• Korean Journal of Materials Research
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• v.14 no.8
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• pp.595-599
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• 2004

We investigated the structural, electrical and magnetic properties of Mn-doped $CuAlO_2$ delafossite ceramics ($CuAl_{1-x}Mn_{x}O_2,\;0\le\;x\;\le0.05$), synthesized by solid-state reaction method in an air atmosphere at a sintering temperature of $1150^{\circ}C$. The solubility limit of Mn ions in delafossite $CuAlO_2$ was found to be as low as about 3 $mol\%$. Positive Hall coefficient and the temperature dependence of conductivity established that non-doped $CuAlO_2$ ceramic is a variable-range hopping p-type semiconductor. It was found that the Mn-doping in $CuAlO_2$ rapidly reduced the hole concentration and conductivity, indicating compensation of free holes. The analysis of the magnetization data provided an evidence that antiferromagnetic superexchange interaction is the dominant mechanism of the exchange coupling between Mn ions in $CuAl_{1-x}Mn_{x}O$ alloy, leading to an almost paramagnetic behavior in this alloy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.271-274
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• 1998

Metallic ferromagnet LA$_{1-x}$ Sr$_{x}$MnO$_3$ has received considerable attentions because of its metallic conductivity and giant magnetic resistivity. It is generally believed that layered perovskite SrO(LA$_{1-x}$ Sr$_{x}$MnO$_3$)$_{n}$ phase is insulating and shows no metallic transition. But recent report revealed that some single crystal SrO(LA$_{1-x}$ Sr$_{x}$MnO$_3$)$_{n}$ phase showed MR effect. In this study, layered perovskite SrO(LA$_{1-x}$ Sr$_{x}$MnO$_3$)$_2$ Phases were synthesized by solid state reaction at 140$0^{\circ}C$ in air atmosphere, for wide range of x and their phases were confirmed by X-ray diffraction. Electrical and magnetic properties were measured down to 10K and the possibility of MR effects was investigated.as investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.242-247
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• 1998

In this study, we have synthesized $ZnGa_2O_4$:Mn,X powder doped with Mn, MnO, $MnF_2$ and $MnCl_2$, low voltage green emitting phosphor, in vacuum atmosphere. From PL spectra, the intensity of the emission peak, the brightness with coactivator show that $ZnGa_2O_4$:Mn,Cl > $ZnGa_2O_4$:Mn,F > $ZnGa_2O_4$:Mn,O > $ZnGa_2O_4$:Mn. These improvement of the brightness are caused by the increase of the concentration of $Mn^{2+}$ ion. In case of $ZnGa_2O_4$:Mn,Cl and ZnGa$_2$O$_4$:Mn,F, the brightness is enhanced much more, which is owed to the decrease of defect of host material. For $ZnGa_2O_4$:Mn,Cl phosphor fabricated with optimized condition, the decay time becomes short from 30 ms of the $ZnGa_2O_4$:Mn and $ZnGa_2O_4$:Mn,O to 6 ms and the brightness of CL at 1 kV, 1 mA is 60 cd/$m^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.415-418
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• 2009

$Zn_{2}SiO_{4}$:Mn green phosphors doped with Mg for PDP were synthesized by solid state reaction method. $Zn_{2}SiO_{4}$:Mn, Mg phosphors with increasing Mg concentration were changed from Rhombohedral to Orthorhombic structure. Photoluminescence intensity of $Zn_{2}SiO_{4}$:Mn phosphors doped with Mg 0.5 mol was definitely higher than that of Mg non-doped sample. The enhanced luminescence with doping Mg in the $Zn_{2}SiO_{4}$:Mn phosphors was interpreted by the increase of energy transfer from host to Mn ions with substitution Mg for Zn in the $Zn_{2}SiO_{4}$:Mn host.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.865-868
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• 2000

It was examined that the relationship between microstructures, electrical properties and crystal structure of (1-x)CaMnO$_3$-xCaTiO$_3$solid solution system which was made by mixing a semiconducting material CaMnO$_3$of low resistance and a dielectric material CaTiO$_3$of high resistance with variable ratios (x=0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0). As the CaTiO$_3$increased, the resistance, B constant and lattice constant were increased, but the grain size was decreased. On particular, above 50wt% of CaTiO$_3$, the resistance at 2 5$^{\circ}C$ was rapidly increased due to the correlation in connectivity of the lattices between the conductive Mn$^{+4}$ octahedron and the insulative Ti$^{+4}$ octahedron.ron.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.392-393
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• 2007

PDP용 녹색 $Zn_2SiO_4$:Mn 형광체의 발광특성과 결정성을 향상시키기 위해 co-dopant로 Mg를 첨가한 $(Zn_{1-x}Mg_x)_2SiO_4$:Mn 형광체를 합성하였다. 합성된 형광체의 발광특성을 PL로 조사한 결과, $Zn_2SiO_4$:Mn 형광체는 Mg의 농도에 관계없이 530nm에서 녹색 발광을 하였고, Mg의 농도가 0.5 mol%일 때 가장 높은 발광세기가 나타났다. 이것은 Zn과 이온반경이 비슷한 Mg가 치환되어 모체에서의 Mn으로의 에너지 전이가 증가하여 발광세기가 증가한 것으로 생각된다.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.443-450
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• 2014

Selective catalytic reduction of nitrogen monoxide by hydrogen ($H_2$-SCR of NO) over platinum catalysts impregnated on zirconia-incorporated silica ($ZrO_2-SiO_2$) and manganese oxide ($MnO_x$) was investigated. $Pt-MnO_x$ catalyst showed low conversions and low yields of $N_2O$ and $NO_2$ at $100{\sim}350^{\circ}C$. On the other hand, NO conversions over $Pt/ZrO_2-SiO_2$ were very high, but $N_2O$ was predominantly produced at $100-150^{\circ}C$ and the yield of $NO_2$ increased with temperature at $200-300^{\circ}C$, resulting in poor $N_2$ yields. $Pt-MnO_x/ZrO_2-SiO_2$ exhibited a small enhancement in $N_2$ yield at $100-150^{\circ}C$ due to the synergy of $MnO_x$ and $ZrO_2-SiO_2$. The surface composition and oxidation state of the catalyst components and the acidity of the catalysts were examined. IR spectra of the adsorption of NO and their subsequent reactions with hydrogen on these catalysts were also recorded. The variations of conversion and product yield according to the catalyst components in the $H_2$-SCR of NO were discussed in relation to their catalytic roles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.555-558
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• 2000

Layered perovskite La$_{2-x}$Ca$_{l-x}$Mn$_2$O$_{7}$ phases were synthesized by solid state reaction. Single phase R-P could be obtained in the range of 0.4$_{2-x}$Ca$_{l-x}$Mn$_2$O$_{7}$. About 30% of MR ratio was obtained at 270K when 5 T of magnetic field was applied.ied.ied.ied.

• Electrical & Electronic Materials
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• v.14 no.12
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• pp.7-10
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• 2001

Orthorhombic type LiCo$_{x}$Mn$_{1-x}$ O$_2$(0$\leq$x$\leq$0.14) oxides have been synthesized by hydrothermal treatment of (Co$_{x}$Mn$_{1-x}$ )$_3$O$_4$precursors and LiOH aqueous solution at 17$0^{\circ}C$. As-synthesized powders showed well-ordered $\beta$-MaMnO$_2$structures, and the products were single crystalline particle oxides from TEM observations. The particle size decreased with increasing the amount of Co substituent. Much more improved capacity upon 100 cyclings was clearly seen in orthorhombic LiCo$_{0.1}$Mn$_{0.9}$O$_2$, comparing to orthorhombic LiMnO$_2$./TEX>.EX>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.7-10
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• 2001

Orthorhombic type $LiCo_{x}Mn_{1-x}O_2$ (0 x 0.14) oxides have been synthesized by hydrothermal treatment of ($Co_{x}Mn_{1-x}$)$_3O_4$ precursors and LiOH aqueous solution at $170^{\circ}C$. As-synthesized powders showed well-ordered ${\beta}$-$NaMnO_2$ structures, and the products were single crystalline particle oxides from TEM observations. The particle size decreased with increasing the amount of Co substituent. Much more improved capacity upon 100 cyclings was clearly seen in orthorhombic $LiCo_{0.1}Mn_{0.9}O_2$, comparing to orthorhombic $LiMnO_2$.