Abstract: In this paper, magnesium aluminate spinel (MgAl₂O₄) materials were prepared by traditional solid-phase sintering method with high purity fused magnesia and calcined active aluminum powder as raw materials, and NiO as additive. The MgO and Al₂O₃ powders were mixed in a theoretical molar ratio of 1∶1, and NiO with mass fraction of 0%, 0.5%, 1.0%, 1.5%, and 2.0% NiO were introduced into the system, respectively. The effects of NiO addition on sintering properties, phase composition and microstructure of MgAl₂O₄ were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the introduction of appropriate amount of NiO can significantly promote the formation of MgAl₂O₄ phase and grain growth. At 1 600 ℃, when the NiO content is lower than 1.5%, NiO can completely dissolve into MgAl₂O₄ crystal lattice and preferentially replace Al³⁺, which improves the defect concentration in MgAl₂O₄ crystal and activates the lattice, thus promoting the sintering of MgAl₂O₄. When the NiO content is higher than 1.5%, more second phase NiO appears in the MgAl₂O₄, which hinders the mass migration and transmission, and it is not conducive to the improvement of sintering performance of MgAl₂O₄.

Key words: magnesium aluminate spinel, NiO, reaction sintering, microstructure, sintering additive, bulk density