Cyclic fatigue behavior of Y-TZP nanostructures with non-homogeneous yttria distribution

Nanostructured Y-TZP samples with Non-Homogeneous Yttria Distribution (NNHYD) were prepared by mixing co-precipitated 3Y-TZP powder (Tosoh TZ-3Y) with yttria-free monoclinic powder (Tosoh TZ-0), yielding an overall yttria content of 2 mol%. The cyclic fatigue behavior of NNHYD was evaluated by Step-Stress Accelerated Life Testing (SSALT) and mechanical cycling in a biaxial flexural strength test (BFST) setup and compared to Conventional Submicrometric 3Y-TZP (CS). Physical, structural, microstructural, and mechanical characterizations of all groups were also evaluated and compared before and after artificial aging in autoclave. NNHYD presented a higher capacity for damage accumulation and maintenance of phase transformation potential than CS, associated with elevated resistance to the propagation of Low-Temperature Degradation (LTD). A nanostructured 3Y-TZP surface layer introduced in NNHYD by dip coating (DC-NNHYD) improved resistance to LTD at the cost of reduced reliability under cyclic fatigue by increasing the stability of the tetragonal phase. This surface alteration highlights the impact of surface properties on mechanical performance. The results of this study present practical possibilities to help achieve the ideal balance between strength, toughness, and LTD resistance to improve the lifetime of zirconia-based biomaterials.