Modeling of poling behavior of ferroelectric 1-3 composites

Piezoelectric 1-3 composites are typically prepared from a polymer matrix a nd an unpoled Pb(ZrxTi1-x)O-3 (PZT) based ceramic. During the subsequent po ling process the PZT cannot strain freely due to the clamping by the surrou nding polymer, which after poling results in the occurrence of residual mec hanical stress in the composite. The poling process is investigated theoret ically by a nonlinear finite element method modeling, which takes into acco unt the ferroelectric and ferroelastic properties of PZT ceramics. Furtherm ore, an analytical model is developed, which predicts the remanent strain o f the composite and the residual mechanical stress. The compressive residua l mechanical stress acting on the PZT in the poling direction increases con tinuously with decreasing volume content v(a) of the PZT ceramic. For value s of v(a) higher than about 20% it is lower than half of the coercive stres s necessary to cause a mechanical depolarization. For v(a) lower than 20% t he residual stress rises rapidly. It may cause a mechanical depolarization of the PZT ceramic for v(a)< 11%. With increasing volume content the longit udinal and the transversal components of the remanent strain increase monot onously in similar way like the corresponding linear effective piezoelectri c coefficients. (C) 2001 American Institute of Physics.