AbstractThe ordered structures in different doping levels (x = 0.1, 0.15, 0.2, 0.25, 0.3) of yttrium doped ceria (YDC, Ce_(1−x)Y_xO_2−δ) electrolytes were investigated by electron diffraction, high-resolution transmission electron microscopy (TEM), scanning TEM, and electron energy loss spectroscopy. Oxygen vacancy ordering was experimentally confirmed within the ordered structures. With increasing the doping level, the concentration of trivalent Ce cations was increased in YDC samples and such trivalent Ce cations were supposed to mainly exist in the ordered structures. Based on our electron microscopic observation and microanalysis, a crystal model for the ordered structures is proposed.