
Silicon nitride (Si3N4) particles embedded in various R-Si-Al-O-N glasses (R = La, Nd, Gd, Yb) have been systematically studied by high-resolution transmission electron microscopy and by analytical electron microscopy. The particles typically show an internal growth band, which is attributed to the enhanced growth of the particles in the supersaturated silicate liquid during cooling and reheating. The electron energy-loss spectroscopy and energy-dispersive X-ray spectroscopy analysis reveal that the growth band typically contains lanthanide elements. This trapping, especially of the lighter lanthanide elements, within the lattice of the beta-SiAlON is obviously beyond the general expectation that the lighter lanthanide ions hardly form solid solutions with either alpha- or beta-Si3N4. This ultimately provides some clues regarding the mobility of the lanthanide ions in the liquids and also revives interest in the general question of the possible effect of a cooling stage on the structures and compositions of the intergranular film and of the grain/glass interface in the Si3N4-based polycrystalline ceramics.