Abstract
Zirconia materials are frequently used in dental applications due to their excellent strength and their tooth-like aspect. Standard yttria stabilized zirconia (Y-TZP) ceramics suffer, however, from moderate toughness and vulnerability to low-temperature degradation. In this study, 1Y6Ce-TZP materials reinforced with different amounts of alumina and/or strontium hexaaluminate were manufactured by slip casting and pressureless sintering at different temperatures to assess their mechanical properties, microstructure, phase composition, and low-temperature degradation stability. Results show that these materials exhibit a high fracture resistance of 10–12 MPa√m, a bending strength between 700–950 MPa, and a Vickers hardness of 1100–1200 HV10. Strontium hexaaluminate (SA6) precipitates were formed in situ by reaction of alumina and strontium zirconate. Although crack deflection at SA6 platelets was clearly visible, a net toughening was not observed. Accelerated ageing tests at 134 °C/3 bar water vapor pressure showed best results for mixed alumina/SA6 reinforcements and a sintering temperature of 1500 °C. Mehl-Avrami-Johnson plots used to describe the ageing kinetics showed clear indications of different ageing mechanisms due to the introduction of the SA6 phase.
Highlights
The excellent mechanical properties of partially stabilized zirconia are caused by transformation toughening (TT), a stress-induced martensitic transformation of metastable tetragonal phase to stable monoclinic phase [1]
In tetragonal zirconia polycrystals (TZP), either yttria or ceria are used as stabilizers, which leads to either very strong materials with moderate toughness (Y-TZP) or extremely tough materials with moderate strength (Ce-TZP) [4]
15 vol% strontium hexaaluminate (15SA6) material sintered at 1500 ◦ C and 1550 ◦ C
Summary
The excellent mechanical properties of partially stabilized zirconia are caused by transformation toughening (TT), a stress-induced martensitic transformation of metastable tetragonal phase to stable monoclinic phase [1]. In tetragonal zirconia polycrystals (TZP), either yttria or ceria are used as stabilizers, which leads to either very strong materials with moderate toughness (Y-TZP) or extremely tough materials with moderate strength (Ce-TZP) [4]. Another critical aspect, especially in biomedical applications issue, is low-temperature degradation (LTD) [5]. During LTD, the stabilizer is hydrolyzed, which eliminates these vacancies and results
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