• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.904-911
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• 2001

High-density lead zirconate titanate(Pb(Zr$\_$0.53/Ti$\_$0.47/)O$_3$, PZT) ceramics were fabricated by a new milling-precipitation(MP) process improved from the conventional solid state process. This process was progressed by a milling impregnation through mixing ZrO$_2$ and TiO$_2$ powders with lead nitrate(Pb(NO$_3$)$_2$) water solution in zirconia ball media, and then milling precipitation was induced from precipitation of PbC$_2$O$_4$ by adding ammonium of oxalate monohydrate((NH$_4$)$_2$C$_2$O$_4$$.$H$_2$O) as a precipitant. As a result of this process, single-phase perovskite structure was formed at the calcination temperature of 750$\^{C}$ for Pb(Zr$\_$0.53/Ti$\_$0.47/)O$_3$ powders. In addition, the highest density at the sintering temperature of 1100$\^{C}$ was obtained, because of the highly sinterable PZT Powders ground through the re-milling process. Piezoelectric and dielectric properties of sintered sample were improved by MP process.

• Korean Journal of Materials Research
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• v.25 no.6
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• pp.288-292
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• 2015

New lead-free piezoelectric ceramics $0.96[\{Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}\}_{1-x}La_x(Ti_{1-y}Nb_y)O_3]-0.04SrTiO_3$ (BNKT-ST-LN, where $x=y=0.00{\leq}(x=y){\leq}0.015)$ were synthesized using the conventional solid-state reaction method. Their crystal structure, microstructure, and electrical properties were investigated as a function of the La and Nb (LN) content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNKT-ST ceramics in this study. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature ($T_m$) shifted towards lower temperatures and the curves became more diffuse with an increasing LN content. At the optimum composition (LN 0.005), a maximum value of remnant polarization ($33C/cm^2$) with a relatively low coercive field (22 kV/cm) and high piezoelectric constant (215 pC/N) was observed. These results indicate that the LN co-modified BNKT-ST ceramic system is a promising candidate for lead-free piezoelectric materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.135-136
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• 2006

Bismuth titanate ($Bi_4Ti_3O_{12}$, BIT) thin film has been studied intensively in the past decade due to its large remanent polarization, low crystallization temperature, and high Curie temperature. Substitution of various trivalent rare-earth cations (such as $La^{3+}$, $Nd^{3+}$, $Sm^{3+}$ and $Pr^{3+}$) in the BIT structure is known to improve its ferroelectric properties, such as remanent polarization and fatigue characteristics. Among them, neodymuim-substituted bismuth titanate, ((Bi, Nd)$_4Ti_3O_{12}$, BNT) has been receiving much attention due to its larger ferroelectricity. In this study, Ferroelectric $Bi_{3.3}Nd_{0.7}Ti_3O_{12}$ thin films were successfully fabricated by liquid delivery MOCVD process onto Pt(111)/Ti/$SiO_2$/Si(l00) substrates. Fabricated polycrystailine BNT thin films were found to be random orientations, which were confirmed by X-ray diffraction and scanning electron microscope analyses. The remanent polarization of these films increased with increase in annealing temperature. And the film also demonstrated fatigue-free behavior up to $10^{11}$ read/write switching cycles. These results indicate that the randomly oriented BNT thin film is a promising candidate among ferroelectric materials useful for lead-free nonvolatile ferroelectric random access memory applications.

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.82-86
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• 2013

A poled lead zirconate titanate (PZT) cube specimen is subjected to impulse-type compressive stress with increasing magnitude in parallel to the poling direction at four room and high temperatures. During the ferroelastic domain switching induced by the compressive stress, electric displacement in the poling direction and longitudinal and transverse strains are measured. Using the measured responses, linear material properties, namely, the piezoelectric and elastic compliance coefficients, are evaluated by a graphical method, and the effects of stress and temperature are analyzed. Finally, the dependency of the evaluated linear material properties on relative remnant polarization is analyzed and discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.9
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• pp.546-550
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• 2017

Ferroelectric properties are governed by domain structures and domain wall motions, so it is of significance to understand domain evolution processes under mechanical stress. In the present study, in situ piezoresponse force microscopy (PFM) observation under compressive stress was carried out for a near-morphotropic PZT. Both $180^{\circ}$ and $non-180^{\circ}$ domain structures were observed from PFM images, and their habit planes were identified using electron backscatter diffraction in conjunction with PFM data. By externally applied mechanical stress, needle-like $non-180^{\circ}$ domain patterns were broadened via domain wall motions. This was interpreted via phenomenological approach such that the total energy minimization can be achieved by domain wall motion rather than domain nucleation mainly due to the local gradient energy. Meanwhile, no motion was observed from curvy $180^{\circ}$ domain walls under the mechanical stress, validating that $180^{\circ}$ domain walls are not directly influenced by mechanical stress.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.164-164
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• 2009

A multilayer piezoelectric transformer(MPT) for step-down voltage was made by ceramic stack process. And then, the characteristics of piezoelectric transformer, such as resonance frequency, matching impedance, electro-mechanical coupling coefficient, voltage gain, heat generation and efficiency, are analyzed. The piezoelectric transformer consists of a lead zirconate titanate ceramic with a high electromechanical quality factor. The piezoelectric transformer, with a multilayered construction in the thickness direction, was formed with dimensions 15mm long, 15mm wide and 5mm thick.

• Journal of the Korean Ceramic Society
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• v.29 no.11
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• pp.870-876
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• 1992

Lead lanthanum zirconate titanate (PLZT, 6/65/35) powders, crack-free and dense thin films have been prepared by polymeric sol-gel process. Pyrolysis of the gel, crystallization and optical transmittance behavior of the PLZT thin film onto sapphire substrate have been studied. Esterification occurs during synthesis of PLZT complexation. Crystalline Pb phase was transiently formed near 450$^{\circ}C$. Content of perovskite phase in the films were increased with increasing thickness of film, but the kinetics of formation of perovskite phase in films was slower than that of powders. Transmittance of the films was decreased with increasing the temperature of heat treatment. Ferroelectric hysteresis loop measurements indicated increments of remanent polarization and coercive field for plenty more of perovskite phase.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.670-676
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• 1989

The PbTiO3 is well known materials having remarkable ferroelectric, piezoelectric, and pyroelectric properties. PbTiO3 thin films with a perovskite structure were successfully fabricated on titanium substrate by chemical vapor deposition. These films were characterized according to composition, crystal structure, and electrical properties. Semi-quantitative compositional analysis of the deposited films was made by Auger Electron Spectroscopy(AES). The PbTiO3 film deposited on titanium substrate at the deposition temperature 75$0^{\circ}C$, the Ti(C2H5O)4 fraction 0.15, and O2 partial pressure 0.06atm, has a columnar structure and grows with(001) preferred orientation, and has stoichiometric composition. A clear dielectric transition and offset in the dc conductivity near the transition temperature(48$0^{\circ}C$) were observed in the deposited lead titanate film.

• Journal of the Korean Ceramic Society
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• v.25 no.4
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• pp.349-356
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• 1988

The PTCR characteristics of (Ba0.8Pb0.2)TiO3 ceramics prepared by the molten salt sysnthesis (MSS) method have been investigated as a function of the amount of Nb2O5 dopant and KCl flux. When the weight ratio of KCl to raw material is 0.8, the resistivity at room temperature decreases with increasing amount of Nb dopant up to 0.6 atom%. It can be explained by compensation for electrons due to Nb+5 ion and holes due to K+ ion. The resistivity of (Ba0.8Pb0.2)(Ti0.994Nb0.006)O3 ceramics at room temperature decreases with increasing the ratio of KCl to raw material up to 0.6, and then increases. These results can be explained by the effect of K+ ion.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.188-191
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• 2005

Taguchi method is used to determine the optimal configuration of PZT (Lead Zirconate-Titanate) patch on the host structure for improving the performance of piezoelectric shunt system. The charges generated on the surface of PZT patch are selected to be the objective function in the Taguchi method. Full three dimensional finite element models are used to simulate vibration of smart panel and to obtain the admittance of the piezoelectric shunt system. Using Taguchi method in Minitab, the optimal model is obtained. The experiment with piezoelectric shunt circuit is performed to verify the validity of the optimal model comparing with initial model.