Yttrium doped cobalt ferrite nanoparticles: Study of dielectric relaxation and charge carrier dynamics

We report the effect of yttrium (Y) doping on structural, optical properties and conductivity relaxation behavior of cobalt ferrite (CFO) nanoparticles prepared via citrate auto-ignition route. Microstructural analysis using XRD study confirms the growth of single phase nanocrystalline CFO, HRTEM images delineate faults in the crystal stacking sequence. UV–vis absorption spectra show a blue shift for optical band gaps of the doped samples. Impedance spectroscopy suggests that both grain and grain boundaries contribute to the conduction process. A universal power law dependence of the conductivity spectra has been observed. Scaling of the conductivity spectra resulted the conduction mechanism to be independent of composition and temperature. Stretched behavior of the dielectric response has been elucidated by Harviliak-Negami (H.N.) model based functions. Defects in the crystal structure played important role on the overall transport properties of the system.