• 한국세라믹학회지
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• 제33권11호
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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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• 제16권2호
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• pp.134-139
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• 2011

Magnetic properties of highly zinc-substituted manganese ferrites are discussed on the basis of cation distribution. High throughput neutron powder diffractometry indicates that the prepared samples possess a nearly normal spinel structure, where the substitution of nonmagnetic zinc ions mainly causes the dilution of magnetic ions in the A-sublattice and consequently affects bond-randomness in the B-sublattice. On the other hand, the estimated occupancy of manganese ions in the B site indicates that random anisotropy effects due to local Jahn-Teller distortions gradually weaken with the substitution. Bulk magnetometry indicates that the substitution smears the transition from a paramagnetic phase to a soft-magnetic phase. Furthermore, at lower temperatures, such a soft-magnetic phase is destabilized and a magnetic glassy state appears. These features of the magnetic properties of dilute spinel ferrites are discussed from the viewpoint of the above-mentioned various types of disorders.

• 한국세라믹학회지
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• 제39권12호
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• pp.1119-1123
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• 2002

Nanostructured spinel NiZn ferrites were prepared by the sol-gel method from metal nitrate raw materials. Analyses by X-ray diffraction and scanning electron microscopy showed the average particle size of NiZn ferrite was under 50 nm. The single phase of NiZn ferrites was obtained by firing at 250${\circ}C$, resulting in nanoparticles exhibiting normal ferrimagnetic behavior. The nanostructured $Ni_{1-X}Zn_XFe_2O_4$ (x=0.0∼1.0) were found to have the cubic spinel structure of which the lattice constants ${\alpha}_2$ increases linearly from 8.339 to 8.427 ${\AA}$ with increasing Zn content x, following Vegard's law, approximately. The saturation magnetization $M_s$ was 48 emu/g for x=0.4 and decreased to 8.0 emu/g for higher Zn contents suggesting the typical ferrimagnetism in mixed spinel ferrites. Pure NiZn ferrite phase substituted by Cu was observed before using the additive but hematite phase was partially appeared at $Ni_{0.2}Zn_{0.2}Cu_{0.6}Fe_2O_4$. On the other hand, the hematite phase in this NiZn Cu ferrite was disappeared after using the additive of acethyl aceton with small amount. The saturation magnetization Ms of $Ni_{0.2}Zn_{0.8-y}Cu_yFe_2O_4$(y=0.2∼0.6) as measured was about 51 emu/g at 77K and 19 emu/g at room temperature, respectively.

• 한국세라믹학회지
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• 제14권2호
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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.

• 한국세라믹학회지
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• 제31권1호
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• pp.62-68
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• 1994

It is compared the structures of the S-block in the Ba-Co-Zn Y-type hexagonal ferrites (Ba2Co2-xZnxFe12O22, x=0~2) and the Co-Zn spinel ferrites (Co1-xZnxFe2O4, x=0~1) expressed by a hexagonal axis system (space group R3m). The structures have been refined with a Rietveld analysis of the powder X-ray diffraction pattern with high precision (Rwp<0.13, RI<0.03). The overal dimension of the S-block is slightly different from the 1/3 of a hexagonal spinel unit cell as follow: 1.6~2.0% longer c-axis, 1.3~1.6% shorter a-axis and about 1% smaller volume. Upto Zn:Co=1:1 in the Ba-Co-Zn Y-type hexagonal ferrites, the zinc substitute primarily the tetrahedral sites in the S-block. Beyond that the zinc seems to go into the T-block as well.

• 한국자기학회지
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• 제3권3호
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• pp.173-178
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• 1993

스피넬구조를 갖는 $AB_{2}O_{4}$에서 A-O-B초교환 상호작용을 고려하여 A(사면체)와 B(팔면체) 자리에 들어 있는 자성원자(Fe)의 환산자발자화와 그 평균치를 환산온도의 함수로 계산하였다. 그 결과를 A-B직접 상호작용을 고려하여 계산한 환산자발자화의 온도의존성과 비교하였다. 보다 정확한 비교를 위하여 두가지 경우에 대한 $M\"{o}ssbauer$ 스펙트럼을 계산하였다.

• 공업화학
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• 제22권2호
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• pp.185-189
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• 2011

본 연구에서는 화학적 공침법을 적용하여 가스상 이산화탄소 분해를 위한 나노크기의 M-페라이트(M=Co, Ni, Cu, Zn)를 제조하였다. 열중량 분석 결과, 시험제조한 모든 시료의 최고 무게 감소율은 $350^{\circ}C$ 미만에서 발생하였다. 소성온도가 증가할수록 결정형은 우수하여 표면촉매활성화를 기대할 수 있지만, 입자결정의 크기가 크고, 비표면적이 낮은 페라이트가 합성됨을 알 수 있었다. FT-IR 분석으로부터 $375{\sim}406cm^{-1}$의 범위에서 octahedral site에 착화물이 존재함을 확인 할 수 있었으며, 이는 페라이트 내 스피넬 구조가 형성되어 있음을 보여주는 것이라고 믿는다. 본 연구로부터 얻은 이산화탄소 분해반응을 위한 금속페라이트의 최적 열처리 온도는 $500^{\circ}C$인 것으로 나타났다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.52.1-52.1
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• 2007

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 추계총회,초청강연,특별강연,연구발표회
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• pp.30.2-30
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• 2000

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2002년도 추계총회 및 연구발표회 초록집
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• pp.152.1-152
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• 2002