DISCOMMENSURATION PATTERNS IN THE BI-SR-CA-CU-O HIGH T-C SUPERCONDUCTORS

We present a transmission electron microscopy study of the discommensu ration (DC) walls in the superconducting bismuth-cuprates. High resolu tion evidence for the translation slip across a wall is obtained for t he first time in these materials, A consistent relationship is establi shed between the observed characteristics of the walls in several phas es of this structural family: number of walls merging at a node, avera ge distance between DCs, and value of the modulation wavenumber. We sh ow that a wide range of 'latent' commensurate periods, between 4b and 9b, determine the characteristics of the walls. (C) 1997 Elsevier Scie nce B.V.