Microstructure and Electromagnetic Properties of Ni-Zn-Co Ferrite up to 20 GHz

Abstract

The present paper examines the relation between different developed microstructures and the microwave electromagnetic properties in Ni-Zn-Co ferrite. To this end, the Ni0.25Zn0.25Co0.5Fe2O4composition has been prepared with the conventional ceramic process with varied prefiringTP(750°C, 1000°C) and sinteringTStop temperatures (1200°C, 1250°C). When lower temperatures are applied in these production stages, incomplete microstructures with low density, higher porosity, or finer grains are achieved. On account of these features, the contributions of domain wall motion and spin rotation to the complex permeabilityμ⁎(f)move to higher frequencies, whereas microwave dielectric permittivityε⁎(f)is decreased. In particular in conjunction with the high Co content, the wall relaxation and spin resonance are interestingly forced to occur at 850 MHz and 8.05 GHz, respectively. Regarding the electromagnetic wave attenuation, the ferrite annealed at lower temperatures exhibits strong return loss peaks at higher frequencies, but without other performance improvement. We should notice that the variations in sintering temperatureTSyield the maximum changes in the recorded parameters, including the coercive field,μ⁎(f),andε⁎(f), indicating the inferior role of prefiringTPin Ni-Zn ferrite.

Novel Low‐Permittivity (Mg1−xCux)2SiO4 Microwave Dielectric Ceramics

“…Li et al also observed similar result in our previous work [10]. is could be due to the interaction of various factors, such as distribution of element, porosity, grain size, presence of liquid-phase, and so on, which made it too di cult to reveal de nitive remarks on grain size loss relationships [15][16][17][18]. e τ f values of all ceramics, on the other hand, appeared to be a slight change (from −60∼−40 ppm/°C) to sintering temperature, as shown in Figure 5.…”

“…But, it increased with increasing sintering temperature to a value of 36,700 GHz for the specimen sintered at 1150 then seldom decreased to 32,600 GHz. e optimum sintering temperature was reduced by 200°C compared to the results of Li et al Based on the classical dielectric theory, the value should increase as the grain size increases, because a reduction in the number of grain boundaries per unit volume would result in materials with a lower loss [12][13][14][15]. In fact, the ceramics had the highest Q × f values when the mean grain size of the ceramics was about 8∼17 μm as shown in Figure 3.…”

Impact of V substitution on the physical properties of Ni–Zn–Co ferrites: structural, magnetic, dielectric and electrical properties

“…Knyazev et al carried out a study on the structural and magnetic properties of Ni-Co-Zn ferrites [19]. Besides, Mohit et al [20], Stergiou et al [21], Ghodake et al [22], Hassan et al [23],…”

Synthesis, Microstructural and Electromagnetic Characteristics of Cobalt-Zinc Ferrite

“…However, the disadvantage of these ferrites is their rather low resonance frequency. The substitution of cobalt or nickel by manganese allows the magnetic properties to be changed significantly, namely, to shift the resonance to higher frequencies and, consequently, to increase Snoek's limit [4]. Now, there are various methods for obtaining both nano-sized and micro-sized ferrite powders using ceramic technologies and from salt solutions [5][6][7].…”