An Oxygen-Rich Pyrochlore with Fluorite Composition

Oxygen has been intercalated into the pyrochlore Ce2Zr2O7 by heating under oxygen at a moderate temperature. A composition approaching fluorite (Ce2Zr2O7.97) has been obtained while retaining pyrochlore cation ordering. Whereas in flourite all oxide ions are in tetrahedral sites, the oxygen-rich pyrochlore exhibits vacancies in some tetrahedral sites and occupancy of a new trigonal site. The latter arises from oxide ions in octahedral 32e sites within the pyrochlore cation array.