Abstract
This paper reports the improvement of microstructural and hardness properties of 3 mol% yttria-stabilized zirconia (3Y-TZP) ceramics with nano TiO2 powders (with 0, 0.9, 1.8, and 2.7 wt%) added using a low-temperature microwave-assisted sintering of 1250 °C. Even at such a low sintering temperature, all sintered samples had the main phase of tetragonal zirconia (t-ZrO2) without the appearance of the secondary monoclinic phase or TiO2 phase, and had high relative densities, larger than 95%. The grain growth was well developed, and the grain sizes were around 300–600 nm. The Ti and O elements appeared at the grain and grain boundary and increased with the increased nano TiO2 contents identified by the element analysis, although the TiO2 phase did not appear in the X-ray pattern. The Vickers hardness was in the range of 10.5 to 14.5 GPa, which first increased with increasing content till 0.9 wt% and then decreased. With citric acid corrosion treatment for 10 h, the Vickers hardness only decreased from 14.34 GPa to 13.55 GPa with the addition of 0.9 wt% nano TiO2 powder. The experiment results showed that 0.9 wt% nano TiO2 addition can improve the densification as well as the Vickers hardness under a low temperature of microwave-assisted sintering.
Highlights
Zirconia (ZrO2 ) has become one of the most important dental materials in the recent development of restorative dentistry, due to the finding of transformation toughening mechanisms [1,2]
Stabilized Zirconia (PSZ) material is well developed by adding a small content of stabilizers, such as Y2 O3, CeO2, and MgO, into ZrO2 -based material to provide various coexistent phases that can hold the tetragonal phase from 1170◦ C to room temperature and prevent the appearance of crack propagation, giving high hardness and fracture toughness [4,5]
In reference [16], the ZrO2 -based ceramics with micro-sized TiO2 additions could be microwave-sintered at 1300 ◦ C; the X-ray diffraction (XRD) results showed the sintered samples had many monoclinic phases instead of the tetragonal phases
Summary
Zirconia (ZrO2 ) has become one of the most important dental materials in the recent development of restorative dentistry, due to the finding of transformation toughening mechanisms [1,2]. Stabilized Zirconia (PSZ) material is well developed by adding a small content of stabilizers, such as Y2 O3 , CeO2, and MgO, into ZrO2 -based material to provide various coexistent phases that can hold the tetragonal phase from 1170◦ C to room temperature and prevent the appearance of crack propagation, giving high hardness and fracture toughness [4,5]. In various PSZ materials, 3 mol% yttria-stabilized zirconia, known as 3 mol% yttria-stabilized zirconia (3Y-TZP), provides a very fine yttria grain in the zirconia polycrystals, showing only the tetragonal phase at room temperature and good mechanical properties, including high hardness, toughness, and strength [6,7,8,9]. The dependence of the nano TiO2 powers with 0, 0.9, 1.8, and 2.7 wt% on the hardness property was investigated to discuss the importance of nano TiO2 addition for the as-sintered samples and the sample with the treatment of citric acid corrosion
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