Competing crystallite size and zinc concentration in silica coated cobalt ferrite nanoparticles

Silica coated (30 wt%) cobalt zinc ferrite (Co_1−xZn_xFe₂O₄, x=0, 0.2, 0.3, 0.4, 0.5 and 1) nanoparticles were synthesized by using sol–gel method. Silica acts as a spacer among the nanoparticles to avoid the agglomeration. X-ray diffraction (XRD) reveals the cubic spinel ferrite structure of nanoparticles with crystallite size in the range 37–45 nm. Fourier transform infrared (FTIR) spectroscopy confirmed the formation of spinel ferrite and SiO₂. Scanning electron microscopy (SEM) images show that the nanoparticles are nearly spherical and non-agglomerated due to presence of non-magnetic SiO₂ surface coating. All these measurements signify that the structural and magnetic properties of Co_1−xZn_xFe₂O₄ ferrite nanoparticles strongly depend on Zn concentration and nanoparticle average crystallite size in different Zn concentration regimes.