TEM investigation of discommensurations in a Bi - Sr- Ca - Cu- O superconductor

We were able to observe, by transmission electron microscopy (TEM), a certain type ot defects in the superconducting bismuth cuprates. High-resolution evidence for the translation slip across a wall is obtained in this material. A consistent relationship is established between the observed characteristics of the walls in this family: number of walls merging at a node, average distance between discommensurations, value of the modulation wavenumber. We show that a wide range of latent commensurate periods 4b, determine the characteristics of the walls.