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Central Peak of Bismuth Layered Ferroelectrics Pb2Bi4Ti5O18 Studied by Brillouin Scattering

Brillouin scattering spectra have been observed in ceramic sample of Bi-Layered Perovskites Pb 2 Bi 4 Ti 5 O 18 using a Sandercock type tandem Fabry-Perot interferometer. A central peak was observed in the spectrum, which shows the anomalous increase of relaxation time with approaching to T 1 = 450 K. The temperature dependences of intensity and width in the central peak spectrum show anomaly at T 2 = 740 K in addition to T 1 . However, no anomalous behavior has been obtained at T c = 583 K reported as a ferroelectric phase transition point with a dielectric measurement by E. C. Subbarao.