An experimental atomic resolution analysis of an undoped Σ = 5 36º [001] tilt grain boundary showed that the structure contained incomplete O octahedra. These incomplete octahedra acted as effective O vacancies and led to a fixed positive boundary charge. Annealing of the boundary in the presence of MnO2 did not change the atomic structure of the boundary plane, and resulted in a high concentration of Mn3+ (acceptor) enrichment at Ti4+ locations which were closest to the effective O vacancies. This was explained in terms of standard charge-compensation models and indicated that the formation of electrical barriers at oxide grain boundaries could be affected by the atomic structure of the boundary plane.

The Influence of Atomic Structure on the Formation of Electrical Barriers at Grain Boundaries in SrTiO3. N.D.Browning, J.P.Buban, H.O.Moltaji, S.J.Pennycook, G.Duscher, K.D.Johnson, R.P.Rodrigues, V.P.Dravid: Applied Physics Letters, 1999, 74[18], 2638-40