The boundaries in Fe-doped material were investigated by means of high-resolution transmission electron microscopy and spatially resolved electron energy loss spectroscopy. It was noted that special boundaries, such as  = 3 (111) and  = 5 (310), were free of any amorphous phase, whereas so-called arbitrary boundaries in polycrystalline material contained an amorphous film with an average thickness of about 0.7nm. Chemical analysis, performed using spatially resolved electron energy loss spectroscopy showed that the Ti/O ratio at the boundaries was higher than that in the bulk. It was concluded that the Ti/O ratio at the boundaries was slightly higher than that in the bulk, and that Fe segregation to the boundaries occurred in materials with high Fe concentrations. A depletion of Sr near to the boundaries was also detected. It was suggested that the grain boundary core in this material was positively charged. It was unclear whether the existence of the amorphous film was due to sintering, or was due to cation segregation.

X.Pan, H.Gu, S.Stemmer, M.Rühle: Materials Science Forum, 1996, 207-209, 421-4