Effect of High-Temperature Aging on the Fracture Toughness of 40 mol% Ceria-Stabilized Zirconia

The 40 mol% CeO 2 -stabilized ZrO 2 ceramic was synthesized by the sol-spray pyrolysis method and aged at 1400°C–1600°C. The effects of high-temperature aging on its fracture toughness were investigated after heat treatments at 1500°C for 6–150 h in air. Characterization results indicated that the activation energy for grain growth of 40 mol% CeO 2 -stabilized ZrO 2 was 593 ± 47 kJ/mol. The average grain size of this ceramic varied from 1.4 to 5.6 μm within the aging condition of 1500°C for 6–150 h. The Ce-lean tetragonal phase has a constant tetragonality (ratio of the c -axis to a -axis of the crystal lattice) of 1.0178 during the aging process. It was found that the fracture toughness of 40 mol% CeO 2 -stabilized ZrO 2 was determined to be 2.0 ± 0.1 MPa·m 1/2 , which did not vary significantly with prolonging aging time. Since no monoclinic zirconia was detected in the regions around the indentation crack-middle and crack-tip, the high fracture toughness maintained after high-temperature aging can be attributed to the remarkable stability of the tetragonal phase in 40 mol% CeO 2 -stabilized ZrO 2 composition.