A study of the growth process of Co3O4 microcrystals synthesized via a hydrothermal method

Pure Co 3 O 4 microcrystals were prepared by a hydrothermal method from Co(NO 3 ) 2 ·6H 2 O and urea solution, and the effect of thermal treatment time on the growth of Co 3 O 4 microcrystals was studied by X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman and UV‐Vis absorption spectra. The results show that with the thermal treatment time increases from 2 h to 12 h, the shape of as‐prepared Co 3 O 4 microcrystals changes from the hedgehog sphere‐like to the as‐cubic one that were stacked by lots of lamella, and finally cubes, and then longer time treatment will only lead to the size growth and agglomeration of particles. In conclusion, the cubic Co 3 O 4 microcrystals of uniform size (∼6 μm) are synthesized via a 12‐h thermal treatment. Moreover, the synthesis mechanism has been studied.