Microstructure and mechanical performances of ZTA/LaAl11O18 composite prepared by a heterogeneous precipitation method

Al2O3 composite combinatively strengthened by ZrO2 and in situ formed LaAl11O18 was prepared by a heterogeneous precipitation method. The sintering temperature was significantly lowered in comparison with monolithic Al2O3. ZrO2 and LaAl11O18 inhibited Al2O3 grain growth, forming fine and uniform microstructure in the material. SEM showed that increasing numbers of Al2O3 and LaAl11O18 grains fractured transgranularly, because of the strengthened grain boundary by residual thermal stress. X-ray diffraction revealed that ZrO2 was exclusively in tetragonal symmetry (t-ZrO2) and did not transformed to m-ZrO2 under the fracture stress. The strength of the material was about 1 GPa, almost doubled over that of monolithic Al2O3.