Homogeneity of lanthanide doped ceria nanocrystal dispersions using high-resolution transmission electron microscopy

Aqueous sols of crystalline 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 square = anion vacancy] were synthesised using inorganic materials. The nanocrystals were dispersed on an amorphous silica support and individual crystals examined for composition and structure by high-resolution transmission electron microscopy (HREM) and energy dispersive analysis of X-rays (EDX). High-resolution pictures showed the nanocrystals to be mainly between 5 and 10 nm in size, rarely elongated and with atomically clean faceted surfaces. Diffractograms were used to measure the lattice parameters of the face-centre-cubic (fee) fluorite structures giving values, depending on dopant species and concentration of dopant, in the range 5.5-5.8 Angstrom. EDX analysis of individual crystals with the same nominal composition compared closely to each other and to that of an average over a large area indicating good homogeneity from the preparation method