2007 Fiscal Year Final Research Report Summary
In-situ observation of the phase conditions of rare erath manganites controlled by structure and crystal structure and application of new properties
| Project/Area Number |
18560662
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | Ryukoku University |
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Principal Investigator |
NAKANO Hiromi Ryukoku University, Faculty of Science and Technology, Senior Teaching Associate (00319500)
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| Co-Investigator(Kenkyū-buntansha) |
SATOH Hirohisa Toyohasi University of Technology, Department of Materials Science, Assistant professor (10215832)
AOI Yoshifumi Ryukoku University, Faculty of Science and Technology, Lecturer (70298735)
KAMEGASHIRA Nahoki Toyohasi University of Technology, Department of Materials Science, Professor emritus (20023153)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Phase transition / Rare erath manganite / High temperature TEM / In-situ observation / Control of structure and crystal structure |
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| Research Abstract |
We synthesized new rare-earth manganites, and analyzed new crystal structures and new properties.
1. Study of new rare earth manganites with K_2NiF_4 structure
New phase of BaLnMnO4 (Ln = Nd, La) was obtained by annealing the single crystal (I4/mmm) in a reducing atmosphere. The structural change was caused by an oxygen deficiency, and a small amount of Mn^<2+> ions was formed by annealing in a reducing atmosphere. Na-oxide has a crystal structure with Fmmm symmetry, and La-oxide has Cccm symmetry.
2. Study of new oxides with perovskite related structures
Many new phases have been synthesized and investigated their structures, electrical properties, thermal properties and magnetic properties. In the case of (A^<0.67>Ln^<0.33>)(Mn^<0.33>Ti^<0.67>)O_3 (Ln=rare earth, A=Ca, Sr), the electrical conductivity was closely related with structural parameters (Mn-O angles, Mn-O distances, ionic radii, t-factors, and coulomb potentials).
3. In-situ observations of phase conditions at elevated temperature
We found a first-order phase transition in BaLn_2Mn_2O_7 with a layered perovskite structure using a high-temperature TEM and XRD. The structure change was caused by a distortion of structure and change in electrical structure. In-situ observation by a high-temperature TEM was effective in order to know the structural change at real time. On the other hand, secondary-order phase transition was observed in perovskites with ABO_3 structure. The phase transition was caused by tilting of octahedra BO_6.
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