Effect of additives on densification and deformation of tetragonal zirconia

The effect of additives (Bi₂O₃, Fe₂O₃) on densification and creep rates of tetragonal ZrO₂-Y₂O₃ has been investigated. In Bi₂O₃-doped Y-TZP, a reactive liquid forms at temperatures above 800–900‡C, which leads to a strong enhancement of densification for concentrations of 1–2 mol % Bi₂O₃. However, during cooling from the processing temperature a strong, undesirable transformation of the tetragonal to the monoclinic phase occurs. The addition of 0.6–1.2 mol % FeO_3/2 promotes densification without destabilizing the tetragonal phase. A concentration of 1.2 mol %, however, induces discontinuous grain growth, while this is not the case for 0.6 mol %. Creep rates of Y-TZP were enhanced by a factor of 4–6 by adding 0.6 mol % FeO_3/2.