Effect of liquid-forming additives on the microstructure of particulate reinforced Al2O3 ceramics

The effect of liquid-forming additives (CaO + SiO2) on the microstructure of particulate reinforced Al2O3 ceramics, e.g., Al2O3-5 vol%ZrO2 and Al2O3-5 vol%SiC, was investigated. When the liquid phase was not formed during sintering (CaO + SiO2 less than or equal to 0.05 mol%), the shape of Al2O3 grains was equi-axed. As the content of additives increased and these additives reacted with Al2O3 to produce the liquid phase along grain boundaries, abnormal grain growth occurred and reinforced particles could not prevent this abnormal growth.