Oxygen exchange properties in the new pyrochlore solid solution Ce2Sn2O7-Ce2Sn2O8

The phase-pure cerium stannate pyrochlore (Ce2Sn2O7) has been prepared for the first rime. The structure and oxidation states of both cations were car efully reviewed, and the compound was unambiguously replaced within the rar e-earth stannate series. As a consequence of the low stability of trivalent cerium in oxide phases, one oxygen per Formula unit could be intercalated by calcination under O-2 at 400 degrees C, leading to the new Ce2S2O8 pyroc hlore. This latter phase is subject to oxygen under-stoichiometry from 400 to 700 degrees C. However, oxygen deintercalation seems to be in competitio n with cerium oxide segregation at high temperature, leading to the formati on of cerium deficient pyrochlore phases. (C) Academie des sciences/Elsevie r, Paris.