The mixed spinel ferrites NiAl_xFe_2-xO₄ with different concentrations of Al content i.e. x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5, were prepared by using the standard double sintering technique by mixing high purity metal oxidesAl₂O₃, NiO and Fe₂O₃. Two probe electrode method was used at room temperature to determine the ac electrical conductivity (σ_ac), real dielectric constant (ε') and imaginary dielectric constant (ε''), and the dielectric loss tangent (tan δ) over a variable applied frequency in range of (10KHz – 1MHz). σ_ac shows a continuous increasing with the increasing of the applied frequency. The obtained results from the dielectric parameter for all the samples decreases with increasing of frequency, which indicated to normal spinel ferrite behavior. The variation of ac and dielectric parameters were explained on the basis of electronic exchange between the ferric ions (Fe³⁺) and ferrous ions (Fe²⁺) or trivalent nickel ions (Ni ³⁺) and divalent nickel ions (Ni ²⁺). The experimental results reveal that the ac electrical and dielectric properties, which can be influenced changed by substitution of the Al content in Ni spinel ferrites. These results of the mixed Al-Ni spinel ferrite suggest uses as a soft ferrite material, which can be used for different an interesting technological and scientific applications.

Al-Ni Spinel Ferrite, Dielectric Properties, ac Electrical Conductivity