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Abstract
The IR reflectivity of PLZT (Pb0.9025La0.0975Zr0.65Ti0.35O3) and PSN (Pb(Sc0.5Nb0.5)O3) ceramics was determined in the spectral range 15 to 2000 cm−1 and temperature region 25 to 200°C around the ferroelectric phase transitions. Kramers-Kronig analysis was used to calculate the dielectric function. In the case of PLZT a strong central-mode-type dispersion was observed both in reflectivity and BWO transmission below ∼ 40 cm−1 which prevents softening of the lowest phonon mode. In the case of less diffusive PSN the central mode is shifted below ∼ 10 cm−1 and a monotonous softening of the lowest phonon mode is observed in the whole temperature range.