Specific features in the behavior of the central peak in Raman spectra of lithium tantalate

Low-frequency Raman spectra of a LiTaO3 ferroelectric crystal are studied in the temperature range 300–1273 K. The central peak associated with the relaxation susceptibility of the crystal lattice is recorded throughout the temperature range covered, including the temperatures both substantially lower and considerably higher than the Curie point (Tc = 900 K). The critical slowing down of the relaxation response time predicted by the Ginzburg-Landau-Devonshire theory is observed in the temperature range from 0.9Tc to 1.1Tc. In contrast to the critical slowing down, the width of the central peak γR increases below 0.9Tc and decreases above 1.1Tc with increasing temperature.