Preparation and homogeneity of lanthanide-doped ceria nanocrystal dispersions

Aqueous sols of solid solutions of the general formula Ce(1-x)Ln(x)O(2-x/2) square(x/2) (Ln = entire lanthanide range, x = 0-0.50 and = anion vacancy) were synthesized using inorganic materials. The sols contained single-phase nanocrystals with particle sizes between 7-20 nm from photon correlation s pectroscopy and crystallite sizes around 5 nm from X-ray diffraction. The n anocrystals were dispersed on an amorphous silica support and individual cr ystals examined for composition and structure by high-resolution TEM/EDAX. High-resolution pictures showed the nanocrystals to be between 4-6 nm in si ze, in agreement with X-ray diffraction results. Conical dark field and bri ght field pictures of the same area highlighted nanocrystals to be analyzed and microdiffraction of these crystals showed spot patterns of various ind ividual planes of the fee fluorite lattice giving lattice parameters, depen ding on dopant, between 5.6-5.9 Angstrom. EDAX analysis of individual cryst als compared closely to each other, to that of an average over a large area and to that of the nominal composition.