Dielectric behaviour of Ni x Mg 1–x Fe 2 O 4 ferrites

The real dielectric constant ε′ and dielectric loss factor tan δ were studied asfunctions of frequency f, temperature T, and composition x for Ni_xMg_1-xFe₂O₄ system ferrites with x = 0, 0.2, 0.4, 0.6, 0.8, and 1 prepared using the usual ceramic technique. The experimental results indicated that ε′ and tan δ decrease as the frequency and Ni ion substitution increase and as the temperature decreases. The observed values of ε′ are high. Dielectric relaxation processes (peaks) were observed in the tan δ curves at relativly high temperatures but were not visible in the ε′ curves. The dielectric relaxation frequencies f_D were found to be shifted to higher values as the temperature increased. The activation energy E_D for the dielectric relaxation and relaxation frequency f_o at infinitely high temperature were found to increase as the Ni ion substitution increased.