From nanosphere to nanorod: Tuning morphology, structure and performance of cobalt ferrites via Pr3+ doping

Nanocrystals of CoFe2−xPrxO4 (x = 0, 0.025, 0.05, 0.075, 0.1) are successfully synthesized by a facile and free-surfactant hydrothermal method. An obvious variation of the particle morphology with increasing the concentration of Pr3+ ion in CoFe2−xPrxO4 ferrites is revealed. As the value x changes from 0 to 0.1, the surface morphology of CoFe2−xPrxO4 particle firstly shows cauliflower like structure, then, the surface becomes more smooth and adhesive, finally the particles lose their sphere shape and change into nanorod. The microstructure and cation distribution of CoFe2−xPrxO4 ferrites are tuned by Pr3+ ion doping. Owing to the increase in the Pr3+ concentration, the saturation magnetization Ms of as-synthesized samples decreases up to 50%. Meanwhile, at x = 0.075, due to the high shape anisotropy, a remarkable enhancement in microwave adsorption properties is shown, where a strong resonant behavior of the corresponding product comes from the natural resonance frequency (up to 6.5 GHz). Additionally, the obtained nanoparticles are successfully applied to adsorb Congo red (CR) dye. The effect of the morphology of nanoparticles on the adsorption properties of CoFe2−xPrxO4 ferrites for CR dye is analyzed. Owing to the bigger particle size, the adsorption capacity qt (56.82 mg g−1) of CoFe2−xPrxO4 particles is the lowest at x = 0.05, and then qt increases with increasing the value x. The corresponding adsorption kinetics and adsorption thermals are analyzed. The present work helps to deeply understand the shape and performance control of ferrites by rare-earth ion substitution, and provides a new method for enhancing the high-frequency electromagnetic performance of the ferrite nanoparticles and their adsorption properties for the dyes.