Concentration profiles across twin boundaries in YBa{sub 2}Cu{sub 3}O{sub 6+{delta}}

Twin boundaries in polycrystalline YBa{sub 2}Cu{sub 3}O{sub 6+{delta}} have been studied by atom-probe field-ion microscopy. Oxygen depletion at a twin boundary in a {delta}=0.6 material was observed. The width of the depleted region was 6{endash}7 nm. It agrees well with the width of oxygen depletion calculated from the oxygen-depleted twin boundary model by Jou and Washburn. However, a twin boundary in a {delta}=0.9 material did not show any oxygen depletion. This study provides direct evidence of oxygen depletion at twin boundaries in polycrystalline YBa{sub 2}Cu{sub 3}O{sub 6+{delta}} ceramics. {copyright} {ital 1997} {ital The American Physical Society}