Abstract:
α-Al
2O
3 is widely used in the fields of machinery, chemical industry, electronics and other fields due to its excellent properties such as high hardness, ultra-high wear resistance, and chemical resistance. At present, most of the methods for preparing
α-Al
2O
3 powders use different precursors calcinated at a certain temperature. In this study,
α-Al
2O
3 was synthesized by using
γ-AlOOH and
γ-Al
2O
3 as precursor materials and using MgO as a doped additive. The phase transition process was characterized by SEM, XRD and particle size distribution. The results show that both
γ-Al
2O
3 and
γ-AlOOH undergo
α phase transition process of
γ-Al
2O
3→
θ-Al
2O
3→
α-Al
2O
3 during calcinations and pure
α-Al
2O
3 phases could be obtained at 1200 °C and 1100 °C, respectively. The temperature for pure
α-Al
2O
3 phase is affected by the particle size distribution of
γ-Al
2O
3 formed during its calcination, and MgO doping additive can promote the
α-Al
2O
3 phase transition process. The promotion effect is most obvious when the doping amount is appropriate and it would be weakened when the doping amount is too high or too low. When the MgO doping amount (mass fraction) is 0.5%, the temperature at which
γ-Al
2O
3 completes the
α phase transformation is 1050 °C, which is 150 °C lower than that without MgO. When
γ-AlOOH is doped with 0.3% and 0.5% MgO, the temperature for complete transition to
α-Al
2O
3 is 1075 °C, which is 25 °C lower than that without MgO. The promotion effect of MgO on the phase transition of different precursors is affected by the size of the primary particles of the powder.