Nanocrystalline Ni_xCo_(0.5−x)Zn_0.5Fe₂O₄ ferrites: fabrication through co-precipitation route with enhanced structural, magnetic and photo-catalytic activity

A series of Ni-substituted Ni_xCo_(0.5−x)Zn_0.5Fe₂O₄ with x = (0.1, 0.2, 0.3, 0.4) spinel ferrites were prepared by co-precipitation method to investigate the effects of Ni compositional variation in the structural, optical, magnetic and photo-catalytic activity. The thermal decomposition of Ni_xCo_(0.5−x)Zn_0.5Fe₂O₄ was investigated by TGA/DTA. XRD results revealed that all the samples were single-phase of cubic spinel with Fd-3m space group. The lattice constant and average particle size decreased simultaneously with the increase in Ni doping amount. TEM and SEM analysis showed the monodispersion and cubic-like nanostructure. Two prominent stretching bands were observed in FT-IR spectra around 400–600 cm⁻¹. These two bands confirmed the spinel structure of the prepared nanoparticles. Raman spectroscopy is used to verify that we have synthesized spinel ferrites and determines their phonon modes. The optical study UV–visible is used to calculate the optical band gap energies. The products exhibited the attractive magnetic properties with high saturation magnetization, which were examined by a vibrating sample magnetometer. On the other part, the photocatalytic activity of our compounds was studied using methylene blue as model organic pollutants, where the results showed that an appropriate amount of Ni dopant could greatly increase the amount of hydroxyl radicals generated by the ferrite nanoparticles, which were responsible for the obvious increase in the photo-catalytic activity.