Segregation of Ti4+ and Ce4+ impurity-cations at the grain boundaries of CeO2-TiO2-ZrO2 ceramics for overcoming strength deterioration after grain coarsening

• The driving force for grain boundary segregation is mainly derived from ionic radius and grain size differences. • Ti 4+ promotes co-segregation of Ce 4+ and Ti 4+ at grain boundary to enhance grain boundary strength. • Strengthening of grain boundaries promotes the change in fracture mode from intergranular fracture to transgranular fracture. • The m -ZrO 2 phase with a long-period stacking ordered structure is formed after compression testing. • The m -ZrO 2 phase inhibits the movement of dislocations and extension of grain boundary cracks. The deterioration of the mechanical properties of ZrO 2 -based ceramics after grain coarsening has become a key challenge hindering their wide application as advanced structural materials. The present work reports that novel TiO 2 -CeO 2 -ZrO 2 ternary ceramics with spontaneous segregation of Ti 4+ impurity-cations at grain boundaries could be successfully realized by TiO 2 composition modulation in 12CeO 2 -ZrO 2 matrix. Experimental results reveal that compared with the 12CeO 2 -ZrO 2 binary ceramics, the 10TiO 2 -12CeO 2 -ZrO 2 ternary ceramic retains high compressive strength (1853 ± 35 MPa) and flexural strength (359 ± 9 MPa) even after grain coarsening. This remarkable performance retention is primarily attributed to three key factors: a high relative density of 99.09 %, a t -ZrO 2 phase with 100 % volume fraction, and the synergistic segregation of Ti 4+ and Ce 4+ at grain boundaries. Especially, the grain boundary segregation enhances grain boundary strength and induces martensitic transformation near the grain boundary to form a m -ZrO 2 phase with long-period stacking order (LPSO) structure. These findings will provide a new strategy for the preparation of coarse-grained ZrO 2 -based ceramics with unique properties.