Cation transport in the vicinity of grain boundaries was investigated by using transmission electron microscopic, EDS, XPS and secondary ion mass spectrometric techniques. The width of the grain boundary was about 1nm where anomalous Ca enrichment was observed. Higher valence states of Cr, such as Cr6+(d0), were detected in the grain boundaries whereas Cr3+(d3) and Cr4+(d2) predominated in the bulk. A very rapid interdiffusion of alkaline earths was observed in the Sr/La0.75Ca0.25CrO3 system. All of the observed phenomena could be correlated by assuming the presence of A-site vacancies which were presumably introduced by the formation of Cr6+ at grain boundaries.

TEM, XPS and SIMS Analyzes of the Grain Boundary of Lanthanum Chromites. N.Sakai, T.Tsunoda, N.Fukumoto, I.Kojima, K.Yamaji, T.Horita, M.Ishikawa, H.Yokokawa, M.Dokiya: Journal of Electroceramics, 1999, 4, 121-8