Nucleation of alpha alumina in boehmite gel

Transformation of boehmitc-derived alumina gel to α–Al₂O₃ in unseeded gels is strongly influenced by the parent phase, θ-Al₂O₃. In seeded gels the perfect structure of the epitaxial substrate (α–Al₂O₃, 0.3 wt. %) influences the surrounding defect θ-phase resulting in (a) fewer imperfections due to lower transformation enthalpy to α–Al₂O₃, and (b) multiple nucleation sites of α–Al₂O₃ at the α–Al₂O₃ seed surface. The rate of transformation expressed for the same number of α–Al₂O₃ nuclei in unseeded and seeded gels indicates that it is faster in the unseeded gel than in the seeded gel.