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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.
crystalsYoneda, Yasuhiro; Kitanaka, Yuki*; Noguchi, Yuji*; Miyayama, Masaru*
Physical Review B, 86(18), p.184112_1 - 184112_11, 2012/11
Times Cited Count：60 Percentile：89.17(Materials Science, Multidisciplinary)The electronic structure of complex oxides is important for understanding their functional properties. Here we report the results of investigating multiferroic BiFeO using various X-ray spectroscopy techniques. Zn- and Mn-codoped and Mn-doped BiFeO samples were prepared with the aim of improving ferroelectric properties of BiFeO. The valences of the doped Mn and host Fe were investigated. When oxygen vacancies exist in the sample, Mn acts as a hole acceptor. Furthermore, Mn and Fe stabilize the perovskite unit by changing their ionic radius. As a result, Mn and Fe atoms exhibit various valence states in the BiFeO system. Evidence of the electronic structure for Fe 
-O 
-Bi 
hybridization is also presented.
Yoneda, Yasuhiro; Noguchi, Yuji*; Miyayama, Masaru*; Kitanaka, Yuki*
no journal, ,
BiFeO is not so large as intrinsic polarization is expected from a crystal structure since the coercive field is very large. However, good hysteresis is obtained by Mn-doping. In order to investigate the Mn dope effect of BiFeO, XAFS measurement was performed by each absorption edge of Bi, Fe, and Mn, and the estimate and local order structure of the valence were conducted. Since the valence and local structure of Mn are changing with annealing, they have suggested the importance of an oxygen deficiency.
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 490
C, 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 (Mg
Nb
)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.
