Dielectric Properties of Nanocrystalline Zn-Doped Lithium Ferrites Synthesized by Microwave-Induced Glycine–Nitrate Process

Abstract

In this study, nanocrystalline Li–Zn ferrites with the chemical composition of Li0.5ZnxFe2.5−xO4 (where 0 ≤ x≤0.5) were synthesized by glycine–nitrate combustion process using glycine as a fuel, nitrate as an oxidizer, and microwave oven as a heat source. The as-synthesized powders were characterized using an X-ray diffraction technique. X-ray diffraction patterns show that nanocrystalline Li–Zn ferrite phase with a spinel structure has been formed successfully in all samples. Dielectric properties including dielectric constants, dielectric loss, AC conductivity, and complex dielectric impedance were measured in the frequency range 20 Hz–10 MHz using a LCR meter. Results show that dielectric constant, as well as dielectric loss, decreases with increasing frequency and then becomes roughly frequency independent at high frequencies. In contrast, AC conductivity follows an upward trend with frequency. Complex impedance spectroscopic studies show the presence of only one semicircle for all samples, suggesting the predominant effect of grain boundary property of the material. It is also found that substitution of Zn for Fe ions leads to a significant decrease in electrical conductivity due to decrease of ferrous and ferric ions available for the hopping process. Similarly, both dielectric constant and dielectric loss show reduction with the increase in Zn content as a result of the reduction of Fe2+/Fe3+ ions.