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Phase segregation in cerium-lanthanum solid solutions

By V. Belliere, G Joorst, O Stephan, FMF de Groot and BM Weckhuysen

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

Topics: RARE-EARTH-OXIDES, X-RAY, SURFACE SEGREGATION, CATALYTIC ACTIVITY, METHANE, OXIDATION, SPECTROSCOPY, COMBUSTION
Year: 2006
OAI identifier: oai:dspace.library.uu.nl:1874/20157
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