Size-Related Lattice Parameter Changes and Surface Defects in Ceria Nanocrystals

TLDR: In this paper, it was shown that significant, but complex, changes in the lattice parameter with size can occur in 2−500 nm crystallites, and that there is a definitive relationship between defect chemistry and lattice parameters in ceria nanocrystals.

Abstract: Ceria (CeO2) has many important applications, notably in catalysis. Many of its uses rely on generating nanodimensioned particles. Ceria has important redox chemistry where Ce4+ cations can be reversibly reduced to Ce3+ cations and associated anion vacancies. The significantly larger size of Ce3+ (compared with Ce4+) has been shown to result in lattice expansion. Many authors have observed lattice expansion in nanodimensioned crystals (nanocrystals), and these have been attributed to the presence of stabilized Ce3+−anion vacancy combinations in these systems. Experimental results presented here show (i) that significant, but complex, changes in the lattice parameter with size can occur in 2−500 nm crystallites, (ii) that there is a definitive relationship between defect chemistry and the lattice parameter in ceria nanocrystals, and (iii) that the stabilizing mechanism for the Ce3+−anion vacancy defects at the surface of ceria nanocrystals is determined by the size, the surface status, and the analysis con...