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Effect of Cation Doping on Mechanical Properties of Yttria Prepared by an Optimized Two-Step Sintering Process


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Undoped Y2O3 and Y2O3 doped with either Si4+, Er3+, Yb3+, Al3+ or Ti4+ were fabricated by a two-step sintering method. The concentration of each dopant cation (Si4+, Er3+, Yb3+, Al3+, and Ti4+) was adjusted so that the dopant:yttria molar ratio was 0.01 and the mechanical properties and the microstructures of each were characterized. The Vickers hardness and the bending strength of cation-doped Y2O3 increased in the order Si4+, Er3+, Yb3+, Al3+, and Ti4+ paralleling increases in the relative density. Ti-doped-Y2O3 had the highest density and the highest strength. Transmission electron microscopy analysis revealed that Ti segregated to the grain boundaries of Y2O3. The two-step sintering method was optimized to enhance the mechanical properties of Y2O3. As a consequence, Ti-doped Y2O3 with the Ti4+:yttria molar ratio of 0.01 sintered at the optimized heating schedule was found to have a Vickers hardness and three-point bending strength as high as 874 Hv and 307.0 MPa, respectively.