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

Abstract Alumina (Al 2 O 3 ) and alumina–yttria stabilized zirconia (YSZ) composites containing 3 and 5 mass% ceria (CeO 2 ) were prepared by spark plasma sintering (SPS) at temperatures of 1350–1400 °C for 300 s under a pressure of 40 MPa. Densification, microstructure and mechanical properties of the Al 2 O 3 based composites were investigated. Fully dense composites with a relative density of approximately 99% were obtained. The grain growth of alumina was inhibited significantly by the addition of 10 vol% zirconia, and formation of elongated CeAl 11 O 18 grains was observed in the ceria containing composites sintered at 1400 °C. Al 2 O 3 –YSZ composites without CeO 2 had higher hardness than monolithic Al 2 O 3 sintered body and the hardness of Al 2 O 3 –YSZ composites decreased from 20.3 GPa to 18.5 GPa when the content of ZrO 2 increased from 10 to 30 vol%. The fracture toughness of Al 2 O 3 increased from 2.8 MPa m 1/2 to 5.6 MPa m 1/2 with the addition of 10 vol% YSZ, and further addition resulted in higher fracture toughness values. The highest value of fracture toughness, 6.2 MPa m 1/2 , was achieved with the addition of 30 vol% YSZ.