Ultrastrong tough zirconia ceramics by defects-engineering

We report the preparation of a category of ultrastrong tough zirconia ceramics by engineering defects using an oscillatory pressure during pressure assisted sintering. The introduced oscillatory pressure enhances the dynamic grain rearrangement, plastic deformation, mass transportation, and pore removal, leading to the formation of pore-free ceramics characterized by the rich coherent grain boundaries among individual mesocrystalline grains with intragranular quasi-interfaces. As a proof of concept, the pressure required by oscillatory pressure sintering (OPS) for preparing fully dense 3Y-TZP ceramics is significantly reduced, which is just ∼1/5 of that required by hot isostatic pressing. The OPS-prepared 3Y-TZP ceramics reached a record-breaking high bending strength and fracture toughness, being up to 1.8 GPa and 16 MPa·m^1/2, respectively. This success illustrates a universal principle of engineering defects for making breakthrough in exploring other ultrastrong tough ceramics.