Influence of the preparation method and aluminum ion substitution on the structure and electrical properties of lithium–iron ferrites

In this study, we report the synthesis of nanosized Al-substituted lithium–iron ferrites Li 0.5 Al x Fe 2.5- x O 4 (0 ≤ x ≤ 1) by sol–gel auto-combustion method and by ceramic method with double sintering. Synthesized materials were studied using X-ray diffraction and impedance spectroscopy. The samples obtained by chemical methods have a higher homogeneity of the distribution of elements by volume, good repeatability of the result, high crystallinity, small crystallite size and perfect stoichiometry. Based on Koop's theory, the basic regularities of the behavior of the dielectric constant and the loss tangent are explained. The jump mechanism of conductivity has been realized by the transition of an electron between iron ions in different valence states. Samples synthesized by the sol–gel auto-combustion show technological characteristics, compared with systems obtained by solid-phase method.