Structural and mechanical properties of Al2O3-ZrO2 dental bioceramics

Abstract

Recently, ceramic materials have been given a lot of attention as candidates for implanting materials as they posses certain highly desirable characteristics for thesis applications. Ceramics used for the repair and reconstruction of debased or damaged part of the body, are known as bioceramics. Ceramics have been used for some time in dentistry owing to their inertness to the body fluids, high compressive strength and good esthetic appearance. One problematic aspect of ceramic materials and of dental ceramics in particular is their low mechanical resistance and fracture toughness. Generally, in dental application, ceramics should have greater stiffness, higher elastic limits, better fracture resistance, and improved wear characteristics. The last point deserves special attention. The alumina-zirconia (Al2O3-ZrO2) composites are one of the relatively good and promising candidates for biomaterials application, due to biocompatibility and their mechanical properties that combines high flexural strength with a high toughness. In the present work ZrO2 toughened Al2O3 (ZTA) composites with 10-40 wt % of ZrO2 were prepared by conventional pressureless sintering technique at 1550, 1600 and 1650 °C for 2 hours. The density, porosity, structural properties and mechanical properties of Al2O3-ZrO2 composites with respect to ZrO2 content as well as sintering temperature have been explored here. Microstructure was observed using scanning electron microscope (SEM) and phase content was detected by mean of X- ray diffraction (XRD). Microhardness was measured using the Vickers indentation technique. The introduction of ZrO2 in Al2O3 as an additive causes the formation of solid solution which may promote the densification process by the introduction of defects. About 22% higher density of ZTA composite has been achieved in the present work and lower modulus of elasticity has been observed for ZTA composite of higher ZrO2 content. The microstructures are highly homogeneous and finer with less porosity when compared to pure Al2O3. From XRD analysis it has been shown that three phases i.e., corundum Al2O3, tetragonal and monoclinic ZrO2 are present and no reaction has been occurred between Al2O3 and ZrO2. For pure Al2O3 the microhardness number is in the range 17-20 GPa while the decreasing of hardness value has been observed with the addition of ZrO2 content as well as sintering temperature. The approach adopted in the present study may provide an alternative to design Al2O3-ZrO2 composites with improved mechanical properties.