Intrinsic Surface Prestressing via Oxygen-Vacancy Regulation Enables High-Strength ZTA Ceramics
Achieving intrinsic surface compressive stress in monolithic oxide ceramics without heterogeneous interfaces remains a persistent challenge. This study introduces oxygen-vacancy compensation prestressing (OVCP), a defect-engineering strategy that generates in situ surface prestressing in zirconia-toughened alumina (ZTA). Oxygen vacancy-rich ZTA was first produced by vacuum hot pressing, followed by air annealing to induce surface reoxygenation and form an oxygen-charged layer (OCL). The optimized treatment increased flexural strength to (1679±78) MPa, a 31% improvement over the unannealed state. Mechanistically, oxygen-vacancy compensation during annealing induces lattice expansion in the near-surface region. Constrained by the less-oxidized interior, this expansion converts into a residual compressive stress field that suppresses bending-induced failure. A simplified bilayer model quantitatively supports the experimentally observed strengthening behavior. These findings establish oxygen vacancy-regulated lattice expansion as an effective mechanism for intrinsic surface prestressing, providing a simple, interface-free route for strengthening oxide ceramics. The approach circumvents delamination and interfacial debonding inherent to conventional coating or laminated architectures, offering a scalable pathway for high-performance structural oxide ceramics.