• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.528-531
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• 2000

Deposition of PZT with UV laser ablatio was applied for realization of thin film sensors and actuators. Deposition rate of more than 20nm/min was attained by pulsed KrF excimer laser deposition, which is fairly better than those obtained by the other methods. Perovskite phase was obtained at room temperature deposition with Fast Atom Beam(FAB) treatment and annealing. Smart MEMS(Micro electro-mechanical system) is now a suject of interest in the field of micro optical devices, micro pumps, AFM cantilever devices etc. It can be fabricated by deposition of PZT thin films and micromachining. PZT films of more than 1 micron thickness is difficult to obtain by conventional methods. This is the reason why we applied excimer laser ablation for thin film deposition. The remanent polarization Pr of 700nm PZT thin film was measured, and the relative dielectric constant was determined to about 900 and the dielectric loss tangent was also measured to be about 0.04. XRD analysis shows that, after annealing at 650 degrees C in 1 hour, the perovskite structure would be formed with some amount of pyrochlore phase, as is the case of the annealing at 750 degrees C in 1 hour.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.885-888
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• 2000

The effects of deposition temperature and post annealing process of ferroelectric PbZr$\sub$0.52/Ti$\sub$0.48/O$_3$(PZT) thin films by pulsed laser deposition (PLD) were investigated. The PZT thin films were deposited at 400, 450, 500, and 550$^{\circ}C$, with/without post annealing at 650$^{\circ}C$ for 30 min. The PZT thin films deposited above 500$^{\circ}C$ without post annealing were crystallized into peroveskite phase, but the PZT thin films deposited below 450$^{\circ}C$ had pyrochlore phase. The PZT thin films deposited below 450$^{\circ}C$ with post annealing also crystallized into pure perovskite. Compared to the PZT thin films which were deposited at 450$^{\circ}C$ and post annealed, the films deposited at 550$^{\circ}C$ have a columnar microstructure and high remnant polarization 28 (${\mu}$C/cm$^2$). With in-situ annealing at oxygen ambient, the PZT thin films reduced oxygen vacancies and increased retained polarization.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.365-366
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• 2005

PZT films are the most intensively investigated because PZT has advantages such as low processing temperature and large remnant values. In this paper, the microstructure and electric properties of $Pb(Zr_x,Ti_{(1-x)})O_3/BaTiO_3$ heterolayered thick films with Zr mole ranging from 30 to 70 % screen printed onto a alumina substrate were studied. $Pb(Zr_x,Ti_{(1-x)})O_3$ and $BaTiO_3$ powders were prepared by the sol-gel method. The $BaTiO_3$ powders were calcined at $700^{\circ}C$ for 2 hours. Structural properties of $Pb(Zr_x,Ti_{(1-x)})O_3/BaTiO_3$ multilayered thick films were investigated. As a result of the X-ray diffraction (XRD) analysis, $Pb(Zr_x,Ti_{(1-x)})O_3/BaTiO_3$ exhibited a perovskite polycrystalline phase without pyrochlore phase or any preferred orientation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.433-438
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• 1987

The current-voltage characteristics of the ZnO varisor with and without Sb2O3 which were fabricated with the various calcination and sintering temperature were discussed by comparing the results of SEM-microstructures and X-ray diffraction analysis. The samples were calcined at the temperature up to 800\ulcorner for 2 hours and they were sintered at 1200-1300\ulcorner for 1 hour. Then, we applied the power up to dc 200 volt to the samples and measured the output current up to 100mA. The samples without Sb2O3 had lower nonlinear resistances at the all calcination and sintering temperatures due to the large grains because of not forming Spinel phase. The other samples contained Sb2O3 could form Pyrochlore and Spinel phases at the all calcination temperatures by X-ray diffraction phase analysis. We found that the Spinel phases which were formed at the calcination process inhibit growth of ZnO grain and give rise to the change of nonlinear resistances by SEM-microstructures. And we found that the base of ZnO grain growth control is strongly dependent on the behavior of Sb2O3 in calcination process.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.3
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• pp.155-160
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• 2000

The piezoelectric properties and the doping effect for$0.95Pb(Zr_xTi_{1-x})O_3+0.05Pb(Mn1/3Nb2/3)O_3$ compositions were studied. Also, the heat generation and the change of electromechanical characteristics, the important problem in practical usage, were investigated under high electric field driving. As a experiment results under low electric field, the values of kp and $\varepsilon33T$ were maximized, but Qm was minimized(Kp=0.57, Qm=1550) in the composition of x=0.51. In order to increase the values of Qm $Nb_2O_5$ was used as a dopant. As the result of that, the grain size was suppressed and the uniformity of grain was improved. Also, the values of kp decreased, and the values of Qm increased with doping concentration of $Nb_2O_5$. As a experiment results under high electric field driving, when vibration velocity was lower than 0.6[m/s], the temperature increase was $20[^{\circ}C]$, and the change ratio of mechanical quality factor was less than 10[%]. So, its electromechanical characteristics was very stable. Conclusively, piezoelectric ceramic composition investigated at this paper is suitable for application to high power piezoelectric devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.969-976
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• 2011

In this study we aims to evaluate the effects of 1/3 mol% $Co_3O_4$ addition on the reaction, microstructure development, resultant electrical properties, and especially the bulk trap and grain boundary properties of $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=2.0, 1.0, and 0.5) system (ZBS). The samples were prepared by conventional ceramic process, and characterized by XRD, density, SEM, I-V, impedance and modulus spectroscopy (IS & MS) measurement. In addition of $Co_3O_4$ in $ZnO-Bi_2O_3-Sb_2O_3$ (ZBSCo), the phase development, density, and microstructure were controlled by Sb/Bi ratio. Pyrochlore on cooling was reproduced in all systems. The more homogeneous microstructure was obtained in ZBSCo (Sb/Bi=1.0) system. In ZBSCo, the varistor characteristics were improved drastically (non-linear coefficient ${\alpha}$=23~50) compared to ZBS. Doping of $Co_3O_4$ to ZBS seemed to form $V^{\cdot}_o$(0.33 eV) as dominant defect. From IS & MS, especially the grain boundary of Sb/Bi=0.5 system is composed of electrically single barrier (0.93 eV) and somewhat sensitive to ambient oxygen with temperature.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1609-1613
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• 2007

(Ba,Sr,Ca)$TiO_3$ powders, which were prepared by sol-gel method using a solution of Ba-, Sr- and Ca-acetate and Ti iso-propoxide, were mixed with organic vehicle and the BSCT thick films were fabricated by the screen-printing techniques on high purity alumina substrates. The structural and dielectirc properties were investigated for various $Dy_2O_3$ doping contents. As a result of thermal analysis, the exothermic peak was observed at around 670^{\circ}C $ due to the formation of the polycrystalline perovskite phase. All BSCT thick films, sintered at $1420^{\circ}C$ for 2h, showed the typical XRD patterns of perovskite polycrystalline structure and no pyrochlore phase was observed. The average grain size of the specimens decreased with increasing amount of $Dy_2O_3$. The average grain size and thickness of the BSCT specimens doped with 0.1 mol% $Dy_2O_3$ were approximately $1.9{\mu}m$ and $70{\mu}m$, respectively. The relative dielectric constant decreased and dielectric loss increased with increasing amount of $Dy_2O_3$, the values of the BSCT thick films doped with 0.1 mol% $Dy_2O_3$ were 3697 and 0.4% at 1 kHz, respectively. The leakage current densities in all BSCT thick films were less than $10^{-9}A/cm^2$ at the applied electric field range of 0-20 kV/cm.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.1
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• pp.14-20
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• 2018

Lead zinc niobate (PZN) added lead zirconate titanate (PZT) thick films with thickness of $5{\sim}10{\mu}m$ were fabricated on silicon and sapphire substrates using aerosol deposition method. The contents of PZN were varied from 0 %, 20 % and 40 %. The initial particles (PZT, 2PZN-8PZT, 4PZN-6PZT) had irregular shape and submicron sizes. The as-deposited film had fairly dense microstructure without any crack, and showed only a perovskite single phase formed with nano-sized grains. The as-deposited films on silicon were annealed at the temperatures of $700^{\circ}C$, and the films deposited on sapphire were annealed at $900^{\circ}C$ in the electrical furnace. The effects of PZN addition on the microstructural evolution were observed using by FE-SEM and HR-TEM.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.233-240
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• 1997

The Ru-based thick film resistor(TFR) for sintering at 90$0^{\circ}C$ was synthesized to prepare the LCR net-work. These compositions of pyrochlore could be prepared by decreasing the amount of PbO and increasing alumina and silica contents of glass frit. In this study, the sheet resistances of the TFTs. which sint-ered at 90$0^{\circ}C$ after printing on alumina substrate, the sheet resistances of the TFRs on inductor and capa-citor substrate and the interphase between TFR and substrate were observed. And the changes of the sheet resistance were obtained with the contents of RuO2. In case of the TFR sintered at 90$0^{\circ}C$, the sheet resis-tances on alumina substrates were in the range of 103~106$\Omega$/$\square$, but the sheet resistances of TFR on in-ductor and capacitor substrate were not obtained.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.20.2-20.2
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• 2011

BMNO dielectric materials with a pyrochlore structure have been chosen and they have quite high dielectric constants about 210 for the bulk material. In the case of thin films, 200-nm-thick BMNO films deposited at room temperature showed a low leakage current density of about $10^{-8}\;A/cm^2$ at 3 V and a dielectric constant of about 45 at 100 kHz. Because high dielectric constant BMNO thin films kept an amorphous phase at a high temperature above $900^{\circ}C$. High dielectric constant BMNO thin films grown at room temperature have many applications for flexible electronic devices. However, because the dielectric constant of the BMNO films deposited at room temperature is still low, percolative BMNO films (i.e., those were grown in a pure argon atmosphere) sandwiched between ultra-thin BMNO films grown in an oxygen and argon mixture have greater dielectric constants than standard BMNO films. However, they still showed a leakage problem at a high voltage application. Accordingly, a new nano-structure that uses BMNO was required to construct the films with a dielectric constant higher than that of its bulk material. The fundamental reason that the BMNO-Bi nano-composite films grown by RF-Sputtering deposition had a dielectric constant higher than that of the bulk material was addressed in the present study. Also we used the graphene as bottom electrode instead of the Cu bottom electrode. At first, we got the high leakage current density value relatively. but through this experiment, we could get improved leakage current density value.