• Title, Summary, Keyword: LiF

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Development of LTCC Materials for RF Module (RF 모듈용 LTCC 소재 개발)

  • 김용철;이경호
    • Journal of the Microelectronics and Packaging Society
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    • v.10 no.2
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    • pp.13-17
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    • 2003
  • In this study, new LTCC materials of $ZnWO_4$-LiF system were developed for the application to RF Module fabrication. Pure $ZnWO_4$ must be sintered above $1050^{\circ}C$ in order to obtain up to 98% of full density. The measured dielectric constant ($\epsilon_r$)quality factor ($Q{\times}f0$), and temperature coefficient of resonant frequency ($\tau_f$ were 15.5, 74000 GHz, and $-70ppm^{\circ}C$, respectively. LiF addition resulted in a liquid phase formation at 81$0^{\circ}C$ due to interaction between ZnWO$_4$ and LiF. Therefore, ZnWO$_4$ with 0.5∼1.5 wt% LiF could be densified at $850^{\circ}C$. In the given LiF addition range, the sintering shrinkage increased with increasing LiF content. Addition of LiF slightly lowered the dielectric constant from 15.5 to 14.2∼15 due to lower dielectric constant of LiF. Qxfo value decreased with increasing LiF content. This can be explained in terms of the interaction between LiF and $ZnWO_4$, and inhomogeneity of grain structure.

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Thermoluminescence of $MgCl_2$-Activated LiF Powder (불순물 $MgCl_2$를 첨가한 LiF 분말의 열형광)

  • 이계철;이상수
    • Nuclear Engineering and Technology
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    • v.2 no.4
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    • pp.269-272
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    • 1970
  • Thermoluminescence (TL) from LiF powder of purity 99.98 % was accomplished and this TL intensity showed glow peaks at 12$0^{\circ}C$, 22$0^{\circ}C$ and 30$0^{\circ}C$. Sintered LiF powder which has an activation of 2% proportion by weight of MgC1$_2$show strong increased TL and this characteristic of the glow curve was investigated precisely. LiF which is used in TL dosimetry has been known to have electrons caused by impurities such as Mg, Mn, etc. This experiment shows that Mg, one of the impurities, is definitely diffused through LiF crystals. The effects of sintering time were detected in this glow curve and it was confirmed that MgC1$_2$also has a TL effect.

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Ditopic Binding of Alkali Halide Ions to Trimethylboroxine

  • Jeong, Kyung-Hwan;Shin, Seung-Koo
    • Mass Spectrometry Letters
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    • v.1 no.1
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    • pp.9-12
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    • 2010
  • Trimethylboroxine (TMB) is a six-membered ring compound containing Lewis acidic boron and Lewis basic oxygen atoms that can bind halide anion and alkali metal cation, respectively. We employed Fourier transform ion cyclotron resonance spectroscopy to study the gas-phase binding of $LiBrLi^+$ and $F^-(KF)_2$ to TMB. TMB forms association complexes with both $LiBrLi^+$ and $F^-(KF)_2$ at room temperature, providing direct evidence for the ditopic binding. Interestingly, the $TMB{\cdot}F^-(KF)_2$ anion complex is formed 33 times faster than the $TMB{\cdot}Li^+BrLi$ cation complex. To gain insight into the ditopic binding of an ion pair, we examined the structures and energetics of $TMB{\cdot}Li^+$, $TMB{\cdot}F^-$, $TMB{\cdot}LiF$ (the contact ion pair), and $Li^+{\cdot}TMB{\cdot}F^-$ (the separated ion pair) using Hartree-Fock and density functional theory. Theory suggests that $F^-$ binds more strongly to TMB than $Li^+$ and the contact ion-pair binding ($TMB{\cdot}LiF$) is more stable than the separated ion-pair binding ($Li^+{\cdot}TMB{\cdot}F^-$).

Separation of Zr metal from $LiF-BeF_2-ZrF_4$ Molten Salt by Electrowinning (Electrowinning에 의한 $LiF-BeF_2-ZrF_4$ 용융염에서 Zr 금속 분리)

  • Woo, Mun-Sik;Yoo, Jae-Hyung;Kwon, Soo-Han
    • Analytical Science and Technology
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    • v.13 no.6
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    • pp.759-765
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    • 2000
  • A study on the separation of Zr metal from $LiF-BeF_2-ZrF_4$ (67-27-6 mol%) molten salt was carried out using electrowinning. The decomposition potentials of the $LiF-BeF_2$ (72-28 mol%) and the $LiF-BeF_2-ZrF_4$ (67-27-6 mol%) molten salts were measured to be -1.55 and -1.35 volt, respectively. The Zr separation voltage from the salt were found to be in a range of -1.4 -1.5 volt. As increasing applied current, the deposition of molten salt on a cathode increases but the current efficiency decreases. In addition, the deposition and current efficiency decreases with increasing temperature.

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Emission Characteristics of OLEDs Using LiF/Al/LiF Structure (LiF/Al/LiF 구조를 적용한 OLED 소자의 발광 특성)

  • Park, Yeon-Suk;Yang, Jae-Woong;Ju, Sung-Hoo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.9
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    • pp.696-700
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    • 2010
  • We fabricated red and blue organic light emitting display (OLEDs) which had the two kinds of multi-structure of ITO/HIL/HTL/EML/ETL/LiF/Al and ITO/HIL/HTL/EML/ETL/LiF/Al/LiF. In the case of red OLED that had LiF/Al/LiF structure compared to LiF/Al structure, the current density increased from 4.3 mA/$cm^2$ to 7.3 mA/$cm^2$, and the brightness increased from 488 cd/$m^2$ to 1,023 cd/$m^2$ at 7.0 V, and as a result the current efficiency was improved from 11.28 cd/A to 13.95 cd/A. Also in the case of blue OLED that had LiF on Al cathode layer, the current density increased from 1.2 mA/$cm^2$ to 1.8 mA/$cm^2$, and the brightness increased from 45 cd/$m^2$ to 85 cd/$m^2$ at 7.0 V, and as a result the current efficiency was improved from 3.69 cd/A to 4.82 cd/A. Through these experimental results it could be suggested that the LiF layer formed on Al prevents the oxidation of Al surface, and the electrode resistance become low with increase of supplied electrons, therefore the brightness and the efficiency are improved from the influence to the well-balanced bonding of electron and hole at emitting layer.

Performance of Three-Layered Organic Light-Emitting Diodes Using the Hole-Transport and Injection Layer of TPD and Teflon-AF, and the Electron-Injection Layer of Li2CO3 and LiF

  • Shin, Jong Yeol;Kim, Tae Wan;Kim, Gwi Yeol;Lee, Su Min;Hong, Jin Woong
    • Transactions on Electrical and Electronic Materials
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    • v.18 no.2
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    • pp.89-92
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    • 2017
  • The performance of three-layered organic light-emitting diodes (OLEDs) was investigated using TPD hole-transport and injection layers, Teflon-AF, and the electron-injection layer of $Li_2CO_3$ and LiF. The OLEDs were manufactured in a structure of TPD/$Alq_3$/LiF, TPD/$Alq_3$/$Li_2CO_3$, and AF/$Alq_3$/LiF using low-molecular organic materials. In three different three-layered OLEDs, it was found that the device with the TPD/$Alq_3$/LiF structure shows higher performance in maximum luminance, and maximum external quantum efficiency compared to those of the device with TPD/$Alq_3$/$Li_2CO_3$ and TPD/$Alq_3$/LiF by 35% and 17%, and 193% and 133%, respectively. It is thought that the combined LiF/Al cathode contributes to a reduced work function and improves an electrical conduction mechanism due to the electron injection rather than the hole transport, which then increases a recombination rate of charge carriers.

Recovery of Uranium in $LiF-BeF_2$ Molten Salt System by Electrowinning ($LiF-BeF_2$ 용융염계에서 전해제련에 의한 우라늄 회수)

  • 우문식;김응호;유재형
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.426-430
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    • 2003
  • Fissionable uranium will be separated from long-lived nuclear materials in pyroprocess for transmutation. This study was measured decomposition voltage and deposition rate on cathode of uranium in $LiF-BeF_2$ molten salt by electrowinning. The result of experimental is that decomposition voltage of $UF_4$ and $LiF-BeF_2$ molten salt is -1.4 and -1.5 volt at $500^{\circ}C$ Deposition rate of uranium on cathode increases with increase of uranium concentration in molten salt.

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Recovery of $ZrO_2$ by Leaching from $LiF-BeF_2-ZrO_2$ Molten Salt in Distilled Water ($LiF-BeF_2-ZrO_2$ 용융염에서 증류수 침출에 의한 $ZrO_2$의 회수 - 증류수에서 $LiF-BeF_2-ZrF_4+ZrO_2$ 용융염의 용해현상 -)

  • Woo, Mun-Sik;Yoo, Jae-Hyung;Park, Hyun-Soo;Kang, Young-Ho;Kwon, Soo-Han
    • Analytical Science and Technology
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    • v.13 no.6
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    • pp.712-721
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    • 2000
  • $LiF-BeF_2-ZrF_4$(63-30-7 mol%) molten salt was dissolved up to 0.02g in 1ml of distilled water at room temperature. $ZrO_2$ oxide made from $ZrF_4$ through pyrohydrolysis was recovered by leaching in distilled water with $LiF-BeF_2-ZrF_4$molten salt including it at room temperature. The crystalline sharpness of recovered $ZrO_2$ oxide was not damaged.

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Improvement of the luminous efficiency of organic light emitting diode using LiF anode buffer layer

  • Park, Won-Hyeok;Kim, Gang-Hun
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.147-147
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    • 2015
  • The multilayer structure of the organic light emitting diode has merits of improving interfacial characteristics and helping carriers inject into emission layer and transport easier. There are many reports to control hole injection from anode electrode by using transition metal oxide as an anode buffer layer, such as V2O5, MoO3, NiO, and Fe3O4. In this study, we apply thin films of LiF which is usually inserted as a thin buffer layer between electron transport layer(ETL) and cathode, as an anode buffer layer to reduce the hole injection barrier height from ITO. The thickness of LiF as an anode buffer layer is tested from 0 nm to 1.0 nm. As shown in the figure 1 and 2, the luminous efficiency versus current density is improved by LiF anode buffer layer, and the threshold voltage is reduced when LiF buffer layer is increased up to 0.6 nm then the device does not work when LiF thickness is close to 1.0 nm As a result, we can confirm that the thin layer of LiF, about 0.6 nm, as an anode buffer reduces the hole injection barrier height from ITO, and this results the improved luminous efficiency. This study shows that LiF can be used as an anode buffer layer for improved hole injection as well as cathode buffer layer.

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Fabrication of Temperature Stable LTCC with Low Loss (온도 안정성 저손실 LTCC제조)

  • 김용철;이경호
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.4 no.4
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    • pp.341-345
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    • 2003
  • ZnWO$_4$shows excellent frequency selectivity due to its high quality factor(Q${\times}$f) at microwave frequencies. However, in order to use ZnWO$_4$as multilayered wireless communication components, its other properties such as sintering temperature(105$0^{\circ}C$). $$\tau$_f$(-70ppm/$^{\circ}C$) and $$\varepsilon$_r$(15.5) should be modified. In present study, TiO$_2$and LiF were used to improve the microwave dielectric and sintering properties of ZnWO$_4$. TiO$_2$ additions to ZnWO$_4$changed $\tau$$_{f}$ from negative to positive value, and also increased $$\varepsilon$_r$, due to its high $$\tau$_f$(+400ppm$^{\circ}C$) and $$\varepsilon$_r$(100). At 20 mol% TiO$_2$ addition, $$\tau$_f$was controlled to near zero ppm/$^{\circ}C$ with $$\varepsilon$_r$=19.4 and Q${\times}$ f=50000GHz. However, the sintering temperature was 110$0^{\circ}C$. LiF addition to the ZnWO$_4$+TiO$_2$ mixture greatly reduced the sintering temperature from 110$0^{\circ}C$ to 85$0^{\circ}C$ due to liquid phase formation. Also LiF addition decreased the $$\tau$_f$value due to its high negative $$\tau$_f$ value. Therefore, by controlling the TiO$_2$and LiF amount. temperature stable LTCC(Low Temperature Cofired Ceramics) material with low loss in the ZnWO$_4$-TiO$_2$-LiF system could be fabricated.d.d.

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