Effects of La2O3 addition on 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 at 1600 °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 reveal the existence of LaAl11O18. The addition of La2O3 incites the sintering, microstructure refinement, densification of ZTA-CeO2 matrix and phase transformation. Hence, the hardness of ZTA-CeO2 ceramics is increased rapidly based on refinement of Al2O3 grains, densification of ZTA-CeO2 composites and porosity reduction. It is observed that the fracture toughness is 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 is proven to be detrimental as it displays poor mechanical properties due to the poor compactness of numerous LaAl11O18 grains, coarsening of Al2O3 grains and decline in density.