並列タイトル等Study on the Local Structure of Lanthanum-Doped Strontium Titanate by Means of X-Ray Fluorescence Holography
授与機関名広島工業大学（Hiroshima Institute of Technology)
学位博士（工学）（Doctoral Dissertation）
一般注記Strontium titanate SrTiO3 of the cubic perovskite structure is a representative of dielectric crystals. Doping lanthanum atoms into SrTiO3 yields conductive mixed crystals Sr1-xLaxTiO3. Excess electrons are doped into the conduction band composed of the Ti-3d state, and then Ti4+ turn into Ti3+. Such electron-conductive perovskite materials have high utility value in thermoelectric materials of high Seebeck coefficients, conductive substrates of high-TC superconductor films and so on. Sr1-xLaxTiO3 also shows the high structural phase transition temperature and the large saturated spontaneous rotation angle of the TiO6 octahedra. In the present study, we carried out X-ray fluorescence holography using the La Lγ1 ray (La Lγ1 XFH) on Sr0.95La0.05TiO3 and obtained the three-dimensional local structure around the La atom at 297 K. The experimentally obtained X-ray fluorescence holograms and the power spectra of the holographic oscillations were reproduced by the atomic cluster model having the radius of 200 Å. The experimentally obtained local structure showed that the La atoms were doped into the Sr sites of the cubic perovskite structure of SrTiO3 and the La-Sr(La) lattice distance was slightly larger than the averaged lattice parameter of Sr0.95La0.05TiO3. The local structure around the La atom plays significant roles in the electron-conduction and the high phase transition temperature through the softenings of the optic and the elastic phonons, respectively. Based on the present study, we proposed the La Lγ1 XFH study on the electron-conduction and the structural phase transition of Sr0.95La0.05TiO3 nanocrystals.
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受理日（W3CDTF）2019-06-03T12:31:31+09:00
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