Effect of CeO2 addition on densification and microstructure of Al2O3–YSZ composites

Alumina and alumina-yttria stabilised zirconia (YSZ) composites containing 3 and 5 mass% CeO2 were prepared by spark plasma sintering (SPS) at temperatures between 1350-1400 C for 300 s under a pressure of 40 MPa. The densification, microstructure and mechanical properties of the Al2O3-based composites were investigated. Fully dense composites with a relative density of approximately 99% were obtained. The grain growth of alumina was inhibited by the addition of 10 vol% zirconia, and the formation of elongated CeAl11O18 grains was observed in the ceria-containing composites sintered at 1400 C. Al2O3-YSZ composites without CeO2 had higher hardness than sintered monolithic Al2O3 bodies and the hardness of Al2O3-YSZ composites decreased from 20.3 to 18.5 GPa when the content of ZrO2 increased from 10 to 30 vol%. The fracture toughness of Al2O3 increased from 2.8 to 5.6 MPa.m1/2 with the addition of 10 vol% YSZ, and further additions resulted in higher fracture toughness values. The highest value of fracture toughness, 6.2 MPa.m1/2, was achieved with the addition of 30 vol% YSZ.