Low temperature ageing in water vapor and mechanical properties of ZTA ceramics

• Published in: Materials letters 2002-11, Vol.56 (6), p.1014-1018
• Main Authors: Guo, Ruisong, Guo, Duoli, Zhao, Dan, Yang, Zhengfang, Chen, Yuru
• Format: Article
• Language: English
• Subjects: Ageing; Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Mechanical property; Structural ceramics; Technical ceramics; ZTA ceramic
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/S0167-577X(02)00666-3

ZTA ceramics were conventionally prepared by mixing Al 2O 3, Y–TZP and sintering aids in water for 2 h, isostatically pressing at 200 MPa and sintering at 1450 °C for 2 h in air. The Y 2O 3 content in Y–TZP was specially designed to be a little high (3 mol%) to obtain good stability of t-ZrO 2. The fraction of t-ZrO 2 up to 93% was retained at room temperature after sintering. The ZTA ceramics were then aged in water vapor at 240 °C for different times to adjust the stability of t-ZrO 2 and furthermore to optimize the zirconia transformation toughening. It was shown that the fraction of t-ZrO 2 gradually decreased to 85% after ageing for 2000 h. In contrast, fracture toughness grew continuously to 7.2 MPa m 1/2. Strength went up to the maximum 680 MPa when aged for short times, and then dropped gradually to 620 MPa, which was still higher than that without ageing. These results showed that this ZTA material is a good candidate for applications in humid environments and at elevated temperatures.