Sintering of alumina using a modified two-step sintering process

A modified two-step sintering process is compared with the conventional two-step sintering process for sintering alumina. In modified two-step sintering, the first step was heated with microwave-assisted conventional heating up to 1500 °C ( T ₁ ) and the second step was heated at 1450 °C ( T ₂ ) with conventional heating alone. T ₁ and T ₂ were maintained the same for both the modified two-step sintering and conventional two-step sintering processes. Results showed that modified two-step sintering produced marginally lesser grain growth but similar densification. A near-full densification (>99%) was obtained on the holding sample for 3 h at T ₂ in both the two-step sintering processes. A minimum grain size of 1.7 and 1.9 µm and a maximum grain size of 3.0 and 3.2 µm were obtained at 0.5 and 3 h sintering durations, respectively, for both processes. Modified two-step sintering produced a Vickers hardness of 18.7 ± 0.2 GPa, and the conventional two-step sintering process produced a hardness of 18.5 ± 0.2 GPa.