Effect of agglomeration on mechanical properties of porous zirconia fabricated by partial sintering

Porous ZrO2 ceramics were fabricated by compacting a fine ZrO2 powder, followed by pressureless sintering. Two unidirectional pressures of 30 and 75 MPa were used to prepare the green compacts. The strength and the fracture toughness of porous ZrO2 specimens sintered from the compacts prepared by 75 MPa were substantially higher than those by 30 MPa, especially for the specimens with low porosity. However, the corresponding Young's moduli were identical. This caused the strain to failure of these porous bodies to increase significantly with increasing compaction pressure. Microstructural analyses showed that a number of voids and small flaws existed in the green compacts prepared by the lower pressure, due to the agglomeration of fine ZrO2 grains. It was revealed that the ZrO2 agglomeration resulted in a localized nonuniform shrinkage and degraded the mechanical properties of porous ZrO2 ceramics.