AINAMORI Frontier Research Center, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan bCREST, Japan Science and Technology Agency, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan cInstitute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan dThe Ultramicroscopy Research Center, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan eInternational Institute for Carbon-Neutral Energy Research, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan As a conventional anode for solid oxide fuel cell, Ni/YSZ has been deeply investigated in many aspects. However, little is known on the atomic structure of the Ni/YSZ interface, which is quite important for the reaction activity and stability. Herein, a conventional cell was prepared by mixing/sintering/reduction process. The crystallographic orientation relationships and contact surfaces between Ni and YSZ were investigated by transmission electron microscopy (TEM), and scanning TEM. The TEM specimens were prepared by focused ion beam-scanning electron microscopy. It was found that the Ni/YSZ orientation relationships are much more complicated than those samples prepared by directionally solidified eutectics and deposition methods. Higher-index and step contact surfaces were observed or estimated, such as Ni(15 13 1)/YSZ(4 4 10). This interface structure was analyzed with the help of atomistic models. The misfits were found to be small in both x and y directions. Further geometric analysis by near coincidence site lattice theory indicates that this interface is relatively stable. It is supposed that various Ni/YSZ interfaces exist in a conventional cell and stay in different energy states. The unstable and metastable interfaces should be considered when we discuss the long term stability of cell during the operation.
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