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Ambient and high-pressure synthesis, composition, and crystal structure of B-mullites
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Lührs, H., Soellradl, S., King, Scott P., Hanna, John V., Konzett, J., Fischer, R.X. and Schneider, H. (2014) Ambient and high-pressure synthesis, composition, and crystal structure of B-mullites. Crystal Research and Technology, Volume 49 (Number 1). pp. 21-31. doi:10.1002/crat.201300210 ISSN 0232-1300.
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Official URL: http://dx.doi.org/10.1002/crat.201300210
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°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 ω 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°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 11B 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.
Item Type: | Journal Article | ||||||||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||
Journal or Publication Title: | Crystal Research and Technology | ||||||||||
Publisher: | Wiley-Blackwell Publishing Ltd. | ||||||||||
ISSN: | 0232-1300 | ||||||||||
Official Date: | 25 January 2014 | ||||||||||
Dates: |
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Volume: | Volume 49 | ||||||||||
Number: | Number 1 | ||||||||||
Page Range: | pp. 21-31 | ||||||||||
DOI: | 10.1002/crat.201300210 | ||||||||||
Status: | Peer Reviewed | ||||||||||
Publication Status: | Published | ||||||||||
Access rights to Published version: | Restricted or Subscription Access |
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