No abstract

The quantum ferroelectric phase transition of 18O-exchanged SrTiO3 (x% exchanged SrTiO3 is abbreviated as STO18-x) was investigated by Raman scattering as a function of x. The result indicates the ideal soft mode-type quantum ferroelectric phase transition of STO18-x, where the 18O exchange enhances the softening of the soft mode by the suppression of quantum fluctuation. In the vicinity of the quantum critical point (x approximately xc=33%), the system results in the ferroelectric-paraelectric phase coexistence state, in clear contrast to the homogeneous ferroelectric phase in STO18-x, whose x is sufficiently larger than xc. Simultaneously, the softening of the soft mode becomes strongly rounded with the underdamped oscillation. The present result indicates that the sensitivity of the soft phonon vibration to the mass disorder is dramatically enhanced in the vicinity of the quantum critical point.

The oxygen isotope effect on the soft-mode dynamics in quantum paraelectric SrTi͑ O atoms are 0.23 ͓STO18-23͔ and 0.32 ͓STO18-32͔, which are less than the critical value x c ͑=0.33͒. In STO18-32, whose exchange rate is just below x c , the soft E u mode shows hardening behavior in a low-temperature region indicating the onset of local ferroelectric order. On the other hand, the soft E u mode in STO18-23 does not show any hardening behavior until 0 K. The enhancement of the inhomogeneity in the crystal by the exchange of 18 O is concluded to play an essential role in the soft-mode dynamics of the quantum paraelectric and ferroelectric STO18-x. The relation between the soft-mode dynamics and quantum fluctuation is discussed.

A two-step process consisting of depolymerization and catalytic cracking without hydrogen addition was carried out to produce phenols from lignin. In the first step, lignin was depolymerized using a silica-alumina catalyst in a water/1-butanol solution at 623K for 5 2 h. After the reaction, lignin-derived slurry liquid was obtained in 67 C-mol% yield. From the model studies, it was considered that lignin was mainly depolymerized via hydrolysis of aryl ether bonds between lignin units. For the second step, the catalytic reaction of the 1-butanol phase of the slurry liquid was carried out over an iron oxide catalyst using a high ・The recovery fraction of phenols increased as the F H2O /F value increased.

We have performed Brillouin studies of acoustic-phonon behavior in barium sodium niobate above and below its phase transition at To --105 K. Anomalies in sound velocity and attenuation are observed for the sound waves corresponding to the Cll and C22 elastic coefficients. Above To the sound-ve1ocity anomalies display lambda-shaped dips af algebraic form V~~( T) = V~(oo ) -P/(T -Tc), with Tc several degrees lower than the actual transition temperature To, this is the form expected for free energies dominated by linear coupling between strain and the order parameter. Below To, V~&(T)= V&(00) P'/(T-, ' -T). The attenuation displays an increase of approximately 100% as the transition temperature is approached from above or below. By combining sound-velocity and attenuation data through a Landau-ghalatnikov approach, we are able to extract a single relaxation time and find that this time~satisfies the expected mean-field dependence