| Project/Area Number |
21360325
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | Gakushuin University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
MORI Daisuke 学習院大学, 理学部, 助教 (00432021)
KATSUMATA Tetsuhiro 東海大学, 理学部, 准教授 (90333020)
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| Project Period (FY) |
2009 – 2011
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| Project Status |
Completed (Fiscal Year 2011)
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| Budget Amount *help |
¥15,730,000 (Direct Cost: ¥12,100,000、Indirect Cost: ¥3,630,000)
Fiscal Year 2011: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2010: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2009: ¥11,830,000 (Direct Cost: ¥9,100,000、Indirect Cost: ¥2,730,000)
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| Keywords | 高圧合成 / 酸化物 / 化学結合 / 極性 / ペロブスカイト / リチウムニオベート / 相転移 / 強誘電性 / ペロブスガイト / リチウム二オベート |
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| Research Abstract |
In this study, we have searched polar oxides by high pressure synthesis and elucidated structure and polar properties and structure-property relation. We have successfully synthesized several LiNbO_3(LN)-type oxides such as CdPbO_3 and PbNiO_3 and discussed the stability of LN-type and perovskite(Pv)-type oxides relative to oxides with other structure for ABO_3 compounds. The tolerance factor of perovskite in terms of ionic radius is not the only predominant one to determine the stability and the crystal field effects of 3d transition metal ions are also important. Furthermore, we found the correlation between the displacements of B-ion from the centro-symmetric position in LN-type oxides and the intensity of second harmonic generation. LN-type MnMO_3(M=Ti, Sn) synthesized under high pressure exhibit polarity, and weak ferromagnetism. Anomalies in the dielectric permittivity were observed at the weak ferromagnetic transition temperature for both the compounds, indicating the correlation between magnetic and dielectric properties. These results indicate that LN-type compounds with magnetic cations are new candidates for multiferroic materials. A perovskite-type PbNiO_3 phase synthesized under high pressure irreversibly transforms to a LN-type phase by heat treatment at ambient pressure. Both phases possess the peculiar valence state of Pb_<4+> Ni_<2+> O_3.The both of Pv-type and LN-type PbNiO_3 undergo antiferromagnetic transition and the transition temperatures depend on the Ni-O distance. Furthermore, we successfully synthesized Pv-type PbMnO_2F under high pressure and found large tetragonal distortion, which indicates that the compound may be a ferroelectric with high spontaneous polarization. Na substituted perovsite-type Bi_<1/2> Ag_<1/2> TiO_3, which was synthesized under oxygen pressure, exhibited ferroelectricity.
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