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$Sr(Zr, Ti)O_3$ 마이크로파 유전체에 첨가된 $Mn_2O_3, Y_2O_3$ 의 영향과 Mn의 산화상태
정하균,박도순,박윤창 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.6
The effects of Mn2O3 and Y2O3 additives on the microstructure and dielectric properties of Sr(Zr, Ti)O3 have been investigated. Powders with Sr(Zr1-xTix)O3(0$\leq$x$\leq$0.1) composition were prepared by the conventional solid state processing from commercial TiO2 and precipitation-processed ZrO2. The powders containing sintering additives of Mn2O3 and Y2O3 were compacted and then sintered at 1,55$0^{\circ}C$ for 4 h to get>97% relative density. Mn2O3 suppressed the grain growth and Y2O3 enhanced the density of sintered body. The oxidation state of Mn ions were determined by a chemical wet method and EPR spectroscopy. Mn ions were present as Mn2+ and Mn4+ in SrZrO3, while as Mn3+ and Mn4+ in Ti-substituted Sr(Zr, Ti)O3. With the substitution of Ti, the lattice parameters of SrZrO3 decreased and its dielectric constant increased with remarkable decrease in Q value. The dielectric constant of Sr(Zr, Ti)O3 was in the range of 30 to 40, Q values 1,200~5,400 at 6 GHz and temperature coefficient of resonant frequency -67~100 ppm/K.
다단 침전법에 의한 구형 BaMgAl<sub>10</sub>O<sub>17</sub>:Eu 형광체의 제조 및 특성
박정민,정하균,박희동,박윤창,Park, Jumg-Min,Jung, Ha-Kyun,Park, Hee-Dong,Park, Yoon-Chang 한국재료학회 2002 한국재료학회지 Vol.12 No.11
A spherical $BaMgAl_{10}$ $O_{17}$ :Eu phosphor has been synthesized by a multi-step precipitation route. In order to successfully synthesize the phosphor with spherical shape, the hydrated-alumina particles should be controlled for spherical shape. In this process, the hydroxypropyl cellulose (HPC) was used as a dispersing reagent. This reagent plays an important role in that the particles were controlled to have the uniform size of sub-micron. The final product prepared by the multi-step precipitation method maintained spherical shape with uniform size of 0.4$\mu\textrm{m}$. It can be seen in X-ray diffraction patterns, formation of the single phase of $BaMgAl_{10}$ $O_{17}$ :Eu phosphor prepared by the multi-step precipitation method at $1350^{\circ}C$. Also, the emission spectra of spherical $BaMgAl_{O}$ $10_{17}$ :Eu phosphor in the present case was compared with those of commercially-available blue phosphor under VUV (Vacuum Ultra Violet) excitation. The luminescence process of the $BaMgAl_{10}$ $O_{17}$ :Eu phosphor is characterized by the $4f^{6}$$5d^1$longrightarrow4f$^{7}$ transition (blue) of the $Eu^{2+}$ ion acting as an activating center and the maximum luminescence intensity was obtained by reduction treatment at 145$0^{\circ}C$.
$Mg_2$$SnO_4$:Mn 녹색 형광체의 저전압 음극선 발광 특성
김경남,정하균,박희동,김도진,Kim, Gyeong-Nam,Jeong, Ha-Gyun,Park, Hui-Dong,Kim, Do-Jin 한국재료학회 2001 한국재료학회지 Vol.11 No.9
Mg$_2$SnO$_4$having an inverse spinel structure was selected as a new host material of $Mn^{2+}$ activator. The luminescence of the $Mg_2$SnO$_4$:Mn phosphor prepared by the solid-state reaction were investigated under ultraviolet and low-voltage electron excitation. The Mn-doped magnesium tin oxide exhibited strong green emission with the spectrum centered at 500nm wavelength. It was explained that the green emission in $Mg_2$SnO$_4$:Mn phosphor is due to energy transfer from $^4T_1to ^6A_1\;of\; Mn^{2+}$ ion at tetrahedral site in the spinel structure. The optimum concentration of $Mn^{2+}$/ion exhibiting maximum emission intensity by the low-voltage electron excitation was 0.6mol%. ?
새로운 $Mg_{2}SnO_{4}:Mn$ 형광체의 광 발광 특성
김경남,정하균,박희동,김도진,Kim, Kyung-Nam,Jung, Ha-Kyun,Park, Hee-Dong,Kim, Do-Jin 한국세라믹학회 2001 한국세라믹학회지 Vol.38 No.9
A new $Mg_{2-x}MN_xSnO_4$ phosphor with an inverse spinel structure was synthesized by the solid-state reaction technique. The photoluminescence properties of the $Mg_2SnO_4$:Mn phosphors were investigated under 147nm -vacuum ultraviolet ray excitation. The Mn-doped $Mg_2SnO_4$ phosphor exhibited high emission intensity with the spectrum centered at 500nm wavelength. It was explained that the green emission in $Mg_2SnO_4$:Mn phosphor has originated from energy transfer from $^4T_1$ to $^6A_1$ of $Mn^{2+}$ ion at tetrahedral site of the spinel structure. The $Mn^{2+}$ ion concentration exhibiting the maximum emission intensity under the excitation of 147nm-vacuum ultraviolet ray was 0.25mol%. And the decay time of the phosphor was shorter than 10ms. 새로운 형광체로 역스피넬 구조를 갖는 $Mg_{2-x}MN_xSnO_4$ 조성을 선정하여 고상반응에 의하여 제조하였다. $Mg_2SnO_4:Mn$의 광발광 특성이 147nm 파장의 진공 자외선 여기하에 측정되었다. Mn의 첨가에 의하여 $Mg_2SnO_4$ 형광체는 500nm 파장에 발광 중심을 가지며 매우 높은 발광강도를 나타내었다. 이것은 스피넬 구조의 산소 사면체 배위에 위치하는 Mg 자리를 치환하여 들어가는 $Mn^{2+}$ 이온의 $^4T_1$ 상태로부터 $^6A_1$ 상태로의 에너지 전이에 의한 발광으로 해석되었다. 진공 자외선 여기하에 최대의 발광강도를 나타내는 Mn 활성제의 농도는 0.25mol%이었고, 잔광시간은 10ms 이하인 것으로 조사되었다.
PMMA 구를 주형으로 이용한 3DOM 전극 구조체의 제조
서경수,정하균,손용근,Seo Kyoung Soo,Jung Ha-Kyun,Son Yongkeun 한국재료학회 2004 한국재료학회지 Vol.14 No.8
Three-dimensionally ordered macroporous (3DOM) structures of the $LiCoO_2$ electrode materials for Li secondary batteries were fabricated by using the close-packed arrays of PMMA spheres served as templates. In order to successfully fabricate the cathode materials with highly ordered array form, the metal citrates were applied to new precursors. The precursor/template composites were prepared by the infiltration with metal citrate precursors into the voids of template. By removing the PMMA templates, then, the inverse opal structures with the uniform pores of narrow size distribution were resulted. It was confirmed that the 3DOM $LiCoO_2$ material is to take a single phase of rocksalt (R3m) structure. In addition, 3DOM $LiNiO_2$ and $LiMn_{2}O_4$ cathode materials were fabricated using an identical preparation procedure. Also, the morphology of the 3DOM cathode materials calcined at $500^{\circ}C\;to\;700^{\circ}C$ was observed by scanning electron microscope.