• 대한전자공학회논문지SD
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• 제37권8호
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• pp.35-41
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• 2000

$LiTaO_3$ 단결정 시료의 초전특성에 대한 주파수 의존성을 dynamic 방법을 이용하여 조사하였다. 2 ~ 1000Hz 주파수 범위에서 $LiTaO_3$ 단결정 시료의 전압응답을 부하 저항의 크기에 따라 초전전압영역 ($U_{PV},\;R_L=17.3G{\Omega}$) 과 초전전류영역 ($U_{PV},\;R_L=1M{\Omega}$) 으로 분류하여 측정하였다. 초전전류영역의 전압응답에 의존하는 초전계수는 40 Hz에서 최대값 $1.56{\times}10^{-8}C/cm^2{\cdot}K$를 나타내었고, 전압감도와 검출능을 위한 재료평가지수는 각각 최대값 $10.8{\times}10^{-11}C{\cdot}cm/J$ 과 $13{\times}10^{-7}C{\cdot}cm/J$을 나타내었다. 전압감도는 초전전압영역의 전압응답에 의존하여 2 Hz에서 488V/W 의 최대값을 나타내었다. 잡음등가전력과 비검출능은 40 Hz에서 각각 최소값 $3.95{\times}10^{-10}W/{\sqrt}Hz$와 최대값 $5.6{\times}10^8cm{\cdot}{\sqrt}Hz/W$이었다.

• 한국재료학회지
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• 제25권8호
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• pp.423-428
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• 2015

Impedancemetric $NO_x$ (NO and $NO_2$) gas sensors were designed with a stacked-layer structure and fabricated using $LaCr_xCo_{1-x}O_3$ (x = 0, 0.2, 0.5, 0.8 and 1) as the receptor material and $Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ plates as the solid-electrolyte transducer material. The $LaCr_xCo_{1-x}O_3$ layers were prepared with a polymeric precursor method that used ethylene glycol as the solvent, acetyl acetone as the chelating agent, and polyvinylpyrrolidone as the polymer additive. The effects of the Co concentration on the structural, morphological, and $NO_x$ sensing properties of the $LaCr_xCo_{1-x}O_3$ powders were investigated with powder X-ray diffraction, field emission scanning electron microscopy, and its response to 20~250 ppm of $NO_x$ at $400^{\circ}C$ (for 1 kHz and 0.5 V), respectively. When the as-prepared precursors were calcined at $700^{\circ}C$, only a single phase was detected, which corresponded to a perovskite-type structure. The XRD results showed that as the Co concentration of the $LaCr_xCo_{1-x}O_3$powders increased, the crystal structure was transformed from an orthorhombic phase to a rhombohedral phase. Moreover, the $LaCr_xCo_{1-x}O_3$ powders with $0{\leq}x<0.8$ had a rhombohedral symmetry. The size of the particles in the $LaCr_xCo_{1-x}O_3$powders increased from 0.1 to $0.5{\mu}m$ as the Co concentration increased. The sensing performance of the stack-structured $LaCr_xCo_{1-x}O_3/Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ sensors was found to divide the impedance component between the resistance and capacitance. The response of these sensors to NO gas was more sensitive than that to $NO_2$ gas. Compared to other impedancemetric sensors, the $LaCr_{0.8}Co_{0.2}O_3/Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ sensor exhibited good reversibility and reliable sensingresponse properties for $NO_x$ gases.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.355-359
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• 2010

A $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ cathode was modified by applying a $ZrF_x$ coating. The surface-modified cathodes were characterized by XRD, SEM, EDS, TEM techniques. XRD patterns of $ZrF_x$-coated $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ revealed that the coating did not affect the crystal structure of the parent powder. SEM and TEM images showed that $ZrF_x$ nano-particles were formed as a coating layer, and EDS data confirmed that $ZrF_x$ distributed uniformly on the surface the powder. Capacity retention of coated samples at high C rates was superior to that of pristine sample. However, as the coating concentration increases beyond the optimum concentration, the rate capability was deteriorated. Whereas, as the increase of coating concentration to 2.0 wt %, the cyclic performances of the electrodes under the severe conditions (high cut-off voltage, 4.8 V, and high measurement temperature, $55^{\circ}C$) were improved considerably.

• 한국염색가공학회지
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• 제22권2호
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• pp.83-87
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• 2010

Crystal structure of coumarin 6 has been solved by X-ray diffraction. The crystals are triclinic, space group P-1, with a=8.823(2) ${\AA}$, b=8.898(2) ${\AA}$, c=11.025(9) ${\AA}$, ${\alpha}$=86.41(3)$^{\circ}$, ${\beta}$=85.39(3)$^{\circ}$, ${\gamma}$=76.23(3)$^{\circ}$, Mr=350.42, V=837.1(3) ${\AA}^3$, Z=2 and R=0.0516. The molecules are packed parallel to each other by weaker ${\pi}{\cdots}{\pi}$ and C-H${\cdots}{\pi}$ interactions. The detailed geometry of C-H${\cdots}{\pi}$ interactions were discussed. The hydrogen bonds and non-traditional C-H${\cdots}O$ interactions join the no-parallel molecules together. All the molecules packed wall-like with the molecular brick.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2000년도 Proceedings of 5th International Joint Symposium on Microeletronics and Packaging
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• pp.112-117
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• 2000

Nd:YAG laser of 355nm wavelength, which amounts to 3.5eV, produced by a harmonic generator was used to create Ag metallic particles as seeds for nucleation in photosensitive glass containing Ag+ and Ce3+. The pulse widths and frequency of the laser were 8ns and 10Hz, respectively. For crystalline growth, heat-treatment following laser irradiation was carried out at $570^{\circ}C$ fur 1h. Then, the LiAlSi3O8. crystal phase appeared in the laser irradiated lithium aluminum silicate glass. We present the effect of laser-induced nucleation compared with spontaneous nucleation by heat treatment for crystallization in the glass.

• 한국광학회지
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• 제5권1호
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• pp.74-79
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• 1994

이 연구에서는 TSSG 법으로 육성한 LiB3O5(LBO) 단결정의 1064nm 광에 대한 type I 및 type II 제 2 조화파 발생(SHG) 특성을 조사하였다. Type I SHG의 위상정합각은 $\theta_m=90^{\circ}, \phi_m=11.6^{\circ}$였고 angular acceptance bandwidth는 각각 $\delta\theta_{int}L_{1/2}=3.3^{\circ}-cm^{1/2}, \theta\phi_{int}L=0.27^{\circ}-cm^{1/2}$로 측정되었다. Type II SHG의 위상정합각은 $\theta_m=20^{\circ}, \phi_m=90^{\circ}$였고 angular acceptance bandwidth는 각각 $\delta\theta_{int}L_=0.65^{\circ}-cm, \theta\phi_{int}L^{1/2}=3.5^{\circ}-cm^{1/2}$로 측정되었다. Type I NCPM SHG 온도는 $149^{\circ}C$였고 temperature bandwidth $\DeltaTL$은 $4.8^{\circ}C-cm$였다. Nd:YAG 레이저의 peak power 가 $171 MW/\textrm{cm}^2$ 일때 두께가 2.6 mm 인 LBO 결정의 SHG 변환효율은 약 1.8%였고, 이차 비선형 계수 $d_{32}는 약 0.74\pm0.05 pm/V$로 측정되었다.

• E2M - 전기 전자와 첨단 소재
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• 제8권4호
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• pp.443-450
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• 1995

A directional coupler which on the X-cut $LiNbO_3$ substrate is fabricated by using proton exchange method and self-aligned method. After proton exchange process, the waveguide is formed by annealing process. The relation ship between refractive index change of waveguide and maximum output was studied along with the annealing time. A self-aligned method was used to simplify the fabrication process of the waveguide and to maximize the efficiency of electric field. The on-off state of modulator has been observered with the switching of the directional coupler by the electric field effect and also the switching voltage of the directional coupler has been measured with 8.0 [V].