Textural and phase stability of CexZr1-xO2 mixed oxides under high temperature oxidising conditions

The textural and structural changes in several Ce-Zr mixed oxides were studied. Changes in the crystal size and specific surface area upon calcination were followed at 1223 K over time. Different gas compositions (O-2, CO2 and H2O) were employed during calcination in order to better understand the sintering process in the CexZr1-xO2 system. From S-BET and mean crystal size (D) curves, we have tried to obtain the kinetic parameters. In order to do that, all curves were fitted using a mathematical expression which allows the derivative and then the kinetic rates for S-BET decrease and D increase with calcination time to be obtained. It was also possible to correlate these rates with the Ce content of the mixed oxide, and to obtain information about the influence of composition on the sintering process at the surface and the crystalline structure of the mixed oxides. Complementary HREM/TEM data are also presented. With the help of this technique, it has been possible to elucidate the morphological and crystallographic changes in the crystallites upon calcination of the samples under oxidising atmospheres. (C) 1999 Elsevier Science B.V. All rights reserved.