Oxygen absorption behavior of Ce2Zr2O7+x and formation of Ce2Zr2O7.5

Abstract

Oxygen absorption behavior of Ce2Zr2O7+x (0≦x≦1) with an ordered arrangement of Ce and Zr ions was studied by X-ray powder diffraction, electron diffraction and thermogravimetric analysis. It is revealed that the oxygen absorption of Ce2Zr2O7 during heating in oxygen proceeds mainly through two reactions: (1) reaction from Ce2Zr2O7 to Ce2Zr2O7.5 around 400 K and (2) reaction from Ce2Zr2O7.5 to Ce2Zr2O8 around 600 K. This behavior suggests the presence of the intermediate phase of the composition, Ce2Zr2O7.5. The intermediate phase, Ce2Zr2O7.5, was found to give extract reflections compared with Ce2Zr2O7, and to belong to space group F4̄3m. This intermediate phase was obtained by oxidation of Ce2Zr2O7 at room temperature for about 1 year, or heating at 473 K or lower temperature in oxygen.