TEM studies on twin boundary in YBa2Cu3O7and YBa2(Cu0.98M0.02)3O7(M = Zn, Al)

Abstract

High resolution electron microscopy of the twin boundary layers in YBa2(Cu1−xMx)3O7+δforx= 0 and 0.02 and M = Zn and Al showed that the boundary widths are ∼1 nm for the pure and the Zn substituted YBa2Cu3O7and ∼3 nm for the Al substituted oxide. From two beam contract studies and the high resolution images, it was concluded that the respective lattice plane across the boundary is shifted by (⅓–½)·2d(110)along the boundary. The broadening of the layer by the Al substitution is also thought to be a cause for the reduction of the twin boundary energy, leading to an increased twin density.