Research on the performance of nickel ferrite ceramics is significant for the practical application. This study prepared Ni_1-xNb_xFe₂O₄ ceramics (x = 0, 0.02, 0.05, 0.07, 0.10, 0.20) via a solid state reaction, and analyzed how Nb doping affected phase compositions, grain sizes, relative densities as well as DC conductivities was investigated. The results showed that the Ni_1-xNb_xFe₂O₄ ceramics contained both NiFe₂O₄ and NiO phases when the Nb doping amount x was less than 0.20. The grain sizes of the Ni_1-xNb_xFe₂O₄ ceramics slowly elevated as the Nb doping amount elevated. The mean grain size of around 50 μm was obtained at the doping amount x of 0.20, 2.5 times higher than that of undoped NiFe₂O₄ ceramics. The relative densities and DC conductivities of the Ni_1-xNb_xFe₂O₄ ceramics first increased and then decreased gradually with the increase of Nb doping amount. When the Nb doping amount x was 0.05, the relative densities and DC conductivities reached the maximum, which were 99.35% and 36.37 S/cm (960 ℃), respectively. The factors affecting the microstructure and DC electrical conductivities of the Ni_1-xNb_xFe₂O₄ ceramics were also discussed in detail.

Keywords: Microstructure, Electrical conductivity, Nickel ferrite, Ceramics.