Abstract

The aim of the present work is to prepare some samples of the S-type spinel ferrite Al_0.51-0.51x Ni_x Fe_2.16-0.16x O₄ and Al_0.51-0.51x Ni_x Fe_2.06-0.16xY_0.1O₄ where (x = 0.0, 0.5, and 1) to investigate some of their structure and different electric properties as a function of temperature, frequency and compositions. The X-ray diffraction analysis of the samples ensures the formation of S-type spinel ferrite with the average particle size estimated as 35.1-35.9nm. Ac conductivity, dielectric constant and loss tangent were investigated by using the complex impedance technique. The conductance results specified two types of conduction mechanisms, hopping conduction and displacement conduction of charge carriers quantum-mechanical-tunneling, QMT and correlated barrier hopping, CBH in the studied range of temperature. Cole-Cole diagrams show as expected the existence of a distribution of relaxation times and gave values of the activation energy of the dielectric relaxation process ranging from -0.022eV to 0.173eV.