• Journal of the Korean Ceramic Society
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• v.17 no.2
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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.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.10
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• pp.534-539
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• 2006

An integrated inductor using the low-temperature co-fired ceramics(LTCC) technology for low-power electronics was fabricated. In the inductor NiZn ferrite sheet$({\mu}_r=230)$, was embedded to increase inductance. The inductor has Ag spiral coil with 14 turns$(7turns{\times}2layers)$, a dimension of 0.6mm in width, 10um in thickness, and 0.15mm pitch. To evaluate the inductance, including the parasitic resistance, the fabricated inductor was calculated and measured. It was confirmed that calculated values were very close to the measured values. Finally as an application of the LTCC integrated inductor to low power electronic circuits, a LTCC boost DC/DC converter with 1W output power and up to 0.5MHz switching frequency using the inductor fabricated was developed.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.730-734
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• 1995

The variation of magnetic permeability and dielectric constant and their relationship with microwave absorbing properties are investigated in sintered Ni-Zn ferrite. Toroid specimens of ${(Ni_{0.5}Zn_{0.5}O)}_{1-y}{(Fe_{2}O_{3})}_{1+y}$ ferrites are prepared by conventional ceramic processing technique. The large change in magnetic permeability is observed by the variation of excess $Fe_{2}O_{3}$ in the Ni-Zn ferrites. The more the iron-excess from y=0.04 to y=0.12, the lower value of both $\mu_{r}'$ and $\mu_{r}"$ is observed. However dielectric permittivity increases with the increase of the increase of the excess $Fe_{2}O_{3}$. The control of permittivity is realized by nitrogen sintering atmosphere and excess $Fe_{2}O_{3}$ respectively.

• Journal of Magnetics
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• v.20 no.3
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• pp.246-251
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• 2015

This study was aimed to study the effect of Zn content on the hyperfine parameters and the structural variation of $Ni_{1-x}Zn_xFe_2O_4$ for x = 0, 0.2, 0.4, 0.6, and 0.8. To achieve this, a sol-gel route was used for the preparation of samples and the obtained ferrites were investigated by X-ray diffraction, scanning electron microscopy, and $M{\ddot{o}}ssbauer$ spectroscopy. The formation of spinel phase without any impurity peak was identified by X-ray diffraction of all the samples. Moreover, the estimated crystallite size by X-ray line broadening indicates a decrease with increasing Zn content. This result was in agreement with the scanning electron microscopy result, indicating the reduction in grain growth with further zinc substitution. The room-temperature $M{\ddot{o}}ssbauer$ spectra show that the hyperfine fields at both the A and B sites decreased with increasing Zn content; however, the rate of reduction is not the same for different sites. Moreover, the best fit parameter showed that the quadrupole splitting values of B site increased from the pure nickel ferrite to the sample with x = 0.8.

• Journal of the Korean Magnetics Society
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• v.14 no.5
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• pp.180-185
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• 2004

The electromagnetic properties and microstructures of the basic composition of (Ni$\sub$0.2/Cu$\sub$0.1/Zn$\sub$0.2/)$\sub$0.5/ (Fe$_2$O$_3$)$\sub$0.5/ were invested by changing of SO$_4$, Cl and NO$_3$ series. We were prepared by coprecipitation method and sintered at temperatures 950$^{\circ}C$, 1150$^{\circ}C$, l350$^{\circ}C$, respectively. When sintering at temperature 950$^{\circ}C$, Cl and NO$_3$ series became perfection sintering. On the other hand, SO$_4$ series showed perfection sintering at temperature 1150$^{\circ}C$. According to particle size analysis result, higher magnetic permeability and magnetization value were observed by Cl series than SO$_4$ or NO$_3$ series.

• Journal of Magnetics
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• v.7 no.2
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• pp.29-39
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• 2002

The initial NiCuZn synthetic ferrite were acquired from thermally decomposing the metal nitrates $Fe(NO_3)_39H_2O, Zn(NO_3)_26H_2O, Ni(NO_3)_26H_2O, and Cu(NO_3)_23H_2O$ at $150^circ{C}$ for 24 hours, and then we calcined the synthetic powder at $500^circ{C}$, pulverized each of those for 3, 6, 9, 12, and 15 hours in a steel ball mill, sintered each at $700^circ{C}$ to $1,000^circ{C}$ for 1 hour, and thus studied their microstructures and electromagnetic properties. We could make the initial specimens chemically bonded in liquidity at a low-temperature $150^circ{C}$, by using the low melting points less than $200^circ{C}$ of the metal nitrates instead of the mechanical ball-mill pulverization, then narrow a distance between the particles into a molecular one, and thus lower the reaction point of sintering by at least $200^circ{C}$ to $300^circ{C}$. Their initial permeability was 50 to 400 and their maximum magnetic induction density and coercive force, 2,400 G and 0.3 Oe to 0.5 Oe respectively, which was similar to those of NiZnCu ferrite synthesized in the conventional process. In the graph of initial permeability by frequencies, a $180^circ{C}$ rotation of the magnetic domains which appears in a broad band of micro-wave before and after the resonance frequency, could be perceived.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.149-154
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• 2000

In this paper, we studied the relation between addition of carbon and electromagnetic wave absorbing properties of ferrite-rubber composite. The ratio of carbon was 7 wt%. As s result, it has been shown that the electromagnetic wave absorbing properties of ferrite-rubber composite are changed by the addition of carbon in composite. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the using of carbon.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.247-250
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• 1999

In this study, three kinds of Mn-Zn ferrite/Ni-Zn ferrite/$Ni_2Y$ ferroxplana prepared by the coprecipitation method was compounded with silicon rubber, and thereafter made ring-type specimens with various compositional ratio. The material constant of ferrite/rubber composite absorbers was obtaibed by the 2-port method. The material constants of the ferrite/rubber composite absorber with various compositional ratio of three kinds of ferrite were used to design the matching frequency and thickness with the impedance matching map. We were able to predict the matching condition from the design method.

• Korean Journal of Materials Research
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• v.13 no.8
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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.

• Proceedings of the Korean Magnestics Society Conference
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• 1997.05a
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• pp.56-57
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• 1997