Twin boundaries in polycrystalline samples were studied by means of atom-probe field-ion microscopy. Depletion of O was observed at a twin boundary in Cu3Ba2YO6.6. The width of the depleted region was 6 to 7nm. This agreed well with the O depletion width which was calculated by using the Jou-Washburn O-depleted twin boundary model. However, a twin boundary in Cu3Ba2YO6.9 did not exhibit any O depletion. This work provided direct evidence for O depletion at twin boundaries in polycrystalline Cu3Ba2YO7 ceramics.

Q.H.Hu, K.Stiller, E.Olsson, H.O.Andrén, P.Berastegui, L.G.Johansson: Physical Review B, 1997, 56[18], 11997-2003