Lanthanum Pyrochlores and the Effect of Yttrium Addition in the Systems La2-xYxZR2O7 and La2-xYxHf2O7

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DOIResolve DOI: http://doi.org/10.1016/j.jssc.2008.11.008
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TypeArticle
Journal titleJournal of Solid State Chemistry
Volume182
Pages442450; # of pages: 9
Subjectpyrochlore; fluorite; ordered defect fluorite
AbstractThe crystal structures of the compounds La2!xYxZr2O7 and La2!xYxHf2O7 with x ¼ 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 have been studied using neutron powder diffraction and electron microscopy to determine the stability fields of the pyrochlore and fluorite solid solutions. The limits of pyrochlore stability in these solid solutions are found to be close to La0.8Y1.2Zr2O7 and La0.4Y1.6Hf2O7, respectively. In both systems the unit cell parameter is found to vary linearly with Y content across those compositions where the pyrochlore phase is stable, as does the x-coordinate of the oxygen atoms on the 48f (x,38 ,38 ) sites. In both systems, linear extrapolations of the pyrochlore data suggest that the disordering is accompanied by a small decrease in the lattice parameter of approximately 0.4%. After the pyrochlore solid solution limit is reached, a sharp change is observed from x#0.41 to 0.375 as the disordered defect fluorite structure is favoured. Electron diffraction patterns illustrate that some short-range order remains in the disordered defect fluorite phases.
Publication date
LanguageEnglish
AffiliationNRC Canadian Neutron Beam Centre; National Research Council Canada
Peer reviewedYes
NPARC number14806199
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Record identifier5e8d20bc-a127-45c0-9578-5f6d15e45a26
Record created2011-02-15
Record modified2016-05-09
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