Wideband dielectric spectra from the kilohertz to terahertz range are discussed for BaTiO3-based ferroelectrics. Ceramics of BaTiO3 (BT), Ba0.6Sr0.4TiO3 (BST-0.6), and BaZr0.25Ti0.75O3 (BZT-0.25) were selected as normal ferroelectrics, ferroelectrics with diffuse phase transition (DPT ferroelectrics), and relaxor ferroelectrics, respectively. The variation of ionic polarization in both BT and BST-0.6 ceramics with temperature could be explained by the softening of the soft phonon mode. In BZT-0.25, a permittivity anomaly at the dielectric maximum temperature (Tm) at low frequencies is not attributed to the softening of the soft phonon mode, but originates from the permittivity derived from the εdipole polarization (dipole). Relaxor behavior in BZT-0.25 is derived from the increase in the depression of εdipole on cooling across the Tm with increasing frequency. In εdipole polarization, BT, BST- 0.6, and BZT-0.25 all exhibited a similar tendency of εdipole above the Curie temperature (Tc) and Tm. However, behavior of εdipole below the Tc can be explained by the ferroelectric domains in BT, whereas the variation of εdipole below the Tm could be explained by growth process of polar nanoregions (PNRs) in BST-0.6 and BZT-0.25. Regarding this, BT can be distinguished from BST-0.6 and BZT-0.25. Relaxation in BT could be interpreted as successive change in polarization mechanism from normal ferroelectrics to relaxor ferroelectrics via DPT ferroelectrics.
|Number of pages
|IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
|Published - Oct 2010
ASJC Scopus subject areas
- Acoustics and Ultrasonics
- Electrical and Electronic Engineering