Search

In this study, a novel NiCuZn (Ni 0.24 Cu 0.21 Zn 0.55 Bi x Fe 2- x O 4 (x = 0,0.025, 0.050, 0.075)) ferrite composition (Ni/Zn molar ratio is 24/55) was successfully prepared by the addition of Bi3+ ion for substitution. It is demonstrated that Bi 2 O 3 served as an effective doping agent to reduce the sintering temperature to 900 °C and enhanced the high-frequency magneto-dielectric properties. Notably, the maximum permeability is ∼118 (@ 13.56 MHz) when x = 0.050 with a cut-off frequency of 47 MHz, which is nearly four times higher than that of the unsubstituted sample. In addition, an NFC antenna employing optimized ferrite as an electromagnetic shield sheet was designed and simulated. The results indicated that the chaotic and weakened magnetic field was recovered, and the biased resonant frequency was restored from 31.87 MHz to 13.68 MHz. These findings hold significant scientific importance and practical value in achieving superior electromagnetic shielding performance and miniaturization in NFC system. [Display omitted] [ABSTRACT FROM AUTHOR]

we deeply dived multi-phase-based 0.16BaFeO3-0.84MgFe2O4 ferrite for VHF antennas. The structural and magneto-dielectric properties synthesized at various temperatures (1100 °C, 1125 °C, 1150 °C and 1175 °C) were investigated. The results demonstrated the coexistence of hexagonal and cubic spinel phases. Microstructure analysis indicated higher temperature induced lager grain size and denser structure. Meanwhile, both the saturation magnetization (from 28 to 25 emu/g) and coercivity (19–5 Oe) decreased. In addition, real permeability (μ′) and permittivity (ε′) arose at higher temperature, promising equivalent permeability and permittivity. What's more, relatively low magnetic and dielectric losses (tanδμ ∼10−2 to 10−3 and tanδε ∼10−3 to 10−4) promote low energy loss. Finally, a miniaturized antenna with relative bandwidth of 14.6 %, peak gain of 0.98 dB, and radiation efficiency of 74.6 % was simulated based on the processed ferrites. In conclusion, the presented investigation greatly improves the magneto-dielectric response, which paves the way to realize high performance in VHF antenna application.

Two phase-based composites comprising barium titanate (BaTiO 3) and spinel magnesium ferrite (1- x)Mg 0.7 Cd 0.3 Fe 2 O 4 + x BaTiO 3 (x = 0.00, 0.03, 0.06, 0.09, and 0.12) were investigated. The phase structure revealed the coexistence of the perovskite BaTiO 3 and spinel MgFe 2 O 4 phases. The microstructural analysis indicated that the average crystallite size initially increased and then decreased, as the increase in x weakened magnetisation, decreased saturation magnetisation (from 47.5 to 35.9 emu/g) and coercivity (150–0 Oe) were obtained, resulting in reduced permeability at low frequency. The permittivity gradually increased owing to tuning by barium titanate, which has strong dielectric properties, promising a relatively large miniaturisation factor. Further, low magnetic loss (tan δ μ ∼10−2) and dielectric loss (tan δ ε ∼ 10−2 to 10−3) guarantee high quality factor. The low losses and enhanced dielectric properties of the as-synthesised composites could be conducive to improving the behaviour of such magneto-dielectric composite systems in microwave applications. [ABSTRACT FROM AUTHOR]

A series of Ba1.5Sr1.5Co2+xZrxFe24‐2xO41 hexaferrites (x = 0.00, 0.01, 0.03, 0.05, 0.07, and 0.09) were successfully prepared by the conventional solid‐state reaction method. It was found that as the Co2+ and Zr4+ ions entered the hexaferrite structure, the lattice parameters increased, whereas the relative density increased when x = 0.00‐0.03 and then decreased. A suitable amount of substitution increased the DC resistivity, reduced the magnetic and dielectric losses, and made the μ′$\mu ^{\prime}$ and ε′$\varepsilon ^{\prime}$ closer to each other. At x = 0.03, the relative density and DC resistivity of the samples reached their maxim. Besides, both the magnetic and dielectric losses were lowest within the frequency range of 10 MHz‐1 GHz. Meanwhile, the hexaferrite was impedance matched to free space, and the miniaturization factor was about 15. Therefore, this low‐loss ferrite with almost equal permeability and permittivity could be meaningful for antenna miniaturization and high‐frequency applications. [ABSTRACT FROM AUTHOR]

The U-type hexaferrites ([Formula: see text][Formula: see text]Co2[Formula: see text][Formula: see text] ([Formula: see text] 0, 0.05, 0.10, 0.15, 0.20, 0.25) have been synthesized by auto-combustion method. The work involves the study of structural, microstructural, dielectric, magnetic and magneto-dielectric properties of the prepared materials. The structural analysis has been done by X-ray diffraction technique along with Le Bail refinement which confirmed the pure hexagonal phase for all the samples. The microstructural analysis has been carried out by field-emission scanning electron microscopy. The vibrating sample magnetometer is used to measure the magnetic properties. The sample with a composition of [Formula: see text] 0.15 has shown the maximum magnetization of approximately 73.31 emu/g with the remnant magnetization of 38.89 emu/g and coercive field of 1.77 kOe at room temperature. Moreover, the same sample has delivered the maximum magneto-dielectric response of about 54.18% at 1.5-T field.

The U-type hexaferrites ( Ba 1 − 3 x La 2 x ) 4 Co2 Fe 3 6 O 6 0 (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25) have been synthesized by auto-combustion method. The work involves the study of structural, microstructural, dielectric, magnetic and magneto-dielectric properties of the prepared materials. The structural analysis has been done by X-ray diffraction technique along with Le Bail refinement which confirmed the pure hexagonal phase for all the samples. The microstructural analysis has been carried out by field-emission scanning electron microscopy. The vibrating sample magnetometer is used to measure the magnetic properties. The sample with a composition of x = 0.15 has shown the maximum magnetization of approximately 73.31 emu/g with the remnant magnetization of 38.89 emu/g and coercive field of 1.77 kOe at room temperature. Moreover, the same sample has delivered the maximum magneto-dielectric response of about 54.18% at 1.5-T field. [ABSTRACT FROM AUTHOR]

The influence of temperature, magnetite shape, and content on the electromagnetic interference shielding properties was determined for dextrin based composites. The absorption properties increase linearly with increasing temperature. The usage of dextrin results in the widening of the absorption frequency region in comparison to the pure magnetite nanoparticles. The composite containing 50 wt% of spherical Fe3O4 NPs has RL

La-Zn substituted Ba2Co2Fe12O22 (Co2Y) hexagonal ferrite was synthesized using a conventional solid-state method with composition Ba2−xLaxCo2Fe12−xZnxO22, where x equals 0.0, 0.1, 0.3 and 0.5. The phase formation behavior and changes in the crystal structure of the substituted ferrite were investigated using x-ray diffraction (XRD) analysis. Accurate lattice parameters were evaluated through Rietveld refinement of the XRD pattern. XRD, as well as energy dispersive spectral analysis, showed the formation of a lanthanum iron oxide phase in x = 0.3 and 0.5 compositions. There was a small increase in unit cell volume with the substitution. The microstructural analysis showed a decrease in grain size with increasing substitution. The magnetic properties; Ms, Mr, and Hc of the ferrite were measured and found to increase with increasing substitution. Permittivity and permeability were measured and found in the range 10-16. It can be concluded that the La-Zn substitution was an effective method for improving magnetic and dielectric properties of the Co2Y ferrite. [ABSTRACT FROM AUTHOR]