• Journal of Electrochemical Science and Technology
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• 제4권3호
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• pp.102-107
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• 2013

The electrochemical properties of Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ and pure $LiFe_{0.5}Mn_{0.5}PO_4$ olivine cathodes are examined and the lattice parameters are refined by Rietveld analysis. The calculated atomic parameters from the refinement show that $Mg^{2+}$ doping has a significant effect in the olivine $LiFeMnPO_4$ structure. The unit cell volume is 297.053(2) ${\AA}^3$ for pure $LiFe_{0.5}Mn_{0.5}PO_4$ and is decreased to 296.177(1) ${\AA}^3$ for Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample. The doping of $Mg^{2+}$ cation with atomic radius smaller than $Mn^{2+}$ and $Fe^{2+}$ ion induces longer Li-O bond length in $LiO_6$ octahedra of the olivine structure. The larger interstitial sites in $LiO_6$ octahedra facilitate the lithium ion migration and also enhance the diffusion kinetics of olivine cathode material. The $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample with larger Li-O bond length delivers higher discharge capacities and also notably increases the rate capability of the electrode.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.548-551
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• 2000

Spinel phase LiF $e_{y}$M $n_{2-y}$ $O_4$samples are synthesized by calcining a LiOH.$H_2O$, Mn $O_2$and F $e_2$ $O_3$mixture at 80$0^{\circ}C$ for 36h in air. Preparing LiF $e_{y}$M $n_{2-y}$ $O_4$showed spinel phase with cubic phase. The ununiform distortion of the crystallite of the spinel LiF $e_{y}$M $n_{2-y}$ $O_4$was more stable than that of the pure. The discharge capacity of the cathode for the Li/LiF $e_{0.1}$M $n_{1.9}$ $O_4$cell at the first than that of the pure. The discharge capacity of the cathode for the Li/LiF $e_{0.1}$M $n_{1.9}$ $O_4$cell at the first cycle and at the 70th cycle was about 113 and 90mAh/g, respectively. This cell capacity was retained about 82% of the first cycle after 70th cycle. Impedance profile of this cell was more stable than that pure. The resistance, the capacitance and chemical diffusion coefficients of lithium ion showed approximately 80$\Omega$, 36133.87$\mu$F ; 1.4$\times$10$^{-8}$ c $m^2$ $s^{-1}$ , respectively. , respectively.ely.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.97-99
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• 1998

A optical phase modulator of 5Gbps was fabricated on LiNbO$_3$ by Ti diffusion for optical communications. In this Paper the pigtailing, mode patterns and insertion loss were discussed. And the device Properties of driving voltage and bandwidth were measured.

• 한국안광학회지
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• 제1권1호
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• pp.1-14
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• 1996

Magic-Angle-Spinning NMR에 나타나는 $Li^+$ 이온의 운동과 관련된 알칼리 혼합 효과에 미치는 전이금속 산화물의 영향을 조사하기 위하여 불순물 $Fe_2O_3$를 0.1 mol% 첨가시킨 혼합 알칼리 Silicate 유리들을 제조하였고, 온도에 따라 $^7Li$ MAS-NMR 스펙트럼과 상온에서 $^7Li$ 스핀-살창 완화시간을 측정하였다. $Fe_2O_3$가 첨가되었을 때, 스펙트럼의 선폭이 조금 변화되었을 뿐이며 선 모양이 거의 변하지 않고 있다. 이 때문에, 스핀-스핀 완화 과정에서는 혼합 알칼리 효과가 충분히 나타나는 것으로 불수도 있지만 반드시 그렇지만은 않아 보인다. $Li^+$ 이온의 활성화 에너지가 혼합 알칼리 유리에서 오히려 감소하는 경향이 나타났다. 이것은 혼합 알칼리 효과가 아니다. 스핀-살창 완화시간, 완화 과정 분석을 통한 $Li^+$ 이온의 확산 환경, 그리고 핵 자가화 (nuclear magnetization) 등의 비교에 의하면, $^7Li$ 스핀-살창 완화 과정에서 알칼리 혼합 효과는 거의 나타나지 않는 것을 확인 할 수 있었다.

• 한국통신학회논문지
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• 제19권9호
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• pp.1782-1792
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• 1994

$Ti:LiNbO_3$채널형 광도파로와 Asymmetric Coplanar Strip(ACPS) 전극구조를 이용해서, $1.3{\mu}m$에서 동작하는 진형파형 위상 광변조기를 설계, 제작한 다음 변조특성을 관찰하였다. 위상정합이 개선되도록 ACPS 진행파형 전극을 설계하기 위해서 전극과 완충박막의 두께를 포함하여, 전극제원의 해석적 함수로 특성저항, 변조파의 유효굴절률 및 전극손실 등을 고려하였다. Ti 확산방법으로 저손실 채널형 광도파로 제작하였으며, double-spin image reversal 공정을 이용해서 $2.5{\mu}m$ 두께의 전극을 형성하였다. 9GHz 부근에서의 전극구조 공진형상 때문에 변조특성이 제한 되었지만, 2.5GHz 까지는 큰 왜곡없이 변조특성이 관찰되었다.

• 공업화학
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• 제7권2호
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• pp.362-370
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• 1996

$Li/V_6O_{13}$ 전지의 성능과 poly(acrylonitrile)[PAN]계 폴리머 전해질의 전기화학적인 성질을 조사 하였다. 폴리머 전해질의 이온 전도도는 상온에서 $2.3{\times}10^{-3}S/cm$를 보였으며 리튬 전극과의 상용성도 우수하였다. 또한 4.3V(vs. $Li^+/Li$)까지의 전기화학적인 안정성이 있는 것으로 나타났다. $Li/V_6O_{13}$ 전지 반응은 $V_6O_{13}$ 전극과 폴리머 전해질간의 계면 저항이 지배적 이었다. $V_6O_{13}$내의 리튬 이온의 확산 계수값은 $2.7{\times}10^{-9}{\sim}4.2{\times}10^{-8}cm^2/sec$로 나타났다. $V_6O_{13}$ 활물질의 이용률은 C/8($50{\mu}A/cm^2$)에서 95%였으며 C/4($100{\mu}A/cm^2$)에서는 82%로 각각 나타났다.

• 방사성폐기물학회지
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• 제18권1호
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• pp.1-18
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• 2020

Molten salt solutions consisting of eutectic LiCl-KCl and concentrations of samarium chloride (0.5 to 3.0 wt%) at 500℃ were analyzed using both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV technique gave the average diffusion coefficient for Sm³⁺ over the concentration range. Equipped with Sm³⁺ diffusion coefficient, the Randles-Sevcik equation predicted Sm³⁺ concentration values that agree with the given experimental values. From CV measurements; the anodic, cathodic, and half-peak potentials were identified and subsequently used as a parameter to acquire EIS spectra. A six-element Voigt model was used to model the EIS data in terms of resistance-time constant pairs. The lowest resistances were observed at the half-peak potential with the associated resistance-time constant pairs characterizing the reversible reaction between Sm³⁺ and Sm²⁺. By extrapolation, the Voigt model estimated the polarization resistance and established a polarization resistance-concentration relationship.

• Journal of Magnetics
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• 제16권3호
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• pp.294-299
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• 2011

Nd-Fe-B high performance magnets were prepared by die-upset forging. The effects of the deformation parameters on magnetic properties and flow stress were studied. Deformation temperatures in the range of $600{\sim}900^{\circ}C$ enable to achieve an effective anisotropy and temperature $800^{\circ}C$ proves to be suitable for deformation of Nd-Fe-B magnets. The amount of c-axis alignment along the press direction seems to depend on the amount of deformation and a saturation behavior is shown at deformation ratio of 75%. Magnetic properties are also related to strain rate, and maximum energy product is attained at an optimum strain rate of ${\varphi}=1{\times}10^{-2}s^{-1}$. By analyzing the relationship of stress and strain at different deformation temperature during die-upset forging process, deformation behavior of Nd-Fe-B magnets was studied and parameters for describing plastic deformation were obtained. Nd-rich boundary liquid phase, which is additionally decreasing the flow stress during deformation, is supposed to play the role of diffusion path and enhance the diffusion rate.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.16-19
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• 1997

We have investigated the optical properties of a Ti:LiNbO$_3$ optical waveguide which was fabricated by Ti-diffusion in a alto atmosphere, and propose an effective method of polishing waveguide. This method was regarded to be applicable to waveguide fabrications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.502-504
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• 1989

An electro-optic cutoff modulator with self-aligned electrode that utilizes a single-mode proton-diffused well-guided channel waveguide in a X-cut Y-propagating $LiNbO_3$ substrate is reported. The self-aligned electrode is formed during proton diffusion process of itself. Nearly linear voltage-intensity relationship has been observed. Over 90 % modulation has been achieved with applied voltage of 25 V.