Interface Energies of Nanocrystalline Doped Ceria: Effects of Manganese Segregation

The thermodynamics of nanoparticles is strongly dependent on their surface energy as it accounts for a large fraction of the total atomic volume. Grain boundary energies are equally important as the formation of this solid solid interface is inevitable during synthesis, processing, and application via agglomeration or sintering. The objective of this work is to apply microcalorimetric techniques and atomistic modeling to understand the role of manganese as a dopant and its impact on the interface energies of ceria nanopartides. Based on the collection of microcalorimetric data, manganese decreases both grain boundary and surface energies with a particularly remarkable effect on the grain boundary energy (0.87 J m(-2) for CeO2 and 0.30 J m(-2) for 10 mol % Mn). This was attributed to segregation of Mn to both grain boundaries and surfaces, as evidenced by electron microscopy and atomistic modeling examining the segregation of Mn to the (111) surface and to grain boundaries (GB) in CeO2. Noteworthy, the segregation was generally greater to grain boundaries than to surfaces, consistently with the larger energy decrease, which suggest that doped nanopartides have stronger driving force for aggregation.