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Yoneda, Yasuhiro
JSAP Review (Internet), 2023, p.230202_1 - 230202_7, 2023/00
It is important to determine whether a sample is a single phase or not in order to improve the quality of ferroelectrics. Therefore, we have succeeded in developing a detection method for trace amounts of segregated phases by using two-body correlation distribution function (PDF) in addition to X-ray diffraction, which has been conventionally used to detect impurities. In the X-ray diffraction pattern of the BaTiO
-BiFeO solid solution, it appears as a single phase with a rhombohedral structure. However, when the PDF was calculated from the obtained diffraction pattern, it was found that not only the component derived from the rhombohedral crystal structure calculated from the average structure but also the BaTiO component was mixed and segregated. By using PDF in this way, it has become possible to detect fine segregation phases on the order of nanoscale.
Yoneda, Yasuhiro
Oyo Butsuri, 91(12), p.729 - 735, 2022/12
It is important to determine whether a sample is a single phase or not in order to improve the quality of ferroelectrics. Therefore, we have succeeded in developing a detection method for trace amounts of segregated phases by using two-body correlation distribution function (PDF) in addition to X-ray diffraction, which has been conventionally used to detect impurities. In the X-ray diffraction pattern of the BaTiO-BiFeO solid solution, it appears as a single phase with a rhombohedral structure. However, when the PDF was calculated from the obtained diffraction pattern, it was found that not only the component derived from the rhombohedral crystal structure calculated from the average structure but also the BaTiO component was mixed and segregated. By using PDF in this way, it has become possible to detect fine segregation phases on the order of nanoscale.
-BaTiO solid solutionsYoneda, Yasuhiro; Kim, S.*; Mori, Shigeo*; Wada, Satoshi*
Japanese Journal of Applied Physics, 61(SN), p.SN1022_1 - SN1022_10, 2022/11
Times Cited Count：1 Percentile：17.38(Physics, Applied)Local structural analysis of the (1-
) BiFeO-BaTiO solid solution was performed by PDF analysis of the data obtained in the synchrotron radiation high-energy X-ray diffraction experiment. First, when XAFS experiments were performed and sample screening was performed, it was found that structural fluctuations were large in the BiFeO-rich composition. Therefore, PDF analysis of a sample with BiFeO-rich composition was performed. As a result, it was found that although the average structure is a cubic structure, the local structure can be reproduced with a rhombohedral crystal structure, and there is a displacement that breaks the symmetry of the rhombohedral structure in a composition with a large fluctuation.
NaTiO in high-temperature phasesYoneda, Yasuhiro; Noguchi, Yuji*
Japanese Journal of Applied Physics, 60(SF), p.SFFA08_1 - SFFA08_10, 2021/11
Times Cited Count：4 Percentile：36.85(Physics, Applied)BiNaTiO (abbreviated as BNT) is a lead-free material but exhibits relatively large piezoelectric properties, a lot of researches have been conducted. We performed local structural analysis using high-quality BNT with a stoichiometrically correct composition, and found a chemical order structure of Bi/Na in locally. BNT undergoes a phase transition to a cubic phase at 400
C. We estimated that a new disorder structure will appear in the high-temperature phase. In the high temperature phase, pair distribution function (PDF) analysis using synchrotron radiation high-energy X-rays was performed. As a result, we found that Bi shifts from 200C, and this shift becomes an order parameter for the phase transition.
Nb
)OYoneda, Yasuhiro; Taniguchi, Hiroki*; Noguchi, Yuji*
Journal of Physics; Condensed Matter, 33(3), p.035401_1 - 035401_8, 2021/01
Times Cited Count：4 Percentile：33.7(Physics, Condensed Matter)Nanoscale structural analysis of relaxor Pb(MgNb)O (PMN) was performed using synchrotron high-energy X-ray diffraction measurements. Although PMN is a well-known relaxor ferroelectric material, the average structure is a cubic structure, and various models have been proposed to explain the ferroelectric microstructure. We performed a wide-range local structure analysis up to 20 nm using the pair distribution function (PDF). As a result, it was found that the structure of PMN changed depending on the distance and it was a glass-like structure.
in high-temperature cubic phaseYoneda, Yasuhiro; Taniguchi, Hiroki*; Kitanaka, Yuki*; Noguchi, Yuji*
Ferroelectrics, 538(1), p.57 - 62, 2019/05
Times Cited Count：5 Percentile：27.39(Materials Science, Multidisciplinary)High-energy X-ray diffraction study was performed on lead titanate (PbTiO). Short-range order structure was revealed using atomic pair-distribution function (PDF) method. In the high-temperature cubic phase, there is a large deviation between local and average structure. Especially, Pb atoms deviated from the cubic lattice framework, but establish Pb-O-Pb random network.
Yoneda, Yasuhiro; Ohara, Koji*; Nagata, Hajime*
Japanese Journal of Applied Physics, 57(11S), p.11UB07_1 - 11UB07_6, 2018/11
Times Cited Count：15 Percentile：59.6(Physics, Applied)Local structure analysis of KNbO, which is the parent compound for lead-free piezoelectric materials, have been performed by X-ray pair-distribution functions (PDF). The refinements of local structure in wide temperature ranges indicates that only the rhombohedral structure can describe the observed bond distributions within the unit cell. The rhombohedral distortion maintained locally in all four phases.
and AgNbO
modified by Li substitutionYoneda, Yasuhiro; Aoyagi, Rintaro*; Fu, D.*
Japanese Journal of Applied Physics, 55(10S), p.10TC04_1 - 10TC04_5, 2016/10
Times Cited Count：6 Percentile：29.26(Physics, Applied)We analyzed the local structures of NaNbO and Na
Li
NbO by combining the X-ray absorption fine structure (XAFS) and atomic pair-distribution function (PDF) techniques. NaNbO is known to be an antiferroelectric material at room temperature. It also undergoes a diffuse phase transition, in which an orthorhombic and a rhombohedral phases coexist over a wide temperature range. We identified a rhombohedral ground state structure of NaNbO and assumed an order-disorder-type phase. We also found a disorder feature in the nearest-neighbor bond distance corresponding to the Nb-O bonds. The disordered bond distribution disappeared when Na was substituted for Li. A similar disorder feature was found in AgNbO.
Yoneda, Yasuhiro
no journal, ,
A 
-type diffractometer, which is dedicated to Japan Atomic Energy Agency, is equipped on a bending magnet beamline at SPring-8. We performed atomic pair-distribution function (PDF) analysis on crystalline materials. For example, local and middle-ranges order analysis of surrogate materials of Dy
Zr
N for nitride fuel was performed by using this apparatus.
Yoneda, Yasuhiro
no journal, ,
An invitation lecture about atomic pair distribution function (PDF) method which is one of the local structural analysis method using synchrotron radiation X-rays was performed. Since the PDF analysis can be clarified the nano-scale order structure, as well as the short-range order structure, the PDF analysis is structural analysis method indispensable to ferroelectric materials with a manifested organization of physical properties through the domain. I showed that the results of the PDF analysis for relaxor ferroelectrics. The PDF is able to visualize the structure of the lead atoms, which deviates from the average structure.
in high-temperature cubic phaseYoneda, Yasuhiro; Taniguchi, Hiroki*; Kitanaka, Yuki*; Noguchi, Yuji*
no journal, ,
Lead titanate, PbTiO, has a tetragonal structure having a large c/a ratio at room temperature. A phase transition to the paraelectric phase at 490C, structural changes to cubic. However, just above the transition point to the paraelectric phase, the phonon modes of the still ferroelectric is observed. Therefore, spontaneous polarization using a sample of reversible high quality, perform high-energy X-ray diffraction experiments were subjected to structural analysis in a wide temperature range from room temperature to 800C. Short range order structure analysis and atomic two pairs distribution function (atomic pair-distribution function, PDF) was performed using. A comparison local structures at room temperature of the observed local structure and relaxor Pb (MgNb)O (PMN) with 800C of PbTiO, network structure similar to the relaxor PMN is present in the high temperature phase of PbTiO It is considered to have.
BaNb
O
in high-temperature phaseYoneda, Yasuhiro; Fu, D.*
no journal, ,
CaBaNbO (CBN) in which Ba of BaNbO is replaced with Ca, which is a ferroelectric substance having a tungsten bronze structure, A single-phase tetragonal phase appears in the composition range where the amount of Ca substitution is 0.19 
0.32. For CBN, superlattice reflection appears in the powder X-ray diffraction pattern even in ceramic samples. There is a long-period structure that is deviated from the average structure. Since superlattice reflection is still observed in the high-temperature phase, structural analysis was performed in the high-temperature phase. It was found that the average structure of the high-temperature phase well reflected the local structure of the room temperature phase. It is considered to be a phenomenon that reflects the reentrant phase transition peculiar to tungsten bronze.
Yoneda, Yasuhiro; Tsuji, Takuya; Matsumura, Daiju; Okamoto, Yoshihiro; Nagai, Takayuki
no journal, ,
In order to establish vitrification technology, it is important to clarify how various substances dispersed in glass exist. We made simulated glass by mixing various substances containing metallic element of the platinum group with raw material glass containing SiO-BO glass as the main component. This simulated glass was heated to 600C just above the melting point and observed by an X-ray diffraction experiment. The obtained X-ray diffraction profile revealed the local structure using the pair distribution function (PDF). Since the network structure of SiO is strong, it is considered that the precipitated fine particles become wedges and the Si-O bond length is modulated.
Yoneda, Yasuhiro; Nakata, Kengo*; Ohara, Koji*
no journal, ,
We analyze real-space fit and inverse Monte Carlo method (RMC) using the same material data and compare the results obtained to characterize each analysis method. We will report the result of barium titanate (BaTiO). BaTiO is one of the substances whose real space fit is very difficult because Ba with high ionicity and Ti with high covalent bond are mixed. We discussed how to extract comparable data from the structural parameters obtained by each analysis method.
Nb)OYoneda, Yasuhiro; Taniguchi, Hiroki*; Noguchi, Yuji*
no journal, ,
Many structural models have been proposed for relaxer ferroelectrics Pb(MgNb
O. We have shown that the Pb-O distance obtained from the mean structure differs from the Pb-O distance obtained from the X-ray absorption fine structure (XAFS). Since the deviation between the average structure and the local structure is considered to be derived from the characteristic environment of the Pb atom, the behavior similar to that of the Pb atom in the pyrochlore type Pb SnO is assumed and the local structure is assumed. I tried structural modeling. A pair-distribution function (PDF) analysis was performed, and as a result of local structure modeling, it was suggested that there is a network structure of Pb atoms that is different from the periodicity of the lattice system.
-BaTiO solid solutionYoneda, Yasuhiro; Kim, S.*; Wada, Satoshi*
no journal, ,
In a solid solution formed with BiFeO and BaTiO, a pseudo cubic phase appears at room temperature with a BaTiO composition of 0.3 to 0.7. Since the ferroelectricity is not lost even in the Cubic structure, a structural analysis using pair distribution function was performed to clarify the origin of the ferroelectricity. The local structure of these solid solutions was consistent with the pure limits of BiFeO and BaTiO, respectively, but when the BaTiO composition was 0.3, a structure peculiar to the solid solution appeared.
Yoneda, Yasuhiro; Yamada, Hiroki*
no journal, ,
In addition to research on structural analysis using binary correlation distribution functions using synchrotron radiation, the diffractometer at SPring-8, a large synchrotron radiation facility, will be introduced. A feature of the atomic pair-distribution function (PDF) is that it can cover not only the local structure region but also the middle-range structure of the nanoscale order. As an example of applying PDF analysis to ferroelectrics, the results of local structural analysis of BiFeO-BaTiO-Bi (MgTi)O (BF-BT-BMT) are shown. When fitted with the cubic crystal structure of the average structure, a large difference occurs at 40 
or less, revealing the existence of lattice strain, which is the mechanism of polarization.
