• 한국전기전자재료학회논문지
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• 제11권7호
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• pp.546-551
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• 1998

$Mn{1-X}Fe{2+X}O_4, Mg_{1-X}Fe_{2+X}O_4$ (x=0.0, 0.025, 0.1, 0.2) for negative temperature coefficient (NTC) thermistor was prepared by calcination at $800^{\circ}C$ and sintering at form 1100 to $1250^{\circ}C$ with $50^{\circ}C$ intervals. The best linear property was obtained in the Mn-based sample sintered at $1200^{\circ}C$ with x=0.0 composition. Temperature coefficient of resistance, $\alpha$, was $-5.6%/^{\circ}C$ in the Mn-based sample, $-5.2%/^{\circ}C$ in the MM-based sample, and $-1.6%/^{\circ}C$ in the Mg-based sample. thermistor parameter, B, was in the range of 2665~7780 K. The results show the possibility that Mn-Ni-Co based thermistor could be substituted by the composition used in this study.

• 한국세라믹학회지
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• 제17권2호
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• pp.89-95
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• 1980

The effect of non-stoichimetry and sintering temperature on the magnetic properties of materials in the system $Ni_{0.39}Zn_{0.61}Fe_{2.0+x}O_4$ have been investigated. The value of x used in initial weighing of oxides were varied from -0.04 to -0.12. The value of x, however, appears to be from +0.04 to -0.04 after ferrite powder preparation due to iron pick up during ball mill mixing and grinding. The densities of specimens which were deficientinrion were higher than those with excess ion. Specimens with near stoichiometric composition showed maximum initial permeability an dminimum coercivity whereas high values of quality factor (Q) were observed in iron deficient specimens. The quality factor decreased monotonically with increasing sintering temperature, but the permeability showed maxima with increasing sintering temperature. Thus highest value of figure of merit $\mu$Q was obtained in composition $Ni_{0.39}Zn_{0.61}Fe_{1.98O4}$ sintered at 100$0^{\circ}C$ for 3 hrs. in an air atmosphere.

• 한국분말재료학회지
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• 제23권2호
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• pp.132-135
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• 2016

This study investigates the influence of sintering temperature on the magnetic properties and frequency dispersion of the complex permeability of Ni-Zn-Cu ferrites used for magnetic shielding in near-field communication (NFC) systems. Sintered specimens of $(Ni_{0.7}Zn_{0.3})_{0.96}Cu_{0.04}Fe_2O_4$ are prepared by conventional ceramic processing. The complex permeability is measured by an RF impedance analyzer in the range of 1 MHz to 1.8 GHz. The real and imaginary parts of the complex permeability depend sensitively on the sintering temperature, which is closely related to the microstructure, including grain size and pore distribution. In particular, internal pores within grains produced by rapid grain growth decrease the permeability and increase the magnetic loss at the operating frequency of NFC (13.56 MHz). At the optimized sintering temperature ($1225-1250^{\circ}C$), the highest permeability and lowest magnetic loss can be obtained.

• 한국자기학회지
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• 제17권6호
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• pp.238-241
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• 2007

복합 전파흡수체로 사용할 Ni-Cu-Zn ferrite는 공침법을 사용하여 제조 하였고,제조 시편의 물리적 특성 및 전파흡수특성은 소결온도 변화에 따라 고찰하였다. Ni-Cu-Zn ferrite의 스피넬 구조는 XRD pattern을 통하며 확인하였다. 소결온도가 $1100^{\circ}C$에서 흡수 능력도 좋아짐을 알 수 있었으며, 소결된 페라이트의 초투자율은 평균 50 정도로 나타났다. $Ni_{0.7}Cu_{0.2}Zn_{0.1}Fe_2O_4$ 조성에서 소결 온도가 $1100^{\circ}C$ 일 때가 복합 전파흡수체로 사용할 조성임을 확인할 수 있었으며, 그 결과 복합 전파흡수체에서 사용할 수 있다고 사료된다.

• 한국재료학회지
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• 제13권8호
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• pp.531-536
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• 2003

The electromagnetic properties and microstructures of the ferrites based on ($Ni_{0.2}$ $Cu_{0.2}$ $Zn_{0.6}$)$_{1.085}$($Fe_2$$O_3$)$_{0.915}$ were investigated by changing the amount of additive SnO$_2$and CaO and the sintering temperatures. Addition of $SnO_2$caused pores in the specimen. There was no variation of grain size by changing the amount of additives. Total loss was reduced when ($Ni_{0.2} $Cu_{0.2}$ $Zn_{ 0.6}$)$_{1.085}$ ($Fe_2$$O_3$)$_{0.915}$ composition was sintered at $1150^{\circ}C$ rather than $1300^{\circ}C$. Addition of CaO was useful to reduce the total loss because it increased the sintering density. The lowest total loss was obtained when 0.06 wt% $SnO_2$and 0.4 wt% CaO were added at the same time.

• 한국분말재료학회지
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• 제21권6호
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• pp.429-433
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• 2014

This study investigated the magnetic properties and frequency dispersion of complex permeability of Ni-Zn-Co ferrites used for magnetic shielding in near field communication (NFC) system. The sintered specimens of $(Ni_{0.7}Zn_{0.3})_{1-x}Co_xFe_2O_4$ composition were prepared by the conventional ceramic processing. The coercive force and saturation magnetization were measured by vibrating sample magnetometer. The complex permeability was measured by RF impedance analyzer in the range of 1 MHz~1.8 GHz. The coercive force increased and saturation magnetization decreased with increasing the Co substitution. The real and imaginary parts of complex permeability decreased and the resonance frequency increased with Co substitution, which was attributed to the increase in crystal anisotropy field and reduction in saturation magnetization. The effect of Co substitution could be found in reducing the magnetic loss to nearly zero at the operating frequency of NFC (13.56 MHz).

• Journal of Magnetics
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• 제19권1호
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• pp.59-63
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• 2014

Nano-sized nickel substituted cobalt ferrite powders, $Ni_xCo_{1-x}Fe_2O_4$ ($0.0{\leq}x{\leq}1.0$), were fabricated by the sol-gel method, and their crystallographic and magnetic properties were studied. All the ferrite powders showed a single spinel structure, and behaved ferrimagnetically. When the nickel substitution was increased, the lattice constants and the sizes of particles of the ferrite powders decreased. The M$\ddot{o}$ssbauer absorption spectra of $Ni_xCo_{1-x}Fe_2O_4$ ferrite powders could be fitted with two six-line subspectra, which were assigned to a tetrahedral A-site and octahedral B-sites of a typical spinel crystal structure. The increase in values of the magnetic hyperfine fields indicated that the superexchange interaction was stronger, with the increased nickel concentration in $Ni_xCo_{1-x}Fe_2O_4$. This could be explained using the cation distribution, which can be written as, $(Co_{0.28-0.28x}Fe_{0.72+0.28x})[Ni_xCo_{0.72-0.72x}Fe_{1.28-0.28x}]O_4$. The two values of the saturation magnetization and the coercivity decreased, as the rate of nickel substitution was increased. These decreases could be explained using the cation distribution, the magnetic moment, and the magneto crystalline anisotropy constant of the substituted ions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1460-1462
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• 2001

초고속 전력선 통신을 위한 고주파수 대역에서 안정적인 자기적 특성을 갖는 Ni-Zn ferrite를 개발하기 위해서 투자율은 낮지만 주파수 특성이 우수한 $Ni_{0.8}Zn_{0.2}Fe_2O_4$를 기본조성으로 입자를 성장시키는 $Bi_2O_3$를 0.7, 비저항을 증가 시키는 CaO를 0.3, 그리고 입자를 균일하게 하는 $V_2O_5$를 0.1 wt% 첨가하여 미세구조를 제어하고, 다시 고주파 특성을 향상시킬 것으로 기대되는 $Co_3O_4$를 0, 0.3, 0.5, 0.7 wt%로 변화시켜 자기적 특성을 조사하였다. $Co_3O_4$가 밀도 및 미세구조에는 영향을 미치지 않았으나 0.3, 0.5 wt% 첨가시 첨가하지 않은 조성보다 투자율은 감소하였으나 사용 한계 주파수로 여겨지는 공명주파수가 각각 19.905, 19.205 MHz로 크게 증가하였다. 그리고 전체 전력 손실도 $Co_3O_4$를 첨가했을 때 감소하였으나 첨가량에는 큰 변화가 없었다. 와전류 손실이 전체 전력손실에 지배적인 영향을 미치고 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.331-334
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• 2001

In this study, the magnetic properties for Ni-Zn ferrite were investigated as the function of $Co_3$ $O_4$ additive contents which was predicted to improve the resonance frequency. Toroid specimens with the composition of N $i_{0.8-x}$Z $n_{0.2+x}$F $e_2$ $O_4$(x = 0, 0.05, 0.1, 0.15) ferrites were preparation by conventional ceramic processing technique. The maximum resonance frequency of 19.905 MHz and the permeability of 90.88 in 10 MHz were attained to the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$with $Co_3$ $O_4$0.3 wt%. Both of the permeability in 10 MHz and the resonance increased to 107.11 and 19.005 MHz respectively for the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$with $Co_3$ $O_4$wt% than the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$/ with the free $Co_3$ $O_4$composition.composition.

• E2M - 전기 전자와 첨단 소재
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• 제4권3호
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• pp.211-219
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• 1991

본 논문은 고주파에서의 Ni-Zn페라이트의 첨가물에 따른 소결특성에 관하여 연구한 것이다. 연구에서 사용한 시편은 20mol% NiO, 30mol% ZnO 및 50mol% Fe$_{2}$ $O_{3}$이 조성으로된 페라이트를 모재로 하고 첨가물로서 각각 0.0025mol%, 0.005mol% 및 0.001mol%의 비율로 Nb$_{2}$ $O_{5}$, Bi$_{2}$ $O_{3}$ 및 V$_{2}$ $O_{5}$를 첨가하였다. 그리고 소결을 1100.deg.C에서 이루어졌다. 초투자율은 V$_{2}$ $O_{2}$가 첨가된 시편의 100KHz-1000KHz주파수대에서 4*$10^{2}$~8*$10^{2}$의 높은 값을 얻었다. 손실계수는 100KHz~500KHz주파수대에서 1*10~3*$10^{-2}$이었다. 1/(.mu.*Q)값은 0.005mo;% Bi$_{2}$ $O_{3}$가 첨가된 시편에서 가장 높은 값을 나타내었다. 자기저항은 초유자율과 반비례의 관계를 나타내었다. 실험의 결과 첨가물에 의한 소결특성은 액상형성에 의하여 고른 입자성장을 확인할 수 있었다. 따라서 0.01mol% V$_{2}$ $O_{5}$를 첨가한 시편이 가장 우수한 자기특성을 나타내고 있음을 확인하였다.