Bulk and Surface Structures of the Aurivillius Phases: Bi4-xLaxTi3O12 (0 ≤ x ≤ 2.00)
| Autor: | Ming-Wen Chu, and Olivier Joubert, Yves Piffard, M. Ganne, Anne-Marie Marie, Luc Brohan, Maria-Teresa Caldes |
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| Rok vydání: | 2003 |
| Předmět: |
chemistry.chemical_classification
Diffraction Surface (mathematics) Materials science biology General Chemical Engineering General Chemistry Polymer Convergent beam biology.organism_classification Crystal Aurivillius Crystallography chemistry Electron diffraction Materials Chemistry Perovskite (structure) |
| Zdroj: | Chemistry of Materials. 16:31-42 |
| ISSN: | 1520-5002 0897-4756 |
| Popis: | A convergent beam electron diffraction (CBED) study of Bi 2 La 2 Ti 3 O 12 was performed. As in the case of Bi 3 LaTi 3 O 12 , it reveals a lowering of symmetry with respect to the idealized structure (space group I4/mmm) of Aurivillius phases. The structure of Bi 4-x La x Ti 3 O 12 (x = 1 and 2) compounds has been refined from powder X-ray diffraction data, showing that the interlayer mismatch between fluorite-like and perovskite-like layers is relieved by the conjuction of cation disorder and lowering of symmetry. HREM studies performed on Bi 4-x La x Ti 3 O 12 (x = 0, 0.75, and 2) compounds show that the La-containing compounds exhibit intergrowth defects within a thickness of ∼5 nm from the crystal surface to bulk. Taking into account both the enrichment of the surface with La and Bi, and the preference of La a+ for a 12-fold coordination, a model is proposed for the formation of such defects. They correspond to the growth of A-site cation-deficient perovskite compounds, (Bi,La) 3.33 Bi 2 Ti 2 O 12 and (Bi,La) 3.66 Bi 3 TiO 12 . |
| Databáze: | OpenAIRE |
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