title: Phase segregation in cerium-lanthanum solid solutions.
abstract: Electron energy-loss spectroscopy (EELS) in combination with scanning transmission electron microscopy (STEM) reveals that the La enrichment at the surface of cerium-lanthanum solid solutions is an averaged effect and that segregation occurs in a mixed oxide phase. This separation occurs within a crystalline particle, where the dopant-rich phase is located at the surface of the dopant-deficient phase. The limiting structure appears to be a solid solution with a La fraction of x = 0.6 in the bulk and x = 0.75 at the surface. Up to a La fraction of 0.6, this phase will coexist with a lanthanum-type structure in different proportions depending on the dopant amount. STEM-EELS appears to be a powerful technique to clarify the existence of a multiphase system, and it shows that XRF, XPS, and XRD measure averaged results and do not show the phase complexity of the solids.
authors.affiliation: Inorganic Chemistry and Catalysis, Department of Chemistry, Utrecht University, The Netherlands.
authors.forename: V
authors.initials: V
authors.lastname: Bellière
authors.forename: G
authors.initials: G
authors.lastname: Joorst
authors.forename: O
authors.initials: O
authors.lastname: Stephan
authors.forename: F M F
authors.initials: FM
authors.lastname: de Groot
authors.forename: B M
authors.initials: BM
authors.lastname: Weckhuysen