Impedance and Dielectric Analysis of Nickel Ferrites: Revealing the Role of the Constant Phase Element and Yttrium Doping

This paper presents the analysis of electrical and dielectric properties of the yttrium-doped nickel ferrite nano-powders synthesized using the co-precipitation method. Impedance and dielectric measurements have been carried out as a function of frequency at different temperatures from 200 to 25 °C in the range of 0.1 kHz–1 MHz. In order to investigate the conduction mechanism and highlight the role of yttrium doping in different concentrations, impedance spectroscopy was employed. The obtained data were analyzed in terms of equivalent circuits made of resistor and capacitor components describing the contributions from different electrical active regions in a material. Further, this study highlights the importance of a single constant phase element (CPE) in the description of dispersion behavior of the impedance response of the investigated samples in the given frequency range. The use of this technique enabled the characterization of grain and grain boundaries contribution in overall conductivity mechanism. The dielectric dispersion nature of all investigated materials is reflected in this study. Very high values of the real part of permittivity at low frequencies are assigned to space-charge polarization. The dependence of the real part of dielectric permittivity values of the yttrium content was also discussed. Doping with yttrium in different concentrations that reflects in different electric and dielectric responses is concluded in this study. The greatest change is noticed for the sample with the minimum dopant content for a x = 0.05 atomic percent share of yttrium. To reveal the potential role of more than one ion contribution to the overall relaxation process in investigated compounds, a modified Debye’s equation was utilized.