Direct observation of the atomic structure of a twin boundary layer in a superconducting Y-Ba-Cu-O ceramic

Abstract

Direct structural images of a twin boundary in a superconducting Y–Ba–Cu–O ceramic have been obtained at 0·19 nm resolution by high-resolution transmission electron microscopy and an image processing technique. It was found that the a and b planes of a twin domain gradually change to the b and a planes of a neighbouring twin domain across a twin boundary. This involves a shifting of the respective planes by a distance (⅓∼½)d₍₁₁₀₎ along the boundary as well as the rotation of the planes by ⊘ ≃ 2(b−a)/(a + b) across the boundary. Also, this transition takes place within approximately four times the (110) interplanar spacing d ₍₁₀₀₎, which is considered as the twin boundary layer thickness.