• Journal of the Korean Magnetics Society
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• v.15 no.5
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• pp.282-286
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• 2005

Ni-Cu-Zn ferrites were prepared by the co-precipitation and ferrite microwave absorbers on low temperature sintering were investigated in this work. The properties of its microwave absorbing and physical were analyzed into variations of Ni addition, calcination temperature, sintering temperature. From the analysis of X-ray diffraction patterns, we can see that all the particles have only a single phase spinel structure. In addition, the powders particle size distribution obtained the nano size. By increasing the Ni additive, the permeability of the powders was decreased and the loss factor increased at sintering temperature $1100^{\circ}C$. Also, we considered that it can used high frequency rage. We found that the $(Ni_{0.7}Cu_{0.2}Zn_{0.1}O)_{1.02}(Fe_{2}O_3)_{0.98}$ appeared microwave absorbing properties better than other composition.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.425-431
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• 2000

Cobalt ferrite thin films on Corming glass substrate were fabricated by a sol-gel method. Cobalt ferrite thin films with the grain size of 20-35 nm and thickness of 50nm were obtained. Rapid thermal annealing (RTA) and Annealing processes were adopted for comparison of characteristics of the films. Coercivity values were changed with thermal condition and magnetization values were increased as a function of soaking time. With prolonged soaking time, however, it was decreased because of the diffusion of cations from the glass substrate. The RTA process in preparation of cobalt ferrite thin film was the effective way to prevent and to form a single spinel phase in reduced soaking time. The film heated at 600$^{\circ}C$ for 30 minutes by RTA had coercivity of 2,600 Oe, saturation magnetization 460 emu/㎤, and Mr$.$$\delta$ of 1.43 memu/$\textrm{cm}^2$.

• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.289-294
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• 1995

As the results of the study on the effects of mixing time for raw materials to the electric and magnetic properties of Mg-ferrite, the fraction of spinel phase after calcination and the geometry density of sintered Mg-ferrite increased from 30% to 100% and from 2.5g/cc to 4.25g/cc respectively due to mixing-homobenity of raw materials. The AC resistivity of grains decreased and lattice parameter, saturation magnetization increased due to the increase in Fe+2 of sintered body. conclusively the characteristic of powder after calcination had strong influence on the microstructure, electric, and magnetic properties in Mg-ferrite sintered body.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.1
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• pp.35-38
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• 2002

Ferrite thin film with glass substrate was prepared by ferrite plating method in order to make sunglass which cut off ultraviolet and electromagnetic field. It has single phase of polycrystalline spinel structure and has gloss like as mirror and has hardness without scratch by scraping with nail. The transmittance of ferrite thin film is lowered near 400nm manifestly, which shows that the ferrite thin film was cut off ultraviolet successfully. Therefore, the sunglass with ferrite plating is use of cut of ultraviolet and electromagnetic field.

• Journal of the Korean Ceramic Society
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• v.14 no.2
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• pp.78-81
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• 1977

The effects of variation in composition and the addition of small amount of the rare-earth oxides La2O3, CeO2 and Sm2O3 on the magnetic properties of Mn-Zn system ferrites, 0.5MnO.0.5ZnO.(1＋0.1X) Fe2O3(X=-1, 0, 1, 2), were investigated in the range of frequencies of 0.1~100 kHz. It was shown that the magnetic permeability of the specimens with the composition Mn 0.5 Zn 0.5 Fe2O4 was maximum in the Mn-Zn system ferrites, and that the addition of a small amount of the rare-earth oxides to the composition 0.5 MnO.0.5ZnO.0.9 Fe2O3 caused the sharp increase of magnetic permeability and the decrease of the loss factors.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1245-1252
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• 1996

The charcteristics for the copper-contained spinel ferrites such as NiCu-and ZnCu ferrites with various copper content are investigated in this study which can provide a explanation for the behavior of copper in sintering at a low temperatuer. The bulk density and the grain size for these sintered ferrites were increased with the larger amount of copper in compositions. In microstructure of copper-contained spinel ferrites copper exists in the grain boundary which is sintering process. Electrical resistivity and frequency range with maximum Q-facor of NiCu-or ZnCu ferrites were decreased as increasing of copper content in ferrite composition.

• Journal of Magnetics
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• v.16 no.1
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• pp.27-30
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• 2011

Nano-sized manganese ferrite powders and films, $MnFe_2O_4$, were fabricated by the sol-gel method, and the effects of annealing temperature on the crystallographic and magnetic properties were studied by using X-ray diffractometry, field emission scanning electron microscopy, M$\"{o}$ssbauer spectroscopy, and vibrating sample magnetometry. X-ray diffraction spectroscopy of powder samples annealed above 523 K indicated the presence of spinel structure, and the film samples annealed above 773 K also had spinel structure. The particle size increased with the annealing temperature. For the powder samples, the Mossbauer spectra annealed above 573 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of $Fe^{3+}$ ions. Using the M$\"{o}$ssbauer subspectrum area ratio the cation distribution could be written as ($Mn_{0.52}Fe_{0.48}$) $[Mn_{0.48}Fe_{1.52}]$ $O_4$. However the spectrum annealed at 523 K only showed as a doublet due to a superparamagnetic phase. As the annealing temperature was increased, the saturation magnetization and the corecivity of the powder samples increased, as did the coercivity of film samples.

• Proceedings of the Korean Magnestics Society Conference
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• 1991.05a
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• pp.93-94
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• 1991

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.255-259
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• 1999

높은 투자율과 낮은 손실특성을 지닌(Mn, Zn)ferrite의 전자기적 특성은 소결공정과 소결분위기에 따라 상당히 다양하게 나타난다. 본 연구에서는(Mn, Zn)ferrite를 소결시킬 때의 승온속도와 냉각속도에 따른 초투자율 특성과 미세구조의 관계에 관하여 고찰하였다. 승온속도의 영향을 고찰하기 위하여 spinel ferrites 생성 및 결정입 성장 거동에 가장 중요한 온도인 800~120$0^{\circ}C$의 범위에서 속도를 변화시켰고, 냉각속도 영향을 살펴보기 위하여 1100~80$0^{\circ}C$ 온도범위를 택하였다. 열처리 온도범위 800~120$0^{\circ}C$에서 승온속도가 증가함에따라 초투자율이 7$^{\circ}C$/min까지는 증가했으나 그 이상의 승온속도에서는 오히려 초투자율이 감소하였다. 또한 1100~80$0^{\circ}C$ 온도범위에선 냉각속도가 증가될수록 초투자율이 감소하는 경향을 나타내었다. 치밀화 및 투자율을 높이기 위하여 첨가된 CaO, SiO2, V2O5의 분포상태를 분석한 결과, 이들 첨가물들은 입자와 입계를 따라 균일하게 분포하는 것으로 나타났다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.93-96
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• 2000

In this study, we investigated the electromagnetic properties of Mn-Zn ferrite doped with rare earth oxide (Dy$_2$O$_3$, Er$_2$O$_3$). The main composition is 52mo1% $\alpha$-Fe$_2$O$_3$, 25mo1% Mn$_3$O$_4$23mo1% ZnO and doped with them(0.05wt%~0.25wt%, step:0.05wt%). An experimental process has advanced by conventional ferrimagnetism manufacturing that was prepared by standard ceramic techniques. The XRD pattern of all doped sample were observed spinel and secondary phase. The density of sample were measured nearly constant value. As increased the additive, resistivity, initial permeability and real component of the series complex permeability increased with setting limits each other. In case of Mn-Zn ferrite excess doped with them, resistivity, initial permeability and real component of the series complex permeability decreased and magnetic loss increased in proportion to increasing the additive.