Remarkable resistivity and improved dielectric properties of Co-Zn nanoferrites for high frequency applications

Cobalt substituted zinc ferrite of the series CoxZn1-xFe2O4 (x = 0.0-0.5) were prepared by using a citrate precursor method. X-ray diffraction (XRD) study confirmed the spinel phase cubic structure of the prepared ferrites with Fd3m group. The average crystallite size of the samples was found in the range 28-36 nm. A high value of porosity was observed between 54% and 72% for the prepared samples. Hopping lengths for the tetrahedral and octahedral sites were found to decrease from 3.657 angstrom to 3.638 angstrom and 0.228 angstrom to 0.193 angstrom respectively with an increase in cobalt ion concentration. The value of strain was found in the range from 0.0039 to 0.0031. Transmission electron microscope (TEM) investigations record crystallite size in the range 30-40 nm which is in good agreement with XRD. Scanning electron microscope (SEM) imaging confirmed agglomerated structure of the ferrite nanoparticles. The dielectric study behaviour was recorded over a frequency from 10 kHz to 10 MHz at room temperature. The real part of dielectric constant was found to be in the range 2.4-8.4, imaginary part of dielectric constant was found to vary from 0.008 to 0.42 and the value of the dielectric loss tangent varied in the range 0.003-0.052 at 1 MHz for different concentration of cobalt ions. The minimum ac conductivity was found to have the value 5.0 x 10(-7) S/cm for composition Co0.3Zn0.7Fe2O4 at 1 MHz. The samples were found to be good insulators with enormous resistivity values ranging from 1.4 x 10(10) Omega-cm to 1.4 x 10(11) Omega-cm as observed from the I-V characterization for different concentration of cobalt ions. So, these observations make these materials suitable for high frequency applications. (C) 2020 Elsevier B.V. All rights reserved.