Effect of Yb_2O_3 doping on the grain boundary of NiFe_2O_4–10NiO-based cermets after sintering

xY b2O3–15(20Ni–Cu)/(85- x)(NiF e2O4–10NiO)(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), YbF eO 3 was produced along the grain boundary. The YbF eO 3 was concluded to not only have formed from the interaction between the NiF e2O4 or Fe2O3 component and Yb2O3 at the grain boundary of the cermets, but also from the decomposition of NiF e2O4 into NiO and Fe2O3 and the subsequent reaction of Fe2O3 with Yb2O3. Thus, the production of YbF eO 3 resulted in a cermet with high relative density, good electrical conductivity, and good corrosion resistance.