Successive Phase Transitions, Incommensurate Structure and Particle-size Effects in Some Dielectric Crystals
| Project/Area Number |
03453070
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
無機工業化学・無機材料工学
|
|---|
| Research Institution | Tokyo Institute of Technology |
|---|
Principal Investigator |
ATAKE Tooru Tokyo Inst. Technol., Res. Lab. Eng. Mater., Professor, 工業材料研究所, 教授 (30028229)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
KAWAJI Hitoshi Tokyo Inst. Technol., Res. Lab. Eng. Mater., Research Associate, 工業材料研究所, 助手 (10214644)
|
|---|
| Project Period (FY) |
1991 – 1992
|
| Project Status |
Completed (Fiscal Year 1992)
|
| Budget Amount *help |
¥6,900,000 (Direct Cost: ¥6,900,000)
Fiscal Year 1992: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1991: ¥5,600,000 (Direct Cost: ¥5,600,000)
|
|---|
| Keywords | Dielectric Substances / Successive Phase Transitions / Incommensurate Structure / Heat Capacity / X-ray Diffractometry / Dielectric Constant |
|---|
| Research Abstract |
A high precision adiabatic calorimeter was constructed. The data acquisition system was fully automated for the heat capacity measurements from liquid helium temperature up to room temperature on the basis of the ITS-90. A cryostat was also made for dielectric measurements under programmed conditions between liquid nitrogen temperature and 200 ﾟC.
The structure and phase relations in BaZnGeO_4 were studied by X-ray diffractometry. The space group of the phase VI which forms only in crystals larger than 0.2 mm has been determined as P6_322 for the sub-lattice and P6_122 or P6_522 for the super-lattice. The phase VI transforms into a new room temperature phase VII of the structure P6_3 or P6_3/m. The particle size effect on the phase transitions in BaZnGeO_4 was discussed on the ground of the crystal structure and phase relations. The incommensurate-commensurate transition was also studied by electron microscopy and diffraction.
The low-temperature phase transition in K_2ZnCl_4 was found to be strongly influenced by small amount of water remaining in the crystals which were grown from aqueous solution. A sharp heat capacity anomaly was at 146.24 K for the dried sample, while a broad anomaly was observed for the as-grown crystals. It was confirmed by repeating the heat capacity measurements that the absorption-desorption process of water (less than 0.1%) in the sample was reversible.
Thermodynamic studies have been made also on some other dielectric compounds such as bis(4-chlorophenyl) sulfone, hexamethylbenzene, C_<60> and so on.
|
Report
(3 results)
Research Products
(19 results)
