Ni substitution effect on the structure, magnetization, resistivity and permeability of zinc ferrites

Zn_1−xNi_xFe₂O₄ferrites up tox= 1.0 with Δx= 0.2 have been synthesizedviasolid state reactions and the sol-gel autocombustion technique with step-by-step co-firing. Data on the chemical composition and the surface morphology of the samples have been obtained using a scanning electron microscope. An X-ray powder diffractometer has been used to establish the phase purity and to determine the unit cell parameters. It has been found that the obtained samples had a spinel structure with theFd3̄m(No. 227) space group. The unit cell parameters decrease with increasing nickel concentration. Theaunit cell parameter decreases almost linearly from ∼8.443 Å forx= 0.0 down to ∼8.337 Å forx= 1.0. TheVunit cell volume decreases almost linearly from ∼601.72 ųforx= 0.0 down to ∼579.52 ųforx= 1.0. The magnetic characteristics of the obtained samples are determined and discussed. The Curie point of obtained samples varies in the range of 803.5-572.7 K. The maximum spontaneous magnetization of ∼74.6 emu g⁻¹at room temperature was fixed for the solid solution withx= 0.6. Ac-resistivity drops by more than 3 orders of magnitude in the frequency range 1-10⁶Hz. The composition withx= 0.6 has the minimum ac-resistivity of 5.3 kOm cm at a frequency of 10⁶Hz. The maximum value of the (μ′) real part of ∼11.2 and (μ′′) imaginary part of ∼5.2 of the permeability in the frequency range of 50 MHz-10 GHz is observed for the composition withx= 0.4. The composite samples for the microwave study were prepared by mixing of the ferrite powders with molten paraffin wax. The volume fraction of the ferrite filler in the composites was 25%. The largest value of the (μ′) real part of ∼3 and (μ′′) imaginary part of ∼0.63 of permeability is found for thex= 0.4 composite. The formation of the composite significantly reduces permeability.