• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.155-161
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• 2000

In this paper, we studied the relation between heat-treatment temperature of ferrite and electromagnetic wave absorbing properties of ferrite-rubber composite. The heat-treatment temperatures of ferrite are 1200 and $1300^{\circ}C$, 2 hr. As s result. it has been shown that the optimum heat-treatment temperature of ferrite for electromagnetic wave absorber are related to the chemical composition. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the control of heat-treatment temperature of ferrite.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.32-33
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• 2003

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1994.10b
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• pp.23-23
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• 1994

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.569-572
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• 2003

전력선 통신용 LC 공진필터에 사용되는 Ni-Zn 페라이트를 제조하기 위해 Ni0.8Zn0.2Fe2O4를 기본조성으로 선택하고 x (Co mol 비)를 변화시켜 전자기적 특성을 조사하였다. $Bi_2O_3$ CaO가 첨가됨으로써 균일한 입자성장과 입계에 고저항층이 형성되어 주파수 손실이 감소하였으며, $Ni_{0.8-x}Zn_{0.2}Co_xFe_2O_{\delta}$의 기본조성에 Co의 함량을 증가시키면 x = 0.05에서 투자율 75, 공진주파수 20 MHz의 특성을 나타내고 결정 입자 크기와 같은 구조적 특성에는 영향을 거의 미치지 않지만 자기이방성 변화에 따라 전자기적 특성에는 영향을 미친다. 또한, $Ni_{0.75}Zn_{0.2}Co_{0.05}Fe_2O_{4.017}$ 조성의 페라이트 코어의 발열량은 큐리온도 이하에서 일어난다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.92-95
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• 2003

전력선 통신용 LC 공진필터에 사용되는 Ni-Zn 페라이트를 제조하기 위해 $Ni_{0.8}Zn_{0.2}Fe_{2}O_{4}$를 기본조성으로 첨가제 $Bi_{2}O_{3}$, CaO와 x (co mol 비)를 변화시켜 전자기적 특성을 조사하였다. $Bi_{2}O_{3}$ CaO가 첨가됨으로써 균일한 입자성장과 입계에 고저항층이 형성되어 주파수 손실이 감소하였으며, $Ni_{0.8-x}Zn_{0.2}Co_{x}Fe_{2}O_{\delta}$의 기본조성에 Co의 함량을 증가시키면 x = 0.05에서 투자율 75, 공진주파수 20MHz의 특성을 나타내고 결정 입자 크기와 같은 구조적 특성에는 영향을 거의 미치지 않지만 전자기적 특성에는 영향을 미친다. 또한, $Ni_{0.75}Zn_{0.2}Co_{0.05}Fe_{2}O_{4.017}$ 조성의 페라이트 코어의 발열량은 큐리온도 이하에서 일어난다.

• Korean Journal of Materials Research
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• v.10 no.6
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• pp.430-436
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• 2000

In this paper, we have studied the effect of constituent ratio NiO, CuO and doped with B-Bi-Zn on proper-ties(microstructure, density, shrinkage, permeability as a function of frequency, etc.) of hexagonal-ferrite for high fre- quency chip-inductor material about several GHz. The permeability were analyzed by impedance analyzer(100 kHz∼ 40 MHz) and network analyzed(30 MHz∼3 GHz). As a result of the characteristics. the B-Bi-Zn glass ceramic was used to lower the sintering temperature for additive as function of frequency from 100kHz to 1.8 GHz showed con-stant tends. The maximum imaginary value of complex permeability was observed near the resonance frequency of 2 GHz.

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.255-260
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• 2006

The basic composition of Ni-Zn ferrite was $(Ni_{0.35}Cu_{0.2}Zn_{0.45})_{1.02}(Fe_2O_3)_{0.98}$ (group A) and $(Ni_{0.4}Cu_{0.2}Zn_{0.4})_{1.02}(Fe_2O_3)_{0.98}$(group B) with additional 0.1 mol% $CaCO_3$ and 0.03 mol% $V_2O_5$. For high permeability and acceleration of grain growth, $CaCO_3$ and $V_2O_5$ was added. The mixture of the law materials was calcinated at $600^{\circ}C$ for 2 hours and then milled. The compacts of toroidal type were sintered at different temperature ($1,050^{\circ}C,\;1,070^{\circ}C,\;1,100^{\circ}C$) for 2 hours in air followed by an air cooling. Then, effects of various composition and sintering temperatures on the microstructure and physical properties such as density, resistivity, magnetic induction, coercive force, initial permeability, quality factor, and curie temperature of the Ni-Zn ferrite were investigated. The density of the Ni-Zn ferrite was $4.90{\sim}5.10g/cm^3$, resistivity revealed $10^8{\sim}10^{12}{\Omega}-cm$. The average grain size increased with the increase of sintering temperatures. The magnetic properties obtained from the aforementioned Ni-Zn ferrite specimens were 4,000 gauss for the maximum induction, 0.25 oersted for the coercive force, 2,997 for the initial permeability, 208 for the quality factor, and $202^{\circ}C$ for the curie temperature. The physical properties indicated that the specimens could be utilized as the core of microwave communication and high permeability deflection yoke of high permeability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.539-542
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• 2004

전자기기의 발달과 더불어 정보통신분야의 발달로 고주파 대역에서 우수하고 안정적인 Ni-Zn 페라이트를 제조하기 위해, Ni(니켈)의 일부를 코발트(Co)로 치환하여 결정자기이방성 상수 값을 증가시켜, 공명 주파수를 고주파 대역으로 높이고자 하였다. Co 함량이 증가함에 따라 투자율은 감소하는데, 이는 결정자기 이방성 상수를 크게 하여 공명 주파수를 높이는 결과를 보였으며, x=0.05에서 투자율 75, 공명 주파수 20MHz의 특성을 나타내었다.

• Proceedings of the Korean Magnestics Society Conference
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• 2001.04a
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• pp.142-143
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• 2001

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.800-804
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• 1995

The complex permeability dispersions and the microwave absorbing phenomena are investigated in ferrite microwave absorber. The complex permeability of NiZn ferrite, NiZnCo ferrite, and Y-type hexagonal ferrite were measured in 200MHz-14GHz range. Two types of resonances, the domain wall and the spin rotational resonance, were observed. With a ferrite particle with a diameter of about $1\;\mu\textrm{m}$, only spin rotational resonance were observed. The theoretical matching frequency is determined by plotting the measured complex permeability locus on the impedance matching solution map. One or two impedance matching phenomena are observed in the ferrite absorbers according to their complex permeability loci on the impedance matching solution map. The first matching frequency, found in the ferrite-rubber composites, which was higher than that of spin rotational resonance, increased with spin rotational resonance frequency.