The lattice dynamical properties have been studied by Raman spectroscopy in bismuth layer-structure oxides Bi4Ti3O12, and ABi4Ti4O15 (A=Ba, Ca, Pb, Sr). The rigid-layer modes were observed in all compounds in the range 57–62.5 cm-1. The lowest mode of Bi4Ti3O12 shows marked softening, and the square frequency of the lowest mode is linearly related to the square of the spontaneous polarization. As for CaBi4Ti4O15 and SrBi4Ti4O15 the underdamped soft modes were also clearly observed. In contrast, in BaBi4Ti4O15 only low-frequency overdamped modes have been observed. In PbBi4Ti4O15 the low-frequency spectra have a complicated structure and the softening of the underdamped modes was not observed clearly.

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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.