Publication: Influence of tungsten trioxide, wo3 on the microstructure and strength of zirconia toughened alumina (ZTA)
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Date
2025-08-08
Authors
Tan, Chor Keat
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Abstract
The addition of stabilized Zirconia (ZrO2) into Alumina (Al2O3) forms the Zirconia Toughened Alumina (ZTA) compound, known for its high strength and hardness. However, its low fracture toughness limits its use in advanced engineering applications. Therefore, this study investigates the potential of Tungsten Trioxide (WO3) as a stabilizing additive to improve the ZTA properties. Solid-state processing was used to fabricate ZTA composites with varying WO3 concentrations (0.0, 0.3, 0.4, and 0.7) weight %. The powder mixture was compacted at 300 MPa and sintered at 1600°C for densification. The key parameters studied were density, porosity, fracture toughness, hardness, and microstructure. Characterization techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Vickers Hardness Testing were utilized to assess the phase composition, microstructural features, and mechanical properties of the sintered bodies. The results show that WO3 did not significantly improve fracture toughness. At higher concentrations of WO3, it led to increased porosity and reduced hardness. The optimal fracture toughness (1.61 MPa.m1/2) was observed with 0.3 wt. % WO3, similar value to pure ZTA but with reduced density from 4.18 g/cm3 (0.7 wt. %) to 3.82 g/cm3 (0.0 wt. %). In conclusion, adding WO3 to ZTA does not significantly improve toughness and hardness. Excess WO3 increases porosity of the material. These suggest that while WO3 stabilizes the zirconia phase, it also induces internal stresses due to thermal expansion mismatches, leading to microcracks and reduced mechanical properties. Analysis by Design Expert Software (DOE) suggested that concentration WO3 amount of 0.2 wt.%, heating rate of 10 °C/min, and soaking time of one hour will improve the performance of ZTA.