Pyrochlore hydroxyfluorides

Influence on the Morphology The synthesis of the pyrochlore hydroxyfluoride using nitrate as precursor leads to the preparation of very well crystallized compounds with the drawback of a very low specific surface area (6m. g ). By replacing nitrate by... 

Figure 2.4 Dependence of the X-ray diffraction powder pattern of the pyrochlore hydroxyfluoride on the nature of the aluminium precursor. For each X-ray diagram, the precursor and the specific surface area is noted...

Our knowledge of the structures of hydroxyhalides is practically confined to hydroxychlorides and hydroxybromides, little being known of the structures of hydroxyfluorides or hydroxyiodides. Anhydrous hydroxyfluorides include Cd(OH)F, Zn(OH)F and other less well-defined phases. In(OH)F2 has a distorted Re03 type of structure, in which In is surrounded octahedrally by 2 OH + 4 F (all at about 2 07 Hydrated oxyfluorides of A1 with the pyrochlore structure ... 

D. Damboumet, A. Demourgues, C. Martineau, E. Durand, J. Majimel, A. Vimont, H. Leclerc, J.-C. Lavalley, M. Daturi, C. Legein, J. Y. Buzare, F. Fayon and A. Tressaud, Stmctural investigation and acidic properties of high surface area pyrochlore aluminium hydroxyfluoride, J. Mater. Chem.18, 2483-2492 (2008). 

Another way to increase resolution while avoiding an excessively long experimental time is to constmct a two-dimensional one pulse (TOP) spectrum [21-23] from a conventional ID MAS spectrum. The TOP spectmm evidences the well-known narrowing of the inner satellite transition line width when the components are not well resolved on the N = 0 cross-section, the projection over the satelhte transitions (N 0) shows a much better resolution as shown in HS pyrochlore aluminium hydroxyfluoride [20] (Figure 5.6), nanostructured Al-based fluoride-oxide materials [24] and aluminium fluoride hydrate with cationic vacancies [25]. 

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