Preparation of Fine-grained 3Y-TZP Ceramics with Enhanced Low-temperature Degradation Resistance

The occurrence of tetragonal to monoclinic phase (t→m) transformation in zirconia ceramics under humid ambient conditions induces the low-temperature degradation (LTD).Such t→m transformation could be suppressed by grain size refinement or/and doping small amounts of alumina.Fine-grained dense 3mol% yttria-doped tetragonal zirconia polycrystal (3Y-TZP) ceramics were prepared by pressureless sintering a zirconia powder doped with 0.25wt% alumina.The LTD behaviors of as-prepared 3Y-TZP ceramics were evaluated by accelerated aging at 134 ℃ in water.The samples sintered at 1 300 ℃ for 2 h achieve the relative density higher than 99.9% with the average grain size of 147 nm.The 3Y-TZP ceramic exhibits excellent LTD resistance that no t→m transformation takes place after 125 h accelerated aging.Large amounts of defects were observed inside grains evidenced by the high-resolution transmission electron microscopic (HRTEM) analysis.It is proposed that the presence of defects enhances the sintering kinetics and favors the present low-temperature densification.Possible reasons for defects formation were discussed and the mechanical properties of the 3Y-TZP ceramic were reported as well.