Morphotropic phase boundary-like effect in hybrid electrically poled, mechanically depolarized ferroelectric ceramics

Abstract

The morphotropic phase boundary (MPB) plays an important role in ferroelectric materials. Typically, two phases coexist in materials near the MPB. Such materials usually exhibit large piezoelectricities, dielectricities, and actuation strains. In this work, we produce an MPB-like effect in hybrid electrically poled, mechanically depolarized (HEPMD) BaTiO3 and lead zirconate titanate ceramics where depolarized region A and vertical electrically poled region C intersect each other with a period of 400 μm in both in-plane directions. The polarization and strain of both HEPMD samples are over 3 times those of conventionally poled samples under unipolar electric loading. The large polarization and strain decrease steadily as the frequency increases and stabilize at approximately twice the values from the conventionally poled samples. Furthermore, the large polarizations and actuation strains of the HEPMD samples are fairly stable and change little after 30 000 cycles of operation. Under bipolar electric loading, the tendencies are similar and the coercive fields of the HEPMD samples are considerably smaller, which is similar to the MPB effect in traditional ferroelectric ceramics. Enhanced polarization and strain occur in HEPMD samples due to reversible ferroelectric domain switching during loading and unloading under large electric fields. In comparison, the small-signal properties, i.e., the d33 and dielectric properties, are slightly larger in HEPMD samples than in conventionally poled ones. The HEPMD method may be applied to all types of multiaxial ferroelectric ceramics to enhance actuation strain and polarization.