Variation in the crystallinity of cobalt oxide nanoparticles with increasing annealing temperature and pH

This study is focused on the effects of annealing temperature and pH on the crystallinity of cobalt oxide (Co3O4) nanoparticles (NPs) synthesized via sol-gel method. X-ray diffraction (XRD) analysis was carried out to investigate the crystalline structure and size of the NPs. The results indicated that increasing the pH from 10 to 14 during NPs synthesis led to an increase in crystallinity, as evidenced by the appearance of Bragg reflections upon calcination. On the other hand, increasing the calcination temperature from 120°C to 800°C also increased the crystallinity of Co3O4 NPs, as seen by the appearance of additional Bragg reflections and an increase in crystallite size. These findings demonstrate the significance of pH and calcination temperature in controlling the crystallinity and properties of Co3O4 NPs.