Direct piezoelectric response of piezopolymer polyvinylidene fluoride under high mechanical strain and stress

We show that the nonlinear piezoelectric response of polyvinylidene fluoride (PVDF) exhibits quite different behavior compared with the piezoceramics. Instead of increasing linearly with the stress amplitude T-ac, d(31) coefficient raises with T-ac(2). Furthermore, the nonlinear effect does not set in until the strain increases beyond 0.3%, indicating very strong barriers to the domain wall motions in PVDF. The electromechanical coupling factor k(31) also exhibits an increase with stress. Furthermore, the piezopolymer can withstand more than 3% strain without degrading the piezoelectric responses. (c) 2007 American Institute of Physics.