• Bulletin of the Korean Chemical Society
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• 제19권1호
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• pp.63-67
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• 1998

The synthesis and characterization of the monomeric group 13 heterocyclic thiosemicarbazone complexes $Me_2M[SC_4H_3CHNNC(S)SCH_3]$ (M=Al (2), Ga (3)) are described. Compounds 2-3 were prepared using $MMe_3$ (M=Al, Ga) in toluene with 2-thiophenecarboxaldehyde-S-methyldithiocarbazat e under anaerobic conditions. These complexes have been characterized by $^1H\;NMR,\; ^{13}C\; NMR$, elemental analyses, and single-crystal X-ray diffraction. 2 crystallizes in the monoclinic space group $P2_1/c$ with unit cell parameters a=10.2930(5) Å, b=18.564 (1) Å, c=7.3812(6) Å, V=1347.9(2) Å3, $D_{calc}=1.342\; gcm^{-3}$ for Z=4, 9281 reflections with $I_o<3{\sigma}\;(I_o),$ R1=0.0500 and wR2=0.0526. 3 crystalizes in the orthorhombic space group $P_{bca}$ with unit cell parameters a=13.340(3) Å, b=19.9070(5) Å, c=11.3690(2) Å, $V=2673.88(9)\;{\AA}^3$, $D_{calc}=1.511\; gcm^{-3}$ for Z=8, 17004 reflections with $I_o>3{\sigma}\;(I_o),$, R1=0.0480 and wR2=0.0524. Compound 3 is a monomeric gallium compound with a weak interaction between the pendant thiophene and the gallium center.

• 한국결정학회지
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• 제6권1호
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• pp.1-13
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• 1995

융액인상법에 의해 Cr:A12O3 및 Ti:A12O3 단결정을 육성한 후 인상속도, 회전속도, 주입이온 및 결정육성 분위기와 같은 결정육성요소가 결정의 품질에 미치는 영향을 조사하고, 육성된 결정의 레이저 효율과 분광학적 물성을 측정하였다. 직경 20mm, 길이 100-135mm 크기의 결정을 <001>방위로 육성하였다. Cr:A12O3의 주입농도 0.5w/o, 인상속도 2.0mm/hr, 회전속도 30rpm으로 할 때 질소기체에 의한 비활성 분위기하에서 양질의 Cr:A12O3 결정이 얻어졌다. Ti:A12O3 단결정은 TiO2를 0.25w/o 주입하고 인상속도 1.5mm/hr, 회전속도 30rpm으로 육성할 때, 수소기체에 의한 환원성 분위기하에서 양질의 결정이 얻어졌다. 원자가가 변화하지 않는 Cr3+이온은 원자가가 변화하는 Ti4+이온을 주입할 때보다 효과적으로 탈포되었으며, Fe3+이온은 Ti3+이온에 대해 탈포를 촉진하는 효과가 있었다. Ti:A12O3 단결정 육성시 90% N2 - 10% H2 혼합기체를 사용하여 환원성 분위기를 조성하는 것이 원자가 변화 및 탈포에 좋은 효과를 나타내었다. 흡수 및 형광방출 스펙트럼 조사 결과 Cr:A12O3 단결정에서 4A2 → 4F2 및 4F1 천이에 의한 흡수와 E→4A2(R1) 및 2A→4A2(R2) 천이에 의한 형광방출 천이를 확인하였다. R1 및 R2 천이의 레이저 주파장은 각각 696±5nm 및 692 ±5nm이고, 각 천이의 형광선폭은 12A, 형광수명은 152 μsec로 측정되었다. Ti:A12O3 단결정에서는 4T2→ 4E의 흡수천이와 4E→4T2의 천이에 의해 650nm-1050nm 범위에서 파장가변이 가능한 형광방출천이가 일어남을 확인하였으며 형광수명은 147μsec, figure of merit는 125.4로 측정되었다. Ti:A12O3 단결정으로부터 제조한 레이저봉을 이용하여 레이저 공진한 결과 레이저 발진효율은 9%로 측정되었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권2호
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• pp.92-97
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• 1999

The mechanical and electrical properties of the hot-pressed and annealed $\beta-Sic$+39vol.%$ZrB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of $Al_2O_3+Y_2O_3(6:4wt%)$. In this microstructures, no reactions and elongated $\alpha$-SiC grains with equiaxed $ZrB_2$, gains were observed between $\beta-SiC$ and $ZrB_2$, and the relative density was over 97.6% of the theoretical density. Phase analysis of the composites by XRD revealedmostly of $\alpha$-SiC(6H, 4H), $ZrB_2$, and weakly $\beta-SiC$(15R) phase. The fracture toughness decreased with increasing $Al_2O_3+Y_2O_3$ contents and showed the highest of $6.37MPa.m^{\fraction ane-half}$ for composite added with 4wt% $Al_2O_3+Y_2O_3$ additives at room temperature. The electrical resistivity increased with increasing $Al_2O_3+Y_2O_3$contents and showed the lowest of $1.51\times10^{-4}\Omega.cm$ for composite added with $Al_2O_3+Y_2O_3$ additives at $25^{\circ}C$. This reason is the increasing tendency of pore formation according to amount of liquid forming additives $Al_2O_3+Y_2O_3$. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) against temperature up to $700^{\circ}C$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.1148-1151
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• 2002

Dielectric ceramics with nominal composition of $(Ba_{0.93}Sr_{0.07}O)-0.5Sm_2O_3-4.5TiO_2$ was prepared using the conventional mixed oxide process-derived powder. Effect of $SiO_2$, $MnO_2$ and $Al_2O_3$ impurity addition on the microwave properties was examined in some detail. Measured relative permittivity $(\varepsilon_r)$ values were in the range of 53 to 59 and showed little dependence on impurity addition. In contrast, quality factor $(Q{\cdot}f)$ and temperature coefficient of resonant frequency $(\tau_f)$ values were greatly influenced by the type and the amount of impurities. It was found that 0.1~0.2wt% addition of $Al_2O_3$ was most effective for improving the properties, where ${\varepsilon}_r$, $Q{\cdot}f$ and $\tau_f$ values were 57.7, 10000, and +7ppm/$^{\circ}C$, respectively.

• Bulletin of the Korean Chemical Society
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• 제28권1호
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• pp.41-48
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• 2007

Large colorless single crystals of sodium zeolite X, stoichiometry |Na80 |[Si112Al80O384]-FAU, with diameters up to 200 μm and Si/Al = 1.41 have been synthesized from gels with the composition of 2.40SiO2 : 2.00NaAlO2 : 7.52NaOH : 454H2O : 5.00TEA. One of these, a colorless octahedron about 200 μm in cross-section has been treated with aqueous 0.1 M KNO3 for the preparation of K+-exchanged zeolite X. The crystal structure of |K80|[Si112Al80O384]-FAU per unit cell, a = 24.838(4) A, dehydrated at 673 K and 1 × 10-6 Torr, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd at 294 K. The structure was refined using all intensities to the final error indices (using only the 707 reflections for which Fo > 4σ (Fo)) R1 = 0.075 (based on F) and R2 = 0.236 (based on F2). About 80 K+ ions per unit cell are found at an unusually large number of crystallographically distinct positions, eight. Eleven K+ ions are at the centers of double 6-rings (D6Rs, site I; K-O = 2.492(6) A and O-K-O (octahedral) = 88.45(22)o and 91.55(22)o). Site-I' position (in the sodalite cavities opposite D6Rs) is occupied by five K+ ions per unit cell; these K+ ions are recessed 1.92 A into the sodalite cavities from their 3-oxygen planes (K-O = 2.820(19) A, and O-K-O = 78.6(6)o). Twety-three K+ ions are found at three nonequivalent site II (in the supercage) with occupancies of 5, 9, and 9 ions; these K+ ions are recessed 0.43 A, 0.75 A, and 1.55 A, respectively, into the supercage from the three oxygens to which it is bound (K-O = 2.36(13) A, 2.45(13) A, and 2.710(13) A, O-K-O = 116.5(20)o, 110.1(17)o, and 90.4(6)o, respectively). The remaining sixteen, thirteen, and twelve K+ ions occupy three sites III' near triple 4-rings in the supercage (K-O = 2.64(3) A, 2.94(3) A, 2.73(5) A, 2.96(6) A, 3.06(4) A, and 3.08(3) A).

• 한국세라믹학회지
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• 제30권6호
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• pp.457-468
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• 1993

In oxide matrix-SiC(W) composites, instability and glassy phase formation due to oxidation at the high temperature and the diffusion of Si, respectively, cause brittle fracture and low reliability for ceramic materials. The mode of contribution in each mechanisms induced by matrix-whisker debonding, varies with the morphology of matrix-whisker interfaces. This work has described the dispersion behaviours and stabilization mechanisms in slip systems, and multiple toughening mechanisms by dint of two second phase different from each other when spherical ZrO2 and chemically stable Al2O3(W) is respectively added in Al2O3 matrix. To obtain complexshaped components, slip casted bodies were sintered at 1$600^{\circ}C$, 2hrs up to 98~99% R.D.. Multiple toughening mechanisms in comparison with theories reported until now will be discussed as a result of the phase analysis of ZrO2 by athermal behaviours and microstructural characterizations as well as measured mechanical properties.

• 한국재료학회지
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• 제10권11호
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• pp.778-783
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• 2000

고주파 스피터 방법으로 제조된 SnO$_2$감지막 위에 에어로졸 화염 증착법으로 알루미나 표면 보호층을 증착하여 SnO$_2$박막 가스 센서의 감지 특성에 미치는 영향에 대햐여 조사하였고, 표면 보호층에 귀금속 Pt를 도핑하여 Pt의 함량이 CO 및 CH(sub)4 가스들의 선택성에 미치는 영향에 대하여 조사하였다. SnO$_2$박막은 R.F power 50 W, 공정 압력 4 mtorr, 기판온도 20$0^{\circ}C$에서 30분간 0.3$\mu\textrm{m}$ 두께로 Pt 전극 위에 제조하였고, 질산알루미늄(Al(NO$_3$).9$H_2O$) 용액을 희석하여 에어로졸 화염증착법으로 알루미나 표면 보호층을 만든후 $600^{\circ}C$에서 6시간동안 산소분위기에서 열처리하였다. 알루미나 표면 보호층이 증착된 SnO$_2$가스 센서소자의 경우 보호층이 없는 가스 센서와 비교하여 CO 가스에 대한 감도는 매우 감소하였으나 CH$_4$가스에 대한 감도 특성은 순수한 SnO$_2$센서 소자와 비슷하였다. 결과적으로 보호층을 이용하여 CH$_4$가스에 대한 상대적인 선택성 증가를 이룰 수 있었다. 특히 표면 보호층에 Pt가 첨가된 센서 소자의 경우 CO 가스에 대해서는 낮은 감도 특성을 나타내었으나 CH$_4$에 대한 감도는 매우 증가하여 CH$_4$가스의 선택성을 더욱 증대시킬 수 있었다. CH$_4$가스 선택성 향상에 미치는 알루미나 표면 보호층과 Pt의 역할에 대하여 고찰해 보았다.

• 한국세라믹학회지
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• 제36권12호
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• pp.1381-1389
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• 1999

• 반도체디스플레이기술학회지
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• 제16권4호
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• pp.1-4
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• 2017

Encapsulation of organic based devices is essential issue due to easy deterioration of organic material by water vapor. Atomic layer deposition (ALD) is a promising solution because of its low temperature deposition and quality of the deposited film. Moisture permeation has a mechanism to pass through defects, Thin Film Encapsulation using inorganic / organic / inorganic hybrid film has been used as promising technology. $Al_2O_3$ / Polymer / $Al_2O_3$ multilayer film has shown excellent environmental protection characteristics despite of thin thicknesses of the films.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.185-188
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• 1999

Biepitaxial Y$_1Ba_2Cu_3O_{7-x}$ (YBCO) and La$_{0.2}Sr_{0.8}MnO_3$ (LSMO) thin films have been prepared on SrTiO$_3$ buffer layer and MgO seed layer grown on Al$_2O_3$(11${\bar{2}}$0)substrates by dc-sputtering with hollow cylindrical targets, respectively. We charaterized Josephson properties and significantly large magnetoresistance in YBCO and LSMO films with 45$^{\circ}$ grain boundary junction, respectively. The observed working voltage (I$_cR_n$) at 77 K in grain boundary junction was below 10${\mu}$V, which is typical I$_cR_n$ value of single biepitaxial Josephson junction. The field magnetoresistance ratio (MR) of LSMO grain boundary juncoon at 77K was enhanced to 13%, which it was significant MR value with high magnetic field sensitivity at a low field of 250 Oe. These results indicate that inserting the insulating layer instead of the grain boundary layer with metallic phase can be possible to apply a new SIS Josephson junction and a novel magnetic device using spin-polarized tunneling junction.