Effect of AlF3 seed concentrations and calcination temperatures on the crystal growth of hexagonally shaped α-alumina powders

To synthesize micro-sized and high crystalline α-alumina particles with uniformly and rapidly at low temperatures, various concentrated AlF3 seeds were added into an anhydrous ethanol solution saturated by an aluminum hydroxide starting material, gibbsite Al(OH)3. Hexagonal shaped α-alumina powders highly crystallized were observed at lower temperature of 750 °C, in the ranges from 0.01–5.0 mol% seed concentrations, and the α-alumina crystal growth depends on the concentrations of added AlF3 seed. When 1.0 mol% AlF3 seeds were added, the largest α-alumina hexagonal crystals (average size about 4.8 m after calcination at 900 °C) were produced. Additionally the crystallinity and size of α-alumina particle increases linearly with the calcination temperature. The size rapidly increased with an increase of calcination temperatures to 800 °C and then gradually increased up to 900 °C. This result shows that crystal growth of α-alumina is affected by seed concentrations and crystallized calcination temperature.