Structural, magnetic, and impedance properties of Co1-xZrxFe2O4 nanocrystallites by PEG-assisted sol-gel route

This work presents the Zr4+-substituted CoFe2O4 nanocrystallites at lower concentrations prepared via sol-gel method in order to investigate their structural and magnetic properties along with their impedance properties. XRD patterns confirm the inverse spinel phase of CoFe2O4 and the presence of zirconium (Zr) nanoparticles in the spinel network. The crystallite size was found to decrease after Zr substitution. CoFe2O4 nanocrystallites of 34-nm size and lattice parameter slightly increase with Zr4+ substitution into cobalt ferrite as observed from the XRD pattern. The presence of all functional groups involved in the present synthesis was determined from FTIR spectroscopy. Characteristic peaks of cubic spinel structured cobalt ferrites are observed in the Raman spectrum of each ferrite composition. The HRSEM images revealed the spherical morphology and nanosize of the Zr4+-doped CoFe2O4 nanocrystallites. EDX analysis confirmed that the applied process for the fabrication of Co1-xZrxFe2O4 nanoparticles is a proper process for the synthesis of spinel cobalt ferrites with homogeneity in composition. The TEM images evidently exposed formation of well-shaped nanoparticles and the fringes are uniform with 0.44-nm width and the selected area electron diffraction pattern exposed periodic arrangements. The results of magnetic hysteresis revealed that the zirconium-substituted cobalt ferrite nanoparticles increase the saturation magnetization and coercivity with increasing zirconium content. Impedance increased when Zr4+ was substituted, but for higher concentration it was reduced.