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

Abstract Nanocrystalline Ni 1− x Zn x Fe 2− y Dy y O 4 ( 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 60 Co γ-radiation with a dose rate of 310 kGy. The lattice parameter of irradiated samples increased attributed to the conversion of smaller size Fe 3+ ions to larger size Fe 2+ ions on ionizing effect of gamma radiation. Experimental results reveal that reduction in dielectric constant ( e ′), loss tangent (tan   δ ), real (Z′) and imaginary (Z′′) impedance and increase in ac conductivity ( σ ac ) have been increased with increasing in frequency. It was found that e′, tan   δ , σac increase, Z′′ and Z′′ reach a maximum value and thereafter decrease with further Zn ion substitution. The values of e ′, tan  δ and σ ac decrease with Dy 3+ substitution and enhanced after irradiation. The complex impedance analysis suggesting predominant contribution to conduction was through the grain boundary.