A process for the production of sub-micron to millimetre sized thermally stable α-alumina spheres

The sol-emulsion-gel method has been employed to produce alumina gel spheres from unseeded as well as seeded alumina sol. Controlled heating of the unseeded gel spheres leads to the formation of α-alumina phase at 1200°C. Various seeds have been tried to determine the effect of seeding on the formation of α-alumina and it is found that seeding with 0.5 wt.% Fe₂O₃ leads to the formation of α-alumina at a relatively low temperature of 950°C. The sizes of the microspheres can be varied in the range between 0.5 μm and 1 mm by suitable choice of the process parameters. The resultant gel spheres on controlled heating transform into thermally stable α-alumina spheres.