Special grain boundaries in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-x</inf> thin films

Grain boundaries described by rotations about the c[001] axis are discussed in terms of a near-CSL model for orthorhombic materials. Grain boundaries in an oriented YBa2Cu3O7-x (YBCO) thin film grown on an (001) ZrO2 substrate by electron-beam coevaporation of the metals have characterized by transmission electron microscopy. Bright-field and dark-field images and selected-area diffraction patterns recorded from near-Σ=1,5,13, 17, and 29 [001] tilt boundaries and near-Σ=3 and 13 [100] tilt boundaries are presented. It is also shown that low-angle grain boundaries with misoreintations near 7° [001] can be introduced at triple junctions containing two high-angle near-CSL boundaries. A table including coincidence, near-coincidence, and "low-index' facet planes expected for near-CSL misorientations is given and some preliminary observations of the faceting behaviour of such grain boundaries are made. © 1991.