Abstract
A detailed study of ferroelectric microregions (FMRs) of SrTi18O3x16O3(1-x) was carried out for x=0.21, 0.47 and 0.99. From the analysis of FMR spectra, the soft mode was found in the paraelectric phase even though the present study could not reveal whether its frequency reaches exactly zero or not. The size of an FMR with x=0.21 becomes larger than those of other species. This result implies that the development of FMRs does not cause the ferroelectric phase transition. It is concluded that the phase transition induced isotopically in SrTiO3 is of the displacive type.
