The nature of [001] tilt grain boundaries in YBa2Cu3O7−x

Abstract
Fifty-two faceted grain boundary segments ([001] tilt boundaries) in clusters of bulk-scale YBa2Cu3O7−xcrystals having coincident c-axes were characterized by optical microscopy techniques. Grain boundary orientations were widely distributed. All grain boundaries, except those far from the symmetric condition and those with {110} facets, exhibited well-developed matching of the twin domains across the boundary. It is suggested that this newly reported phenomenon of twin pattern matching occurs due to a local coordination of the tetragonal → orthorhombic transformation strain across grain boundaries and may be beneficial with regard to electrical transport in highly textured polycrystalline material.