Phase Transition Mechanisms in Polyhedral Network Compounds
| Project/Area Number |
11694084
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B).
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
機能・物性・材料
|
|---|
| Research Institution | Hiroshima University |
|---|
Principal Investigator |
OKUDA Tsutomu Hiroshima Univ., Graduate School of Science, Professor, 大学院・理学研究科, 教授 (20033847)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
YAMADA Koji Hiroshima Univ., Graduate School of Science, Associate Professor, 大学院・理学研究科, 助教授 (10166704)
|
|---|
| Project Period (FY) |
1999 – 2000
|
| Project Status |
Completed (Fiscal Year 2000)
|
| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥1,600,000 (Direct Cost: ¥1,600,000)
|
|---|
| Keywords | phase transition / NMR / NQR / infinite network structure / ionic conductor / ionic motion / 相移転 / NOR |
|---|
| Research Abstract |
RSn_2F_5 (R=alkali metals) have been studied by means of NMR, X-ray diffraction, and AC conductivity. The conductivities of the K and Rb salts were high but those of the Na and Cs salts were low even near 500 K.X-ray diffraction was measured for a single crystal of the Rb salt at 370 K.The crystal consists of anion layers formed by the terminal, bridging, and triple-bridging fluorine atoms. Powder X-ray diffraction measurements at various temperatures clarified that the c axis becomes contracted and the ab plane is expanded after the phase transition to the high-temperature phase and that new triple-bridging fluorine sites are formed by Sn atoms.
^<87>Rb NMR showed that all Rb sites are equivalent in the high-temperature phase. ^<19>F NMR showed a broad spectrum with half width of about 50 kHz at low temperature, indicating the presence of three kinds of fluorine atoms. With increasing temperature, the spectrum decreased its width and was sharp at room temperature, suggesting anion diffusion. ^<119>Sn NMR showed a sharp spectrum after the phase transition to the high-temperature phase, supporting that the environment around Sn becomes cubic symmetry and anion layers were formed between Sn layers.
The Rietveld analysis of powder X-ray diffraction was carried out for KSbF_4. The high-temperature phase forms a fluorite type structure with space group Fm3m. The K and Sb atoms occupy cation sites at random, and F atoms occupy not only anion sites of the fluorite type structure but also interstitial sites surrounded octahedrally by cations. ^<19>F NMR for the high-temperature phase showed the spectrum with line width of about 2 kHz after the phase transition and remains the same line width as that at high temperature down to room temperature, indicating anion diffusion remains at room temperature.
|
Report
(3 results)
Research Products
(17 results)
