Intrinsic Surface Prestressing via Oxygen-Vacancy Regulation Enables High-Strength ZTA Ceramics

• • Flexural strength reaches (1679±78) MPa after OVCP treatment, a 31% improvement over the unannealed baseline, directly enabling ZTA components to withstand higher bending loads in cutting tools and biomedical implants without geometric redesign. • • Oxygen-vacancy compensation during air annealing generates a residual compressive stress field via constrained lattice expansion in the near-surface region, suppressing surface crack initiation under bending and eliminating the delamination failure mode of coated systems. • • The simplified bilayer model quantitatively captures the dependence of surface stress on oxygen-charged layer (OCL) thickness, providing a predictive design tool for tuning prestress levels through annealing time and temperature. • • The interface-free OVCP strategy avoids heterogeneous interfaces that cause thermally induced stress concentration and spallation in conventional prestressed ceramics, offering a cost-effective, scalable route for monolithic oxide strengthening.