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 (Ce2Zr 2O7.97) has been obtained while retaining pyrochlore cation ordering. Where as in flourite all oxide ions are in tetrahedral sites, the oxygen-rich pyr ochlore exhibits vacancies in some tetrahedral sites and occupancy of a new trigonal site. The latter arises from oxide ions in octahedral 32e sites w ithin the pyrochlore cation array. (C) 1999 Academic Press.