2005 Fiscal Year Final Research Report Summary
Building up of concerted electronic material possessing hybridized conduction band
| Project/Area Number |
15360346
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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 | Osaka University |
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Principal Investigator |
OMATA Takahisa Osaka University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (80267640)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUO Shinya Osaka University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (90029299)
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| Project Period (FY) |
2003 – 2005
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| Keywords | pyrochlore-type oxide / precursor oxidation / electronic conduction / fluorite structure / electronic structure / crystal structure / phase transformation / oxygen release behavior |
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| Research Abstract |
In this project, we have attempted to design and synthesize novel materials in which the bottom of the conduction band consists of hybridization between s- and d-bands or s- and f -bands. These materials are termed "hybridized conduction-band materials" in this project. The elucidation of the energy band structure, electron doping and searching of novel properties under strong magnetic field have been carried out for these materials.
By oxidation of precursor pyrochlore-type oxide of Sn^<II>_2M^V_2O_7 (MV=Nb, Ta) at 〜673K, novel metastable oxides of Sn^<IV>M^VO_<4+x>, in which the cations of Sn^<IV> and M^V were respectively ordered similar manor observed in the precursor pyrochlore structure, were successfully synthesized. The energy of Sn 5s and Nb 4d or Ta 5d orbital was very close in these oxides. The crystal structure of these oxides was elucidated by Rietveld analysis using XRD, and the transformation mechanism has been proposed based on the crystal chemistry. For the SnTaO4+x and
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CeSnO4, in which the energy of Ce 4f and Sn5s are very close, the electron doping by generation of oxygen vacancies, which were induced by annealing the samples under diluted hydrogen atmosphere, became successful. For instance, we have succeeded to synthesize hybridized conduction-band materials. The electrical conductivity of the SnTaO_<4+x> and CeSnO_4 were measured under strong magnetic field of 7T on a quest to finding out of novel properties such as magnetoresistance. However, we could not find out unfortunately. It was inferred that the hybridization between Sn 5s and Ta 5d or Sn 5s and Ce 4f is insufficient in the present materials. The oxygen release from fluorite related SnTaO_<4+x> was started at very low temperature of 670K under reducing atmosphere, while the α-PbO_2 type SnTaO_<4+x> was start reducing at comparatively high temperature of 820K. Such a property is available for the oxygen storage material in exhaust gas cleaning. It was shown that the hybridized conduction band materials synthesized in the present project show distinctive properties in chemical property. Less
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