• Journal of Magnetics
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• 제4권2호
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• pp.65-68
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• 1999

The M-type barium ferrite ($BaFe_{12}O_{19}$) is well known magnetic material to be used as a permanent magnet due to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ sublattices reduces the uniaxial anisotropy and those compounds open a new application field of noise suppressor at high frequencies. In this study, the magnetic and microwave absorbing properties are investigated in Ti-and Co-substituted barium ferrites ($BaFe_{12-2X} Ti_XCo_XO_{19}$). The saturated magnetization decreases linearly with the substitution of Ti and Co. The rapid drop in coercive force is observed with Ti and Co substitution upto x=1.2. The magnetic permeability spectrum shows the natural magnetic resonance in the specimens with small coercive force and large attenuation of microwave is predicted in those specimens at high frequencies (above 4 GHz).

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.383-388
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• 2000

In these days, there are out of natural sands in the construction field. It is required that development of substitute material for natural material. The blast-furnace slag could be a good alternative material in this situation. It can help resource recycling and the protection of environment. This study presents that the strength properties of mortar using air-cooled blast-furnace slag sand and water-cooled blast-furnace slag sand. The mixing design of this study have a few factors, three type of unit water, four types of W/C, five types of substitution rate. When air-cooled furnace slag sand used in mortar, as substitution rate is higher, 3, 7-days compression strength and flexural strength are going up. But, in case of water-cooled furnace slag sand mortar, strengths are going down.

• 한국전기전자재료학회논문지
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• 제13권3호
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• pp.214-219
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• 2000

In this paper the structural dielectric and piezoelectric properties of Pb［(M $g_{1}$2// $W_{1}$2/)$_{x}$-(N $i_{1}$3//N $b_{2}$3/)$_{0.15-x-(Zr_{0.5})}$ $Ti_{0.5}$)$_{0.85}$］ $O_3$ (x=0.0~0.10) ceramic were investigated with the substitution of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$. According to the substitution of Pb(M $g_{1}$2//W/1/2/) $O_3$ curie temperatures were slightly decrease due to the decrease of the tetrag-onality of crystal structure and coercive fields were decreased. Up to the substitution of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$ 3mol%,remnant polarization dielectric constant piezoelectric constant were increased. Dielectric constant and electro-mechanical coupling factor( $k_{p}$, $k_{31}$ ) were appeared the highest value of 2230, 0.64, and 0.38 and piezoelectric constant( $d_{33}$ , $d_{31}$ ) was the largest value of 418, 202($\times$10$^{-12}$ /C/N), respectively, when the substitution amount of Pb(M $g_{1}$2// $W_{1}$2/N) respectively, when the substitution amount of Pb(M $g_{1}$2// $W_{1}$2/) $O_3$ was 3mol%.s 3mol%.%.

• 한국자동차공학회논문집
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• 제19권5호
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• pp.100-112
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• 2011

This paper studied on a theoretical approach to predict structural performances and weight -reduction rates of hybrid bodyshells in case that the material of underframe structure is substituted. To choose other light-weight materials to be substituted for the original underframe material, compressive, bending and twisting deformations are considered under constant stiffness and strength conditions, which derive some new weight-reduction indices from a structural performance point of view. Next, these weight-reduction indices were verified using the finite element analyses of some simplified examples. It is shown that the derived indices to estimate the weight-reduction can be utilized as a good criterion for material substitution of the underframe at a basic design stage.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.294-294
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• 2007

Spinel cathode material $LiMn_2O_4$ is currently studied as a promising cathode material for lithium ion secondary batteries for future applications because of it is low cost, easy to be prepared and capable to be operated in high voltage range. However as a cathode material, $LiMn_2O_4$ performs a poor capacity retention which leads to short cycle life. In this study, stoichiometric $LiMn_2O_4$ was synthesized with granulation method with ion substitution to stabilize its structure and niobium doping to improve its conductivity. These well-mixed powders were calcined at $850^{\circ}C$ for 6 hours and its properties were investigated. Correlations of dopant and electrochemical properties were examined as well.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.181-182
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• 2005

In this study, in order to develop multilayer piezoelectric transformer, PMN-PZT ceramics were fabricated according to PFW substitution using $Li_2CO_3-CaCO_3$ as sintering aids and their dielectric and piezoelectric characteristics were investigated. As increasing the amount of PFW substitution, density was slightly increased due to the increased sinterability. At the 1[mol%] PFW substituted PMN-PZT ceramic sintered at 950[$^{\circ}C$], density, dielectric constant $\varepsilon_r$, electromechanical coupling factor kp, mechanical quality factor Qm and piezoelectric $d_{33}$ constant showed the optimum value of 7.761[$g/cm^3$], 1251, 0.479, 1425 and 282[pC/N], respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.257-260
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• 2003

In this study, the structural, dielectric and piezielectric properities of $xPb(Mg_{1/3}Nb_{2/3})O_3-(0.5-x)Pb(Ni_{1/3}Nb_{2/3})O_3-0.5Pb(Zr_{0.3}Ti_{0.7})O_3$ ceramics were investigated with the substitution of $PbMg_{1/3}Nb_{2/3}O_3$. The results showed that the substitution of the $PbMg_{1/3}Nb_{2/3}O_3$ was effective in increasing the dielectric constant and electromechanical coupling factor $(K_p)$. The dielectric constant, dielectric loss and Kp showed the highest values of 4293, 2.4%, 0.59 relatively, when the substitution of amount of $PbMg_{1/3}Nb_{2/3}O_3$ was 5 mol%.

• 한국전기전자재료학회논문지
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• 제29권6호
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• pp.332-336
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• 2016

In this study, in order to develop the composition ceramics for ultrasonic sensor with high $d_{33}*g_{33}$, $Pb_{1-3x/2}Bix(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3$(PMW-PNN-PZT) system ceramics were prepared using CuO as sintering aids. And then, their microstructure, piezoelectric and dielectric characteristics were systemetically investigated with bismuth substitution. The PMW-PNN-PZT ceramic specimens could be sintered at sintering temperature of $940^{\circ}C$ by adding sintering aids. At x=0.015 specimen, the density, electromechanical coupling factor($k_p$), dielectric constant, piezoelectric constant($d_{33}$) and piezoelectric figure of merit($d_{33}*g_{33}$) indicated the optimal properties of $7.90g/cm^3$, 0.67, 2,511, 628 pC/N, and $17.7pm^2/N$, respectively, for duplex ultrasonic sensor application.

• 한국전기전자재료학회논문지
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• 제28권9호
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• pp.577-580
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• 2015

In this paper, in order to develop the composition ceramics with the outstanding piezoelectric properties, $Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3$ ceramics substituted with $BiFeO_3$ were prepared by the conventional solid-state reaction method. The addition of small amount of $Li_2CO_3$ and $CaCO_3$ as sintering aids decreased the sintering temperature of the ceramics. The effects of $BiFeO_3$ substitution on their piezoelectric and dielectric properties were investigated. when 0.015 mol $BiFeO_3$ was substituted, the optimal physical properties of $d_{33}=590pC/N$, $E_c=8.78kV/mm$ were obtained.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.277-278
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• 2007

In this study, in order to develop multilayer piezo-actuator, PMN-PNN-PZT ceramics were fabricated using $Li_2CO_3,\;Na_2CO_3$, ZnO as sintering aids and their piezoelectric and dielectric properties were investigated according to the Bi substitution. Bi substitution enhanced electromechanical coupling factor$(k_p)$ and dielectric constant$({\varepsilon}_r)$. However, mechanical quality factor was deteriorated. At the sintering temperature of $870^{\circ}C$ and Bi substitution of 1mol%, density, electromechanical coupling factor$(k_p)$, mechanical quality factor$(Q_m)$, Dielectric constant$({\varepsilon}_r)$ and piezoelectric constant$(d_{33})$ of specimen showed the optimum value of $7.878g/cm^3$, 0.608, 835, 1603 and 397pC/N, respectively.