Asian Journal of Physical and Chemical Sciences

Chromium substituted Co-ferrite nanoparticles with general formula Cr_xCoFe_2−xO₄ (0≤ x ≤0.5) have been synthesized by using sol-gel technique. The samples were sintered at 900°C for 3hours. The effect of chromium substitution on dielectric properties of Co-ferrites is reported in this paper. The X-ray diffraction patterns indicate the formation of single phase spinel structure for all the samples. The particle size of all samples was calculated using Debye- Scherer's formula and it is in the range of 56-75 nm. The investigation on dielectric constant (ε'), dissipation  factor(D) and AC conductivity(σ_ac) was carried out at a fixed frequency 1kHz and in the frequency range of 100Hz to 1MHz at room temperature using LCR meter. The frequency dependence of the dielectric constant (ε') and AC conductivity (σ_ac) show a normal dielectric behaviour. The frequency dependence of dissipation factor (D) of the chromium substituted cobalt ferrite samples displays a relaxation peak at certain frequency. This peak suggests the presence of relaxing dipoles in the Cr-Co nano ferrite samples. It is also observed that the broadening of the relaxation peak with chromium-content(x) in dissipation factor versus frequency curve is due to the strengthening of dipole-dipole interactions. The dielectric behaviour of the Cr-doped cobalt nano ferrites is explained based on Koop’s two layer model and Maxwell- Wagner interfacial polarization theory and Debye-relaxation theory.