Effect of Yb₂O₃ doping on the grain boundary of NiFe₂O₄–10NiO-based cermets after sintering

xYb₂O₃–15(20Ni–Cu)/(85 - x)(NiFe₂O₄–10NiO) (x = 0, 0.25, 0.5, 0.75, 1.0, 2.0, and 10.0) cermets for aluminum electrolysis were prepared to investigate the effect of Yb₂O₃ doping on the grain boundary of the cermets after sintering. The results showed that each interface was very clear and that with increasing Yb₂O₃ content, most of the Yb was evenly distributed at the grain boundary. Moreover, according to the phase composition and microstructural analysis by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), and electron probe microanalysis (EPMA), YbFeO₃ was produced along the grain boundary. The YbFeO₃ was concluded to not only have formed from the interaction between the NiFe₂O₄ or Fe₂O₃ component and Yb₂O₃ at the grain boundary of the cermets, but also from the decomposition of NiFe₂O₄ into NiO and Fe₂O₃ and the subsequent reaction of Fe₂O₃ with Yb₂O₃. Thus, the production of YbFeO₃ resulted in a cermet with high relative density, good electrical conductivity, and good corrosion resistance.