Ceramics-Silikáty 53, (2) 118 - 127 (2009) |
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CORRELATION BETWEEN LOCAL STRUCTURES AND PARTIAL ELECTRONIC BAND STATES IN FERROELECTRIC Bi4–XLaXTi₃O₁₂; 0.0≤x≤1.46
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Hidaka Masanori 1, Wijesundera Ruwan Palitha 1,4, Kumara Rosantha ,
Noguchi Yuji 2,
Miyayama Masaru 2,
Choi Sun-Hee 3,
Sung Nark Eon 3,
Kim Min Gyu 3
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1 Department of Physics, Faculty of Science, Kyushu University, 33, Fukuoka 812-8581, Japan
2 Research Center for Advanced Science and Technology, The University of Tokyo,
4-6-1 Komaba, Meguro-Ku, Tokyo 153-8904, Japan
3 Beamline Department, Pohang Accelerator Laboratory, Pohang University of Science and Technology,
San31, Hyoja–doing, Pohang, 790-784, Korea
4 Department of Physics, University of Kelaniya, Kelaniya, Sri Lanka
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Keywords: Ferroelectric thin film, Bi4–XLaXTi₃O₁₂, EXAFS, XANES
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The local structures and the partial band states near a Fermi level (EF) have been studied at room temperature in the
ferroelectric phase of Bi4–XLaXTi₃O₁₂ (BLT) with 0.00 ≤ x ≤ 1.46 by means of X-ray absorption spectra (XAS) including EXAFS
and XANES. The EXAFS spectra suggest that, as increasing the substituted La ions, the local structures around Ti and Bi
ions in perovskite-blocks of (Bi4–XLaXTi₃O₁₀)⁻² are gradually deformed till x = 0.85, and are largely changed by a structural
phase transition occurring between x = 0.85 and 1.20. The XANES spectra suggest that there is a strong hybridization
between Ti-3d(t₂g) and O-2p bands and between Bi-6s and O-2p bands in the valence band states, while between Ti-3d(eg)
and O-2p bands and Bi-6p and O-3s bands in the conduction band states. All of the XAS show interesting dependency on
the concentration of the substituted La ions in BLT. The results suggest that, in BLT, a reducing spontaneous polarization
induced by the La-substitution results from the deformation of the local structures around Ti and Bi ions and from modulation
of the hybridized band states near EF. |
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