Effect of Fe₂O₃ Addition and Sintering Temperature on mechanical Properties and Translucence of Zirconia Dental Ceramics with Different Y₂O₃ Content

The influence of Fe₂O₃ additions on the microstructure, mechanical properties and translucence of zirconia with 3 mol-% or 5 mol-% Y₂O₃ was evaluated. Samples were pressed with different thickness and sintered at 1475, 1500, 1550 and 1600°C for 2 h. Density, phases, microstructure, roughness, strength and translucency were analyzed. All samples showed densification greater than 99%. After sintering at 1600^°C, the phase analysis revealed only tetragonal ZrO₂ in samples with 3% Y₂O₃, while in samples with 5% Y₂O₃ the cubic ZrO₂ phase was identified. Significant increase in the grain size was noted, when increasing the Y₂O₃ content from 3% to 5% from 0.8 µm to 2.3 µm for sintered samples at 1600°C. The strength was affected with Y₂O₃ content and no relevant influence of the Fe₂O₃ on density, microstructure or mechanical properties. Visible reflectance spectroscopy analyses, related to the CIELab scale, indicate variation in the contrast ratio as function of thickness of samples and coloring agent Fe₂O₃ content.

Keywords:
dental materials; yttria-stabilized zirconia ceramics; Fe₂O₃; optical properties; flexural strength