Preparation and properties of Al₂O₃-Fe₂O₃/3Y-TZP gradient composite ceramics with multilayer ceramic structure

In order to achieve a better close shade of artificial restoration match with natural dentition, a color-gradient 3 mol% Y₂O₃-stabilized ZrO₂ (3Y-TZP) ceramics for dental restoration was prepared by forming and sintering process with powders of Fe₂O₃ (0.01wt%-0.09wt%)-Al₂O₃ (0.1wt%)/3Y-TZP as the raw materials. Their colorimetric characterization, sintering performance, and mechanical properties were tested, and the effect of Fe₂O₃ and Al₂O₃ on 3Y-TZP ceramics was studied. The results show that the color of the gradient Al₂O₃-Fe₂O₃/3Y-TZP changing from saffron yellow to white gradually, which matches with the natural dentition. In addition, the doping of trace Al₂O₃ (0.1wt%) on uncolored porcelain layer can avoid the cracking between porcelain layers during the presintering process. The flexural strength changes of gradient and can meet the need of dental restoration (≥ 800 MPa). The doping of trace Fe₂O₃ (0.01wt%) and Al₂O₃ (0.1wt%) can improve the densification and grain growth during the sintering process. And the doping of trace Fe₂O₃ (0.01wt%) and Al₂O₃ (0.1wt%) in 3Y-TZP can increase the flexural strength of the Al₂O₃-Fe₂O₃/3Y-TZP, but the flexural strength decreases when more Fe₂O₃ is doped (≤ 0.09wt%) in 3Y-TZP.