Preparation of ceria–zirconia and yttria–zirconia mixed oxides of unusual pore structures

Highly ordered particulate assemblies of mixed CeO2–ZrO2 and Y2O3–ZrO2 materials have been prepared using a gel-synthesis method. The majority of the particles observed have very regular shapes consisting of sandwiches of parallel pores perpendicular to layers of denser layers. These appear to form from polymeric units of hydrolysed zirconium precursors which facilitate directional growth of the macroscopic moieties. Detailed adsorption experiments and electron microscopy show that two types of pore systems exist in these materials with sizes below 10 nm together with larger more macroscopic pores of the order of 100 nm. The preparation is sensitive to the conditions used in synthesis.