The fluorite-pyrochlore transformation of Ho2-yNdyZr2O7
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Twelve members of the Ho2-yNdyZr2O7 series, prepared using conventional solid state methods, have been characterised by neutron powder diffraction. Ho2Zr2O7 has a defect fluorite structure whereas Nd2Zr2O7 is found to adopt the ordered pyrochlore structure with the composition induced fluorite-pyrochlore transformation occurring near y=1. Rietveld analysis on the neutron data for all the compositions reveals an increase in lattice parameter as a function of y across the entire series, with a small discontinuity associated with the transformation. The neutron profile results suggest that domains of pyrochlore-type initially begin to form before crystallising into a separate phase, and therefore that anion and cation ordering processes are distinct. There is a strong correlation between the extent of disorder in the anion sublattice and the x-parameter of 48f oxygen. These results point the way to a better understanding of the stability observed in pyrochlore structures.(C) 2011 Elsevier Inc.
Neutron diffraction, Fluorite, Transformations, Defects, Pyrochlore, Synchrotrons
Clements, R., Hester, J.R., Kennedy, B.J., Ling, C.D., Stampfl, A.P.J. (2011), The fluorite-pyrochlore transformation of Ho2-yNdyZr2O7, Journal of Solid State Chemistry, 84(8), 2108-2113. doi:10.1016/j.jssc.2011.05.054