Effect of 60Co gamma irradiation on dielectric and complex impedance properties of Dy3+ substituted Ni-Zn nanoferrites

Nanocrystalline Ni1−xZnxFe2−yDyyO4 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0; y=0.0 and 0.1) ferrites were synthesized by combustion method. Ni-Zn-Dy nanoferrites were investigated by X-ray diffraction, scanning electron microscopy, dielectric and impedance properties, before and after γ-irradiation process by 60Co γ-radiation with a dose rate of 310 kGy. The lattice parameter of irradiated samples increased attributed to the conversion of smaller size Fe3+ ions to larger size Fe2+ ions on ionizing effect of gamma radiation. Experimental results reveal that reduction in dielectric constant (ε′), loss tangent (tan  δ), real (Z′) and imaginary (Z′′) impedance and increase in ac conductivity (σac) have been increased with increasing in frequency. It was found that ε′, tan  δ, σac increase, Z′′ and Z′′ reach a maximum value and thereafter decrease with further Zn ion substitution. The values of ε′, tan δ and σac decrease with Dy3+ substitution and enhanced after irradiation. The complex impedance analysis suggesting predominant contribution to conduction was through the grain boundary.