Fabrication of submicron α-Al₂ O₃ by the transformation of microcrystalline γ-Al₂ O₃ under high-pressure

Microcrystalline γ-Al₂O₃is used as raw material to prepare α-Al₂O₃from γ-Al₂O₃using the hinge-type cubic press under the pressure of 5 GPa with different temperatures. The results of X-ray diffraction analysis show that the obtained powders and bulk materials are pure α-Al₂O₃phase. The scanning electron microscope analysis shows that the minimum grain size of the α-Al₂O₃is about 80 nm and the average grain size of the α-Al₂O₃synthesized under the pressure of 5 GPa and the temperature of 800 ℃ is 340 nm. Experimental results show that the submicron α-Al₂O₃is fabricated by high pressure phase transformation of microncrystalline γ-Al₂O₃. Compared with the normal pressure sintering method, the complete phase transformation from γ-Al₂O₃to α-Al₂O₃can be achieved at 600 ℃ by high pressure sintering, which obviously reduces the synthesis temperature of α-Al₂O₃materials.