Anomalous lattice parameter increase in alkali earth aluminium substituted tungsten defect pyrochlores
- Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234 (Australia)
- School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia)
- Bragg Institute, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234 (Australia)
The structures of the defect pyrochlores AAl{sub 0.33}W{sub 1.67}O{sub 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 {sup 27}Al MAS NMR studies of this pyrochlore system reveal shifts in the {delta}{approx}21-22 ppm range that are indicative of pseudo-5 coordinate Al environments and emanate from distorted Al octahedral with one abnormally long Al-O bond. Solid state {sup 39}K, {sup 85}Rb, {sup 87}Rb and {sup 133}Cs MAS and static NMR studies reflect the local cation disorder demonstrated in the structural studies. - Graphical abstract: Diagram showing general disorder of K cations in KAl{sub 0.33}W{sub 1.67}O{sub 6}.
- OSTI ID:
- 21212214
- Journal Information:
- Journal of Solid State Chemistry, Vol. 182, Issue 3; Other Information: DOI: 10.1016/j.jssc.2008.11.014; PII: S0022-4596(08)00575-6; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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