Direct precipitation of spinel type oxide ZnGa2O4 from aqueous solutions at low temperature below 90°C

Ultrafine ZnGa₂O₄ spinel particles ranging from 4 to 11 nm of crystallite size were directly precipitated by dropping a mixed solution of zinc sulfate and gallium sulfate into aqueous NH₃ at a temperature of 25 to 90°C with stirring. They were also precipitated by aging the mixed solution in the presence of either urea or hexamethylenetetramine at 90°C. The crystallite size of the precipitates decreased with increasing concentration of the metal ions in the solution and with decreasing temperature of the solution, which is explained by the formation of a large number of nuclei.