Synthesis of MgAl₂O₄ spinel: seeding effects on formation temperature

Four different methods of MgAl₂O₄ spinel synthesis in the presence and absence of seeds were studied. The four methods used for MgAl₂O₄ synthesis were (a) one sol (boehmite) and one solution [Mg(NO₃)₂]; (b) two sols (boehmite and magnesia); (c) two nitrates (Al and Mg nitrates) and two alkoxides (Al isopropoxide and Mg ethoxide). The use of a nitrate route led to the formation of spinel at the lowest temperature without the influence of seeding. Seeding with spinel crystallites of all the powders except the one-sol and one-solution diphasic gels apparently resulted in a lower formation temperature of MgAl₂O₄ spinel, and this lowering of crystallization temperature can be explained by the nucleation and epitaxial growth mechanism.