The influence of citric acid on the microstructure and magnetic properties of cobalt ferrite nanoparticles synthesized by hydrothermal method

Cobalt ferrite nanoparticles were synthesized by the citric acid-assisted hydrothermal method with the citric acid to metal ion molar ratio (C/M) 0.5, 1, and 1.5. Nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and vibrating sample magnetometer (VSM) techniques. The coarse cobalt ferrite particles are synthesized along with hematite impurities when using the routine hydrothermal method. However, the results showed that single-phase and uniform cobalt ferrite nanoparticles were formed in the presence of citric acid. The obtained results also revealed that by changing the C/M ratio from 0.5 to 1 and 1.5, the mean crystallite size and maximum magnetization were changed from 7.8, 4.7, and 7.3 nm and 50.3, 40, and 48.2 emu/g, respectively. Therefore, citrate acid concentration plays a significant role in the final properties of synthesized particles. Moreover, this parameter is a powerful tool for regulating the properties of nanoparticles. In addition, in this study, a mechanism for synthesis producer and role of the chelating agent concentration, based on the stability of the formed complexes during the synthesis process and its effect on the nucleation temperature, has been presented.