Abstract
The presented work concerns the development and investigation of three different grades of ZrO2 materials containing Al2O3 particles (ATZ-Alumina Toughened Zirconia ceramics with 2.3–20 vol.% of alumina). The zirconia powders containing 3 mol.% of yttria were synthesized by a precipitation/calcination method and fabricated from two different zirconia powders with different yttria content. Then, the selected ATZ composites (ATZ-B, ATZ-10 and ATZ-20) were prepared by means of conventional mixing, compacting and sintering at 1450 °C for 1.5 h. The phase composition, microstructure, relative density and basic mechanical properties were determined. Uniform microstructures with relative densities over 99% of theoretical density, hardness values between 12.0–13.8 GPa, flexural strength up to 1 GPa and outstanding fracture toughness of 12.7 MPa⋅m1/2 were obtained. The aging susceptibility of alumina toughened zirconia materials, as a consequence of hydrothermal treatment, was investigated. The aim of this study was to determine the influence of LTD (low temperature degradation) on the tetragonal to monoclinic phase transitions and on the flexural strength of hydrothermally aged specimens. The results were compared to those obtained for commercially available tetragonal zirconia-based materials containing 3 mol.% of yttria. This research shows that ATZ composites that have excellent mechanical properties and sufficient hydrothermal aging resistance can be attained and later used in technical and biomedical applications.
Highlights
The system of zirconia (ZrO2 )-alumina (Al2 O3 ) is gaining increasing attention due to its inherent intrinsic properties and its applicability in structural and biomedical ceramics [1,2,3,4,5,6]
This suggested that the addition of Al2 O3 particles in the ZrO2 matrix acts as an inhibitor of grain growth, which agrees with Nevarez-Rascon et al [30]
The analysis indicated the change in fracture mode from intergranular to transgranular observed in the ATZ composites, which increases the energy required for crack propagation
Summary
The system of zirconia (ZrO2 )-alumina (Al2 O3 ) is gaining increasing attention due to its inherent intrinsic properties and its applicability in structural and biomedical ceramics [1,2,3,4,5,6]. Tetragonal zirconia-based ceramics show excellent toughness and high bending strength, properties that are obtained because of undergoing a tetragonal to monoclinic (t–m) phase transformation that increases the mechanical properties of these materials. There is critical minimum and maximum oxygen vacancy concentration which, when exceeded, results in a phase transformation. Both counterparts are characterized by excellent biocompatibility. The use of the synergistic effect of improving the mechanical properties in ATZ composites allows the significant increase in the fracture toughness (11 MPa·m1/2 ) and flexular strength (>1.5 GPa) of these ceramics, which strictly depends on the phase composition and obtained microstructure [9,10]
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