Investigation of structural, morphological, electric modulus, AC conductivity characteristics, and validation of software-based simulated impedance/material parameters of bicomponent Co-Al doped Ba-Sr ferrites

Abstract

In this report, Co2+ and Al3+ doped M-type Ba-Sr hexagonal ferrite has been synthesized using sol-gel method. The crystal structure and grain morphology have been examined by x-ray Diffraction (XRD), and Field Emission Scanning Electron Microscope (FESEM). The optical band gap of the prepared compositions was determined by ultra violet visible spectroscopy (UV–vis). The dielectric, impedance, electric modulus, and conductivity characteristics have been investigated by an impedance analyzer at room temperature. The structural parameters confirmed the formation of an M-type hexagonal crystal structure along with traces of spinel and magnetite phase. The doping Co2+/Al3+ manifests the contraction of the unit cell accompanied by a reduction in lattice constants at a large doping level. The grain morphology revealed a change in grain shape with doping and the formation of needle-shaped as well as hexagonal-shaped grains. The study of the dielectric spectrum exhibited a doping-dependent decrease in dielectric constant and an increase in loss tangent. The electric modulus spectra confirmed the non-Debye type behavior of the material and conductivity relaxation was exhibited in conjunction with different relaxation times. Both relaxation time and ac conductivity decreased with an increase in doping content. The simulated complex impedance curves using electrochemical impedance spectroscopy (EIS) software are in agreement with the measured impedance values of prepared compositions. The observed trend in calculated grain and grain boundary parameters is in agreement with the grain/grain boundary distribution depicted in micrographs.