Crystal-chemistry of mullite-type aluminoborates Al{sub 18}B{sub 4}O{sub 33} and Al{sub 5}BO{sub 9}: A stoichiometry puzzle

Journal Article · Sat Jan 15 00:00:00 EST 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2010.10.032· OSTI ID:21494176

Fisch, Martin ^[1]; Armbruster, Thomas ^[1]; Rentsch, Daniel ^[2]; Libowitzky, Eugen ^[3]; Pettke, Thomas ^[4]

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1. Mineralogical Crystallography, Institute of Geological Sciences, University of Bern, Freiestrasse 3, CH-3012 Bern (Switzerland)
2. EMPA, Swiss Federal Laboratories for Materials Science and Research, Laboratory for Functional Polymers, Uberlandstrasse 129, CH-8600 Duebendorf (Switzerland)
3. Institut fuer Mineralogie und Kristallographie, Universitaet Wien - Geozentrum, Althanstrasse 14, A-1090 Wien (Austria)
4. Rock-Water Interaction Group, Institute of Geological Sciences, University of Bern, Baltzerstrasse 1-3, CH-3012 Bern (Switzerland)

Orthorhombic Al{sub 2}O{sub 3}-rich aluminoborate is an important ceramic material for which two slightly different compositions have been assumed: Al{sub 5}BO{sub 9} (5Al{sub 2}O{sub 3}:B{sub 2}O{sub 3}) and Al{sub 18}B{sub 4}O{sub 33} (9Al{sub 2}O{sub 3}:2B{sub 2}O{sub 3}). The formula Al{sub 18}B{sub 4}O{sub 33} (=Al{sub 4.91}B{sub 1.09}O{sub 9}) was derived from results of chemical analyses when crystal structure data were not yet available. Subsequent structural investigations indicated Al{sub 5}BO{sub 9} composition. Nevertheless, Al{sub 18}B{sub 4}O{sub 33} was still accepted as the correct stoichiometry assuming that additional B replaces 9% Al. Powder samples of both compositions and ones with excess boron were prepared by solid state reactions between {alpha}-Al{sub 2}O{sub 3} and B{sub 2}O{sub 3}/H{sub 3}BO{sub 3} at temperatures above 1100 {sup o}C and single-crystals were grown from flux at 1100 and 1550 {sup o}C. Products were investigated by single-crystal and powder XRD, {sup 11}B and {sup 27}Al solid-state MAS-NMR, Raman and FTIR spectroscopy as well as Laser-ablation ICP-MS. No indication of the predicted 9% B{yields}Al substitution was found. LA ICP-MS indicated 12.36(27) wt% B{sub 2}O{sub 3} corresponding to Al{sub 4.97}B{sub 1.03}O{sub 9}. Hence, the suggested Al{sub 18}B{sub 4}O{sub 33} stoichiometry can be excluded for all synthesized samples. A very low amount of Al vacancies at a five-fold coordinated site are likely, charge balanced by an additional nearby three-fold coordinated B site. All evidences indicate that the title compound should be reported as Al{sub 5-x}B{sub 1+x}O{sub 9} with x<0.038(6), which is close to Al{sub 5}BO{sub 9}. -- Graphical abstract: A chemical composition of Al{sub 18}B{sub 4}O{sub 33}=Al{sub 4.91}B{sub 1.09}O{sub 9}=9Al{sub 2}O{sub 3}:2B{sub 2}O{sub 3} has been assumed for mullite-type aluminoborate with Al{sub 5}BO{sub 9} structure. However, samples prepared by different routes showed compositions close to 5Al{sub 2}O{sub 3}:B{sub 2}O{sub 3}. Display Omitted

• OSTI ID: 21494176
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 1; Other Information: DOI: 10.1016/j.jssc.2010.10.032; PII: S0022-4596(10)00489-5; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABLATION
ALUMINIUM OXIDES
BORATES
BORIC ACID
BORON OXIDES
CERAMICS
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
ICP MASS SPECTROSCOPY
INFRARED SPECTRA
MONOCRYSTALS
MULLITE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
ORTHORHOMBIC LATTICES
STOICHIOMETRY
TEMPERATURE RANGE 1000-4000 K
VACANCIES
X-RAY DIFFRACTION
ALUMINIUM COMPOUNDS
BORON COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL DEFECTS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DIFFRACTION
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INORGANIC COMPOUNDS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MAGNETIC RESONANCE
MASS SPECTROSCOPY
MATERIALS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
POINT DEFECTS
RESONANCE
SCATTERING
SPECTRA
SPECTROSCOPY
TEMPERATURE RANGE