Hydrothermal Aging Property and Mechanism of Zirconia Ceramics with Different Stabilizers

Composite stabilizer-stabilized (C-TZP), Y₂O₃-stabilized (Y-TZP) and CeO₂-stabilized (Ce-TZP) tetragonal zirconia polycrystalline ceramics were hydrothermally treated at 200℃ for 0-45 h. The micromorphology, phase composition, and the mechanical properties at different hydrothermal time of the ceramics before and after hydrothermal treatment were studied. The hydrothermal aging mechanism was also analyzed. The results show that with the increase of hydrothermal time, the hardness, bending strength and fracture toughness of three zirconia ceramics all decreased, among which the decrease range of the Y-TZP ceramics was the largest, followed by that of the C-TZP ceramics. Comparing to that before hydrothermal treatment, the volume fraction of the monoclinic phase in Y-TZP ceramics increased by 58% after hydrothermal treatment for 30 h, while that in Ce-TZP and C-TZP ceramics increased relatively little after hydrothermal treatment for 45 h. The hydrothermal aging resistance of the Y-TZP ceramics was the worst. The direct reason for the hydrothermal aging was because of the addition of Y₂O₃. Decreasing the Y₂O₃ content and increasing the CeO₂ content was in favor of controlling the hydrothermal aging. The hydrothermal aging process coincided well with the chemical etching model of the zirconia ceramics.