• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.333-333
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• 2003

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.233-239
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• 2013

We collected Seokganju minerals (regions in Gyeryong Mountain, Sangsin-ri, Banpo-myeon, Gongju Chungcheongnam-province), which were used as natural color pigments for grayish-blue during the 15th~16th centuries of the Joseon era, and investigated their crystallographic features to develop a black pigment having a spinel structure. By a Raman analysis, the color of Seokganju under transparent glaze as a pigment for painting was black because hematite ($Fe_2O_3$) in Seokganju was converted to magnetite ($Fe_3O_4$) However, Seokganju into the transparent glaze as a pigment was brown because of hematite ($Fe_2O_3$) and small amounts of maghemite (${\gamma}-Fe_2O_3$) in Seokganju minerals. Only Seokganju mineral is used, it is not suitable for black pigment into the transparent glaze. This study tried to develop a spinel crystal black pigment stabilized by Seokganju with CoO, $Cr_2O_3$, NiO, and $MnO_2$ at $1280^{\circ}C$. A Raman spectroscopy analysis was performed to verify the presence of Mn The results showed that it existed as spinel, and two crystal phases $CoFe_2O_4$ and $MnFe_2O_4$ were mixed. $CoFe_2O_4$ spinel has a dark grayish black color and $MnFe_2O_4$ spinel has a greenish black color, and these two appeared as black. The color of a specimen calcined by adding 6 wt% of pigment mixed with 5 wt% of $MnO_2$ added to lime glaze was analyzed with a UV spectrophotometer. When applying the color pigment, it appeared black stabilized with $L^*$24.23, $a^*$ 0.12, $b^*$ -2.29 at $1260^{\circ}C$ oxidative calcination, With $1240^{\circ}C$ reduction firing, it is appeared black stabilized with low brightness of $L^*$ 23.13, $a^*$ -1.12, $b^*$ 0.54.

• Journal of Information Display
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• v.2 no.3
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• pp.13-17
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• 2001

The manganese-doped magnesium tin oxide with spinel structure was selected as a green phosphor for FED application and was synthesized by the solid state reaction. Its luminescence properties were investigated under low-voltage electron excitation. The $Mg_2SnO_4$:Mn phosphor showed green emission with the spectrum centered at 500 nm due to energy transfer from $^4T_1$ to $^6A_1$ of $Mn^{2+}$ ion. Optimum Mn concentration was 0.6 mole % and the decay time was shorter than 10 ms.

• Journal of the Korean Applied Science and Technology
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• v.17 no.1
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• pp.49-53
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• 2000

For decompose carbon dioxide, manganese oxide was synthesized with $0.25M-MnSO_{4}{\cdot}nH_{2}O$ and 0.5M-NaOH by coprecipitation. We made magnetite deoxidized manganese oxide by hydrogen reduction for 1hour at $330^{\circ}C$. We investigated characteristics of catalyst, hydrogen reduction degree and decomposition rate of carbon dioxide. The structure of the hausmannite certified spinel type. The specific surface area of synthesized hausmannite and deoxidized hausmannite were $22.36m^{2}/g$, $33.56m^{2}/g$ respectively. The decomposition rate of $CO_{2}$ of deoxidized hausmannite was 57%.

• Korean Journal of Crystallography
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• v.12 no.1
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• pp.20-24
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• 2001

NiZn-ferrite was synthesized usign waste iron oxide catalysts which were produced from styrene monomer process and buried underground as an industrial wastes. The spinel type ferrite was obtained by calcination and sintering of the mixture of finely ground waste catalysts, nickel oxide and zinc oxide powders. The sintered body of Ni/sub 0.5/Zn/sub 0.5/Fe₂O₄ composition at 1230℃ for 5 hours showed the density of 5.38g/㎤, and initial permeability of 59 at 1 kHz. Not only cerium oxide, which existed as a major component in the catalyst, but also unicorporated NiO and ZnO into spinel structure remained as second phases after sintering.

• Korean Journal of Crystallography
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• v.14 no.2
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• pp.110-114
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• 2003

LiAl/sub 0.24/Mn/sub 1.76/O/sub 4-y/S/sub y/ (y=0, 0.02) were synthesized by the sol-gel method. Both structures were refined by Rietveld method, its structure refined as a cubic spinel, space group Fd-3m, a=8.17937(30) Å and 8.18331(19) Å respectively. Though it has been made a charge/discharge experiment above 20 times, there was no change of 3 V/4 V capacity degradation. It was considered that the volume change of MnO/sub 6/ octahedron induced by sulfur substitution plays a key role in keeping the 3 V/4 V capacity. The refined composition of the compound could be confirmed with the ICP analysis.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.2
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• pp.82-86
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• 2002

A series of $Ni_xZn_yFe_{3-x-y}O_4$ films were prepared by spin-spray ferrite plating on glass substrates from aqueous solution at $90[^{\circ}C]$. The magnetic properties in terms of contents of Ni and Zn in the plated films are presented. All the films are polycrystalline with spinel structure. At x+y=0.58, the film presents preferential orientation. As composition of y in the films increases grain size and void in the films increases, while saturation magnetization and coercive force of the films decrease.

• Journal of the Korean Ceramic Society
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• v.31 no.1
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.707-710
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• 2002

Spinel $LiMn_2O_4$ and $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4$ powders were synthesized by solid-state method at $800^{\circ}C$ for 36h. Crystal structure and electrochemical properties were analyzed by X-ray diffraction, charge-discharge test, cyclic voltammetry and ac impedance to $LiMn_2O_4$ and $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4/Li$. All cathode material showed spinel structure in X-ray diffraction. $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4/Li$ cell substituted $Mg^{2+}$ and $Zn^{2+}$ showed excellent discharge capacities than other cells, which it presented about 120mAh/g at the 1st cycle and about 73mAh/g at the 250th cycle, respectively. AC impedance of $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4/Li$ cells showed the similar resistance of about $65{\sim}110{\Omega}$ before cycling.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.859-862
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• 2001

The crystal structure and magnetic properties of the $Ni_{1-x} Cd_xFeAlO_4$(0$\leq$x$\leq$0.5) have been investigated by means of X-ray diffractometry and Mossbauer spectroscopy. The samples($0\leq$x$\leq$0.5) have been prepared by the ceramic sintering method. The X-ray diffraction pattern shows that the crystal structure of the samples is a cubic spinel type. The lattice constant has been found by extrapolation using the Nelson- Riley function and it increases slightly from $8.321{\AA}$ to $8.410{\AA}$ with Cd concentration. The Mossbauer spectra for x<0.4 show a superposition of two sextets and a paramagnetic doublet at room temperature. The cation distribution for x=0 was determined to be $[Fe_{0.75}Al_{0.25}]^A[NiFe_{0.25}Al_{0.75}^BO_4$. The superparamagnetic doublet for x< 0.4 seems to be due to A1 ion in tetrahedral site by the superparamagnetic clustering effect.