Microstructure and the influence of spontaneous strain in LaCoO3, La0.8Sr0.2CoO3 and La0.8Ca0.2CoO3 |
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| Authors: | J. C. Walmsley A. Bardal K. Kleveland M.-A. Einarsrud T. Grande |
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| Affiliation: | (1) SINTEF Materials Technology, N-7465 Trondheim, Norway;(2) SINTEF Materials Technology, N-7465 Trondheim, Norway;(3) Department of Chemistry, Norwegian University of Science and Technology, N-7491 Trondheim, Norway |
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| Abstract: | Transmission Electron Microscopy has been conducted on rhombohedral perovskite oxides with composition LaCoO3, La0.8Sr0.2CoO3, and La0.8Ca0.2CoO3. Thin foils prepared within the first weeks of sintering showed macroscopic strain and a very high defect density, which included fault-related superlattice structures. Samples prepared several months after sintering, showed no significant macroscopic strain and the main defect was found to be domains due to reflection twinning in the pseudo-cube plane. The behaviour is likely to be related to accomodation of spontaneous strain arising upon cooling of the material from the sintering temperature. The presence of twin domains illustrates the lowering of lattice symmetry as compared to the ideal cubic perovskite structure, and is relevant for explaining recent observations of ferroelastic behaviour of these materials. |
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