• 한국세라믹학회지
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• 제31권2호
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• pp.213-219
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• 1994

The formations of spinel and colors of ZnO-Fe2O3-TiO2-SnO2 system have been researched on the basis of ZnO-Fe2O3 system. Specimens were prepared by substituting Fe3+, with Ti4+ or Sn4+ when mole ratios between Fe3+ and Ti4+ or between Fe3+ and Sn4+ were 0.2 mole. The reflectance measurement and X-ray diffraction analysis of the formation of spinel and the colors of there specimens were carried out. ZnO-Fe2O3 system in which Fe2O3 was substituted with SnO2 and TiO2 was formed the spinel structure of 2ZnO.TiO2, 2ZnO.SnO2, ZnO.Fe2O3. The stable stains which were colored with yellow and brown could be manufactured.

• 센서학회지
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• 제30권4호
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• pp.191-195
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• 2021

Pure ZnFe₂O₄ and Fe₂O₃-ZnFe₂O₄ hetero-composite spheres were prepared by ultrasonic spray pyrolysis of a solution containing Zn- and Fe-nitrates. Additionally, the sensing characteristics of these spheres in the presence of 5 ppm ethanol, benzene, p-xylene, toluene, and CO (within the temperature range of 275-350 ℃) were investigated. The Fe₂O₃-ZnFe₂O₄ hetero-composite sensor with a cation ratio of [Zn]:[Fe]=1:3 exhibited a high response (resistance ratio = 140.2) and selectivity (response to p-xylene/response to ethanol = 3.4) to 5 ppm p-xylene at 300 ℃, whereas the pure ZnFe₂O₄ sensor showed a comparatively lower gas response and selectivity. The reasons for the superior response and selectivity to p-xylene in Fe₂O₃-ZnFe₂O₄ hetero-composite sensor were discussed in relation to the electronic sensitization due to charge transfer at Fe₂O₃-ZnFe₂O₄ interface and Fe₂O₃-induced catalytic promotion of gas sensing reaction. The sensor can be used to monitor harmful volatile organic compounds and indoor air pollutants.

• 전기학회논문지
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• 제57권4호
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• pp.625-628
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• 2008

Ba-Zn ferrite powders for electromagnetic insulator were synthesized by self-propagating high-temperature synthesis(SHS) with a reaction of $xBaO_2+(1-x)ZnO+0.5Fe_2O_3+Fe{\rightarrow}Ba_xZn_{1-x}Fe_2O_4$. In this study, phase indentification of SHS products was carried out by using x-ray diffractometry and quasi-nano sized Ba-Zn powders were prepared by a pulverizing process. SHS mechanism was studied by thermodynamical analysis about oxidation reaction among $BaO_2,\;ZnO,\;Fe_2O_3$, and Fe. As oxygen pressure increases from 0.25 MPa to 1.0 MPa, the SHS reactions occur well and make clearly the SHS products. X-ray analysis shows that final SHS products formed with the ratio of $BaO_2/ZnO$ of 0.25, 1.0 and 4.0, are mainly $Ba_xZn_{1-x}Fe_2O_4$. Based on thermodynamical evaluation, the heat of formation increases in the order of $ZnFe_2O_4,\;BaFe_2O_4$, and $Ba_xZn_{1-x}Fe_2O_4$. This supports that $Ba_xZn_{1-x}Fe_2O_4$ phase is predominately formed during SHS reaction. The SHS reactions to form $Ba_xZn_{1-x}Fe_2O_4$ depends on oxygen partial pressure, and the heat of formation during the SHS reaction. The SHS reactions tends to occur well with increasing the oxygen partial pressure and BaO2/ZnO ratio in the reactants This means that the SHS reaction for the formation of Ba-Zn ferrite includes the reduction of BaO2/ZnO and the oxidation of Fe. $Ba_xZn_{1-x}Fe_2O_4$ powders after pulverizing is agglomeratedwith a size of about $50{\mu}m$, in which quasi-nano sized particles with about 300nm are present.

• 한국자기학회지
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• 제3권1호
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• pp.18-22
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• 1993

$Cu_{x}Zn_{1-x}Fe_{2}O_{4}(0{\leq}x{\leq}1)$의 이온분포 및 자기적 성질을 X-선 회절법과 $M\"{o}ssbauer$ 분광법으로 연구하였다. 결정구조는 $0{\leq}x{\leq}0.9$의 영역에서 입방 스피넬이다. $ZnFe_{2}O_{4}$의 이온분포는 ${(Zn_{1-x}Fe_{x})}_{A}{[Zn_{x}Fe_{2-x}]}_{B}O_{4}$:x=0.1 이다. Curie 온도 이하의 $M\"{o}ssbauer$ spectrum에서 $Fe^{3+}$ 이온의 분포상태를 $0{\leq}x{\leq}1$의 전 영역에서 얻었다. Cu의 농도 x가 증가함에 따라서 사면체자리에 들어가는 $Fe^{3+}$ 이온의 수가 증가하고 Cu-Zn 훼라이트의 Curie 온도가 높아진다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.21.2-21.2
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• 2011

$Fe_3O_4$ having half metallic property is one of the efficient spin filtering materials which are widely used in spintronic research field and ZnO is wide band gap semiconductor which can be used by tunnel barrier or semiconductor channel in spin MOSFET. We investigated the magnetic and the electric properties of $Fe_3O_4$/ZnO multilayer fabricated on c-$Al_2O_3$ substrate by pulsed laser deposition (PLD). For multilayer films, PLD was performed at variable temperatures such as $200{\sim}750^{\circ}C$ and at target distance from 40 to 80 mm, KrF eximer laser of 1.5 $J/cm^2$ and a reputation rate of 2Hz. $Fe_3O_4$/ZnO multilayers were deposited at $4{\times}10^{-6}$ Torr. After fabricating $Fe_3O_4$/ZnO multilayers, $Fe_3O_4$/ZnO multilayers were treated by RTA(Rapid Thermal Annealing) at various temperature to change magnetic phase. The magnetism of the multilayer is changed by thickness of the ZnO tunnel barrier. Magnetic phase of FexOy showed a very small magnetism due to $Fe_2O_3$ ${\alpha}$-phase, but large magnetism from $Fe_3O_4$ or $Fe_2O_3$ ${\gamma}$-phase was observed. In the present study, effect of the ZnO thickness on the MR (magnetoresistance) ratio was investigated in detail.

• 한국자기학회지
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• 제21권3호
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• pp.88-92
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• 2011

Pulsed Laser Deposition 방법을 사용하여 $Zn_{0.4}Fe_{2.6}O_4$ 박막을 증착하였으며 이의 결정성 및 자기적 특성을 증착온도의 함수로 조사하였다. 증착온도가 $300^{\circ}C$었을 경우 박막은 코런돔(corundom) ${\alpha}-$Fe_2O_3$ 또는 워자이트(wurzite) ZnO 구조를 지니고 있었으나 증착온도가 $500^{\circ}C$로 증가되었을 경우에는 $Zn_{0.4}Fe_{2.6}O_4(111)/Al_2O_3(0001)$의 결정 방향을 지닌 매우 안정된 역스피넬(inverse spinel) 성장이 이루어졌으며 또한 표면의 거칠기도 증착온도가 $300^{\circ}C$ 일 때 보다 더 평평하여졌다. 이러한 역스피넬 $Zn_{0.4}Fe_{2.6_O_4$ 박막에서는 X-선 산란 분석 결과 ${\alpha}-$Fe_2O_3$, ZnO에 해당하는 픽들은 전혀 관측되지 않았으며 이러한 사실들은 Zn가 증착온도를 높여줌에 따라 역스피넬의 사면체 자리에 치환되었음을 의미한다. M-H 곡선의 측정 결과 증착온도 $300^{\circ}C$ 박막은 자성 특성이 거의 관측되지 않은 반면 $500^{\circ}C$ 박막의 경우에는 매우 뚜렷한 강자성 특성을 확인할 수 있었으며 벌크보다 작은 포화자화 값은 팔면체 자리의 Fe 스핀들의 삐뚤림(canting)에 의한 것으로 이해된다.

• 한국세라믹학회지
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• 제28권4호
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• pp.305-314
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• 1991

This study was conducted to research the formation and the color development of NiO-ZnO-Fe2O3-TiO2-SnO2 system for the purpose of synthesizing the spinel pigments which are stable at high temperature. After preparing ZnO-Fe2O3 as a basic composition, {{{{ chi }}NiO.(l-{{{{ chi }})ZnO.Fe2O3 system, {{{{ chi }}NiO.(l-{{{{ chi }})ZnO.TiO2 system, and {{{{ chi }}NiO.(l-{{{{ chi }})ZnO.SnO2 system were prepared with {{{{ chi }}=0, 0.2, 0.5, 0.7, 1 mole ratio respectively. The manufacturing was carried out at 128$0^{\circ}C$ for 30 minutes. The reflectance measurement and the X-ray analysis of these specimens were carried out and the results were summarized as follows. 1. In the specimens which included NiO, it was difficult for the spinel structure to be formed. 2. As increasing the contents of NiO and Fe2O3, all the groups which were yellow or green colored changed to brown. 3. NiO-ZnO-Fe2O3 system and NiO-ZnO-TiO2 system formed the spinel structure and the illmenite structure appeared in NiO-TiO2 system.

• 한국세라믹학회지
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• 제28권11호
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• pp.897-907
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• 1991

This study was conducted to research the formation and the color development of CoO-ZnO-Fe2O3-TiO2-SnO2 system for the purpose of synthesizing the spinel pigments which are stable at high temperature. After preparing CoO-ZnO-Fe2O3, in which CoO causes the color, as a basic composition, $\chi$CoO.(1-$\chi$)ZnO.Fe2O3 system, $\chi$CoO.(1-$\chi$)ZnO.TiO2 system and $\chi$CoO.(1-$\chi$)ZnO.SnO2 system were prepared with $\chi$=0, 0.2, 0.5, 0.7, 1.0 mole ratio respectively. The manufacturing was carried out at 128$0^{\circ}C$ for 90 minutes. These specimens were analyzed by the reflectance measurement and the X-ray diffraction analysis and the results were summarized as follows: 1. All of the specimens formed the spinel structure and were colored with stable yellow or blue. 2. As the content of CoO and Fe2O3 in the specimens being increased, the reflectance of each specimen was measured becoming lower and the colors were changed from yellow to greyish blue and from blue to dark blue. 3. As the substituting amount of Co2+ ion for Zn2+ ion in $\chi$CoO-ZnO-TiO2-SnO2 system being increased, the colors were changed from blue to greyish blue. The colors were changed from yellow to grayish green owing to the tetrahedral Co2+ ions being increased, the octahedral Co2+ ions being decreased with increasing the amount of Sn4+ ions. 4. CoO-ZnO-Fe2O3-TiO2-SnO2 system, in which Zn2+ was substituted with Co2+ and Fe3+ was substituted with Ti4+ and Sn4+, easily formed the spinel structure without regard to the amount of substitution or the ion owing to the selectivity of the coordination number: 4 of Zn2+, 4 of Co2+, 6 of Fe3+ or 6 of Ti4+ and Sn4+.

• Journal of Magnetics
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• 제10권3호
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• pp.84-88
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• 2005

Nanoparticles $Ni_{0.7}Zn_{0.3}Fe_2O_4$ is fabricated by a sol-gel method. The magnetic and structural properties of powders were investigated with XRD, SEM, $M\ddot{o}ssbauer$ spectroscopy, and VSM. $Ni_{0.7}Zn_{0.3}Fe_2O_4$ powders annealed at $300^{\circ}C$ have a spinel structure and behaved superparamagnetically. The estimated size of $Ni_{0.7}Zn_{0.3}Fe_2O_4$ nanoparticle is about 11 nm. $Ni_{0.7}Zn_{0.3}Fe_2O_4$ annealed at 400 and $500^{\circ}C$ has a typical spinel structure and is ferrimagnetic in nature. The isomer shifts indicate that the iron ions were ferric at the tetrahedral (A) and the octahedral (B). Blocking temperature $(T_B)\;of\;Ni_{0.7}Zn_{0.3}Fe_2O_4$ nanoparticle is about 260 K. The magnetic anisotropy constant of $Ni_{0.7}Zn_{0.3}Fe_2O_4$ annealed $300^{\circ}C$ were calculated to be $1.7X10^6\;ergs/cm^3$. Also, temperature of the sample increased up to $43^{\circ}C$ within 7 minutes under AC magnetic field of 7 MHz.

• 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.