• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.805-809
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• 1995

In order to widen the band-width of ferrite absorber, compositional effect on the complex permeability of Ni-Zn ferrite and the structure of grid absorber were studied. From the experimental results, we could determine the optimum composition composition of Ni-Zn ferrite and the structure of grid absorber. Also, we manufactured grid absorber and investigated its microwave absorbing characteristics. Calculation shows that the ferrite frid absorber suppresses reflection ${\leq}-20dB$ from 30 MHz to 700 MHz and the conventional ferrite tile absorber suppresses reflection ${\leq}20dB$ in the frequency range of 30 MHz-400 MHz. It was found that the microwave absorbing performance of the ferrite grid absorber was superior to the ferrite tile absorber.

• Resources Recycling
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• v.13 no.6
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• pp.37-42
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• 2004

The power loss analysis was carried out for Ni-Cu-Zn ferrite sample with different content of NiO and ZnO. The power loss, Pcv decreases monotonically with increasing temperature and attains to a certain value at around 100~120 degrees Celsius. The frequency dependence of Pcv can be explained by Pcv~f$^n$, and n is independent of the frequency, f up to 1 MHz. The Pcv decreases with an increase in ZnO/NiO. The Pcv was separated to hysteresis loss(Ph) and residual loss(Pcv-Ph). The temperature characteristics and compositional dependence of Pcv can be attributed to the Ph, while Pcv-Ph is not affected by both temperature and ZnO/NiO. By analyzing temperature and composition dependence of Ph and initial permeability, ${\mu}_i$ like following equations could be formularized. ${\mu}_i{\mu}_0=I_s^2/(K_I+b{\sigma}_0{\lambda}_s)$ Wh=13.5(I$_s^2/{\mu}_i{\mu}_0)$ Where ${\mu}_0$ is permeability of vacuum, I$_s$ is saturation magnetization, K$_I$ is anisotropy constant, $s_0$ is internal heterogeneous stress, ${\lambda}_s$ is magnetostriction constant, b is unknown constant, and Wh is hysteresis loss per one cycle of excitation (Ph=Wh${\times}$f). Steinmetz constant of Ni-Cu-Zn ferrite, m=1.64~2.2 is smaller than that of Mn-Zn ferrites, which suggests the difference of loss mechanisms between these materials.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.256-256
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• 2012

SoP용 재료에 응용하기 위하여 NiCuZn 페라이트계 이용한 이종접합의 관한연구를 하였다. NiCuZn 페라이트계와 유전체의 이종접합특성은 XRD, Dilatometer, LCR meter, FE-SEM, EDS 이용하여 물리 화학적 특성을 조사하였다. NiCuZn 페라이트계는 일반적인 세라믹 제조공정을 이용하여 분말을 제조하였으며, 이종접합은 모든 시편에서 잘 진행되었으며 일부 유전체의 이온들이 페라이트 쪽으로 확산이 진행되었으며 NCZF700계는 $900^{\circ}C$ 소결 시편에서 확산이 진행되지 않은 현상이 나타났다.

• Journal of Magnetics
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• v.21 no.3
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• pp.308-314
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• 2016

Cobalt-, zinc-, and nickel-zinc-substituted nano-size manganese ferrite powders, $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, $Mn_{0.8}Zn_{0.2}Fe_2O_4$ and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$, were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently studied. The $MnFe_2O_4$ ferrite powder annealed at temperatures above 523 K exhibited a spinel structure, and the particle size increased as the annealing temperature increased. All ferrites annealed at 773 K showed a single spinel structure, and the lattice constants and particle size decreased with the substitution of Co, Zn, and Ni-Zn. The $M{\ddot{o}}ssbauer$ spectrum of the $MnFe_2O_4$ ferrite powder annealed at 523 K only showed a doublet due to its superparamagnetic phase, and the $M{\ddot{o}}ssbauer$ spectra of the $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, and $Mn_{0.8}Zn_{0.2}Fe_2O_4$ ferrite powders annealed at 773 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. However, the $M{\ddot{o}}ssbauer$ spectrum of the $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$ ferrite powder annealed at 773 K consisted of two Zeeman sextets and one quadrupole doublet due to its ferrimagnetic and paramagnetic behavior. The area ratio of the $M{\ddot{o}}ssbauer$ spectra could be used to determine the cation distribution equation, and we also explained the variation in the $M{\ddot{o}}ssbauer$ parameters by using this cation distribution equation, the superexchange interaction and the particle size. Relative to pure $MnFe_2O_4$, the saturation magnetizations and coercivities were larger in $Mn_{0.8}Co_{0.2}Fe_2O_4$ and smaller in $Mn_{0.8}Zn_{0.2}Fe_2O_4$, and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$. These variations could be explained using the site distribution equations, particle sizes and magnetic moments of the substituted ions.

• Korean Journal of Materials Research
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• v.16 no.9
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• pp.578-583
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• 2006

We studied the physical properties of Ni-Zn ferrites by adding different chemicals such as $SO_4$, Cl, and $NO_3$. Specimens were prepared by the coprecipitation method and sintered at temperatures $950^{\circ}C,\;1,150^{\circ}C,\;and\;1,350^{\circ}C$, respectively. X-ray diffractions showed a spinel structure and the optical microscopy revealed grain size of 0.3 to 0.6 ${\mu}m$. The optimum sintering temperature to obtain fine, sintered microstructure depended on the additive : Cl and $NO_3\;at\;950^{\circ}C\;and\;SO_4\;at\;1,150^{\circ}C$. According to particle size analysis, higher magnetic permeability and magnetization value were observed with Cl and $NO_3\;than\;SO_4$. As sintering temperature was raised from $950^{\circ}C$ to $1,350^{\circ}C$, the average grain diameter, initial permeability and the magnetic moment also increased.

• Korean Journal of Materials Research
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• v.12 no.10
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• pp.791-795
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• 2002

We studied the physical properties of $Co_3$$O_4$-added Ni-Zn ferrite which were sintered at 1050~110$0^{\circ}C$ for 2 hours. X-ray diffraction showed a spinel structure, and optical microscopy showed grain sizes of 5 to 10 $\mu\textrm{m}$. As the sintering temperature was increased from $1050^{\circ}C$ to $1070^{\circ}C$, the initial permeability and magnetic induction increased, and both of the loss factor and the coercive force decreased. The Curie temperatures were about $^234~245{\circ}C$ with added $Co_3$$O_4$. The initial permeability was 350 to 420 and maximum magnetic induction density and coercive force 4870G to 4980G and 0.15 Oe to 0.21 Oe, respectively which were similar to those of Ni-Zn ferrite synthesized in the conventional process. The frequency of specimen was in the range of 1MHz to 300MHz. In the plot of initial permeability vs. frequencies, a $180^{\circ}C$ rotation of the magnetic domain could be perceived in a broad band of microwave before and after the resonance frequency.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.160-164
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• 2000

In this paper, we studied the relation between using amount of Ferrite and electromagnetic wave absorbing properties of ferrite-rubber composite. The variation of using amount of Ferrite have been 52 wt.% ~ 62 wt.%. As s result, it has been shown that the electromagnetic wave absorbing properties of ferrite-rubber composite are related to the using amount of Ferrite in composite. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the control of using amount of Ferrite.

• Journal of the Korean Ceramic Society
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• v.28 no.7
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• pp.556-560
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• 1991

The behavior of Ni-Zn ferrite/Mn-Zn ferrite composite electromagnetic absorber was investigated. The imaginary part of complex permeability of the composite was higher than that of either ferrite alone at all frequency range (50∼1400MHz) studied. The difference, which was pronounced in low frequency range, was reached the maximum value when the composite consisted of constituent ferrites with equal amount. Since the thickness in inversely proportional to the imaginary part of complex permeability for the ferrite absorber, it was possible to reduce the thickness of electromagnetic absorber by employing a composite of two different ferrites.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.30-36
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• 2005

Recently, It has been reported that the spin sprayed ferite film shows better magnetic properties at high frequeny that the ferrite by co-firing over $800^{\circ}C$ . Besides, there is no limitation to select the substrate materials because it can be processed with relatively low temperature below $100^{\circ}C$. Therefore, we fabricated film inductor as a passive device for DC-DC converter by a use of spin sprayed embedded form was completed by via hole process of pad opening. Saturation magnetization of 0.61 T and real part of permeability of 110 were obtained in Ni-Zn ferrite. In addition, inductance of 1.52 ${\mu}H$, quality factor of 24.3 at 5 MHz were measured with spiral 16 turn inductor. The rated current of inductor was 863 mA.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.150-158
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• 2016

This paper reports on a study of LiNiZn-ferrite composite as a radiation absorbent material (RAM). The electromagnetic (EM) wave absorbers are composed of an EM wave absorbing material and a polymeric binder. The surface morphology, chemical composition, weight percent of the ferrite composite of the toroid sample, magnetic properties, and return loss are investigated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and network analyzer. For preparing the absorbing sheet, chlorinated polyethylene (CPE) is used as a polymeric binder. The EM wave absorption properties of the prepared samples were studied at 4 - 8 GHz. We can confirm the effects of the thickness of the samples for absorption properties. An absorption bandwidth of more than a 10-dB return loss shifts toward a lower frequency range along with an increase in the thickness of the absorber.