Modeling of poling behavior of ferroelectric 1-3 composites

Piezoelectric 1-3 composites are typically prepared from a polymer matrix and an unpoled Pb(ZrxTi1-x)O-3 (PZT) based ceramic. During the subsequent poling process the PZT cannot strain freely due to the clamping by the surrounding polymer, which after poling results in the occurrence of residual mechanical stress in the composite. The poling process is investigated theoretically by a nonlinear finite element method modeling, which takes into account the ferroelectric and ferroelastic properties of PZT ceramics. Furthermore, an analytical model is developed, which predicts the remanent strain of the composite and the residual mechanical stress. The compressive residual mechanical stress acting on the PZT in the poling direction increases continuously with decreasing volume content v(a) of the PZT ceramic. For values of v(a) higher than about 20% it is lower than half of the coercive stress necessary to cause a mechanical depolarization. For v(a) lower than 20% the residual stress rises rapidly. It may cause a mechanical depolarization of the PZT ceramic for v(a)< 11%. With increasing volume content the longitudinal and the transversal components of the remanent strain increase monotonously in similar way like the corresponding linear effective piezoelectric coefficients. (C) 2001 American Institute of Physics.