• Journal of the Korean Ceramic Society
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• v.33 no.6
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• pp.672-678
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• 1996

The relationship between domain switching and acoustic emission (AE) during poling was investigated using the tetragonal ferroelectric ceramics with composition of (Pb,La)TiO3+0.01MnO2 The amount of AE generation during poling increased with increasing dc electric field and raising temperature. It was confirmed that the change of the amount of AE generation with poling condition resulted from the difference of the amount of 90$^{\circ}$ domain switching and total amount of AE generation for 10 minutes was approximately proportional to the amount of 90$^{\circ}$domain switching. The A generations of two specimens which have different tetragonality rations(c/s rations) 15 at% and 24at% La-doped were also investigated. The sample with c/a ratio of 1.012 where 90$^{\circ}$ domains are dominate had larger amount of AE generation and 90$^{\circ}$ domain switching compared with the sample with c/a ratio of 1.004 where 180$^{\circ}$ domains are dominant.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.18-18
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• 2002

Although it was suggested in 1962 that an efficient wavelength conversion could be achieved using ferroelectric crystals of periodic 180° domains, it was not until 1990's that quasi-phase-matching (QPM) became realized, as technology for periodic poling of LiNbO₃ crystals was readily available. Since ferroelectric domain inversion brings about change of the sign of second-order nonlinear susceptibility, periodically poled ferroelectric structures provide an ideal way of achieving QPM for second-harmonic generation and optical parametric oscillation. Periodically poled ferroelectric domains can also be utilized for optical devices, such as Brags electrooptic modulators. fabrication of stable periodic domain structures depends on a number of poling parameters of a ferroelectric crystal, such as coercive field, internal field and electrical conductivity. We present poling kinetics of KNbO₃ crystals, which involve domain nucleation and growth, backswitching, relaxation of internal field. Optimum poling conditions were established by designing a proper wave shape of external field. We demonstrate an efficient second-harmonic generation using QPM in a periodically poled KNbO₃ crystal.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.7
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• pp.550-554
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• 2013

Carbon nanotubes (CNT) / polyvinylidene fluoride (PVDF) piezoelectric composite films for nanogenerator devices were fabricated by spray coating method. When the CNT/PVDF mixture solution passes through the spray nozzle with small diameter by the compressed nitrogen gas, electric charges are generated in the liquid by a triboelectric effect. Then randomly distributed ${\beta}$ phase PVDF film could be re-oriented by the electric field resulting from the accumulated electrical charges, and might be resulted in extremely one-directionally aligned ${\beta}$ phase PVDF film without additional electric field for poling. X-ray diffraction patterns were used to investigate crystal structure of the CNT/PVDF composite films. It was confirmed that they revealed extremely large portion of the ${\beta}$ phase PVDF crystalline in the film. Therefore we could obtain the poled CNT/PVDF piezoelectric composite films by the spray coating method without additional poling process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.20-24
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• 2019

Ferroelectric material properties are strongly governed by domain structures and their evolution processes, but the evolution processes of complex domain patterns during a macroscopic electrical poling process are still elusive. In the present work, domain-evolution processes in a PZT ceramic near the morphotropic phase-boundary composition were studied during a step-wise electrical poling using piezoresponse force microscopy (PFM). Electron backscatter diffraction was used with the PFM data to identify the grain boundaries in the region of interest. In response to an externally the applied electric field, growth and retreat of non-$180^{\circ}$ domain boundaries wasere observed. The results indicate that ferroelectric polarization-switching nucleates and evolves in concordance with the pattern of the pre-existing domains.

• Bulletin of the Korean Chemical Society
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• v.6 no.4
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• pp.218-221
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• 1985

Transient charging and discharging currents as well as space charge limited currents have been measured in biaxially stretched poly(vinylidene fluoride) film under various poling fields and temperatures. At low temperatures and short poling times, the I-V characteristics showed shallow trap behavior. When the current values extrapolated to the infinite time, the I-V characteristics indicate that the distribution of the trap energy levels is uniform or very broad. The abnormal suppression of current at higher poling voltages and the high discharge rate observed also in the same voltage range are attributed to the morphological changes due to dipole reorientation.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.86.2-86.2
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• 2000

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.423-427
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• 2003

Effect of the thermal poling on the 1.55 fm emission spectra in various Er$^{3+}$ -doped glasses was investigated with a special attention on the changes in the values of FWHM(Full Width at Half Maximum) intensity. Tellurite glasses poled at 28$0^{\circ}C$ with an electric voltage of 4 kV resulted in an approximately 6% increase in FWHM values compared with their unpoled counterparts. On the other hand, values for glasses, such as aluminosilicate, sulfide and chalcohalide, either decreased or remained unchanged. The characteristic results from tellurite glasses are most probably due to the presence of lone-pair electrons in the TeO$_4$ hi-pyramidal units that form the main network structure of tellurite glasses.

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.377-381
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• 1997

Poling condition in 2 mol% MgO-doped $LiNbO_3$ crystals is investigated by varying the amplitude of poling electric field from 3V/cm to 7V/cm. It is found that 5V/cm is the best value for the formation of single domain by analysing the characteristics of the second harmonic generation(SHG) as the function of temperature. The temperature dependence of the phase-matching profile of SHG for the crystal applied by a spatially modulated electric field is observed to be very different from the simple sinc function. The distorted profile can be consistently fitted with the numerical simulations. This shows that the crystal homogeneity can be tested by the SHG temperature phase-matching profile. In addition, the thermo birefringence coefficient and electro birefringence coefficient of SHG were measured from the temperature dependence of phase-matching profile and shifts of phase-matching temperature by appling electric field along c-axis.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.291-295
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• 2000

The pyroelectric property of $Pb_{0.9}La$_{0.1}TiO_3$ceramics in a range of 1.3-4.1$\mu\textrm{m}$, fabricated by conventional solid sintering, was investigated as a function of poling field. The pyroelectric of the 4.1$\mu\textrm{m}$ of $Pb_{0.9}La$_{0.1}TiO_3$ceramics is higher than that of the 1.3$\mu\textrm{m}$ and 1.7$\mu\textrm{m}$ of $Pb_{0.9}La$_{0.1}TiO_3$ceramics at a low poling field and the pyroelectric coefficient is 25nC/$\textrm{cm}^2$K at a 4kV/mm poling field in every grain size. In order to explain this phenomenon, the intrinsic and extrinsic effects in view of the definition of the pyroelectric coefficient are introduced. The intrinsic and extrinsic effects on the pyroelectric property were investigated by measuring the tetragonal ratio and the $I_{002}$ with temperature with high temperature X-ray diffractometer. The change of spontaneous polarization and the $90^{\circ}$domain wall motion with temperature in the 1.3$\mu\textrm{m}$ and 4.2$\mu\textrm{m}$ of $Pb_{0.9}La$_{0.1}TiO_3$ceramics have no effects on the pyroelectric coefficient. In our study, it can be seen that the pyroelectric coefficient is related to the quantity of $180^{\circ}$domain switching after poling treatment.

• Current Photovoltaic Research
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• v.3 no.1
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• pp.5-9
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• 2015

Absorption and luminescence characteristics of disperse red-19 (DR-19) and $TiO_2$ composite have been investigated with various poling electric field strengths. Two step synthetic processes were employed to employ the DR-19 to the $TiO_2$ sol-gel. Firstly, urethane bond formation between DR-19 (-OH) and 3-isocyanatopropyl triethoxysilane (ICPTES, -N=C=O) performed (ICPDR) prior incorporation to the $TiO_2$ sol-gel. Secondary, the hydrolysis of the ethoxy group from the ICPTES and condensation reaction between silanol groups from ICPTES and $TiO_2$ sol-gel were performed. The ICPDR and $TiO_2$ sol-gel ($DRTiO_2$) were mixed and stirred for several days. The composite was coated to the ITO coated glass substrate. Corona poling were performed before drying the composite with various electric field strengths. The absorption intensity decreased with the increase of the poling field strength, which resulted in the increase of poling efficiency. The photoluminescence also decreased as the poling field strength increased. There is long luminescence tail for the poled $DRTiO_2$ film compared with unpoled $DRTiO_2$ film. The luminescence long tail indicates that the self-trapped excitons and polarons were generated when the $DRTiO_2$ film was poled with electric field.