Abstract

The complex dielectric constant of hexagonal BaTiO 3 , (h-BT) along the ferroelectric axis has been measured in the frequency range from 10 3 Hz to 10 9 Hz. It is found that the specimen cooled in a strong d.c. electric field exhibits resonant-type dielectric dispersions around 1 MHz and 300 MHz both in the phase II (222 K> T > T c =62 K) and the phase III ( T c > T ). The dispersion around 1 MHz does not appear for the specimen cooled without the d.c. electric field. The effect of the field-cooling on these dispersions is discussed in connection with the twin structure expected from a group theoretical consideration. The dielectric anomaly around T c diminishes in the damped dielectric constant, indicating that the ferroelectric phase transition in h-BT is closely related to an elastic instability.

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