Order and disorder in cerium-rich ceria-zirconia solid solutions revealed from reverse Monte Carlo analysis of neutron and x-ray total scattering

A reverse Monte Carlo analysis of neutron and x-ray total scattering data from two ceria-zirconia samples of composition Ce0.75Zr0.25O2 is performed to analyze the distribution of cations and to examine the possibility of oxide-ion disorder. For the first material, heated in air under moderate conditions (800?), the structure is a single-phase solid-solution with the statistical distribution of cations, but a local tetragonal symmetry is found, consistent with the different coordination preferences of Ce and Zr. For the second material, heated under H-2 at 1050? followed by reoxidation at 400 ?, the structure shows a considerable disorder, with evidence for oxygen interstitials (Frenkel-ion defects) and a non-statistical distribution of cations with significantly higher concentrations of like-like cation nearest neighbors, highlighting the existence of cation-rich nano-domains. The results highlight the dynamic nature of this solid-solution, with structural evolution upon thermal treatment, which is of relevance to understanding its stability under redox catalytic conditions in practical applications.

Automated summary

Reverse Monte Carlo analysis was performed on neutron and x-ray total scattering data from two ceria-zirconia samples to analyze the distribution of cations and examine oxide-ion disorder. The first sample heated in air at moderate conditions showed a single-phase solid-solution structure with statistical distribution of cations, but a local tetragonal symmetry was observed. The second sample heated under H-2 followed by reoxidation exhibited considerable disorder and a non-statistical distribution of cations, indicating the presence of cation-rich nano-domains.