Role of addition of La2O3 on the phase contents, microstructure and mechanical properties of ZTA-MgO ceramics

Abstract Addition of MgO into Zirconia Toughened Alumina (ZTA) enhanced the Vickers hardness (1710 HV) but reduced the fracture toughness (3.38 MPa.m1/2). The reason is attribute to the formation of MgAl2O4 phase in the ZTA-MgO system. Hence, the La2O3 was added to ZTA-MgO compounds to acquire both high hardness and fracture toughness. The mixtures were prepared with addition of La2O3 (0.1 wt.% to 10.0 wt.%) to ZTA/1.0 wt% MgO. The mixtures were pressed to a rectangular bar of (54*12*5) mm3 at 1600 oC for 4 hrs. The characterisation of phase contents, microstructure, density, porosity and mechanical properties were done through XRD, SEM, Archimedes principle and Vickers indentation technique, respectively. The optimum La2O3 addition was between (0.7 wt. % - 1.0 wt.%) for better fracture toughness of ZTA ceramics with a reasonable high hardness. The addition of La2O3 has a significant effect on the formation of finer Al2O3 grains, creating strong interface between the Al2O3 grains and LaAl11O8 grains result in denser ZTA-MgO ceramics of hardness of 2028 HV. Also, the presence of rodlike LaAl11O8 and/or LMA grains in the ZTA-MgO ceramics improved the fracture toughness up to 6.67 MPa.m1/2.