• 한국결정성장학회지
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• 제17권1호
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• pp.11-17
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• 2007

The spherical NiZn ferrite particles were prepared by ultrasonic spray pyrolysis with mixed solution of aqueous metal nitrates. The NiZn ferrite particle was observed with nano-sized primary particles of about 10 nm or less before annealing which represented as paramagnetic behavior measured at 77 K and room temperature. The typical abnormal growth of primary particles like polyhedral primary particles was observed by annealing at 1273 K with Zn-concentration dependency. The XRD patterns showed good crystallinity of NiZn ferrite powder after annealing. In annealing process, the intra-particle sintering phenomenon was observed and the spherical particle morphology was collapsed at 1673 K. The saturation magnetization of NiZn ferrite powder for each annealing temperature was decreased with measuring temperature of $77{\sim}$300K.

• 한국세라믹학회지
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• 제40권1호
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• pp.31-36
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• 2003

본 연구에서는 칩 인덕터용 코어 소재로 사용되는 NiCuZn-ferrite를 공침법을 이용하여 나노크기의 초미세 분말로 합성하고, 합성된 NiCuZn-ferrite의 하소 온도에 따른 저온소결 특성 및 전자기적 특성에 관하여 고찰하였다. 조성은 (N $i_{0.4-X}$C $u_{x}$Z $n_{0.6}$)$_{1+w}$(F $e_2$ $O_4$)$_{1-w}$에서 x 값을 0.2, w 값은 0.03으로 고정하였고, 하소는 30$0^{\circ}C$에서 7$50^{\circ}C$의 온도범위에서 진행하였다. 하소 후 90$0^{\circ}C$에서 소결한 시편의 특성을 측정한 결과, 공침법으로 합성한 NiCuZn-ferrite는 90$0^{\circ}C$의 저온에서 소결밀도 4.90g/㎤, 초기투자율 164, Q-factor 72임을 확인하였다. 또한, NiCuZn-ferrite의 미세구조는 하소온도가 증가함에 따라 입자가 커지고 불균일한 상태가 되며, 초기투자율 등의 ferrites의 전자기적 특성이 저하되었다.되었다.

• Journal of Magnetics
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• 제18권1호
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• pp.21-25
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• 2013

Nickel substituted manganese ferrites, $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.6$), were fabricated by sol-gel method. The effects of sintering and substitution on their crystallographic and magnetic properties were studied. X-ray diffractometry of $Mn_{0.6}Ni_{0.4}Fe_2O_4$ ferrite sintered above 523 K indicated a spinel structure; particles increased in size with hotter sintering. The M$\ddot{o}$ssbauer spectrum of this ferrite sintered at 523 K could be fitted as a single quadrupole doublet, indicative of a superparamagnetic phase. Sintering at 573 K led to spectrum fitted as the superposition of two Zeeman sextets and a single quadrupole doublet, indicating both ferrimagnetic and paramagnetic phase. Sintering at 673 K and at 773 K led to spectra fitted as two Zeeman sextets due to a ferrimagnetic phase. The saturation magnetization and the coercivity of $Mn_{0.6}Ni_{0.4}Fe_2O_4$ ferrite sintered at 773 K were 53.05 emu/g and 142.08 Oe. In $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.6$) ferrites, sintering of any composition at 773 K led to a single spinel structure. Increased Ni substitution decreased the ferrites' lattice constants and increased their particle sizes. The M$\ddot{o}$ssbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and the octahedral sites of the $Fe^{3+}$ ions. The variations of saturation magnetization and coercivity with changing Ni content could be explained using the changes of particle size.

• Journal of Magnetics
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• 제21권3호
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• pp.308-314
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• 2016

Cobalt-, zinc-, and nickel-zinc-substituted nano-size manganese ferrite powders, $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, $Mn_{0.8}Zn_{0.2}Fe_2O_4$ and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$, were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently studied. The $MnFe_2O_4$ ferrite powder annealed at temperatures above 523 K exhibited a spinel structure, and the particle size increased as the annealing temperature increased. All ferrites annealed at 773 K showed a single spinel structure, and the lattice constants and particle size decreased with the substitution of Co, Zn, and Ni-Zn. The $M{\ddot{o}}ssbauer$ spectrum of the $MnFe_2O_4$ ferrite powder annealed at 523 K only showed a doublet due to its superparamagnetic phase, and the $M{\ddot{o}}ssbauer$ spectra of the $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, and $Mn_{0.8}Zn_{0.2}Fe_2O_4$ ferrite powders annealed at 773 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. However, the $M{\ddot{o}}ssbauer$ spectrum of the $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$ ferrite powder annealed at 773 K consisted of two Zeeman sextets and one quadrupole doublet due to its ferrimagnetic and paramagnetic behavior. The area ratio of the $M{\ddot{o}}ssbauer$ spectra could be used to determine the cation distribution equation, and we also explained the variation in the $M{\ddot{o}}ssbauer$ parameters by using this cation distribution equation, the superexchange interaction and the particle size. Relative to pure $MnFe_2O_4$, the saturation magnetizations and coercivities were larger in $Mn_{0.8}Co_{0.2}Fe_2O_4$ and smaller in $Mn_{0.8}Zn_{0.2}Fe_2O_4$, and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$. These variations could be explained using the site distribution equations, particle sizes and magnetic moments of the substituted ions.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.104-105
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• 2002

Ni$_{1-x}$-Zn$_{x}$ ferrite는 매우 큰 저항과 적은 eddy current loss를 가지고 있어 transfomer core나 radio frequency coil같은 high power device등의 전자 재료로 이용된다[1]. Ni$_{1-x}$-Zn$_{x}$ ferrite의 합성에는 여러 가지 방법이 이용되고 있으나 oxide/carbonate를 이용하여 120$0^{\circ}C$ 이상의 고온의 열을 가해 하소하는 solid-state reation과 diethylamine을 이용하여 metal nitrate를 공침 하는 coprecipition방법, sol-gel 방법 등의 wet chemical method가 가장 일반적이다[2-3]. (중략)

• 한국자기학회지
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• 제24권3호
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• pp.81-85
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• 2014

$BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ 나노복합체 페라이트는 솔-젤 연소법으로 합성하였고, 합성된 나노복합체 페라이트를 $600{\sim}900^{\circ}C$ 범위에서 1시간 동안 하소하였다. XRD 분석 결과, 경자성/연자성 나노복합체에서 경자성과 연자성이 공존하고 있음을 확인하였다. 나노복합체의 입자크기는 90 nm보다 작게 나타났다. 나노복합체는 단일 페라이트의 hysteresis 곡선과 같은 모양을 나타내었으며, 이로서 경자성과 연자성 사이에 exchange coupling이 잘 되었음을 확인할 수 있었다. 경자성/연자성 나노복합체 페라이트의 포화자화 값은 연자성보다 낮고 경자성보다 높았다. 잔류자화 값은 경자성과 연자성보다 크게 나타났고, 전체적으로 $(BH)_{max}$이 향상되었음을 확인할 수 있었다.

• 한국표면공학회지
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• 제50권3호
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• pp.212-218
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• 2017

$Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrite powders were prepared by self-propagating high temperature synthesis followed by classifying with an ultrasonic wet-magnetic separation unit to get high pure nano-sized particles. The $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrites were well formed by using several powders like iron, nickel oxide, zinc oxide and magnesium oxide at 0.1 MPa of oxygen pressure. The ultrasonic wet-magnetic separation of pre-mechanical milled ferrite powders resulted in producing the powders with average size of 800 nm. The addition of a surfactant during the wet-magnetic separation process improved productivity more than twice. The coercive force, maximum magnetization and residual magnetization of the $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ nano-powders with 800 nm size were 3651 A/m, $53.92Am^2/kg$ and $4.0Am^2/kg$, respectively.

• 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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• 제15권5호
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• pp.282-286
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• 2005

공침법으로 제조한 Ni-Cu-Zn ferrite를 사용하여 전파흡수체로 사용할 저온소결용 ferrite를 연구하였다. Ni 첨가량에 따른 조성비 및 가소온도와 소결온도 변화를 시켜 전파흡수특성 및 물리적 특성을 고찰하였다. XRD pattern을 통하여 spinel구조를 가짐을 확인하였고, 공침법으로 제조된 Ni-Cu-Zn ferrite 미분말이 나노입자 크기를 보였다 소결온도가 $1100^{\circ}C$이고 Ni 함량이 많을 수록 투자율이 낮고 손실계수도 높게 측정되어 흡수 능력도 좋아짐을 알 수 있고, MHz 영역에서 사용할 수 있다고 사료된다. 그리고 소결온도 $1100^{\circ}C$이고 $(Ni_{0.7}Cu_{0.2}Zn_{0.1}O)_{1.02}(Fe_{2}O_3)_{0.98}$ 조성일 때가 가장 손실이 크므로 전파흡수체로 사용할 조성임을 확인 할 수 있었다.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2002년도 추계총회 및 연구발표회 초록집
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• pp.93.2-93
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• 2002