AbstractThe microstructure and mechanical properties of hot pressed Al2O3–ZrO2ceramics prepared from ultrafine powders were studied by means of hardness and fracture toughness tests, X-ray diffraction, scanning and transmission electron microscopy, and electron probe microanalysis. Experimental results show that Al2O3–ZrO2ceramics combine the high modulus of Al2O3and phase transformation toughening of ZrO2and give good mechanical properties. The fracture toughness of the samples increases monotonically with increasing ZrO2content. When the content of ZrO2is low, the ZrO2particles are surrounded by Al2O3grains and the matrix is thus strengthened, but when the content of ZrO2is high, the microcracks resulting from the tetragonal monoclinic phase transformation decrease the strength of the material. The relative density of the samples also increases with increasing ZrO2content, which is beneficial to both strength and toughness. Banded abnormal growth of the Al2O3grains parallel to the hot pressing plane was found in the samples. This phenomenon is considered to be a result of the priority of Al2O3grain growth and aggregation of ZrO2along the pressing direction in the later stages of hot pressing.MST/1359