A combination of transmission electron microscopy (TEM) and laser-assisted three-dimensional atom probe (3DAP) is employed to study the nanostructure of Dy-doped CeO2, which is a promising ionic conductor. Segregation of Dy atoms at grain boundaries is observed by electron energy loss spectroscopy (EELS) elemental maps. The segregation is checked and confirmed by laser-assisted 3DAP. Moreover, the enrichment of Dy and deficiency of Ce at grain boundaries are quantitatively identified by the 3DAP
