90° Domain Reorientation and Electric-Field-Induced Strain of Tetragonal Lead Zirconate Titanate Ceramics

The effect of the reorientation of 90° domains on the electric-field-induced strains was studied for tetragonal lead zirconate titanate (PZT) ceramics. An in situ X-ray diffraction (XRD) method was used to evaluate the 90° domain reorientation under electric fields. The strains caused by the reorientation were calculated and compared with the electric-field-induced longitudinal strains measured with a laser displacement meter and the strains expected from piezoelectric d-constants. It was experimentally confirmed that the electric-field-induced strains of PZT ceramics were composed of strains due to the piezoelectric effect and the 90° reorientation. After poling treatment, a small portion of the 90° domains relaxed and reoriented, giving rise to a reversible reorientation of the 90° domains by the electric field. These reversible reorientations contributed to the electric-field-induced strains. In "soft" PZT ceramics, the degrees of 90° reorientation caused by poling and by the subsequent application of an electric field had a close correlation with the tetragonality of the crystal lattice rather than with the coercive field.