Study of Microstructures, Mechanical and Electrical Properties of Al2O3-30 WT. % ZrO2 Composite Ceramics Doped with MgO

Abstract

The composite of Aluminum Oxide (Al₂O₃) and Zirconia (ZrO₂) is a hybrid ceramic possessing remarkably improved mechanical properties including hardness, toughness, bending strength etc. A number of experimental observations reveal that such excellent ceramic would be a potential candidate for many biomedical applications e.g. in dental applications etc. Mechanical properties of composite materials are greatly affected by their shapes, sizes, relative density of bulk-grains and in the same way these parameters are dependent on doping condition, doping materials, sintering temperatures etc. In this work, the composite Al₂O₃- ZrO₂ has been doped with magnesium oxide (MgO) at different wt%. The effect of addition of MgO to this composite in suppressing grain growth and in enhancing fracture toughness by transforming the mechanism of crack growth (at nanoscale) is analyzed. The sintering temperature was kept fixed as 1650⁰C for each composite. Since MgO possesses low dielectric losses, besides mechanical and morphological studies, electrical properties (such as resistivity, conductivity and permittivity) of these composites have also been observed. With the increase of the wt% of MgO, the resistivity is decreasing and the conductivity is increasing against frequency but the permittivity exhibits somewhat different behavior.

Microstructural characterization of the sintered samples was made through the Scanning Electron Microscope (SEM). It is observed that the presence of MgO on the grain boundaries effectively limits a rapid grain growth of Al₂O₃ and ZrO₂. Average grain size increases with the change of the additive wt% of MgO (i.e., Average grain size increased with the increase in doping content of MgO). The flexural strength and hardness of the sintered compositions tend to increase with the variation of additive wt% of MgO. It is found that the maximum flexural strength of 174.8 MPa for the composition Al₂O₃-30wt%3 SYZ+3wt%MgO which is attributed to the homogeneity as well as the reduction in grain size and increase in relative density, and the maximum Vickers hardness of 9.08 GPa for the composition Al₂O₃-30wt%3 SYZ+3wt%MgO.

• Supervision