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

•Gd substituted Ni-Zn nanoferrites were synthesized via Low-temperature citrate precursor method.•Rietveld refinement suggests the formation of a good nanocrystalline phase in the samples.•Maximum dielectric constant with a minimum dielectric loss obtained for x = 0.4 and y = 0.1.•With the increase in the Zn+2 concentration, a reduction in the Curie temperature is observed. We report on the preparation and transport properties of Gadolinium substituted Ni(1-x)ZnxGdyFe(2-y)O4 (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.