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.

Functionalization of morphology in optimization of dielectric, electrical/impedance modulus, and relaxation mechanisms of Co-Ni doped M-type Sr nanoferrites

“…M has two basic features, the first sigmoidal step in Mʹ and the second broad asymmetric peak in M″ [22,23]. It can be noted that a similar trend has been reported in earlier reports [24]. The value of Mʹ is low at low frequencies, however, it first increases, and after that saturated at high frequencies being the highest for x = 0.4.…”

“…The value of Mʹ is low at low frequencies, however, it first increases, and after that saturated at high frequencies being the highest for x = 0.4. The reason behind these observations may be the lack of restoring force that governs the mobility of charge carriers [24]. The sigmoidal increase is associated with the charge carrier's short-range mobility; however, saturation assists the long-range mobility.…”

“…Where σ dc is the dc conductivity that is independent of frequency while σ ac is the frequency-dependent ac conductivity of the material. The ac conductivity (σ ac ) is related to the dielectric relaxation which follows the empirical power law [28] A and n are constants that depend on the temperature and composition of the sample [24].…”

“…Where A and n are fitted parameters of CPE and R is the resistance value determined from the equivalent circuit model [24].…”

Exploration of the charge transport mechanism, complex impedance, dielectric/electric modulus and energy storage characteristics of the aloe vera (Aloe Barbadensis Miller) plant

“…The dependence of dielectric parameters with frequency is similar to conventional synthesized metal-based compounds/oxides/dielectrics as shown in figure 7. Dispersion accompanied by rapid fall in ε′ and ε″ in the low-frequency region can be observed showing that electrons can follow the applied signals up to a certain frequency forming the polarization [38]. As the frequency increases the electrons are unable to get in sync and lag behind the applied field [39].…”