• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.56-64
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• 1996

A large amount of papers about the cubic-to-tetragonal phase transition the ferroelectric domain structures of the BaTiO3 were already reported but there exist still some needs to observe the domain behaviors directly. In this study the domain structures of the tinned plates prepared from ta single crystal grown by the TSSG technique were observed using a polarizing microscope TE and X-ray topography. The spatial relation be-tween the orientation states of domains was investigated and the effects of external stresses and electric fields on the behaviors of ferroelectric and ferroelastic domains were studied. All the 90$^{\circ}$walls cut off in the crystal are the wedge shaped lamellar domains and all the straight boundaries in the observed domain patte군 can be interpreted as the head-to-tail 90$^{\circ}$walls. The irregular overlapped boundaries commonly observed by using a polarizing microscope and X-ray topography are complex combinations of well-known 90$^{\circ}$walls and are domain walls were predominant and were stabilized after surface polishing. In the paraelectric phase region the domain walls vanished but the residual surface strain patterns could be seen at the same positions of the stabilized 90$^{\circ}$a-a walls in the tetragonal phase region, These stabilized walls resulted from the surface strain had a memory effect in domain formation during the repeated phase transitions and could notr be affected by an external electtric field.

• Journal of the Korean Ceramic Society
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• v.33 no.2
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• pp.228-234
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• 1996

It is very important to understand the domain structures of ferroelectric BaTiO3 in the poling process. Especially because {111} twinning is frequently observed in most BaTiO3 ceramics it is required to know the relations between the ferroelectric domains and the structural twin. In this study the domain structures of a {111} twinned crystal sample were observed under a polarizing microscope. and the relation between the {111} twin and the domain configurations could be classified into two types of 'V'-shape and linear shape penetrating perpendicular to the twin boundary. Domain formation obeys the symmetry of the {111} twining when a new domain structure is developed by heat treatment and surface deformation due to domain formation is also occured symmetrically between the both sides of the{111} twin boundary. This symmetrical behavior of the domains could be interpreted with the "head-to-tall" orientation of the domains across the {111} twin boundary.

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1047-1057
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• 2003

A sub-nanometer resolution Scanning Nonlinear Dielectric Microscope (SNDM) was developed for observing ferroelectric polarization. We also demonstrate that the resolution of SNDM is higher than that of a conventional piezo-response imaging. Secondly, we report new SNDM technique detecting higher nonlinear dielectric constants $\varepsilon$$\_$3333/ and $\varepsilon$$\_$33333/. Higher order nonlinear dielectric imaging provides higher lateral and depth resolution. Finally, the formation of artificial small inverted domain is reported to demonstrate that SNDM system is very useful as a nano-domain engineering tool. The nano-size domain dots were successfully formed in LiTaO$_3$ single crystal. This means that we can obtain a very high density ferroelectric data storage with the density above 1T-bits/inch$^2$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.73.1-73.1
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• 2007

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.620-626
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• 1996

$LiNbO_{3}$ single crystals were grown using a self-designed radio-frequency heating Czochralski crystal grower. Congruently melting composition was used and the optimum growth conditions were established. The compensated power control method was very effective to control the outer diameter of the crystal ingots within ${\pm}5\;%$. Scanning electron microscopy was performed to characterize the effect of the $Mg^{2+}$ ions on the formation of the ferroelectric domain in $LiNbO_{3}$.

• Macromolecular Research
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• v.12 no.1
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• pp.1-10
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• 2004

The structural changes occurring in the isothermal crystallization processes of polyethylene (PE), poly-oxymethylene (POM), and vinylidene fluoridetrifluoroethylene (VDFTrFE) copolymer have been reviewed on the basis of our recent experimental data collected by the time-resolved measurements of synchrotron-sourced wide-angle (WAXS) and small-angle X-ray scatterings (SAXS) and infrared spectra. The temperature jump from the melt to a crystallization temperature could be measured at a cooling rate of 600-1,000 $^{\circ}C$/min, during which we collected the WAXS, SAXS, and infrared spectral data successfully at time intervals of ca. 10 sec. In the case of PE, the infrared spectral data clarified the generation of chain segments of partially disordered trans conformations immediately after the jump. These segments then became transformed into more-regular all-trans-zigzag forms, followed by the formation of an orthorhombic crystal lattice. At this stage, the generation of a stacked lamella structure having an 800-${\AA}$-long period was detected in the SAXS data. This structure was found to transfer successively to a more densely packed lamella structure having a 400-${\AA}$-long period as a result of the secondary crystallization of the amorphous region in-between the original lamellae. As for POM, the formation process of a stacked lamella structure was essentially the same as that mentioned above for PE, as evidenced from the analysis of SAXS and WAXS data. The observation of morphology-sensitive infrared bands revealed the evolution of fully extended helical chains after the generation of lamella having folded chain structures. We speculate that these extended chains exist as taut tie chains passing continuously through the neighboring lamellae. In the isothermal crystallization of VDFTrFE copolymer from the melt, a paraelectric high-temperature phase was detected at first and then it transferred into the ferroelectric low-temperature phase at a later stage. By analyzing the reflection profile of the WAXS data, the structural ordering in the high-temperature phase and the ferroelectric phase transition to the low-temperature phase of the multi-domain structure were traced successfully.

• Korean Journal of Materials Research
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• v.29 no.3
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• pp.150-154
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• 2019

This study investigates the effect of MnO2 and CuO as acceptor additives on the microstructure and piezoelectric properties of $0.96(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}Nb_{0.93}Sb_{0.07}O_3-0.04BaZrO_3$, which has a rhombohedral-tetragonal phase boundary composition. $MnO_2$ and CuO-added $0.96(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}Nb_{0.93}Sb_{0.07}O_3-0.04BaZrO_3$ ceramics sintered at a relatively low temperature of $1020^{\circ}C$ show a pure perovskite phase with no secondary phase. As the addition of $MnO_2$ and CuO increases, the sintered density and grain size of the resulting ceramics increases. Due to the difference in the amount of oxygen vacancies produced by B-site substitution, Cu ion doping is more effective for uniform grain growth than Mn ion doping. The formation of oxygen vacancies due to B-site substitution of Cu or Mn ions results in a hardening effect via ferroelectric domain pinning, leading to a reduction in the piezoelectric charge coefficient and improvement of the mechanical quality factor. For the same amount of additive, the addition of CuO is more advantageous for obtaining a high mechanical quality factor than the addition of $MnO_2$.