A new class of pyrochlore solid solution formed by chemical intercalation of oxygen

Oxygen intercalation into a pyrochlore at room temperature is reported. A simple chemical route was employed. Previously only perovskite or a few closely related phase have demonstrated an ability to act as hosts for such intercalation. The specific system studied was the interstitial solid solution Ce2Zr2O7+x (0 less than or equal to x less than or equal to 0.36). Neutron diffraction reveals that interstitial oxygen enters the tetrahedral 8b sites (space group <Fd(3)over bar m>), which are empty in stoichiometric pyrochlore, but displacement of existing oxygen from the tetrahedral 8a sites also occurs. The lattice contracts on intercalation due to oxidation of Ce3+. The changes in structure and the diffusion pathways for oxygen are discussed.