Sin-Ichi Hamazaki

Crystallization of amorphous bismuth titanate

We studied the transformation of amorphous bismuth titanate by heat treatments. After an as-quenched amorphous sample was annealed at 500 °C, the lowest Raman peak became intense like a boson peak for glass. This fact indicates the formation of intermediate range order. The medium range correlation length of 7 nm calculated from the boson peak frequency is in agreement with the mean cluster size measured by atomic force microscopy (AFM). The differential thermal analysis (DTA) shows the two-step crystallization at 608 and 830 °C on heating. It suggests the existence of a metastable state. The samples annealed at 770 and 1000 °C are identified as the pyroclore and the layered perovskite structures, respectively. It strongly suggests that at first a three-dimensional (3D) crystalline state appears by nucleation process from a 3D amorphous state and secondly it transforms into the pseudo-2D layered perovskite structure.

Raman study of ferroelectric bismuth layer-oxides ABi4Ti4O15

Abstract The optical phonon modes have been studied by Raman spectroscopy in bismuth layer-structure oxides ABi 4 Ti 4 O 15 (ABa, Ca, Pb, Sr). Although the bands higher than 50cm −1 reveal no remarkable temperature dependence, the low frequency modes change markedly. As for CaBi 4 Ti 4 O 15 and SrBi 4 Ti 4 O 15 the underdamped soft modes were clearly observed. In contrast, in BaBi 4 Ti 4 O 15 only low-frequency overdamped modes have been observed. In PbBi 4 Ti 4 O 15 the low-frequency spectra have a complicated structure and the softening of the underdamped modes was not observed clearly.

AFM Observation of 90° Domains of BaTiO3 Butterfly Crystals

We used atomic force microscopy (AFM) to study the surface morphology of tetragonal barium titanate BaTiO 3 at room temperature. An undulation of the surface was observed around the boundary of 90° domains of the as-grown surface of the so-called butterfly crystals, which can be reasonably explained by the tetragonality of this crystal at room temperature.

Atomic Force Microscope Observation of Ferroelectrics: Barium Titanate and Rochelle Salt

We applied atomic force microscopy (AFM) to study the surface morphology of ferroelectric BaTiO3 (barium titanate, BT) and NaKC4H4O64H2O (Rochelle salt, RS). At room temperature, an undulation of the crystal surface was observed around the 90° domain boundary in BT and around the monoclinic domain boundary in RS.

Temperature Dependent Surface Images of BaTiO3 Observed by Atomic Force Microscopy

We used an atomic force microscope (AFM) to study the surface morphology of butterfly-like crystals of BaTiO3. Observations were made while varying the temperature from room temperature to 150°C and the annihilation process of the surface structure due to 90° domain boundaries was detected. The relationship between the surface gradient change at the domain boundaries and the tetragonal distortion was discussed.

Search for New Ferroelectrics in Tl 2 ZnI 4 Group

Our work of new ferroelecric survey was reviewed. A 2 BX 4 -type compounds having Sr 2 GeS 4 structure, where A = K, Rb, Tl and Cs, B = Zn, Co, Cd and Hg, X = I and Br, were synthesized by the Bridgman method. Their dielectric and phase transitional properties were investigated. From the results, several empirical relations among phase transition points and including elements were pointed out.

Observation of Crystallization Process from Amorphous Bi4Ti3O12 Prepared by Rapid Quenching Method.

We studied the crystallization of amorphous samples of Bi4Ti3O12 prepared by rapid quenching. Differential thermal analysis, powder X-ray diffraction and Raman spectral measurements revealed that the amorphous sample first crystallizes at approximately 610°C to a metastable Bi2Ti2O7 phase and then transforms irreversibly to the stable Bi4Ti3O12 phase at approximately 830°C.

Observation of 90° domains in BaTiO3 by atomic force microscopy

Abstract The visualization of the so-called 90° domains in the ferroelectric barium titanate BaTiO3 with atomic force microscopy (AFM) is reported. At room temperature it is revealed that the as-grown surface of a thin plate crystal bends at the boundary of 90° domains.

Dielectric Properties and Crystallization in Amorphous Bi4Ti3O12

We studied the physical properties of amorphous Bi4Ti3O12 prepared by rapid quenching. The surface change related to glass transition and crystallization was visualized by scanning probe microscopy. For crystallized samples, a 50 Hz D–E hysteresis loop observation was carried out to confirm ferroelectric activity.

Dielectric Properties of Crystallization Process from Amorphous Bi4Ti3O12.

The dielectric constant of amorphous Bi4Ti3O12 prepared by a rapid quenching method was measured. It was found that the as-quenched sample shows a distinct dielectric anomaly at approximately 600°C. With further heating, the dielectric constant shows an anomalously high value above 750°C. In the sample heated to the 900°C range, the recovery of the ferroelectric Bi4Ti3O12 crystalline phase was confirmed by observing the dielectric anomaly at the Curie point.