The hysteretic response of lead zirconate titantate ceramics after mechanical depolarization

The hysteretic response of mechanically depoled polycrystalline PZT specimens was investigated. Results show that the mechanically depoled domains can be repoled to their original state by electric fields much lower than their coercive electric field. Such a phenomenon is attributed to two factors: (i) during mechanical depoling, some energy was stored in the form of domain interactions and these released energy to help domains switch back during repoling; (ii) an internal bias electric field. During the second cycle of unipolar electric field loading, polarizations and longitudinal strains induced by electric fields increased with increasing depolarization stress, indicating that the number of irreversible domains increased in mechanically depoled specimens. During bipolar electric field loading, the hysteresis loops and butterfly curves of the mechanically depoled specimen nearly overlapped with those of an un-depoled one, demonstrating that an internal bias electric field cannot be eliminated by mechanical depolarization.