Neutron scattering study of the relaxor ferroelectric K1−xLixTaO3

Neutron scattering experiments using triple axis spectrometers have been performed for the relaxor ferroelectric materials K1−xLixTaO3 (x=0.05, 0.10) in order to study the behavior of the zone-center (ZC) transverse-optic (TO) phonon mode (ferroelectric mode). A major contrast between the x=0.05 and 0.10 samples is the ferroelectric transition-observed only for the latter material at TC=115 K on warming and as detected by dielectric measurements and neutron diffraction. The ZC TO mode for x=0.05 shows monotonic softening with decreasing temperature down to 10 K, whereas the x=0.10 sample shows a phonon component below TC which hardens with decreasing temperature in addition to a phonon mode which behaves similarly to that of the x=0.05 sample. This suggests a phase separation of the x=0.10 sample into ferroelectric and relaxor states below TC, possibly originating from a percolative nature of the ferroelectric state.