Abstract
A 180° Raman scattering experiment has been performed in Bi4-x Sm x Ti3O12 (BSmT-x) single crystals with x = 0, 0.15, 0.3, 0.46, and 0.61 in the temperature range between room temperature and ∼ 600°C. These materials were reported to undergo successive phase transitions at T H and T L (≤ T H). In every BSmT-x, we have found the mode that has been assigned to a ferroelectric soft mode in Bi4Ti3O12. There is quite a possibility that this mode is not a ferroelectric soft mode but an antiferrodistortive soft mode associated with T L. The squared frequency ωA 2 of the mode can be scaled with a temperature difference (T - T L) regardless of x, that is, the temperature T dependence of ωA 2 can be expressed by a straight line of −α (T- TL ) + β, where α = 0.60 ± 0.01 cm−2/°C and β = 360 ± 10 cm−2.
Published Version
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