期刊
JOURNAL OF SOLID STATE CHEMISTRY
卷 182, 期 3, 页码 442-450出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jssc.2008.11.008
关键词
Pyrochlore; Fluorite; Ordered defect fluorite
资金
- Natural Environment Research Council [NE/C004035/1] Funding Source: researchfish
- NERC [NE/C004035/1] Funding Source: UKRI
The crystal structures of the compounds La2-xYxZr2O7 and La2-xYxHf2O7 With x = 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 La(0.8)y(1.2)Zr(2)O(7) 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 48 integral (X, 3/8, 3/8) 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 similar to 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. (C) 2008 Elsevier Inc. All rights reserved.
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