The effects of sintering additives on the mechanical properties and microstructure evolution of 3 mol% Y-TZP

The current work investigates the effects of sintering additives, particularly focused on 0.5 wt% manganese oxide (MnO₂) and 0.1 wt% alumina (Al₂O₃), and co-doping both additives together (i.e. MnO₂ + Al₂O₃), on the microstructure and mechanical properties of 3 mol% Y-TZP. The doped powders were prepared by attrition milling and subsequently green samples were sintered in air at temperatures ranging from 1250 to 1550°C with 2 hrs holding time. The results showed that the dopants have not disrupted the tetragonal phase stability. All the dopants aided sintering at 1250°C but with MnO₂ being most effective in promoting densification with samples, recording about 97.6% relative density. Similar improvement in the mechanical properties was also observed for the doped zirconia. Young’s modulus, Vickers hardness and fracture toughness as high as 192 GPa, 13.6 GPa and 4.6 MPam^1/2, respectively were obtained for both, the MnO₂-doped and co-doped Y-TZPs, when sintered at low temperature of 1250°C. Microstructural examination, however revealed that the MnO₂ dopant promoted exaggerated grain growth when sintered at higher temperatures.