Synthesis of plate-like α-Al2O3 single-crystal particles in NaCl–KCl flux using Al(OH)3 powders as starting materials

Plate-like α-Al2O3 single-crystal particles were successfully synthesized in NaCl–KCl flux using Al(OH)3 powders as starting materials, and the influence of pre-calcining of Al(OH)3 powders on the phase formation and morphology of α-Al2O3 powders was focused. When Al(OH)3 powders are used as starting materials, the synthesized product at 900 °C is mainly composed of α-Al2O3 and κ-Al2O3, and most synthesized particles show alveolate morphology. At 1100 °C, single-phase α-Al2O3 powders are developed, in which there are many aggregations of intensively bound plate-like particles. In contrast, using porous amorphous Al2O3 powders obtained by pre-calcining Al(OH)3 powders at 550 °C for 3 h as the starting material, plate-like α-Al2O3 single-crystal particles can be well developed above 900 °C. The reason of the influence of pre-calcining of Al(OH)3 powders on the phase formation and morphology of α-Al2O3 powders is also discussed in the paper.