THE DENSIFICATION AND MICROSTRUCTURAL DEVELOPMENT OF AL2O3 WITH MANGANESE OXIDE ADDITION

The effect of MnO2 as an additive on the densification behaviour and microstructural evolution of alpha-Al2O3 has been investigated over a wide sintering regime. A colloidal technique was applied for the mixing of MnO2 in order to achieve a uniform distribution and homogeneous microstructures. Sintered density, average grain size and microstructural features were elaborated along with the microhardness and mechanical strength measurements. Manganese oxide was found to promote grain growth and an intergranular second phase formation was detected for additions over 0.5 wt% MnO2. Excessive grain growth and draining of the second phase were observed in the samples with 3 wt% MnO2 additions sintered above 1500 degrees C.