Effects of La_(2)O_(3) addition on microstructure development and physical properties of harder ZTA-CeO_(2) composites with sustainable high fracture toughness

The influence of La_(2)O_(3) inclusion(0-3 wt%) on the micro structure,phase formation and mechanical properties of zirconia toughed alumina(ZTA) added with 5.0 wt% CeO_(2) was investigated.ZTA CeO_(2) composites were sintered at 1600℃ 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 LaAl_(11)O_(18).The addition of La_(2)O_(3) incites the sintering,microstructure refinement,densification of ZTA-CeO_(2) matrix and phase transformation.Hence,the hardness of ZTA-CeO_(2) ceramics is increased rapidly based on refinement of Al_(2)O_(3) grains,densification of ZTA-CeO_(2) composites and porosity reduction.It is observed that the fracture toughness is enhanced through in situ formation of elongated LaAl_(11)O_(18) grains.The addition of 0.7 wt% La_(2)O_(3) culminated in the achievement of the optimum findings for density(4.41 g/cm^(3)),porosity(0.46%),hardness(1792 HV) and fracture toughness(8.8 MPa·m^(1/2)).Nevertheless,excess La_(2)O_(3) is proven to be detrimental as it displays poor mechanical properties due to the poor compactness of numerous LaAl_(11)O_(18) grains,coarsening of Al_(2)O_(3) grains and decline in density.