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 hos ts for such intercalation. The specific system studied was the interst itial solid solution Ce2Zr2O7+x (0 less than or equal to x less than o r equal to 0.36). Neutron diffraction reveals that interstitial oxygen enters the tetrahedral 8b sites (space group <Fd(3)over bar m>), whic h are empty in stoichiometric pyrochlore, but displacement of existing oxygen from the tetrahedral 8a sites also occurs. The lattice contrac ts on intercalation due to oxidation of Ce3+. The changes in structure and the diffusion pathways for oxygen are discussed.