Papers by Keyword: TZP

Abstract: Phase transformation of 3Y-TZP with different ternary oxide additions (Al2O3, La2O3, Sc2O3 and CeO2) was evaluated by hydrothermal degradation tests in water vapor at 180°C. Monoclinic phase quantification from XRD patterns showed an improved degradation resistance of the specimens with oxide additions in comparison to the 3Y-TZP base material. Cross sectional sample analysis showed that, even though for all the compositions the exposed surface became saturated with monoclinic phase, the penetration of the transformation varied. Alumina-lanthana doped materials exhibited the thinnest degraded layer.

Abstract: The 4mol%Sc2O3 doped ZrO2 (4ScSZ) showed a superplastic-like large elongation in a range of strain-rate at 1773K. The large elongation was caused by both of high strain-rate sensitivity and high strain hardening during the deformation. Ion conductivity of the 4ScSZ, deformed superplastically at a relatively high strain-rate region, was higher than that of non-deformed one, suggesting that superplastic deformation can improve its conductivity. These results are discussed with probable microstructural evolution.

Abstract: Microstructure and mechanical properties of CeO2/Y2O3/ZrO2 ceramics were investigated using ultrafine CeO2/Y2O3/ZrO2 powder as the starting material. The structures of CeO2/Y2O3/ZrO2 containing 8~12mol% CeO2 were composed of tetragonal phases. They exhibited an extremely high bending strength (950 MPa) and fracture toughness (12MPa·m1/2). The structural details of CeO2/Y2O3/ ZrO2 were studied by TEM, SEM and XRD. The effects of the structure on mechanical properties were discussed. Plungers and ball valves by the CeO2/Y2O3/ZrO2 ceramics have higher wear resistance and corrosion resistance than metal. Their service life is about 6 ~ 10 fold more than that of metal.

Abstract: This paper explores the effects of dopant content on the aging behavior of tetragonal zirconia polycrystal (TZP). TZP powders with varying Y2O3 content (1.75-3mol%) were synthesized by co-precipitation. After the green body of as-prepared TZP powders being isostatically pressed at 200 MPa and sintered at 14000C for 3 h in air, a range of TZP ceramics were fabricated. As-synthesized TZP ceramics annealed at relatively low temperatures with the presence of water or water vapor. XRD analysis was conducted for phase identification and determined a tetragonal to monoclinic transformation. Microscope imaging displayed the changes of aged TZP surface structure. It is believed that the degradation of TZP might be caused by the reaction between Y2O3 and H2O. The mechanism of low temperature degradation of TZP was discussed.

Abstract: Superplastic behaviors were investigated for fine-grained yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) from a viewpoint of GeO2 or TiO2 doping. It was found that both dopants enhance the ductility in TZP. In particular, elongation to failure of 988% could be obtained in 3Y-TZP co-doped with 2mol%GeO2 and 2mol%TiO2. In addition, it was revealed that lower flow stress did not always give a larger elongation in this system. On the other hand, the strong segregation of dopants along grain boundaries was confirmed by high-resolution electron transmission microscopy study (HRTEM) with X-ray energy dispersive spectrometer (EDS). The unique phenomena observed in the relation between flow stress and ductility is closely related to the strong segregation of dopants along grain boundaries in this system. The grain size at fracture is determined by covalency because of the dopant segregation. It could be concluded that elongation to failure is closely related to a balance between grain size at fracture and grain growth rate during deformation.