Crystallization of ceramic pigment CoAl₂O₄ nanocrystals from Co-Al metal organic precursor

We synthesized ceramic pigment CoAl₂O₄ nanocrystals by a polymerized complex technique. Cobalt nitrate, aluminum nitrate, citric acid, and ethylene glycol were used as precursor materials. The formation of pure crystallized CoAl₂O₄ nanocrystals occurred when the precursor was heat-treated at 350°C in air for 2 h. We propose a model for CoAl₂O₄ formation from the polymeric precursor. The model contains a series of steps such as the transformation of the precursor to amorphous cobalt aluminate, three-dimensional nucleation and growth, and solid-state reaction.