Abstract: The AlN ceramics were hot pressed by the addition of nanoscale ZrO2 power as second phase and Y2O3.The results show that AlN ceramics mainly comprise main phase AlN phase, grain boundary phase Al5Y3O12 and new phase ZrN.With the addition of ZrO2, the Vickers hardness of AlN ceramics has no significant change, while fracture toughness gradually increase.This is because the transformation of fracture mode from intergranular fracture to mixed fracture including intergranular fracture and transgranular fracture which is induced by the formation of ZrN due to the reaction between ZrO2 and AlN, strengthened the grain boundary and then improved fracture toughness.

Key words: The AlN ceramics were hot pressed by the addition of nanoscale ZrO2 power as second phase and Y2O3.The results show that AlN ceramics mainly comprise main phase AlN phase, grain boundary phase Al5Y3O12 and new phase ZrN.With the addition of ZrO2, the Vickers hardness of AlN ceramics has no significant change, while fracture toughness gradually increase.This is because the transformation of fracture mode from intergranular fracture to mixed fracture including intergranular fracture and transgranular fracture which is induced by the formation of ZrN due to the reaction between ZrO2 and AlN, strengthened the grain boundary and then improved fracture toughness.