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WO
below 300 KYoneda, Yasuhiro; Takeda, Hiroaki*; Tsurumi, Takaaki*
JPS Conference Proceedings (Internet), 1, p.012103_1 - 012103_4, 2014/03
BiWO is the simplest member of the Aurivillius family of (BiO)(A
B
O
) with one oxygen octahedron sandwiched between two BiO layers (m=1). We report the high-energy synchrotron X-ray diffraction study of ferroelectric BiWO at low temperatures, and a new phase transition was found around 200 K. The mechanism of this phase transition was examined by atomic pair-distribution function (PDF) method.
WOYoneda, Yasuhiro; Kohara, Shinji*; Takeda, Hiroaki*; Tsurumi, Takaaki*
Japanese Journal of Applied Physics, 51(9), p.09LE06_1 - 09LE06_6, 2012/09
Times Cited Count：15 Percentile：51.2(Physics, Applied)Local structure analysis of BiWO was performed by high-energy X-ray atomic pair-distribution function (PDF) analysis. We found a deviation between local and average structures owing to the different coherence length between BiO and WO layers. Bi atoms were displaced toward the 
-axis of the orthorhombic 
structure. The local off-center shift of Bi atoms coupled with thermal factor and negrected in the average structure. The coherence length of BiO layer increased with increasing temperature and splead in the whole crystal when the average structure changed from to 
structure.
imaging device of high spatial resolution ZnO scintillatorNakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Takeda, Kohei*; Nishi, Ryosuke*; Minami, Yuki*; Cadatal-Raduban, M.*; Sarukura, Nobuhiko*; Nishimura, Hiroaki*; et al.
Japanese Journal of Applied Physics, 50(12), p.122202_1 - 122202_4, 2011/12
Times Cited Count：10 Percentile：37.91(Physics, Applied)We demonstrate the potential of a hydrothermal method-grown ZnO as a high-spatial resolution imaging device for in-situ soft X-ray laser diagnostics by characterizing the exciton emission patterns. By plotting the emission pattern radii at each position, we estimated the evolution of the beam radius around the focal point. The beam profile of the Ni-like Ag ion plasma laser was estimated from the waist radii as 29 and 21
m, the divergence angle as 7.2 and 11 mrad and the M2 factor as 47 and 50 in the horizontal- and vertical-axis, respectively. Spatial resolution of the magnifier was estimated to be 6m and is expected to improve by optimizing the optics of the magnifier and using a telescope. Our results would enhance the use of ZnO as an imaging device that would play a crucial role in the development and application of soft X-ray light sources.
Ta
Ga
O
crystal grown by Czochralski methodYoneda, Yasuhiro; Mizuki, Junichiro; Takeda, Hiroaki*; Shiosaki, Tadashi*
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 55(5), p.971 - 974, 2008/05
We performed synchrotron X-ray topography on a LaTaGaO (LTG) crystal grown by the Czochralski (Cz) method. Since the synchrotron X-ray source can provide high-energy X-rays, one can detect bulk-sensitive information by the X-ray topography. LTG is one of the most attractive piezoelectric crystals like La
Ga
SiO (LGS), because of excellent acoustic properties (temperature compensation of acoustic losses). Since LTG single crystals can be grown from stoichiometric melt, single crystals with good crystal quality can be obtained comparing to LGS which can not be grown from stoichiometric system but from congruent melt. The 60-keV X-ray topography revealed that the LTG crystal quality was not the same crystalline quality. The crystal quality of a center parts was worse than that of surroundings.
Ga
SiO crystalYoneda, Yasuhiro; Takeda, Hiroaki*; Shiosaki, Tadashi*; Mizuki, Junichiro
Japanese Journal of Applied Physics, Part 1, 46(10B), p.7163 - 7166, 2007/10
Times Cited Count：1 Percentile：5.41(Physics, Applied)The langasite (LaGaSiO, LGS) crystal grown by the Czochralski technique was investigated by X-ray diffraction measurements. The X-ray diffraction profiles of the LGS were consisted with sharp Bragg peaks and large amount of diffuse scatterings. The diffuse scattering inducated the existence of the local structure which is different from the average structure. The local structure was analyzed by the pair-distrivution function method. The local structure fluctuated by the chemical ordering of Ga and Si, and the local disordering feature of La.
GaSiO single crystalYoneda, Yasuhiro; Okajima, Yuka; Takeda, Hiroaki*; Shiosaki, Tadashi*; Mizuki, Junichiro
Transactions of the Materials Research Society of Japan, 31(1), p.7 - 10, 2006/03
no abstracts in English
TaGaO single crystalYoneda, Yasuhiro; Okajima, Yuka; Mizuki, Junichiro; Takeda, Hiroaki*; Shiosaki, Tadashi*
no journal, ,
no abstracts in English
WOYoneda, Yasuhiro; Kohara, Shinji*; Han, J. S.*; Takeda, Hiroaki*; Tsurumi, Takaaki*
no journal, ,
BiWO of a bismuth layered compound is expected as non-lead system ferroelectric. The Curie point is in about 1000
C. Therefore, it was thought that it became possible to synthesize below the Curie point, and the sample of a single domain was obtained easily in crystal breeding by the flux method and the thin film making by the PLD method. However, a lot of observations not thought about were found with a single domain as for the BiWO crystal actually made. Then, it is a purpose of this experiment to perform high-temperature X-ray diffraction of BiWO, and to verify the phase transition system again. As a result of the experiment, it has been understood that additional structural phase transition exists also below the Curie point. The domain configuration changes by the existence of another phase transition caused during cooling afterwards even if the crystal is promoted below the Curie point at the high temperature.
