Synthesis of Nanocrystalline CeO 2 −ZrO 2 Solid Solutions by a Citrate Complexation Route: A Thermochemical and Structural Study

The synthesis of nanocrystalline solid solutions of general formula Ce x Zr 1− x O 2 ( x = 0.1, 0.25, 0.5, 0.75, and 0.9) using a citrate complexation technique was followed with thermochemical methods, and the resulting powders were characterized using X-ray diffraction (XRD) and electron microscopy (scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM)). Qualitative analysis of XRD data indicated that the samples exhibited either a cubic ( Fm 3 m ) or a tetragonal ( P 4 2 / nmc ) phase, depending on CeO 2 content. Electron diffraction results were consistent with the XRD findings. In HRTEM, the internal crystal structure of the nanoparticles was observed to be highly ordered and primary particle size data were collected. Average crystallite size, obtained from the XRD data, was 4.8−8.3 nm, with the larger values at the compositional extremes. A similar trend was observed in HRTEM, although values were generally slightly higher. The Ce 0.5 Zr 0.5 O 2 solid solution had the smallest crystallites (4.8 nm) and the highest specific surface area (45.8 m 2 ·g −1 ).