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Crystal structure of synthetic Al4B2O9: A member of the mullite family closely related to boralsilite

Fischer, Reinhard X. and Kahlenberg, Volker and Voll, Dietmar and MacKenzie, Kenneth J. D. and Smith, Mark E. and Schnetger, Bernhard and Brumsack, Hans-Juergen and Schneider, Hartmut (2008) Crystal structure of synthetic Al4B2O9: A member of the mullite family closely related to boralsilite. American Mineralogist, 93 (5-6). pp. 918-927.

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The crystal structure of Al4B2O9, synthesized from Al(NO)(3)center dot 9H(2)O and B(OH)(3) via a sol-gel process, is studied and characterized by Rietveld refinements and grid search analyses combined with (11) B and Al-27 MAS NMR spectroscopy. The aluminum borate with a unit-cell composition of Al32B16O72 is closely related to the boralsilite (Al32B12Si4O74) Structure with Si replaced by B and to mullite (Al4+2xSi2-2xO10-x) It crystallizes in the monoclinic space group C2/m, a = 14.8056(7) angstrom, b = 5.5413(2) angstrom, c = 15.0531(6) angstrom, beta = 90.913(2)degrees, Z = 8 for Al4B2O9. The main structural units are isolated chains of edge-sharing AlO6-octahedra running parallel to b that is a characteristic feature of the mullite-type crystal structures. The octahedral chains are crosslinked by AlO4, AlO5, BO3, and BO4 groups with two B atoms and one O atom (O5') disordered on interstitial positions. Al-27 and B-11 NMR studies confirm the presence of sixfold (octahedral), fivefold, and fourfold (tetrahedral) coordinated Al (sixfold: [fourfold + fivefold] =similar to 50%:50%) and of threefold and fourfold coordinated B (similar to 80%:20%).

Item Type: Journal Article
Journal or Publication Title: American Mineralogist
Uncontrolled Keywords: aluminum borate, boron aluminate, Al4B2O9 boralsilite, crystal structure, Rietveld refinement, MAS NMR spectroscopy
Departments: VC's Office
ID Code: 52844
Deposited By: ep_importer_pure
Deposited On: 29 Feb 2012 09:00
Refereed?: Yes
Published?: Published
Last Modified: 19 Jun 2018 03:10
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