Abstract
Experimental studies were carried out on infrared-active phonons in the Aurivillius ferroelectric (SBT), using reflectivity measurements (down to ) and transmission measurements (down to ) on crystals, pellets, and thin films. An analysis was done of the contrasting consequences of the competing orthorhombic and pseudotetragonal symmetries in SBT. Reflectivity results for light polarized in the plane show that the anisotropy in this plane is small in the frequency range from 300 to indicating the influence of the approximate tetragonal symmetry. Dielectric dispersion properties were derived for this polarization in this frequency range. The transverse-optical (TO) and longitudinal-optical (LO) frequencies corresponding to the dominant band are 613 and respectively. This strong, high-frequency band arises from a mode dominated by the motion of the oxygen sublattice; its TO and LO frequencies yield an oxygen-ion Szigeti effective charge of Frequency estimates for the TO (LO) pairs of other strong bands are 188(330) and for and 610(675) and for In addition to the main infrared bands, the main Raman bands of SBT are also reported.
- Received 29 September 1997
DOI:https://doi.org/10.1103/PhysRevB.57.5715
©1998 American Physical Society