Elucidating structural order and disorder phenomena in mullite-type Al 4 B 2 O 9 by automated electron diffraction tomography
Veröffentlichungsdatum
2017-05
Zusammenfassung
The crystal structure and disorder phenomena of Al4B2O9, an aluminum borate from the mullite-type family, were studied using automated diffraction tomography (ADT), a recently established method for collection and analysis of electron diffraction data. Al4B2O9, prepared by sol-gel approach, crystallizes in the monoclinic space group C2/m. The ab initio structure determination based on three-dimensional electron diffraction data from single ordered crystals reveals that edge-connected AlO6 octahedra expanding along the b axis constitute the backbone. The ordered structure (A) was confirmed by TEM and HAADF-STEM images. Furthermore, disordered crystals with diffuse scattering along the b axis are observed. Analysis of the modulation pattern implies a mean superstructure (AAB) with a threefold b axis, where B corresponds to an A layer shifted by ½a and ½c. Diffraction patterns simulated for the AAB sequence including additional stacking disorder are in good agreement with experimental electron diffraction patterns.
Schlagwörter
Electron diffraction
;
Aluminum borate, chemical synthesis, mullite-type structure, X-ray diffraction, NMR spectroscopy, thermal analysis
;
Crystal structure determination
;
Superstructure
;
Disorder
Institution
Fachbereich
Dokumenttyp
Artikel/Aufsatz
Zeitschrift/Sammelwerk
Startseite
114
Endseite
123
Zweitveröffentlichung
Nein
Sprache
Englisch
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122_Post.pdf
Description
Postprint
Size
1.59 MB
Format
Adobe PDF
Checksum
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