Effects of applied electrical field on piezoelectric property and compressive strength of PZT

Variations of piezoelectric properties and compressive strengths of PZT ceramics with the strength and the direction of poling were investigated. With increasing the applied electric field, the coupling constant, k(33), increased constantly and the volume fraction of grain boundary fracture also increased. This suggests that the rearrangement and the anisotropic stretching of domains during the poling process led to weakening the grain boundaries. Anisotropical compressive and tensile internal stresses of 137 MPa and 76 MPa were induced perpendicular and parallel to the poling direction, respectively. The isotropic compressive strength of 52 MPa was found in the unpoled PZT specimens. The change of internal stress of poled PZT by electrical field was coincident with that of compressive strength. The compressive strength of the specimen revealed to be higher in parallel to the poling direction, but the internal stress in parallel to the poling direction was smaller than the internal stress in perpendicular.