Investigation of electrical, dielectric, and relaxation phenomenon of Co–Cr substituted SrM hexaferrite: Validation of measured and simulated parameters

Abstract

Chromium (Cr) and Cobalt (Co) substituted hexaferrite with composition Sr(CoCr)xFe(12−2x)O19 (x=0.0to 0.6) has been synthesized via the Sol-gel combustion technique. The phase purity, morphology, and electrical characteristics of all sintered hexaferrite have been analyzed. XRD measurements showed that all sintered hexaferrite exhibit a magnetoplumbite structure. The substitution of Cr–Co ions in a crystal lattice resulted in a meager decrease in lattice constant value ‘a’ and a considerable decrease in lattice constant value ‘c’. FTIR spectra revealed the existence of three precise absorption bands at 419.59, 539.71, and 580.37 cm−1 which were predicted to be due to Fe–O vibrations. Impedance spectroscopy has been carried out on a wide range of frequencies (20 Hz–2 MHz). The investigated parameters have been considerably affected by dopant-tuned morphology through a decrease in grain size and the formation of grain clusters. The loss tangent and dielectric constant of the Cr–Co substituted SrM hexaferrite is found to be increased with substitution. Substitution causes a decrease in the AC conductivity value in the high-frequency region from 9.57 × 10−4 to 3.05 × 10−4 Ω−1m−1. The non-Debye behavior is observed in the material by analyzing the dielectric and electric modulus spectra. The simultaneous contribution of grain/grain boundaries demonstrated by Cole-Cole plots (M″ vs M′) in the x = 0.4 sample is consistent with SEM micrographs. The charge transport mechanism that occurs in the synthesized samples can be explained with SEM/FESEM micrographs as well as with calculated values of grain and grain boundary resistance/capacitance from EIS software. The two incomplete semicircular arcs have been observed in the x = 0.6 sample in Z″ vs Z′ plots. The conductivity relaxation is significantly improved with Cr–Co substitution.