INELASTIC NEUTRON-SCATTERING OF LITHIUM TANTALATE STUDIED IN THE FERROELECTRIC AND PARAELECTRIC PHASES

Inelastic neutron scattering measurements on single-crystal LiTaO3 in the temperature range from room temperature to 800-degrees-C show evid ence of overdamped scattering, both below and above the ferroelectric- to-paraelectric phase transition. The results are qualitatively discus sed in comparison with the recent Raman studies. The measurements fail ed to observe any well defined underdamped soft mode in the experiment al setting that favours detection of the ferroelectric mode (the lowes t-frequency A1(TO) mode), thereby not supporting a conventional displa cive picture of phase transition in the crystal. We also measured some low-frequency phonon dispersions along two symmetry directions at roo m temperature.