Induced effects of Zn ⁺² on the transport and complex impedance properties of Gadolinium substituted nickel-zinc nano ferrites

We report on the preparation and transport properties of Gadolinium substituted Ni _(1-x) Zn _x Gd _y Fe _(2-y) O ₄ (0⩽x⩽1,y=0.1) nano particles using low temperature citrate precursor combustion method. The Rietveld refinement of PXRD data suggests the crystal structure of sample belongs to Fd-3m space group with an octahedral occupation of Gd ⁺³ ions. FESEM micrographs show the existence of porosity in the samples. The dielectric studies reveal the good dielectric behaviour with high dielectric constant in Zn ⁺² substituted sample (x = 0.4). An increase in a.c conductivity observed in the Zn ⁺² substituted sample due to the hopping mechanism. The impedance spectroscopy of the samples shows the existence of high grain boundary resistance and an alternate switching of dielectric relaxation from non-Debye to Debye type. The activation energies and Curie temperature estimated using D. C. conductivity measurements drop linearly with an increase in Zn ⁺² concentration. We attribute the observed transport properties mainly to the hopping of Fe ⁺² ↔ Fe ⁺³ ions.