• The Korean Journal of Ceramics
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• v.4 no.1
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• pp.43-46
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• 1998

We have investigated the formation and thermal stability of cobalt aluminide(CoAl) thin films on GaAs. In order to obtain cobalt-aluminide thin films, we deposited a multilayer of Co/Al on GaAs, and subsequently annealed the samples at 80$0^{\circ}C$ for 30 min. After annealing, single-phase cobalt aluminide was produced showing a flat and uniform interface with GaAs. which indicates that cobalt aluminide (CoAl) is thermally stable with GaAs. In addition, the adherence and mechanical properties of the as-deposited, and annealed Co/Al multilayer structure on GaAs are compatible with those required for device fabrication processes. The electrical property of the CoAl/GaAs contact shows rectifying characteristics, indicating that the diodes were usable as rectifying gate electrodes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.594-597
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• 2003

In the present study, the piezoelectricity and polarization of multilayer ceramic actuator, being designed to stack PMN-PZ-PT ceramic layers and Ag-Pd electrode layers alternatively, were investigated under a consideration of geometric factor, the volume ratio of the ceramic to the electrode layers. The actuators were fabricated by tape casting of 0.2Pb(Mg1/3Nb2/3)O3-0.38PbZrO3-0.42PbTiO3 followed by lamination and burnout & co-firing processes. The actuators of 10 10 0.62 nm3 in size were formed in a way that 60 200 m thick ceramics were stacked alternatively with 5 m thick electrode layer. Increases in polarization and electric field-induced displacement with thickness of the ceramic layer were attributed to change of 90o/180o domain ratio, which was affected by interlayer internal stress. The piezoelectricity and actuation behaviors were found to depend upon the volume ratio (or thickness ratio) of ceramic to electrode layers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.325-326
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• 2006

In this study, in order to develop piezoelectric device for multilayer piezoelectric ultrasonic motor, low temperature sintering $Pb(Mn_{1/3}Nb_{2/3})_{0.02}(Ni_{1/3}Nb_{2/3})_{0.12}(Zr_{0.48}Ti_{0.52})_{0.86}O_3$ system ceramics were fabricated according to the variations of forming pressure of casting sheet. At the 300[$kgf/cm^2$] forming pressure, the maximum density of 7.8[$g/cm^3$] was obtained. At the 350[$kgf/cm^2$] forming pressure, the maximum values of effective electromechanical coupling factor $k_{cff}\;=\;0.24$ and mechanical quality factor Qm=628 were obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.254-256
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• 2007

In this study, in order to develop low temperature sintering ceramic ultrasonic nozzle, single-layer and multilayer ring-type piezoelectric vibrators were manufactured using PMN-PNN-PZT ceramics, And then the electrical properties were investigated. The piezoelectric vibrator were sintered at low temperature of $940^{\circ}C$. The resonant resistance decreased with the increases of the number of layer. And also, the capacitance increased with the increases of the number of layer. The mechanical quality factor (Qm) decreased with the increases of the number of layer.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.601-610
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• 1997

In cofiring of multilayered alumina with tungsten, the change of camber with lamination condition was experimented and the effect of sintering shrinkage of alumina and tungsten was investigated. From the exact measurement of sintering shrinkage of tungsten thick film, as lamination pressure increased, the sintering shrinkage of alumina decreased but that of tungsten thick film was not changed. So it was though that the main factor which induced the sintering shrinkage difference between ceramics and metal with lamination condition was the change of sintering shrinkage of ceramics. In case of high lamination pressure, high green sheet density, the cofired specimen showed low camber due to low shrinkage difference between alumina and tungsten and there was a linear relation between camber and shrinkage difference. It was found that this shrinkage difference could change the thickness of tungsten film and the microstructure within via hole during cofiring.

• Electrical & Electronic Materials
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• v.10 no.1
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• pp.20-25
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• 1997

In this study, piezoelectric actuator samples were fabricated using 0.375PMN-0.37OPT-0.255PZ system ceramics with Barium substitution and the strain properties of them were investigated. Dielectric constant of the specimens increased with the increase of Ba content up to 5mol% and decreased with futher addition of Ba. The largest piezoelectric coefficient and electromechanical coupling coefficient were observed at the sintering temperature of 1250'C and Barium content of 5mol%. The characteristics of strain hysteresis was found largely with varing the sintering temperature on the single round type, and the strain is proportional to piezoelectric coefficient.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.253-254
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• 2007

In this study, in order to develop low temperature sintering multilayer piezoelectric actuator, PMN-PNN-PZT system ceramics were fabricated using $Li_2CO_3-Bi_2O_3$-CuO as sintering aids and their piezoelectric and dielectric characteristics were investigated as a function of heating rate. At sintering temperature of $900^{\circ}C$, with increasing heating rate, electromechanical coupling factor(kp), mechanical quality factor(Qm) and dielectric constant $({\varepsilon}_r)$ were increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.322-332
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• 2022

Energy storage capacitors based on dielectric ceramics with superior polarization properties and dielectric constant can provide much higher output power density due to their very fast energy charging/discharging rates, which are particularly suitable for operating pulsed-power devices. For an outstanding energy storage performance of dielectric capacitor, a large recoverable energy density could be derived by introducing a slim polarization-electric field hysteresis loop into dielectric materials by various technical approaches. Many research teams have explored various dielectric capacitor technologies to demonstrate high output power density and ultrafast charging/discharging behavior. This article reviews the recent research progress in high-performance dielectric capacitors for pulsed-power electronic applications.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.357-362
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• 1999

ZnO varistors containing cobalt, praseodymium and calcium oxides were prepared. The current-voltage charcteristics and microstructures of the specimens were investigated with respect to calcium addition and sintering temperature. The potential barrier heights and the carrier densities were estimated from C-V relations. The compatibility of Ag-Pd as an internal electrode for multilayer chip varistor was also examined.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2004.05a
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• pp.263-267
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• 2004

This study presents the combined effect of electric field application and mechanical compressive stress loading on deformation in a multilayer ceramic actuator, designed with stacking 0.2($PbMn_{1/3}Nb_{2/3}O_{3}$)-0.8($PbZr_{0.475}Ti_{0.525}O_{3}$) ceramics and Ag-Pd electrode, alternately. The deformation behaviors were attributed to relative $180^{\circ}$domain, determined by pre-loaded compressive stress and electric field. The non-linearity of piezoelectricity and strain are dependent upon the young's modulus resulting from the domain reorientation.