• 자원리싸이클링
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• 제16권5호
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• pp.46-50
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• 2007

[ $Eu^{2+},\;Nd^{3+}$ ]로 도핑된 $CaAl_2O_4$ 청색 형광체를 고상반응법으로 제조하였다. 1 mol% $Eu^{2+}$로 doping된 형광체에 다양한 조성의 $Nd^{3+}$를 co-doping함에 따라 고휘도, 장잔광 특성을 보였다. 제조한 형광체에 대하여 XRD, SEM, TEM, 빛발광 특성을 조사하였다. $CaAl_2O_4:Eu^{2+}:Nd^{3+}$의 넓은 밴드의 UV로 여기된 빛발광 특성이 $Eu^{2+}$의 $4f^65d^1$에서 $4f^7$ 상태로 천이에 의해 기인된 청색영역(${\lambda}_{max}=440\;nm$)에서 관찰되었다. $Nd^{3+}$로 co-doping한 형광체는 여기광을 차단하였을 때 장잔광 발광 특성을 나타내었다.

• 한국결정학회지
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• 제5권2호
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• pp.51-66
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• 1994

융액인상법으로 Y3Al5O12 및 Nd: Y3Al5O12단결정을 육성하였다. 인상속도, 회전속도 및 Nd3+이온의 주입농도가 결정의 품질에 미치는 영향을 분석하였다. 광탄성효과및 화학부식 법을 이용하여 여러가지 종류의 결함을 검출하 고, 육성된 결정의 분광학적 성질과 레이저 기능성을 조사하였다. 양질의 단결정을 육성하기 위한 인상속도는 Nd3+이온의 주입농도에 따라 달라진다. Y3Al5O12단결정은 2∼4mm/hr, Nd3+이온 주입농도가 3.0∼3.5a/o 일때 0.6∼0.5mm/hr,4.Oa/o 이상일 때 04mm/hr 이하가 적당하였다. 회전속도가 27∼60rpm 일때 볼록하고, 80∼100rpm 일 때 오목한 고액계면을 형성하였다. 육성된 결정은 <111> 방위로 성장되었으며 격자상수는 12.Ol7A로 측정되었다. 결함으로서 core, (211)facet 줄무의, 금속입자 함유물, 전위 및 광학적 불균질상이 검출되었다. Y3AlO12단결정에 대한 Nd3+이온의 4준위 레이저 천이과정을 확인하고, 육성된 결정으로부터 직경 4.0mm 길이 63mm크기의 레이저 발진봉을 제조한 후 레이저 공진한 결과 lasing threshould 1.8lJ, slope efficiency 0.49%로 측정되었다.

• 한국세라믹학회지
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• 제30권8호
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• pp.671-677
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• 1993

Effects of PbTiO3 addition on dielectric properties and extent of PbO loss in Nd-doped Pb(Mg1/3Nb2/3)O3 system were investigated. As the proportion of dopping increased, the phase transition temperature shifted to low region, and the dielectric constant at room temperature decreased rapidly. But as the proportion of PbTiO3 increased, the phase transition temperature shifted to high retion, and the dielectric constant at room temperature increased. The substitution of Nd3+ for Pb2+ decreased the amount of PbO evaporation, therefore the sample sintered well in case of only 1 mole% adding excess PbO.

• 한국세라믹학회지
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• 제31권3호
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• pp.249-256
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• 1994

By surface structure and X-ray topographic observation, growth mechanism of NAB single crystal grown by TSSG technique using a BaB4O7 flux was studied. Surface structure of grown crystals were investigated by optical microscope. Growth history and crystal defects included within grown crystal were investigated using X-ray topography. The {001} faces were grown by 2-D nucleation growth. As decreasing cooling rate, growth mechanism of {111} and {11} was changed from 2-D nucleation growth to the growth by screw dislocation. Only surface striations developed parallel to a-axis were observed on {010} faces. Growth sector of NAB crystals were divided into {001}, {111}, {010}, {021}, {11}. The inclusion which was usually trapped between {001} faces was investigated.

• 한국세라믹학회지
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• 제30권5호
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• pp.339-346
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• 1993

Inproving laser efficiency, optimum content of Nd3+ which is active ion and effect of Cr3+ as a sensitizer are investigated in 60SiO2.30Li2O.10CaO host glass. The glasses are fabricated with the addition of Nd3+, Cr3+ and then optical properties such as absorption spectrum, fluorescence spectrum and fluorescence lifetime were studied. Finally, lasing efficiency was measured. From this study, optimum content of Nd2O3 appeared to be 3.5wt% and it was observed that the energy absorbed by optical exicitation of the Cr3+ is transfered to the Nd3+. Addition of Cr2O3 tend to improve characteristic of laser oscillation for the laser glass.

• 한국재료학회지
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• 제6권2호
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• pp.133-137
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• 1996

본연구에서는 n-type 세라믹 초전도체인 Nd2-xCexCuO4상의 산소함량에 따른 \ulcorner기적저항의 변화를 고찰하고자 하였다. 일반적인 소결과 어닐링과정을 결쳐 제조된 Nd1.85Ce0.15CuO4-x 시편을 여러 온도와 산소분압의 분위기하에서 어닐링시킴으로써 산소의 함유량이 다른 시편들을 준비하였고 각각의 시편의 산소함량은 TGA(Thermogravimetric Analysis0에 의해 측정하였다. Nd1.85Ce0.15CuO4-x시편의 전기적 저항 측정은 표준 4-탐침방법을 이용하여 액체헬륨을 주입시켜 상온으로부터 4K까지 측정하였다. Nd1.85Ce0.15CuO4-x시편의 산소함량, 3.96$\leq$4-x$\leq$4.0의 범위에서 전기적저항을 측정한 결과 초전도특성이 나타나기 시작한 임계산소함량은 4-x=3.990이었고 이때의 임계온도 Tc=12K이었다. 또한 임계온도, Tc는 산소함량 4-x=3.96에서 24K로 측정되었다. 특이할 만한 현상은 CuO/Cu2O 열역학적 상전이가 일어나는 조건이 Nd1.85Ce0.15CuO4-x 시편의 초전도가 일어나는 임계와 일치하였다. 즉, Cu2O가 안정한 영역에서는 초전도특성이 나타났고 CuO가 안정한 영역에서는 초전도특성이 나타나지 않았다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.91-94
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• 2002

The conditions of zone-melting method such as a sample travel speed in a furnace, content of Nd422, control of melting temperature, and heat-treatment with/without Ar gas for $NdBa_{2}Cu_{3}O_{7-\delta}$ superconductor was optimized, As a results, a $NdBa_{2}Cu_{3}O_{7-\delta}$ sample with a surface area of $25mm^{2}$ showed a good superconducting properties when its travel speed was 6 mm/h, The improvement of superconductivity added with 10~20 wt% of Nd422 phase increasing pinning effect was also shown. The critical current density, $J_{c}$ was remarkable affected by the condition of heat-treatment temperature of $NdBa_{2}Cu_{3}O_{7-\delta}$superconductor with/without Ar ambient gas.

• 한국세라믹학회지
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• 제30권2호
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• pp.101-106
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• 1993

Effects of CaO on microwave dielectric properties of (Ba, Pb)O-Nd2O3-TiO2 ceramic ystem were investigated. As the content of CaO increases, the sintered bulk density decreases due to the decrease of sinterability. However, with increasing the sintering tmperature, the relative dielectric constants increases. This has been attributed on the formation of the 2nd phase inclusion, TiO2(rutile). The Q values increase due to the compensation effect of Ca ions up to 1 wt%, and then decrease due to the interfacial relaxation effects. The temperature coefficient of resonance frequency increases to a positive direction with increasing the amounts of CaO.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.603-610
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• 2021

The major drawback of zirconia-based materials, in view of their applications as targets for minor actinide transmutation, is their poor thermal conductivity. The addition of MgO, which has high thermal conductivity, to zirconia-based materials is expected to improve their thermal conductivity. On these grounds, the present study aims at phase characterization and thermophysical property evaluation of neodymium-substituted zirconia (Zr_0.8Nd_0.2O_1.9; using Nd₂O₃ as a surrogate for Am₂O₃) and its composites with MgO. The composite was prepared by a solid-state reaction of Zr_0.8Nd_0.2O_1.9 (synthesized by gel combustion) and commercial MgO powders at 1773 K. Phase characterization was carried out by X-ray diffraction and the microstructural investigation was performed using a scanning electron microscope equipped with energy dispersive spectroscopy. The linear thermal expansion coefficient of Zr_0.8Nd_0.2O_1.9 increases upon composite formation with MgO, which is attributed to a higher thermal expansivity of MgO. Similarly, specific heat also increases with the addition of MgO to Zr_0.8Nd_0.2O_1.9. Thermal conductivity was calculated from measured thermal diffusivity, temperature-dependent density and specific heat values. Thermal conductivity of Zr_0.8Nd_0.2O_1.9-MgO (50 wt%) composite is more than that of typical UO₂ fuel, supporting the potential of Zr_0.8Nd_0.2O_1.9-MgO composites as target materials for minor actinides transmutation.

• E2M - 전기 전자와 첨단 소재
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• 제10권9호
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• pp.901-908
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• 1997

The microwave dielectric properties of (Na.$_{1}$2//Sm$_{1}$2/)TiO$_3$and (Li$_{1}$2//Nd$_{1}$2/)TiO$_3$ceramics were investigated. Dielectric constant quality factor and temperature coefficient of resonant frequency of (Li$_{1}$2//Nd$_{1}$2/)TiO$_3$ceramics sintered at 145$0^{\circ}C$ for 2 hours were 86.2, 2780(at 3.8GHz) and 215ppm/$^{\circ}C$respectively. The solid solution of X(Na.$_{1}$2//Sm$_{1}$2/)TiO$_3$-(1-X)(Li$_{1}$2//Nd$_{1}$2/)TiO$_3$increased delectric constant and quality factor were decreased. Whereas temperature coefficient of resonant frequency was optimized to zero at the composition of 0.6(Li$_{1}$2//Sm$_{1}$2/)TiO$_3$-0.4(Li$_{1}$2//Nd$_{1}$2/)TiO$_3$where dielectric constant and quality factor were 86.2, 95-(at 3.8GHz) respectively. Also band-pass filters made of this material were examined.