Cerium Reduction at the Interface between Ceria and Yttria-stabilised Zirconia and Implications for Interfacial Oxygen Non-stoichiometry

CeO2 and Y2O3-stabilized zirconia (YSZ) are two typical candidates for electrolyte materials in solid oxide fuel cells attributed to their high ion conductivities. However, the conductivities of these materials are closely connected with high temperatures. Therefore, it is important to develop electrolyte materials which can conduct oxygen ions at lower temperatures. Recent experiments have shown that hetero-structures consisting of alternating layers of Gd-doped CeO2 and YSZ exhibit higher ionic conductivity compared to either of the bulk materials [1]. However, the mechanism for the high ionic conductivity of these hetero-structures is still unclear. Theoretical calculations indicate that the oxygen vacancy formation energy is considerably reduced at the interfaces and oxygen vacancies expected to segregate to the interfaces might provide highways for rapid ion conduction [2]. The aim of our work is to obtain insights into the structure and chemistry of interfaces between CeO2 and YSZ by scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS).