Size Control of α‐Alumina Particles Synthesized in 1,4‐Butanediol Solution by α‐Alumina and α‐Hematite Seeding

Abstract

The effects of seed particles and shear rate on the size and shape of α‐Al2O3 particles synthesized in glycothermal conditions are described. It is proposed that seed particles provide a low‐energy, epitaxial surface in solution to lower the overall surface energy contribution to the nucleation barrier, thus increasing nucleation frequency and subsequently reducing the particle size of hexagonal α‐Al2O3 platelets or polyhedra, depending on synthesis conditions, in 1,4‐butanediol solution. Seeds have a significant effect on the size of hexagonal α‐Al2O3 platelets in samples with high seed concentration. The particle size of α‐Al2O3 platelets decreases from 3 to 4 µm to 100 to 200 nm by increasing the number concentration of seeds. In the case of α‐Fe2O3 seeding, the effect of seeding on the size of α‐Al2O3 particles closely resembles the effects obtained with α‐Al2O3 seeding. Regardless of seed concentration, high stirring rate promotes the formation of hexagonal platelets with high aspect ratio, whereas medium and low stirring rates promote the formation of elongated platelets and polyhedra with 14 faces, respectively.