Barium hexaaluminoferrites with new structural features
| Autor: | A. Kahn-Harari, J. Thery, V. Delacarte |
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| Rok vydání: | 1993 |
| Předmět: |
Structural type
Chemistry Stereochemistry Mechanical Engineering chemistry.chemical_element Barium Structure type Barium hexaferrite Composition (combinatorics) Condensed Matter Physics Crystallography Mechanics of Materials Inflection point Group (periodic table) General Materials Science Powder diffraction |
| Zdroj: | Materials Research Bulletin. 28:435-443 |
| ISSN: | 0025-5408 |
| Popis: | Barium hexaferrite and hexaaluminate are of hexagonal symmetry (P63mmc) with a structure respectively of magnetoplumbite (MP) and s-alumina (s) type. The BaAlxFe12−xO19 phases (BAF) have been synthesized by solid state reactions at high temperatures (1350°C – 1500°C). The X-ray powder diffraction patterns are close to those of a MP or s structure type but for 4 < x < 8 they also exhibit some extralines. These new lines can be interpreted as 001, 1 = 2n+1 which are “forbidden” reflexions in the P63/mmc space group. Their intensities are particularly strong for BaAl6Fe6O19 (x = 6) and decrease apart from this composition. The a unit cell constant shows a linear decrease with increasing x, whereas the c vs. x curve presents a marked inflection point for intermediate x values. The c/a ratios show that for x ≤ 4 the structure should be of MP-type while compounds with x ≥ 9 would adopt the s structure. For the intermediate compositions, corresponding to the appearance of the extra lines, a new structural type appears. Models are proposed to describe these new phases. |
| Databáze: | OpenAIRE |
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