Anomalous lattice parameter increase in alkali earth aluminium substituted tungsten defect pyrochlores

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Date
2009-03
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
The structures of the defect pyrochlores AAl(0.33)W(1.67)O(6) where A = K, Rb or Cs have been investigated using X-ray and neutron powder diffraction methods as well as the ab initio modelling program VASP The three cubic pyrochlores exhibit a non-linear increase in lattice parameter with respect to ionic radius of the A cation as a consequence of displacive disorder of the A-type cations. Solid state Al-27 MAS NMR studies of this pyrochlore system reveal shifts in the delta-21-22 ppm range that are indicative of pseudo-5 coordinate Al environments and emanate frorn distorted Al octahedral with one abnormally long Al. O bond. Solid state K-39, Rb-85, Rb-87 and Cs-133 MAS and static NMR Studies reflect the local cation disorder demonstrated in the structural Studies. © 2008, Elsevier Ltd.
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Keywords
Lattice parameters, Alkaline earth metal compounds, Pyrochlore, Tungsten, Neutron diffraction, Diffuse scattering
Citation
Thorogood, G. J., Kennedy, B. J., Peterson, V. K., Elcombe, M. M., Kearley, G. J., Hanna, J. V., & Luca, V. (2009). Anomalous lattice parameter increase in alkali earth aluminium substituted tungsten defect pyrochlores. Journal of Solid State Chemistry, 182(3), 457-464. doi:10.1016/j.jssc.2008.11.014
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