Effect of Fe2O3 and MgO on Gelcasting and Sinterability of Alumina Ceramics.

The sinterability of gelcast Fe₂O₃-doped and MgO-doped alumina ceramics containing 55 vol.-% solid loading was studied at different temperatures and compared with gelcasted sintered pure alumina. Physical properties (bulk density and apparent porosity), phase composition, microstructure and mechanical properties (microhardness and toughness) of the sintered bodies were investigated. The results revealed that the sintered doped bodies exhibited dense and compact microstructure as compared with pure alumina bodies. The hardness of Fe₂O₃-doped bodies showed the lowest values among the others due to the lower elastic modulus of the secondary phases formed and due to the enhanced grain growth after addition of a higher amount of Fe₂O₃. On the contrary, the addition of a small amount of MgO reduced the grain growth which enhanced hardness. Fracture toughness results showed a great increase in Fe₂O₃ doped ceramics due to the presence of large grains, while in MgO-doped ceramics, the facture toughness increase was related to a residual decrease in porosity. [ABSTRACT FROM AUTHOR]