Effects of La2O3 addition on the microstructure development and physical properties of harder ZTA-CeO2 composites with sustainable high fracture toughness

Abstract The influence of La2O3 inclusion (0 – 3 wt%) on the microstructure, phase formation and mechanical properties of Zirconia Toughed Alumina (ZTA) added with 5.0 wt% CeO2 was investigated. ZTA CeO2 composites were sintered at1600 °C for 4 h. The microstructure, phase formation, density, fracture toughness and hardness properties were characterised through FESEM, Microscopy Image Analysis Software and XRD diffractometer, Archimedes principle and Vickers indentation technique, respectively. The XRD, image processing and FESEM revealed the existence of LaAl11O18. The addition of La2O3 incited the sintering, microstructure refinement, densification of ZTA-CeO2 matrix and phase transformation. Hence, the hardness of ZTA-CeO2 ceramics was increased rapidly based on refinement of Al2O3 grains, densification of ZTA-CeO2 composites and porosity reduction. It was observed that the fracture toughness was enhanced through in situ formation of elongated LaAl11O18 grains. The addition of 0.7 wt% La2O3 culminated in the achievement of the optimum findings for density (4.41 g/cm3), porosity (0.46 %), hardness (1792 HV) and fracture toughness (8.8 MPa·m1/2). Nevertheless, excess La2O3 was proven to be detrimental as it displayed poor mechanical properties due to the poor compactness of numerous LaAl11O18 grains, coarsening of Al2O3 grains and decline in density.