Abstract

The influences of solution pH, cation concentration, treatment temperature, time, and ZnO/Ga₂O₃ molar ratio of the starting solution on the crystallite size, morphology, lattice parameters and chemical composition of hydrothermally synthesized ZnGa₂O₄ spinel particles were investigated. Nanocrystalline ZnGa₂O₄ spinel particles were prepared from gallium sulfate and zinc sulfate in the presence of aqueous ammonia under hydrothermal conditions in the pH range of 2.5 to 10. Their crystallite size increased and their chemical composition approached ZnO/Ga₂O₃ = 1 with increasing treatment temperature, time, and starting ZnO/Ga₂O₃ molar ratio. ZnGa₂O₄ spinel particles with a stoichiometric composition were synthesized by controlling the starting ZnO/Ga₂O₃ molar ratio under hydrothermal conditions at 240 °C for 50 h. The formation mechanism of the ZnGa₂O₄ spinel particles was discussed, and the diffusion of Zn²⁺ ions seemed to be the key for the synthesis and growth of the spinel, especially for obtaining a stoichiometric composition.