The Eu3+ could be dissolved into CaAl12O19 crystallites to be formed a solid solution. Plate-like grains are easier to be generated by adding Eu2O3 into alumina ceramics. The grain-boundary cohesion becomes weaker compared with undoped-Eu2O3 of alumina ceramics. The fracture mode changes from transgranular to intergranular when doped with Eu2O3.