• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.120-125
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• 2005

Effect of transverse electric fields on fracture behavior in ferroelectric ceramics under purely electrical loading is investigated. It is shown that the shape and size of the domain switching zone depend strongly on the ratio of the transverse electric field to the coercive electric field as well as the direction of the applied electric field. Under small-scale conditions, the crack-tip mode I and II stress intensity factors induced by ferroelectric domain switching are numerically obtained. The crack kinking in ferroelectric ceramics is also discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.577-584
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• 2003

A crack with growth in ferroelectric ceramics under purely electric loading is analyzed. The crack tip stress intensity factor for the growing crack under small-scale conditions is evaluated by employing the model of nonlinear domain switching. The crack tip stress intensity factor increases or decreases with crack growth, depending on the electrical nonlinear behavior and the direction of an applied electric field. It is shown that the ferroelectric material can be either toughened or weakened as the crack grows. The steady state crack growth in ferroelectric ceramics is also discussed.

• Journal of the Korean Ceramic Society
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• v.56 no.4
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• pp.412-420
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• 2019

In this study, the dielectric and polarization properties of manganese (Mn% = 0.0, 0.1, 0.2, 0.5) doped (Pb_0.93La_0.07)(Zr_0.82Ti_0.18)O₃ (PLZT 7/82/18) anti-ferroelectric ceramics were studied for energy storage capacitor and pyroelectric applications. A systematic investigation demonstrated that the electric properties of PLZT 7/82/18 ceramics are affected significantly by the Mn-doping content. A maximum dielectric constant of ~ 2,128 at 1 kHz was found for 0.1% Mn-doped PLZT ceramics with a low dielectric loss of 0.018. The bipolar polarization versus electric field (P-E) hysteresis loops were traced for all compositions showing a typical anti-ferroelectric nature. The breakdown field was found to decrease with Mn-doping. The energy storage density and efficiency were found to be 460 J/㎤ and ~ 63%, respectively, for 0.2% Mn-doped PLZT ceramics. The pyroelectric coefficient of PLZT ceramics shows an increase based on the amount of Mn-doping.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.286-291
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• 1998

Dielectric properties of $Pb(Mg_{1/3}Nb_{2/3})O_{3}-PbTiO_{3}$, ceramics prepared by the columbite precursor method have been investigated as a function of the sintering temperature in the range of 1000∼$1250^{\circ}C$. The $Pb(Mg_{1/3}Nb_{2/3})O_{3}-PbTiO_{3}$ ceramics show typical relaxor ferroelectric behavior. As the sintering temperature increased, the dielectric constant increased and the phase transition temperature shifted to lower temperature. The TCK(temperature coefficient of dielectric constant) and VRK (variation rate of dielectric constant) increased with increasing sintering temperature. The $Pb(Mg_{1/3}Nb_{2/3})O_{3}-PbTiO_{3}$ compositions sintered at $1250^{\circ}C$ appear to be suitable for ferroelectric bolometer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.164-167
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• 2016

In this study, in order to develop relaxor ferroelectric ceramics for refrigeration device application with large electrocaloric effect, PLZT(8/65/35) composition was fabricated using conventional solid-state method. The Curi temperature of this composition PLZT ceramics was $230^{\circ}C$, and the P-E hysteresis loops of the PLZT ceramics as a fuction of temperature became slim by degrees with higher temperatures. The maximum value of ${\Delta}T$ of $0.243^{\circ}C$ in ambient temperature of $215^{\circ}C$ with 30 kV/cm was appeared. It is considered that PLZT ceramics possess the possibility of refrigeration device application.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.142-149
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• 2003

Domain switching effect on crack growth in ferroelectric ceramics under combined electric and mechanical loading is investigated. The shape and size of the switching zone is shown to depend strongly on the relative magnitude between the applied electric field and stress field as well as on the ratio of the coercive electric field to the yield electric field. The toughening mechanism is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. Crack-tip stress intensity factor induced by domain switching for the steady state crack growth is numerically obtained.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.29.2-29.2
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• 2011

B-site substitution with isovalent and donor impurities was compared in terms of the piezoelectric properties of Bi-based ABO3 perovskite ceramics. X-ray diffraction study revealed that both impurities bring about degradation in their ferroelectric properties as well as piezoelectric characteristics. However, there existed a difference between the isovalent and heterovalent impurities that influence a phase transformation of ferroelectric anisotropic-to-electrostrictive pseudocubic symmetry. Based upon analyses including the crystal, microstructure, dielectric, ferroelectric properties, we believed that A-site vacancies in the ABO3 ceramic significantly contribute to a ferroelectric-nonpolar phase transition, which give rise to lead to a giant strains. The present paper will discuss the origin of giant strains in Bi-based perovskite ceramics.

• Journal of the Korean Ceramic Society
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• v.29 no.6
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• pp.459-462
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• 1992

It has been reported that the size and characteristics of ferroelectric domains which have an essential role on the ferroelectric properties depend on the grain size of ferrolectric ceramics. Therefore understanding the change of domain characteristics with grain size is so important to know the dependence of dielectric constant, dielectric loss and aging on the grain size. In this research, the equilibrim domain with is calculated as d={{{{ SQRT { { 64 pi sigma a} over {3C11Ss2 } } }}. This calculated value is nearly same to the measured value of BaTiO3 and Pb(Zr0.4Ti0.6)O3 ceramics 90$^{\circ}$domain wall width. The calculated 90$^{\circ}$domain wall enerygy in Pb(Zr0.4Ti0.6)O3 which is obtained through the model is approximately 2$\times$10-2J/$m^2$.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.262-266
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• 2000

We investigated the effect of the grain size on the photovoltaic current in (Pb$_{1-x}$La$_x$)TiO$_3$ceramics, and the photoinduced domain switching in (Pb$_{0.85}$La$_{0.15}$)TiO$_3$and BaTiO$_3$ceramics. These behaviors in ferroelectric ceramics were attributed to the grain boundary at which photoexcited electrons were trapped. As the charged grain boundary acted as an electro-potential barrier which impeded the movement of electrons, the photovoltaic current showed a peak at a critical grain size. The space charge field built by the electrons trapped at the grain bound-aries was accounted for the photoinduced domain switching, and AE experimental results support well this account.

• Journal of the Korea Computer Industry Society
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• v.6 no.5
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• pp.741-748
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• 2005

Power saving module which is consisted of ferroelectric ceramic capacitor and time delay switching circuit was installed into electronic ballast in order to enhance energy efficacy and extend life time of fluorescent lamp. The impedance matching of negative resistance characteristics of F/L was optimized with the characteristics of ferroelectric ceramics capacitor to increase the light efficiency of the electronic ballast. The high efficiency of the electronic ballast was achieved by minimizing wasted power at the filament of F/L during the lighting by using the switching function of time delay circuit from preheating mode to non-preheating mode. The life time of F/L was also extended by eliminating the reverse electromotive force using time delay circuits to minimize the impacts to the filament of F/L from unwanted high voltage peaks during light-up period. As the results, the electronic ballast with the first grade energy efficiency was developed using ferroelectric ceramics and time delay module.