Low-Temperature Fabrication of Plate-like α-Al₂O₃ with Less NH₄F Additive

Fluorinated compounds are effective mineralization agents for the fabrication of plate-like α-Al₂O₃. However, in the preparation of plate-like α-Al₂O₃, it is still an extremely challenging task to reduce the content of fluoride while ensuring a low synthesis temperature. Herein, oxalic acid and NH₄F are proposed for the first time as additives in the preparation of plate-like α-Al₂O₃. The results showed that plate-like α-Al₂O₃ can be synthesized at a low temperature of 850 °C with the synergistic effect of oxalic acid and 1 wt.% NH₄F. Additionally, the synergistic effect of oxalic acid and NH₄F not only can reduce the conversion temperature of α-Al₂O₃ but also can change the phase transition sequence.