Universität zu Köln

Luehrs, H., Soellradl, S., King, S. P., Hanna, J. V., Konzett, J., Fischer, R. X. and Schneider, H. (2014). Ambient and high-pressure synthesis, composition, and crystal structure of B-mullites. Cryst. Res. Technol., 49 (1). S. 21 - 32. WEINHEIM: WILEY-V C H VERLAG GMBH. ISSN 1521-4079

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Abstract

The chemical compositions of several B-doped mullite samples were analyzed using prompt gamma activation analyses (PGAA) indicating that 15% of the Si in the crystal structure of mullite can be replaced by B during sol-gel synthesis at ambient pressure and 1200 degrees C without the formation of impurities. Furthermore the PGAA results agree very well with the chemical compositions derived from Rietveld refinements based on neutron diffraction data. High-pressure and high-temperature synthesis yielded a B-mullite with significantly higher B-content than observed before (close to composition Al8Si2B2O19). The results of PGAA, XRD, and neutron diffraction experiments show linear behavior of lattice parameters b and c as well as of the inclination angle. of the AlO6 octahedra in the ab-plane with increasing B-content. The Rietveld refinements support the substitution mechanism known for B-mullites, involving the formation of oxygen vacancies and the replacement of 40% of the tetrahedral Si by BO3 units during the synthesis at 875 degrees C and 10 kbar. However, the refined chemical composition as well as a very low lattice parameter a suggest a second mechanism for the incorporation of B into mullite. This is clearly supported by the B-11 MAS NMR experiment indicating the presence of B in BO4 configuration but BO3 being dominant. Here for the first time a B-mullite crystal structure is presented yielding BO3 and BO4 units in space group Pbam. (c) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Luehrs, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Soellradl, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED King, S. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hanna, J. V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Konzett, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Fischer, R. X. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schneider, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-450173
DOI:	10.1002/crat.201300210
Journal or Publication Title:	Cryst. Res. Technol.
Volume:	49
Number:	1
Page Range:	S. 21 - 32
Date:	2014
Publisher:	WILEY-V C H VERLAG GMBH
Place of Publication:	WEINHEIM
ISSN:	1521-4079
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SOLID-STATE NMR; BORON-MULLITE; BORALSILITE; SPECTRA; PROGRAM; SIO2 Multiple languages Crystallography Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/45017