Wide Band Dielectric Spectroscopy at Ferroelectric Phase Transition of BaTiO3 Ceramics

概要

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Ultrawide band dielectric spectra from kHz to THz were measured to investigate quantitatively the contributions of ionic and dipole polarizations to the ferroelectric phase transition in BaTiO3 (BT) ceramics. Permittivity derived from ionic polarization ($\varepsilon_{\text{ionic}}$) exhibited its maximum at the Curie temperature ($T_{\text{c}}$), attributing to the softening of the soft phonon mode. Permittivity derived from dipole polarization ($\varepsilon_{\text{dipole}}$) was nearly constant below the $T_{\text{c}}$, while $\varepsilon_{\text{dipole}}$ remained above the $T_{\text{c}}$ and $\varepsilon_{\text{dipole}}$ increased on cooling, exhibiting its maximum near the $T_{\text{c}}$. The behavior in $\varepsilon_{\text{dipole}}$ above the $T_{\text{c}}$ could be interpreted as precursor phenomenon of ferroelectric phase transition and the $\varepsilon_{\text{dipole}}$ above the $T_{\text{c}}$ was due to the local tetragonal type distortion in paraelectric phase.
2010-04-25