Microstructure and mechanical properties of Y2O3-doped melt-grown Al2O3-ZrO2 eutectic ceramic

The microstructure and mechanical properties of the melt-grown Al2O3/ZrO2 eutectic bulks containing 0-12 mol% Y2O3 (with respect to zirconia) prepared at the low G/v ratio (thermal gradient G divided by growth rate v) were investigated. As Y2O3 content increases, except for the cellular to dendritic transition for the colony morphology, the average interphase spacing λ in the colony decreases to a minimum (≈1.1 µm) at the 3 mol% Y2O3, and then increases slightly. It appears likely that with the Y2O3 content increasing the transport mechanism for dominating the crystal growth changed from heat conduction to chemical diffusion, which corresponds to the LGK (Lipton, Glicksman, and Kurz) model. The highest hardness (close to 18 GPa) was also found at the 3 mol% Y2O3. However, the fracture toughness, KIC, estimated from the indentation method decreased with the increase of Y2O3 content.