Effects of MgO addition on the phase, mechanical properties, and microstructure of zirconia-toughened alumina added with CeO_2 (ZTA-CeO_2) ceramic composite

摘要

The effects of MgO addition on properties such as density, firing shrinkage, microstructure, Vickers hardness, and fracture toughness of ZTA-CeO_2 ceramics composites were investigated. The amount of CeO_2 used in the experiment was fixed at 5.0 wt% while the MgO addition was varied from 0 wt% to 2.0 wt%. Each composition was weighed, mixed, and pressed using hydraulic press under 300 MPa into 13 mm pellets. The pellets were sintered at 1600 ℃ for 4 h under pressureless condition. Vickers hardness and fracture toughness of the sintered samples were measured using the Vickers indentation method. Based on the SEM microstructures, elongated secondary phase, i.e. MgAl_(11)CeO_(19), started to occur at 0.5 wt% MgO. This elongated phase was responsible for the increase in fracture toughness of the ceramic composites. Similarly, the addition of more than 0.5 wt% MgO produced another secondary phase (MgAl_2O_4), as detected by XRD. This phase was shown to have low intrinsic fracture toughness. Therefore, the sample with 0.5 wt% MgO showed the optimum properties with the highest fracture toughness (9.14 MPa m~(1/2)) and Vickers hardness (1591 HV) values.