Mass diffusion phenomena in cerium oxide

Abstract Mass diffusion in the solid state is the way materials are structured from the atomic level to the macroscale, controlling the evolution of composition and microstructure, thus governing final properties and functionalities. In ceria and its solid solutions, solid-state diffusion controls grain size, boundary composition, surface, and interfaces, accordingly influencing sintering characteristics; densification/porosity; and, eventually, final properties, such as surface chemical reactivity, electrical conductivity, and mechanical performances. In this chapter, we elucidate the importance of mass diffusion phenomena in ceria compounds by approaching fundamental concepts of existing theoretical models and reporting experimental evidence and novel findings. Particularly, we describe current models explaining how cations, oxygen, and defect interplay in mass diffusion phenomena and how dopants and other phases, including reactive gases, other solid, and porosity, can influence mass migration at high temperatures. For the experimental part, we report some relevant cases concerning self-diffusion, e.g., in sintering, particle coarsening, and doping, as well as interdiffusion between ceria and other functional oxides such as zirconia and alumina.