Abstract
Investigations of ceramics with a different ratio of Al2O3 - 3Y-TZP (tetragonal polycrystalline zirconium doped with 3 mol% Y2O3) oxides formed by the isostatic molding technology followed by free sintering are shown in the paper. Microstructural investigations of ceramic materials show that increasing the 3Y-TZP content from 0 to 85 wt. % leads to an alumina grain size decrease from 2.5 µm to 0.4 µm. At the same time it is found that the higher the concentration of zirconium in the sintered ceramic the higher the volume fraction of defects remaining after sintering. It is shown that an addition and increase in the zirconium content in the alumina ceramic result in a decrease in relative density from 98,8 % to 93,7 %. The above changes in the content and microstructure of the studied ceramic influence the material’s mechanical properties. It is stated that the relationship between material hardness and the second phase concentration is linear. If the concentration of zirconium dioxide increases from 0 % to 100 %, the hardness of the produced ceramic decreases from 20,0 ± 1,5 GPa to 12,9 ± 0,6 GPa. Any influence of microstructural features on ceramic hardness is not detected. At the same time the structural features mentioned above have a significant impact on a material’s bending strength. Since the effects of grain size decreasing and porosity increasing have an opposite influence on a material’s strength, the resulting relationship between a material’s strength and its content is maximal. Analysis of results of mechanical properties measurement allows establishing an optimum ratio of ceramic components. It is revealed that a ceramic with an equal weight ratio of the components possesses maximum bending strength (950 ± 50 MPa) and moderate hardness of about 18,2 GPa.
Keywords: bioceramics, structural ceramics, alumina, partially stabilized zirconia, unpressurized sintering, cold isostatic pressing, ZTA ceramics, three-point bending strength, hardness
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