High-resolution transmission electron microscopy and analytical electron microscopy were carried out on Si-doped sintered α-phase material. High-resolution transmission electron microscopy showed that there was no amorphous phase at the grain boundaries. The Si-segregated boundaries were found to be much more sensitive to irradiation damage than were undoped alumina grain boundaries. Analytical electron microscopy, with energy dispersive X-ray spectroscopy, revealed significant Si segregation at grain boundaries, and analytical electron microscopy, with electron energy-loss spectroscopy, revealed the existence of 6-fold coordinated Si at the grain boundaries. Theoretical results which were obtained by using the molecular orbital method supported the data which were obtained by using electron energy-loss spectroscopy.

K.Kaneko, I.Tanaka, M.Yoshiya: Applied Physics Letters, 1998, 72[2], 191-3