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127 results on '"Yokota, Hiroko"'

1. Impact of Oxygen Pressure on Ferroelectric Stability of La-doped Hafnia Grown by PLD

Author

Rao, Badari Narayana, Yasui, Shintaro, and Yokota, Hiroko

Subjects
Condensed Matter - Materials Science
Abstract

Thin films of HfO2 doped with 4% La were fabricated on LSMO/STO (100) substrates using pulsed laser deposition. The stability of the ferroelectric orthorhombic phase in the hafnia films was investigated with respect to varying oxygen pressure during deposition. X-ray diffraction and X-ray photoelectron spectroscopy measurements were carried out to analyze the structure and composition of the films and correlated with their ferroelectric properties. Surprisingly, the ferroelectricity of the hafnia films showed a dependence on oxygen pressure during deposition of LSMO bottom electrode as well. The reason for this dependence is discussed in terms of the active role of non-lattice oxygen in the ferroelectric switching of hafnia.

Published
2023

4. Second harmonic generation and X-ray diffraction studies of pretransitional region in relaxor K(1-x) LixTaO3

Author

Yokota, Hiroko, Uesu, Yoshiaki, Malibert, Charlotte, and Kiat, Jean-Michel

Subjects
Condensed Matter - Materials Science
Abstract

Optical second-harmonic-generation(SHG) observations and precise X-ray diffraction experiments have been performed on quantum paraelectrics KTaO3 (KTO) and relaxor K(1-x)LixTaO3 with x=3% (KLT-3) and 7% (KLT-7). It is found in KLT-3 and KLT-7 that a pretransitional region exists between two characteristic temperatures Td and Tp (

Published
2006
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5. SHG microscopic observations of polar state in Li-doped KTaO3 under electric field

Author

Yokota, Hiroko, Ohyama, Taeko, and Uesu, Yoshiaki

Subjects
Condensed Matter - Materials Science
Abstract

Incipient ferroelectric KTaO3 with off-center Li impurity of the critical concentration of 2.8 mol% was investigated in order to clarify the dipole glass state under electric field. Using optical second-harmonic generation (SHG) microscope, we observed a marked history dependence of SHG intensity through zero-field cooling (ZFC), zero-field heating (ZFH), field heating after ZFC (FH/ZFC) and FH after field cooling (FH/FC). These show different paths with respect to temperature: In the ZFC/ZFH process, weak SHG was observed at low temperature, while in the FH/ZFC process, relatively high SHG appears in a limited temperature range below TF depending on the field strength, and in the FC and FH/FC processes, the SHG exhibits ferroelectric-like temperature dependence: it appears at the freezing temperature of 50K, increases with decreasing temperature and has a tendency of saturation. These experimental results strongly suggest that dipole glass state or polar nano-clusters which gradually freezes with decreasing temperature is transformed into semi-macroscopic polar state under the electric field. However at sufficiently low temperature, the freezing is so strong that the electric field cannot enlarge the polar clusters. These experimental results show that the polar nano-cluster model similar to relaxors would be more relevant in KTaO3 doped with the critical concentration of Li. Further experiments on the anisotropy of SHG determine that the average symmetry of the field-induced polar phase is tetragonal 4mm or 4, which is also confirmed by the X-ray diffraction measurement., Comment: 26 pages, 8 figures, 1 table

Published
2005
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10. Tuning of Polar Domain Boundaries in Nonpolar Perovskite

Author

An, Zheyi, primary, Yokota, Hiroko, additional, Kurihara, Kyomaru, additional, Hasegawa, Nozomu, additional, Marton, Pavel, additional, Glazer, Anthony Michael, additional, Uesu, Yoshiaki, additional, Ren, Wei, additional, Ye, Zuo‐Guang, additional, Paściak, Marek, additional, and Zhang, Nan, additional

Published
2023
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12. Optical second-harmonic generation microscopy as a tool for ferroelastic domain wall exploration.

Author

Yokota, Hiroko and Uesu, Yoshiaki

Subjects
*DOMAIN walls (String models), *SECOND harmonic generation, *MICROSCOPY, *HIGH temperatures
Abstract

Domain walls (DWs) of four typical ferroelastics, CaTiO3 (CTO), LaAlO3 (LAO), Pb3(PO4)2 (PPO), and BiVO4 (BVO), were observed by the second harmonic generation (SHG) microscopy, and the results were compared. The DWs of the examined ferroelastics are all polar. This fact does not depend on whether the crystal is an insulator (CTO, LAO, and PPO) or a semiconductor (BVO), on whether it has ferroelectric instability (CTO) or not (LAO, PPO, and BVO), or on the DW state, namely, whether the DW is crystallographically prominent or non-prominent. The symmetry of these DWs was determined from the SHG anisotropy, and it was clarified that they are a subgroup of the high temperature phase. In the cases of CTO and PPO, stress was applied to move the DW, and its polarity and symmetry were examined. The main characteristics did not change even when stress was applied. In all samples, uniform SHG was observed for each DW. This indicates that the DWs of the examined ferroelastics seem to be in a ferroelectric single domain state. [ABSTRACT FROM AUTHOR]

Published
2021
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16. Enhancement of polar nature of domain boundaries in ferroelastic Pb3(PO4)2 by doping divalent-metal ions

Author

Yokota, Hiroko, Matsumoto, Suguru, Hasegawa, Nozomu, Salje, EKH, Uesu, Yoshiaki, Salje, Ekhard [0000-0002-8781-6154], and Apollo - University of Cambridge Repository

Subjects
domain boundary, second harmonic generation, domain boundary engineering, ferroelastics
Abstract

The effect of doping metal ions in ferroelastic Pb3(PO4)2 (PPO) on the polar nature of domain boundaries (DBs) was investigated using a second harmonic generation (SHG) microscope. It has been already reported that (DBs) of non-doped PPO is SH active and polar. The present study reveals that DBs of Ca-doped and Mg-doped PPO show greatly enhanced SH activity. This indicates that doping by metal ions enhances the polar nature of the DBs of PPO. This is important for future applications of DB nanotechnology. The enhancement of SH intensity is explained by a larger displacement of Ca2+ and Mg2+ ions in DBs due to smaller ionic radii. Analyses of the SH anisotropy experiments reveal that the symmetry-adapted W-wall belongs to monoclinic m and the non-adapted W'-wall to monoclinic 2. Both point groups are classified as the polar classes, which coincides with the case of pure PPO.

Published
2020

18. Domain wall generated polarity in ferroelastics: Results from resonance piezoelectric spectroscopy, piezoelectric force microscopy, and optical second harmonic generation measurements in LaAlO3 with twin and tweed microstructures

Author

Yokota, Hiroko, primary, Haines, C. R. S., additional, Matsumoto, Suguru, additional, Hasegawa, Nozomo, additional, Carpenter, Michael A., additional, Heo, Yooun, additional, Marin, Alexe, additional, Salje, E. K. H., additional, and Uesu, Yoshiaki, additional

Published
2020
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22. Lesson Program for Spatial Composition of 'House' with Different Structural Methods by Third Graders of Primary School

Author

Okinishi, Keiko, Yokota, Hiroko, Hattori, Futoshi, Sendai, Shouichirou, and Hikita, Atsushi

Abstract

本年度は，３年生児童によるワークショップを実施し，「結ぶ」，「組む」という異なる二つの製作手法を用いた，「安全な家」の模型づくりの授業を構成した。製作模型では，児童によって多少の個人差はあるが，床や屋根の構造のつくり方と制作のプロセスの変化に一定の類型があることが明らかになった。また、製作前後で行ったアンケートの分析では、「結ぶ」手法から「組む」手法へと変わった際に、空間に対して求めるものが変化することが分かった。模型製作手法という外的要因が児童の安全に対する意識に影響を与えたことを明らかにしたことが最大の成果である。児童の生活環境との相関，床面の構成の分析などが，今後の空間構成に関する研究の上での課題として残された。, In this year, we had the workshop by third grade students and make the lesson program for the making of a model as “secure house” with structural methods of “tying” and “wooden jointing”. In the making of models, though there are some individual differences, we found the definite types to make models: the floor or the roof structure, and the making process itself. In analysis of questionnaire before and after the workshop, what children desired for living space changed, when the method was changed from “tying” to “wooden jointing”. It is the important result that children’s conscious for secure was affected by external factor; the model making method. Theme relation of children’s living environment and analysis of structure of floor require further study.

Published
2017

23. A Examination about Course-specific Ability on the Subjects in the Course of Arts and Crafts and Arts.: Through the Visualization of Idea Processes

Author

Amano, Shinichi, Shimatani, Ayumi, Yamamoto, Fusami, Matsumoto, Hiroko, Matsuzaki, Shinichi, Yokota, Hiroko, Mine, Kazunami, and Yata, Chikahiko

Abstract

図画工作科・美術科固有の能力を形成する「発想」がどのようにして生まれ，促され，構想へと高まっていくのか，実際の授業場面でそのプロセスを可視化することは容易ではない。そしてこれが，美術教育に関する専門性や経験の十分でない多くの指導者にとって，この教科の指導を困難なものとする一因にもなっている。そこで，小・中学校の様々な発達段階の児童・生徒を対象とする具体的な授業実践を通して，絵画及び立体表現における発想プロセスの可視化を図るとともに，これを手がかりに「発想や構想の能力」を高める上で効果的な授業構想や手立ての在り方について探ることを目的に本研究に取り組んだ。学習過程を横軸，発想喚起要素（題材の特性にかかわる要素と技能的要素）を縦軸としたマトリクス表に基づく題材分析，発想を促すことに焦点化した手立ての吟味，ポートフォリオを活用した経過観察，そして個別に実施した自己評価アンケートの分析を通して，発達段階による発想の広がり方の違いや，発想に影響を与える様々な要素（鑑賞，材料，用具，協働的な学び等）についてある程度の知見を得ることができた。, We practiced lessons on elementary school children and junior high school students, and tried this visualization of ideas process on painting and stereoscopic expression. We did this research so that we could explore effective lesson plans and methods to raise "ability to create ideas and concepts." We got some findings about the differences in how the ideas spread in the developmental stage and various factors that influence ideas (appreciation, materials, tools, collaborative learning etc.). This analysis based on the matrix table with the horizontal axis of the learning process and the vertical axis of the elements that inspire ideas (elements related to the characteristics of the material and skill elements), and the examination of the methods focused on encouraging the ideas, and the follow-up observation using portfolios, and the analysis of self-evaluation questionnaires conducted individually.

Published
2017

26. New method to measure domain‐wall motion contribution to piezoelectricity: the case of PbZr0.65Ti0.35O3 ferroelectric.

Author

Gorfman, Semën, Choe, Hyeokmin, Zhang, Guanjie, Zhang, Nan, Yokota, Hiroko, Glazer, Anthony Michael, Xie, Yujuan, Dyadkin, Vadim, Chernyshov, Dmitry, and Ye, Zuo-Guang

Subjects
LATTICE constants, MOTION, FERROELECTRIC crystals, SIGNAL generators, ELECTRIC fields, PIEZOELECTRICITY
Abstract

A new data analysis routine is introduced to reconstruct the change in lattice parameters in individual ferroelastic domains and the role of domain‐wall motion in the piezoelectric effect. Using special electronics for the synchronization of a PILATUS X‐ray area detector with a voltage signal generator, the X‐ray diffraction intensity distribution was measured around seven split Bragg peaks as a function of external electric field. The new data analysis algorithm allows the calculation of 'extrinsic' (related to domain‐wall motion) and 'intrinsic' (related to the change in lattice parameters) contributions to the electric‐field‐induced deformation. Compared with previously existing approaches, the new method benefits from the availability of a three‐dimensional diffraction intensity distribution, which enables the separation of Bragg peaks diffracted from differently oriented domain sets. The new technique is applied to calculate the extrinsic and intrinsic contributions to the piezoelectricity in a single crystal of the ferroelectric PbZr1−xTixO3 (x = 0.35). The root‐mean‐square value of the piezoelectric coefficient was obtained as 112 pC N−1. The contribution of the domain‐wall motion is estimated as 99 pC N−1. The contribution of electric‐field‐induced changes to the lattice parameters averaged over all the domains is 71 pC N−1. The equivalent value corresponding to the change in lattice parameters in individual domains may reach up to 189 pC N−1. [ABSTRACT FROM AUTHOR]

Published
2020
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30. Three-dimensional observations of polar domain structures using a confocal second-harmonic generation interference microscope.

Author

Kaneshiro, Junichi, Kawado, Satoshi, Yokota, Hiroko, Uesu, Yoshiaki, and Fukui, Tatsuo

Subjects
MAGNETIC domain, FERROMAGNETIC materials, CONFOCAL microscopy, THREE-dimensional imaging, VISUALIZATION, MATHEMATICAL models, LASER beams, STOICHIOMETRY
Abstract

The necessary conditions for nondestructive and three-dimensional (3D) observations of inverted polar domain structures using the second-harmonic generation interference microscope (SHGIM) are examined experimentally and theoretically using MgO doped congruent LiNbO3 and periodically poled (PP) MgO doped near stoichiometrical LiNbO3. The results can be explained well by the Boyd and Kleinman theory of strongly focused optical systems. To obtain clear 3D images of domain structures by SHGIM, the sign of the wave number Δk offset of the fundamental and SH waves should be negative and the SHG tensor components d31 should be used for both samples when they are observed with a wavelength of 1064 nm at room temperature. Under these conditions, 3D PP domain structures are clearly revealed by SHGIM. General conditions for the 3D visualization of polar domain structures are discussed for the cases of sum-frequency and difference-frequency generations. [ABSTRACT FROM AUTHOR]

Published
2008
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31. 図画工作科・美術科における教科固有の能力に関する検討 : 発想プロセスの可視化を手がかりに

Author

Amano, Shinichi, Shimatani, Ayumi, Yamamoto, Fusami, Matsumoto, Hiroko, Matsuzaki, Shinichi, Yokota, Hiroko, Mine, Kazunami, Yata, Chikahiko, Amano, Shinichi, Shimatani, Ayumi, Yamamoto, Fusami, Matsumoto, Hiroko, Matsuzaki, Shinichi, Yokota, Hiroko, Mine, Kazunami, and Yata, Chikahiko

Abstract

図画工作科・美術科固有の能力を形成する「発想」がどのようにして生まれ，促され，構想へと高まっていくのか，実際の授業場面でそのプロセスを可視化することは容易ではない。そしてこれが，美術教育に関する専門性や経験の十分でない多くの指導者にとって，この教科の指導を困難なものとする一因にもなっている。そこで，小・中学校の様々な発達段階の児童・生徒を対象とする具体的な授業実践を通して，絵画及び立体表現における発想プロセスの可視化を図るとともに，これを手がかりに「発想や構想の能力」を高める上で効果的な授業構想や手立ての在り方について探ることを目的に本研究に取り組んだ。学習過程を横軸，発想喚起要素（題材の特性にかかわる要素と技能的要素）を縦軸としたマトリクス表に基づく題材分析，発想を促すことに焦点化した手立ての吟味，ポートフォリオを活用した経過観察，そして個別に実施した自己評価アンケートの分析を通して，発達段階による発想の広がり方の違いや，発想に影響を与える様々な要素（鑑賞，材料，用具，協働的な学び等）についてある程度の知見を得ることができた。, We practiced lessons on elementary school children and junior high school students, and tried this visualization of ideas process on painting and stereoscopic expression. We did this research so that we could explore effective lesson plans and methods to raise "ability to create ideas and concepts." We got some findings about the differences in how the ideas spread in the developmental stage and various factors that influence ideas (appreciation, materials, tools, collaborative learning etc.). This analysis based on the matrix table with the horizontal axis of the learning process and the vertical axis of the elements that inspire ideas (elements related to the characteristics of the material and skill elements), and the examination of the methods focused on encouraging the ideas, and the follow-up observation using portfolios, and the analysis of self-evaluation questionnaires conducted individually.

Published
2017

32. 模型製作手法の違いによる小学生3年生の「家」の空間構成に関する授業構成

Author

Okinishi, Keiko, Yokota, Hiroko, Hattori, Futoshi, Sendai, Shouichirou, Hikita, Atsushi, Okinishi, Keiko, Yokota, Hiroko, Hattori, Futoshi, Sendai, Shouichirou, and Hikita, Atsushi

Abstract

本年度は，３年生児童によるワークショップを実施し，「結ぶ」，「組む」という異なる二つの製作手法を用いた，「安全な家」の模型づくりの授業を構成した。製作模型では，児童によって多少の個人差はあるが，床や屋根の構造のつくり方と制作のプロセスの変化に一定の類型があることが明らかになった。また、製作前後で行ったアンケートの分析では、「結ぶ」手法から「組む」手法へと変わった際に、空間に対して求めるものが変化することが分かった。模型製作手法という外的要因が児童の安全に対する意識に影響を与えたことを明らかにしたことが最大の成果である。児童の生活環境との相関，床面の構成の分析などが，今後の空間構成に関する研究の上での課題として残された。, In this year, we had the workshop by third grade students and make the lesson program for the making of a model as “secure house” with structural methods of “tying” and “wooden jointing”. In the making of models, though there are some individual differences, we found the definite types to make models: the floor or the roof structure, and the making process itself. In analysis of questionnaire before and after the workshop, what children desired for living space changed, when the method was changed from “tying” to “wooden jointing”. It is the important result that children’s conscious for secure was affected by external factor; the model making method. Theme relation of children’s living environment and analysis of structure of floor require further study.

Published
2017

35. Local structures and temperature-driven polarization rotation in Zr-rich PbZr1-<italic>x</italic>Ti<italic>x</italic>O3.

Author

Wang, Zhen, Zhang, Nan, Yokota, Hiroko, Glazer, A. M., Yoneda, Yasuhiro, Ren, Wei, and Ye, Zuo-Guang

Subjects
PIEZOELECTRICITY, POLARIZATION (Nuclear physics), SYNCHROTRONS, MONTE Carlo method, DISTRIBUTION (Probability theory)
Abstract

PbZr1-xTixO3, which has abundant structural variations in the corresponding physical properties, has been used in a large variety of applications. To understand the effect of the structure on its high-performance piezoelectric properties, its local and average structures are studied. Total scattering data have been obtained from high-energy synchrotron powder diffraction experiments at 20 K and 300 K. Using the reverse Monte Carlo method, information on cation displacements has been extracted from X-ray Pair Distribution Function data. This suggests that the local disorder of the B cations is mainly driven by thermal motion, while the local disorder of Pb is most likely caused by more complex factors, such as displacive disorder. Both rhombohedral and monoclinic local polarizations are observed in Zr-rich PZT, whose directions depend on temperature. [ABSTRACT FROM AUTHOR]

Published
2018
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36. Optical Second Harmonic Generation Microscopy as a Tool of Material Diagnosis

Author

Yokota, Hiroko, Kaneshiro, Junichi, and Uesu, Yoshiaki

Subjects
Article Subject
Abstract

The second harmonic generation microscope (SHGM) constructs images of intensity distributions of SH waves produced by the interaction of fundamental waves with a polar material. We have developed this nonlinear optical microscope in order to make possible nondestructive, three-dimensional (3D) observations of various kinds of inorganic and organic materials. The SHGM can disclose also inverted domain structures of antiparallel spontaneous polarizations using the interference with the reference SH waves. The observation principle and several applications to structural characterizations of LiNbO3 and LiTaO3 quasi-phase matching devices, domain structure analyses of a relaxor/ferroelectric solid solution Pb(Zn1/3Nb2/3)O3-9%PbTiO3 at the morphotropic phase boundary, development of order parameter in a quantum paraelectric relaxor Li-doped KTaO3, and antiphase polar domain structures of muscle fibers and myofibrils are surveyed by stressing the high effectiveness of the SHGM as a tool of material diagnosis.

Published
2012
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