Electrical and dielectric properties of Ni0.5Co0.5GaxFe1.8-xO4 (x ? 1.0) spinel ferrite microspheres

Microspheres of Ni0.5Co0.5GaxFe2_xO4(x <= 1.0) microsphere spinel ferrites (NiCoGaFe-MSFs) and carbon spheres were prepared via a hydrothermal technique. The microstructure of microspheres was investigated through scanning and transmission electron microscopy (SEM and TEM), respectively, and X-ray diffraction (XRD). The electrical and dielectric properties of NiCoGaFe-MSF at temperatures ranging from 20 to 120 degrees C (between 293.1 x 103 and 393.1 x 103) for f <= 3.0 MHz were systematically studied as a result of 3D graphical drawing of the data obtained from an impedance analyzer. Relevant parameters such as ac/dc conductivity, dielectric loss, dielectric constant, activation energy, dissipation factor and Cole-Cole impedance spectra were extensively evaluated for various Ga ion mole ratios in the substitution where x <= 1.0. We notice that the ac conductivity mostly obeys exponential power law rules, which vary significantly with the substitution ratios of Ga ions. Impedance analyses confirm that differences in conduction mechanisms in NiCoGaFe-MSFs are mainly due to grain-to-grain boundaries related to Ga ion substitution ratios. The change in dielectric constant of NiCoGaFe-MSFs is strongly dependent on the substitution rates and results in a normal dielectric distribution with frequency. The tangential loss for all microspheres is observed to vary with measured temperatures and their frequency dependencies can be attributed to the conduction mechanism similar to Koop's phenomenological model. It is clearly seen that the formation of semicircles is dominated by all the NiCoGaFe-MSFs and the diameter of the semicircles mostly decreases with increasing temperature, as evidence of a temperaturedependent relaxation mechanism. (c) 2022 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

Automated summary

Microspheres of Ni0.5Co0.5GaxFe2-xO4 (x≤1.0) spinel ferrites (NiCoGaFe-MSFs) and carbon spheres were synthesized via a hydrothermal technique. The microstructure of the microspheres was characterized using SEM, TEM, and XRD. The electrical and dielectric properties of NiCoGaFe-MSF were systematically studied at temperatures ranging from 20 to 120 degrees C (293.1 x 103 to 393.1 x 103) and frequencies up to 3.0 MHz. The results showed that the conductivity, dielectric properties, and impedance spectra of NiCoGaFe-MSFs were influenced by the Ga ion substitution ratios. The formation of semicircles in the impedance spectra was temperature-dependent, indicating a relaxation mechanism. The findings provide valuable insights for the design and application of spinel ferrite-based materials.