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 or 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 th e observed characteristics of the walls in this family: number of wall s merging at a node, average distance between discommensurations, valu e of the modulation wavenumber. We show that a wide range of ''latent' ' commensurate periods ''4b'', determine the characteristics of the wa lls.