• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.58-61
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• 2001

Metal-insulator-semiconductor (MIS) C-V properties with high dielectric AIN thin films showed no hysteresis and good interface properties. The dielectric constant of the AIN film calculated from the capacitance at the accumulation region in the capacitance-voltage(C-V) characteristics was about 8. The C-V characteristics of MFIS capacitor showed a hysteresis loop due to the ferroelectric nature of the LiNbO$_3$ thin films. Typical dielectric constant value of LiNbO$_3$ film of MFIS device was about 23. The memory window width was about 1.2V at the gate voltage of $\pm$5 V ranges. Typical gate leakage current density of the MFIS structure was the order of 10$^{-9}$ A/cm$^2$ at the range of within $\pm$500 kV/cm. The ferroelectric capacitors showed no polarization degradation up to about 10$^{11}$ switching cycles when subjected to symmetric bipolar voltage pulse(peak-to-peak 8V, 50% duty cycle) in the 500kHz.

• Electrical & Electronic Materials
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• v.6 no.2
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• pp.122-128
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• 1993

본 연구에서는 0.45Pb(Fe$_{1}$2/Nb$_{1}$2/)O$_{3}$- (0.55-xPb(Fe$_{2}$3/W$_{1}$3/)O$_{3}$ (x=0.20, 0.25, 0.30) 세라믹을 950~990[.deg.C]에서 2시간 유지시켜 일반소성법으로 제작하였다. 제작된 시편에 대해 적층 세라믹 캐패시터로의 응용가능성을 고찰하기 위해 조성비와 소결온도에 따른 구조적, 유전적 특성을 조사하였다. PMN의 첨가량이 증가할수록 결정립 크기는 감소하였으며 상전이 온도는 증가하였다. 소결밀도는 970[.deg.C]에서 소결된 0.45PFN-0.30PFW-0.25PMN 시편에서 7.86[g/cm$_{3}$]의 최대값을 나타내었다. 유전상수는 990[.deg.C]에서 소결된 0.45PFN-0.25PFW-0.30PMN 시편에서 20,751의 최대값을 나타내었으며 유전손실은 모든 조성에서 5[%]이상을 나타내었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.2
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• pp.155-165
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• 1996

Growth of $LiNbO_3$ single crystal by Czochralski method was carried out to study the piezoelectric effects. Piezoelectric coefficients and elastic compliances of the $LiNbO_3$ single crystal were determined by the resonance method of length-extentional mode of bar resonator from the room temperature up to $100^{\circ}C$. Two dielectric constants of $LiNbO_3$ were also determined by measuring the capacitance of the plate specimen. Measured constants were piezoelectric coefficients $d_{15},d_{22},d_{31},d_{33}$ elastic compliances $s^E_{11},s^E_{33},2s^E_{13}+2s^E_{44},s^E_{14}$ and dielectric constants $K^T_{11},K^T_{33}$. As temperature increased, elastic compliances changed very slowly while piezoelectric coeffiecients and dielectric constant $K^T_{33}$ changed very rapidly. Electromechanical coupling constant of zyw ($45^{\circ}C$)-bar was as high as 0.51 in room temperature and nearly constant up to $1000^{\circ}C$. The increase of piezoelectric coefficients was mainly due to the increase of dielectric permittivity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.10
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• pp.901-905
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• 2008

In this study, $0.95(K_{0.5}Na_{0.5})NbO_{3}-0.05Li(Sb_{0.8}Nb_{0.2})O_{3}+0.2\;wt%Ag_{2}O$ were investigated as a variations of sintering times in order to improve dielectric and piezoelectric properties of lead-free piezoelectric ceramics. $Ag_{2}O$ were used as sintering aids and the specimens were sintered during 3, 5, 7, 9 and 11 hours, respectively. At the specimen sintered during 7 hour, Electromechanical coupling factor ($k_p$), density, dielectric constant (${\epsilon}_{\gamma}$), piezoelectric constant ($d_{33}$) and curie temperature ($T_c$) of composition ceramics showed the optimal value of 0.450, 4.274 $[g/cm^3]$, 1007, 257 [pC/N] and $396^{\circ}C$, respectively.

• Journal of the Korean Institute of Telematics and Electronics
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• v.10 no.3
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• pp.53-60
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• 1973

Calculations of the temperature coefficients of the elastic surface wave velocity and delay time were performed for the propagation along the X axis of rotated Y cut plane of the LiNbO3 and LiTaO3. Measurements of the temperature dependence of delay time of the elastic surface wave were also performed for the propagation along the X axis of a 130" rotated Y cut plane of the LiNb03 at the temperature range from liquid He to room temperature. Experimental value 70$\times$10-6/$^{\circ}C$ of the temperature coefficient of the delay time of the elastic surface wave agrees well with the calculated value 72.7$\times$10-a/$^{\circ}C$. The temperature coefficient of delay time of elastic surface wave propagating along the X axis of a 130$^{\circ}$ rotated Y cut plane o( the LiNbO3 is approximately 16$\times$10-6/$^{\circ}C$ at the near temperature of liquid He.d He.

• Electrical & Electronic Materials
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• v.9 no.9
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• pp.900-905
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• 1996

We have investigated dielectric properties of low fired ceramics BiNbO$_{4}$ containing 0.05[wt%] V$_{2}$O$_{5}$ and x[wt%l Cr$_{2}$O$_{3}$ (x=0, 0.2, 0.4, 0.8, 1.2). By substituting Cr for Bi, dielectric constant .epsilon.$_{r}$ and quality factor Q.f increased and temperature coefficient of resonant frecquency .tau.$_{f}$ changed to positive value. In the composition of BiNbO$_{4}$+0.05 [Wt%] V$_{2}$O$_{5}$+0.8[wt%]Cr$_{2}$O$_{3}$ sintered at 960[.deg. C], we could obtain microwave dielectric properties of .epsilon.$_{r}$=49, Q.f.simeq.3000[GHz](at 4.8[GHz]), .tau.$_{f}$.simeq.0[ppm/.deg. C]. As the above ceramics can be sintered near 960[.deg. C], it is applicable to multilayer microwave device with Ag conductor.tor.tor.tor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.292-293
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• 2006

$ZnNb_2O_6$ ceramics were sintered under the presence of zinc-borosilicate(ZBS) glass and resultant microwave dielectric properties were investigated with a view to applying the composition to LTCC technology. The addition of 10~30 wt% ZBS glass ensured successful sintering below $900^{\circ}C$. In general, increased addition of ZBS glass increased sinterability but it decreased the dielectric properties significantly due to the formation of an excessive liquid and second phases. The sintered $ZnNb_2O_6$ ceramics at $900^{\circ}C$ with 25 wt% ZBS glass demonstrated 15.8 in dielectric constant(${\varepsilon}_r$), 5,400 in quality factor($Q{\times}f_0$), and $-98\;ppm/^{\circ}C$ in temperature coefficient of resonant frequency(${\tau}_f$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.313-314
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• 2006

$BiNbO_4$ ceramics were sintered under the presence of zinc-borosilicate(ZBS) glass and resultant microwave dielectric properties were investigated with a view to applying the composition to LTCC technology. The addition of 5~20 wt% ZBS glass ensured successful sintering below $900^{\circ}C$. In general, increased addition of ZBS glass increased sinterability and temperature coefficient of resonant frequency(${\tau}_f$), but it decreased the dielectric constant(${\varepsilon}_r$) and quality factor($Q{\times}f_0$) significantly due to the formation of an excessive liquid. The sintered $BiNbO_4$ ceramics at $900^{\circ}C$ with 15 wt% ZBS glass demonstrated 25 in dielectric constant(${\varepsilon}_r$), 3,700 in quality factor($Q{\times}f_0$), and -32 $ppm/{\circ}C$ in temperature coefficient of resonant frequency(${\tau}_f$).

• Korean Journal of Metals and Materials
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• v.49 no.12
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• pp.917-923
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• 2011

Dissolution and precipitation behaviors of complex carbonitrides in austenite of a V-Nb microalloyed steel were quantitatively examined through electrical resistivity measurement and transmission electron microscopy. The electrical resistivity increased with solution treatment temperature up to $1240^{\circ}C$ and then was saturated at $225n{\Omega}m$ for a holding time of 10 min. The electrical resistivity method was also used to quantitatively measure the isothermal precipitation kinetics of the complex carbonitrides in austenite. Nb-rich precipitates were observed in austenite at the early stages of precipitation, but Nb was replaced by V up to the equilibrium amount within the precipitates with further holding time. The time-temperature-precipitation diagram showed a C-type curve; nose temperature and its incubation time were $900^{\circ}C$ and 100 s, respectively.

• Journal of Korea Foundry Society
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• v.20 no.5
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• pp.323-329
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• 2000

The HSS consists of hard carbide and matrix of martensite, and so its characteristics of wear resistance, fracture resistance, and surface roughness are good. This study was undertaken to investigate the influence of Nb and V and manufacturing conditions on microstructural behaviors and characteristics in the HSS cylindrical specimens(90 $mm^{O.D.}$ ${\times}$ 60 $mm^{I.D.}$ ${\times}$ 50 $mm^H$) manufactured using VCC(Vertical Centrifugal Casting). In the specimen of Fe-2C-6Cr-1.5W-3Mo-4V alloy, the amount of MC carbide was increased and $M_7C_3$ carbide was decreased with the increase of V and Nb contents. The primary VC carbide was formed and followed by the rod-type eutectic MC carbide was formed in the cell boundary in 9%V added specimen. MC carbide was increased, and $M_7C_3$ carbide was decreased with the addition of Nb content. In the specimen containing more than 3%Nb, primary NbC carbide was formed within the cell of matrix. With increase in rpm, cell and carbides became fine, and amount of carbide $M_7C_3$ was decreased due to increase in cooling rate.