Strain-gradient-induced electric polarization in lead zirconate titanate ceramics

Strain-gradient-induced polarization or flexoelectricity was investigated in unpoled soft lead zirconate titanate (PZT) ceramic where the texture symmetry (infinityinfinity)m forbids macropiezoelectricity. Even under high strain gradient (1 m(-1)) the induced polarization is small (1.6 muC/m(2)) at 20degreesC. Higher strain gradients induce ferroelastic poling and an additional extrinsic contribution to the flexoelectric coefficient mu(12) raising the value from 0.5 to 2.0 muC/m. Cooling through the Curie point (T-C) under maximum stress (80 MPa) where the peak permittivity (similar to20 000) could raise mu(12) to 20 muC/m, the equivalent electric field is still only similar to1 kV/m, inadequate to achieve significant ferroelectric poling. The situation may be different in thin PZT films where much larger strain gradients can occur. (C) 2003 American Institute of Physics.