Effects of powder preparation method on the microstructure and mechanical performance of ZTA/LaAl11O18 composites

ZTA/LaAl11O18 (ZAL) composites were prepared by two different methods, and were denoted as ZAL-F and ZAL-C, respectively. In both of the materials, ZrO2 was exclusively in tetragonal symmetry and did not transform to m-ZrO2 after the fracture of the samples. TEM, SAED and HRTEM observations indicated that the LaAl11O18 grains took a platelet-like morphology, with their main surface planes parallel to the (001) plane. The ZAL-F sample showed a higher sintering ability, more homogeneous microstructure and finer Al2O3 grains than ZAL-C. And owing to the higher grain boundary strength in ZAL-F, the Al2O3 grains there showed a higher propensity to transgranular fracture than those in ZAL-C. The strength of ZAL-F was about 1 GPa, almost 20% higher than that of ZAL-C, although their toughness was very close.