Mechanisms of nanostructural and morphological evolution of CeO2 functional films by chemical solution deposition

Tuning the interfacial area is essential for the optimization of nanostructured CeO2 in a variety of applications. In this work, we investigate the microstructural mechanism of an oxidation-induced transition from a partially oriented, granular and porous nanostructure to a dense epitaxial one in CeO2 films deposited from chemical solutions. Crystallization under reducing atmospheric conditions results in a nanometric granular microstructure with a high fraction of C decorating grain boundaries and interstitial cavities. Annealing in oxidizing conditions removes C impurities and promotes grain growth, resulting in a fully epitaxial film, as well as stabilizing the otherwise energetically prohibitive polar (001) planes. A mechanism that considers an impurity induced grain boundary blocking mechanism and the stabilization of (001) planes via surface oxidation is proposed.