| 研究課題/領域番号 |
25810040
|
|---|
| 研究種目 |
若手研究(B)
|
| 研究機関 | 京都大学 |
|---|
研究代表者 |
タッセル セドリック 京都大学, 白眉センター, 助教 (60597798)
|
|---|
| 研究期間 (年度) |
2013-04-01 – 2015-03-31
|
| キーワード | Oxyhydride / Perovskite / High Pressure / New Materials |
|---|
| 研究概要 |
As our project consists in the synthesis of novel oxyhydride compounds, we have investigated more than 10 compositions using high pressure solid state synthesis. Among these 10, we have discovered two novel cubic perovskites with the unique ABO2H composition. Both SrCrO2H and BaScO2H are stoichiometric and new.
- Both compounds were studied using neutron diffraction and mass spectroscopy and showed an ABO2H composition.
- All compounds were also investigated using synchrotron x-ray diffraction and transmission electronic microscopy in order to observe possible superstructures.
We have found that all materials are cubic as we predicted from our proposal.
Proton Nuclear magnetic resonance was performed on BaScO2H and showed the sole presence of the hydride ion H- (vs. H2 or H+). Furthermore, no ordering of the ScO4H2 configuration, that is cis vs trans could be observed. SrCrO2H displays a cubic structure with magnetic Cr3+ (d3 S=3/2) ions. This compound was found using nuclear powder diffraction to be an antiferromagnet up to 383 K which is one of the highest ordering temperature ever reported for a chromate. Theoretical calculations are now on the way to understand the remarkable properties of both compounds. The novel compounds BaScO2H and SrCrO2H are now under investigation at the ICMCB in Bordeaux for the topotactic exchange of H- and F- in order to produce novel compounds with different properties.
Finally, two papers are now under preparation to report these novel materials.
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
The investigation of the synthesis of novel perovskite started with several systems and among them two exotic perovskites have been produced: SrCrO2H and BaScO2H. Within this fiscal year: We have set up experiments and successfully produced 2 novel perovskites. Furthermore, we have investigated their structures and reactivity through synchrotron, neutron diffraction, transmission electron microscopy and mass spectroscopy.
The two novel materials are unique and the only examples of stoichiometric perovskite oxyhydrides. (1) Presence of H-, with possibly high ionic polarizability, and O2- in BaScO2H should give high dielectric values (now under investigation). (2) Presence of H- in the SrCrO2H allows it to have a unique structure and one of the highest Neel temperature (383 K) observed in chromate materials. This allows to improve our understanding of the nature of magnetic interactions (superexchange) and chemical bonding.(3) A novel project has been developed in collaboration with Bordeaux University in order to substitute the H- for F-.
The successful synthesis of these materials indicate that their existence can be predicted from simple calculations based on structural features. We hope that this achievement and future ones will allow developing a novel family of exotic materials with possible application.
|
| 今後の研究の推進方策 |
Continuation of the project
(1) The local structural investigation of our novel materials are on the way using NMR and other techniques. We have already characterized both on the long range. (2) This year, theoretical calculations to understand the impact of hydrogen on the structure of BaScO2H and SrCrO2H are also on the way. Further calculations will be required for the comprehension of the magnetism of the chromate. (3) Doping of these system, using aliovalent and isovalent substitutions, is also on the way. (4) Two publications are now under preparation for reporting the successful synthesis of both materials and their properties as well as other specificities.
Expansion of the project
- I am now trying to expand this research to other systems than perovskites, that is spinels, pyrochlores and ruddlesden-Popper structures.
- We have also started developing collaborations with other laboratories (Lille and Bordeaux) in order to topochemically exchange hydrogen in our structures with fluorine and oxygen.
|
