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Atomic structure of grain boundaries and surfaces in YBa2Cu3O7?δ and LaBaCaCu3O7?δ |
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| Authors: | H W Zandbergen R Gronsky G van Tendeloo |
| Affiliation: | 1. Gorlaeus Laboratories, State University Leiden, P.O. Box 9502, 2300, RA Leiden, The Netherlands 2. National Center for Electron Microscopy, Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, 94720, Berkeley, California 3. Universiteit Antwerpen, RUCA, Groenenborgerlaan 171, B-2020, Antwerpen, Belgium |
| Abstract: | High-resolution electron microscopy (HREM) studies of grain boundaries and fractured surfaces in both the tetragonal and orthorhombic phases of dense (>90%) YBa2Cu3O7?δ and tetragonal LaBaCaCu3O7?δ have been conducted. Grain boundaries in polycrystalline YBa2Cu3O7?δ are found to be frequently parallel to a (001) plane of one of the adjacent grains, with a structure similar to that of the (001) surface of fractured YBa2Cu3O7-gd. Matching of experimental and calculated images shows that the outermost surface layer in this compound is a deformed BaO layer. Both grain boundaries and fractured surfaces in LaBaCaCu3O7?δ show no such tendency for preferential orientation of the interface plane. Results indicate that the low critical currents observed in sintered materials are caused by textured grain growth in combination with the atomic structure of the grain boundary plane, and the intercalation of off-stoichiometric species near the grain boundary. |
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