The generation of mesostructured crystalline CeO2, ZrO2 and CeO2-ZrO2 films using evaporation-induced self-assembly

Mesostructured thin films of CeO2, ZrO(2)and CeO2-ZrO2 mixed oxides with highly crystalline pore walls and ordered arrays of mesopores were obtained by a straightforward fabrication process employing evaporation-induced self-assembly (EISA) and a well-designed temperature treatment, taking advantage of a novel type of amphiphilic block copolymer as template. The mesostructure and crystallinity were studied in detail using small-angle and wide-angle X-ray scattering and electron microscopy. The mesostructured CeO2 films are crack-free, possess a final pore size of ca. 10 nm, and the mesopores are surrounded by an almost completely crystalline matrix of nanoparticles of ca. 5-7 nm in size, as revealed by high-resolution electron microscopy. Additionally, the mesoscopic order (bcc structure) shows high thermal stability. The crystallization of the walls is usually accompanied by stresses and strong uniaxial structural shrinkage, which can, however, be significantly diminished by making mixed CeO2-ZrO2 mesostructured systems. Here, the crystallites represent "solid solutions'' of both binary oxides and exhibit an even higher thermal stability, while the constituting nanocrystals are smaller compared to the pure CeO2.