Ce_2Zr_2O_7とβ-Ce_2Zr_2O_<7.5>の結晶構造

概要

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The crystal structures of Ce_2Zr_2O_7 and β-Ce_2Zr_2O_<7.5> were precisely determined by the Rietveld refinement of powder X-ray diffraction data. The present refinement revealed that the structure of β-Ce_2Zr_2O_<7.5> was formed by filling a half of oxygen vacancies of Ce_2Zr_2O_7 in the specific ordered manner. The oxygen vacancy site is divided into two equivalent sites, one of which is completely occupied, when the composition becomes Ce_2Zr_2O_<7.5>. The formation of β-Ce_2Zr_2O_<7.5> can be well explained on the basis of the argument that Zr^<4+> ions tend to be 7-fold coordination at low temperatures. The derived local atomic displacements associated with the oxygen absorption/release, particularly those of oxygen at the specific sites, could be a key issue to solve the reason why Ce_2Zr_2O_<7+x> exhibits the excellent property of oxygen release and absorption even at relatively lower temperatures.
社団法人日本セラミックス協会の論文
2004-08-01