• 한국세라믹학회지
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• 제35권8호
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• pp.843-849
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• 1998

Fine powders of Mn-Zn ferrite were prepared by the alcoholic dehydration method and densification beha-vior of synthesized powder was investigated. The concentration and pH of solution for optimal precipitation was 0.4M and 2.5 respectively. The spinel single phase metastable state was formed by thermal decom-position of precipitate and then spinel phase was disintegrated into hematite and spinel {{{{ { { ZnFe}_{2 }O }_{4 } }} at 600$^{\circ}C$ With increase of temperature reaction of solid solution between hematite and spinel was proceeded and resulted in the spinel single phase (Mn, Zn Fe){{{{ { {Fe }_{2 }O }_{4 } }} On account of high reactivity of uncalcined powders densification started at 200$^{\circ}C$ lower and completed at 50$^{\circ}C$ lower in comparison with calcined powders.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1991년도 추계연구발표회 논문개요집
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• pp.58-59
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• 1991

• 한국자기학회지
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• 제16권1호
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• pp.1-5
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• 2006

결정구조는 같은 spinel 구조이나, 자기적으로는 각각 반강자성과 준강자성 특성을 띠고 있는 $Co_3O_4$와 자철광 $Fe_3O_4$의 혼성 Co-ferrite인 $Co_xFe_{1-x}O_4$ 박막을 sol-gel법으로 제조하여, Fe 이온에 대한 Co 이온 치환으로 발생된 양이온 거동이 Co-ferrite 박막의 결정구조 및 자기적 특성에 미치는 효과를 XRB 실험, VSM 측정, 그리고 Conversion Electron Mossbauer Spectroscopy (CEMS) 실험으로 조사하였다. 그 결과 $Co^{3+}$ 이온이 주로 $Fe^{3+}$ 이온을 치환하여 단위정의 크기가 감소를 가져오며, 결정구조는 inverse spinel 구조에서 normal spinel 구조로 변환된다. CEMS 분광실험을 통하여 확인된 Fe 이온의 site preference는 주로 $Fe^{3+}$ 이온이 $Co^{3+}$ 치환됨을 보여주고 있으며, 동시에 B-site의 $Co^{2+}$ 이온은 A-site로 이동된다. 자화곡선 측정결과 Co 조성값의 증가로 자기 moment값이 감소되는 것으로 나타났는데, 이것은 low spin상태의 $Co^{3+}$이 high spin상태의 $Fe^{3+}$이온을 치환하여 주로 발생한 것이다.

• 한국세라믹학회지
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• 제30권1호
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• pp.25-33
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• 1993

Formation reaction of Mn-Zn ferrite depending on various synthetic conditions of wet process was investigated using FeCl2.nH2O(n≒4), MnCl2.4H2O, ZnCl2 as starting materials. A stable intermediate precipitate was formed by the addition of H2O2. And the precipitate was hard to transform to spinel phase of Mn-Zn Fe2O4. Single phase of Mn-Zn Fe2O4 spinel was obtained above 8$0^{\circ}C$ reaction temperature. The powder had spherical particle shape and 0.02~0.05${\mu}{\textrm}{m}$ particle size. Fe(OH)2 solid solution, -FeO(OH) solid solution, -FeOOH, Mn-Zn Fe2O4 spinel were formed with air flow rate 180$\ell$/hr. However, single phase of Mn-Zn Fe2O4 spinel with cubic particle shape and 0.1~0.2${\mu}{\textrm}{m}$ particle size was formed with synthetic conditions of 8$0^{\circ}C$ and 90 munutes. The particle shape of the -FeOOH was needle-like.

• Journal of Magnetics
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• 제15권1호
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• pp.25-28
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• 2010

This study examined the crystallographic and magnetic properties of vanadium-substituted lithium cobalt titanium ferrite, $Li_{0.7}Co_{0.2}Ti_{0.2}V_{0.2}Fe_{1.7}O_4$. Ferrite was synthesized using a conventional ceramic method. The samples annealed below $1040^{\circ}C$ showed X-ray diffraction peaks for spinel and other phases. However, the sample annealed above $1040^{\circ}C$ showed a single spinel phase. The lattice constant of the sample was $8.351\;{\AA}$, which was relatively unaffected by vanadium-substitution. The average grain size after vanadium-substitution was $13.90\;{\mu}m$, as determined by scanning electron microscopy. The M$\ddot{o}$ssbauer spectrum could be fitted to two Zeeman sextets, which is the typical spinel ferrite spectra of $Fe^{3+}$ with A and B sites, and one doublet. From the absorption area ratio of the M$\ddot{o}$ssbauer spectrum, the cation distribution was found to be ($Co_{0.2}V_{0.2}Fe_{0.6})[Li_{0.7}Ti_{0.2}Fe_{1.1}]O_4$. Vibrating sample magnetometry revealed a saturation magnetization and coercivity of 36.9 emu/g and 88.6 Oe, respectively, which were decreased by vanadium-substitution.

• 한국세라믹학회지
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• 제32권3호
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• pp.394-402
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• 1995

Electrical conductivity and thermoelectric power of the ferrous ferrite system of (Mg0.29-yMnyFe0.71)3-$\delta$O4 have been measured as function of the thermodynamic variables, cationic composition(y), temperature(T) and oxygen partial pressure(Po2) under thermodynamic equilibrium conditions at elevated temperatures. On the basis of the electrical properties-phase stability correlation, the stability regions of the ferrite spinel and its neighboring phases have been subsequently located in the log Po2 vs. y and log Po2 vs. 1/T planes in the ranges of 0 y 0.29, 1100 T/$^{\circ}C$ 1400 and 10-14 Po2/atm 1. The stability region, Δlog Po2(y, 1/T), of the ferrite spinel single phase widens with increasing Mn-content(y) and the boundaries of each region are linear against 1/T with negative slopes.

• 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.

• 한국자기학회지
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• 제19권3호
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• pp.106-112
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• 2009

상온에서 준강자성을 띠는 $Ni_{1-x}Mg_xFe_2O_4$ ferrite 내에 존재하는 금속양이온 Ni을 Mg로 대치시킬 때 나타나는 결정학적 구조의 변화와 자기적 성질 변화, 그리고 양이온의 분포를 X-선 회절무늬와 $M{\ddot{o}}ssbauer$ spectrum을 측정하고 분석하여 연구하였다. $NiFe_2O_4$ ferrite의 $M{\ddot{o}}ssbauer$ spectrum 공명흡수면적비(oct/tet)는 1.007로서 거의 완전한 inverse spinel 구조를 형성하나 Mg의 함량인 x가 증가함에 따라 Mg 이온이 tetrahedral site를 점유하게 되어 면적비(oct/tet)가 점차 증가하여 $MgFe_2O_4$의 경우 1.449로서 불완전한 inverse spinel 구조를 형성한다. 시료들의 isomer shift 값으로부터 $Ni_{1-x}Mg_xFe_2O_4$ ferrite계 내에 존재하는 Fe는 $Fe^{3+}$ 상태임을 알 수 있다. 비자성 이온인 Mg의 함량이 증가함에 따라 최인접 금속 양이온에 의해 발생되는 A-B exchange interaction이 발생할 확률이 작아져서 magnetic hyperfine field가 감소하며 Yafet-Kittel 자기구조를 나타낸다.

• 한국항해학회지
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• 제23권1호
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• pp.15-22
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• 1999

In this paper, ferrite-rubber composite has been studied in order to apply to RF-A-PF in a super wideband electromagnetic absorber in RF-A-PF type, which can be used for a general purpose anechoic chamber. $Ni_x - Mn_0.1 - Zn_{(1-x-0.1)}ㆍFe_2O_4$ ferrite powder has been fabricated, then, using this, 〔$Ni_x - Mn_0.1 - Zn_{(1-x-0.1)}ㆍFe_2O_4$〕-Rubber composite for RF-layer in the RF-A-PF type absorber has been fabricated and it's characteristics have been analyzed. As a result, it has been clearly shown that the 〔$Ni_x - Mn_0.1 - Zn_{(1-x-0.1)}ㆍFe_2O_4$〕-Rubber composite has excellent electromagnetic wave absorbing properties.

• 한국분말재료학회지
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• 제2권1호
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• pp.29-35
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• 1995

In this study the calcined condition and characteristic of Cu-Ni-Zn ferrite powder were investigated. The Cu-Ni-Zn ferrite powder has been synthesized by the thermal decomposition of the organic acid salt. This process did not require a strict pH control and provided the uniform composition and fine powder with about 0.3 $\mu\textrm{m}$. The XRD diffraction pattern of this powder showed about 50% spinel phase. The optimum calcination was found to be done at $700^{\circ}C$ for one hour. After the calcination, the amount of spinel increased to 90%. The distribution of the particle size showed bimodal peaks, one was about 0.5 $\mu\textrm{m}$ and the other was about 20 $\mu\textrm{m}$. The large particles of 20 $\mu\textrm{m}$ were the agglomeration of fine Particles. The mean Particle size of the powder was about 0.4 $\mu\textrm{m}$. The powder was compacted under 100 MPa pressure and sintered at 1100~ $1250^{\circ}C$ for one hour in air. The density of ferrites specimen was a function of the sintering temperature. The higher the temperature, the denser the ferrite. The maximum relative density of the sintered ferrite was about 93% at $1250^{\circ}C$. The grain size of sintered specimen at $1200^{\circ}C$ was 5 $\mu\textrm{m}$ and homogeneous.