Structural, magnetic and electrical properties of Zr-substitued NiZnCo ferrite nanopowders

Zr-substituted NiZnCo ferrite nanopowders, Ni(0.4-x)Zn(0.5)ZrxCo(0.1)Fe(2.0)O(4) (0 <= x <= 0.20), were synthesized by the sol-gel auto-combustion method. The effects of Zr substitution on the structural, magnetic and electrical properties have been investigated. The DTA and TG results indicate that there are three steps of combustion process. The X-ray diffraction patterns show that the lattice parameter and the average crystallite size increase with the increase of Zr substitution. The saturation magnetization increases with the increase of Zr substitution when x <= 0.05, and then decreases when x > 0.05. Meanwhile, the coercivity initially decreases with the increase of Zr substitution when x <= 0.05, and then increases when x > 0.05. The polarization behavior for all the samples in the test frequency range from 100 Hz to 10 MHz obeys the charge polarization mechanism, which happens since the frequency of the hopping of electron exchange between Fe2+ and Fe3+ ions are far from the frequency of alternating-current field. And the dielectric constant increases with the increase of Zr substitution. The relaxation peak of the frequency dependence of dielectric loss is observed for x >= 0.10, which is due to the frequency of charge hopping between the Fe2+ and Fe3+ exactly matches with the frequency of the external applied field. Electrical transport behavior of the ferrite nanopowders is found to follow the impurity semiconductor, and the effect of Zr substitution on the temperature dependence of dc resistivity is observed . (C) 2017 Elsevier B.V. All rights reserved.