| Abstract
| - After being heated in a flow of 5% O2/He, at 1073 or 1123 K for 30 min, a Ce0.62Zr0.38O2 sample showing an ordered cationic sublattice had very subtle surface nanostructural changes induced on it. In parallel with them, a significant loss of low-temperature (T ≤ 773 K) oxygen storage capacity (OSC), with no modification of its high-temperature (T ≥ 973 K) redox response, was observed. These nanostructural and chemical features characterize the very first stage of the process leading to the destruction of the ordered Ce−Zr sublattice, a structural phenomenon playing a key role in the control of redox behavior of ceria−zirconia mixed oxides. The reported results, including OSC, hydrogen chemisorption, and nanostructural and nanoanalytical data, lend further support to a model providing a comprehensive interpretation of the complex relationship linking thermal aging conditions, nanostructural properties, surface chemistry, and redox behavior in these materials.
- The application of a short oxidizing pretreatment, at either 1073 or 1123 K, to a Ce0.62Zr0.38O2 sample with an ordered cationic sublattice caused a significant loss of its low-temperature (T ≤ 773 K) oxygen storage capacity, without altering its high-temperature (T ≥ 973 K) redox behavior. This chemical effect is shown to be due to surface nanostructural changes occurring at the very first stage of the order−disorder process, leading to the destruction of the pyrochlore-related structure exhibited by the starting oxide.
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