Effect of manganese addition on sintering behavior and mechanical properties of alumina toughened zirconia

The effect of MnO2 additives on the sintering behavior and mechanical properties of alumina-toughened zirconia (ATZ, with 10 vol% alumina) composites was investigated by incorporating different amounts of MnO2 (0, 0.5, 1.0, and 1.5 wt%) and sintering at various temperatures ranging from 1300 to 1450 °C. The addition of MnO2 up to 1.0 wt% improved the sintered density, hardness, flexural strength, and fracture toughness of the composite. However, the addition of 1.5 wt% MnO2 degraded the relative density, hardness, and flexural strength of the composite due to the transformation of the ZrO2 phase from tetragonal to monoclinic and grain coarsening. Optimal results were obtained with 1.0 wt% MnO2 and sintering at 1450 °C, which improved the mechanical properties (hardness: 13.5 GPa, flexural strength: 1.2 GPa, fracture toughness: 8.5 MPa m1/2) and lowered the sintering temperature compared to the conventional sintering temperature of ATZ composites (1550 °C). Thus, the ATZ composite doped with MnO2 is a promising material for structural engineering ceramics owing to its improved mechanical properties and lower sintering temperature.