Eisuke Suzuki

Structural phase transition in ReO3 under high pressure

Structural phase transitions in ReO3 were studied under high pressure with the angle-dispersive x-ray diffraction method using synchrotron radiation. The pressure range of 8–18 GPa was clarified to be the coexistence region of the cubic phase and rhombohedral I phase. In addition, the apparent change of diffraction pattern observed above 38 GPa defined the unit cell of the rhombohedral II phase.

Phase Transitions in CsH 2 PO 4 Under High Pressure

Dielectric constant measurements at low temperature and X-ray diffraction measurements at room temperature were carried out under high pressure up to 1.42 GPa and 10 GPa, respectively, for a hydrogen-bonded crystal CsH 2 PO 4 . By the dielectric measurements, we found a new antiferroelectric phase (AFE II), that is probably the phase predicted theoretically by Schuele and Schmidt. The locations of the two triple points were determined at m 153.4C and 0.59 GPa for PE, FE and AFE I, and at m 168.5C and 1.11 GPa for of PE, AFE I and AFE II. By X-ray diffraction, we confirmed the high-pressure phase V proposed by Rapoport et al. and found a new high-pressure phase VII.

Powder x-ray diffraction system with a curved monochromator for high-pressure and low-temperature use

A powder x-ray diffraction system operated at high pressure and low temperature has been developed for a conventional x-ray generator. An incident x ray is focused by a curved monochromator on a sample in a diamond anvil cell coupled with a cryostat with a helium gas closed-cycle refrigerator. We demonstrated a high-quality diffraction pattern with sufficient signal-to-noise ratio obtained for sodium chloride at 12 GPa and 6 K by this system using an imaging-plate detector.

Pressure-Induced Structural Transition in TGS

Tri-glycine sulfate ((CH 2 NH 2 COOH) 3 H 2 SO 4, abbreviated to TGS) has been studied at high pressure up to 3.5 GPa using a diamond anvil cell and synchrotron radiation. A structural transition from the ambient-pressure phase to a high-pressure phase was observed at 2.5 GPa, which coincides with previous results obtained by dielectric constant and Raman scattering measurements.