Effects of additives on the densification and microstructural evolution of fine θ-Al2O3 powder

The effects of MgO and NiO dopants on the densification and microstructural evolution of fine θ-Al2O3 powders have been investigated. The additives were added and mixed by solution coating and co-precipitation methods. The solubility diagrams of Al, Mg and Ni in aqueous solution were generated using computer programs DIASTAB for optimizing the mixing process. The results showed that small amount of both MgO and NiO dopants improve the densification and retard the grain growth of Al2O3 compacts during sintering. The average grain size of both Mg- and Ni-doped specimens are around 1.8 μm, and θ-Al2O3 transformed to α-Al2O3 completely during sintering at 1100 °C and higher temperatures.