1995 Fiscal Year Final Research Report Summary
Investigation of Metal-Insulator transition of Perovskite-type Oxides
| Project/Area Number |
06453078
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | Okayama University |
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Principal Investigator |
TAGUCHI Hideki Okayama University, Faculty of Science, Associate Professor, 理学部, 助教授 (20188139)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Perovskite-type structure / Metal-insulator transition / Rietveld method / Manganite / Electrical properties / Crystal structure / Band structure / Semiconductor |
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| Research Abstract |
Both the Mn^<3+> and Mn^<4+> ions coexist in the perovskite-type (Ln_<1-x>Ca_x) MnO_3 (Ln : the rare earth elements). These oxides are semiconductors at low temperature, and are metallic conductors at high temperature. These electrical properties indicate that these oxides exhibit the metal-insulator transition. X-ray diffraction data of (Ln_<1-x>Ca_x) MnO_3 were collected at room temperature and low temperature, and it is obvious that the metal-insulator transition occurs without the phase transition of the crystal structure. The crystal structure was refined by the Rietveld method. It is apparent that the variation of the average Mn-O distance and the average angles for Mn-O-Mn corresponds to the electrical properties. The number of 3d electrons in the Cr^<3+> and Mn^<3+> ions corresponds to those of the Mn^<3+> and Mn^<4+> ions, respectively. Therefore, Nd (Cr_<1-x>Mn_x) O_3 and Nd (Cr_<1-x>Co_x) O_3 were synthesized to investigate the relationship between the electrical properties and the overlap of depsilon and p_<pi> orbitals. From the refinements of the crystal structure, it is obvious that the overlap of depsilon and p_<pi> orbitals in very important factor to explain the electrical properties.
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