Densification and microstructure of magnesium aluminate spinel for adding method of Sc2O3

The effect of adding method of Sc2O3 on the densification and microstructure of magnesium aluminate spinel prepared by co-precipitated method was investigated. Sintered products were characterized in terms of densification, phase analysis, quantitative elemental analysis, microstructure and flexural strength. Sintering additives were added in the form of Sc salt and in the form of scandium oxide, respectively. No matter in what way to add, sintering additives exist in the form of Sc2O3. Moreover, incorporating of Sc3+ into the spinel structure increases lattice parameters, which improves the diffusion, mass transfer, and densification. The microstructure of sintered samples with adding Sc salt as a sintering additive is more compact and the grain size distribution is more uniform although their grain size is larger compared with that of sintered samples with adding scandium oxide as a sintering additive. Moreover, the optimum flexural strength (97 MPa) of the sintered products is obtained on sintering at 1650 °C with the addition of Sc salt.