Nonlinear contributions to the dielectric permittivity and converse piezoelectric coefficient in piezoelectric ceramics

A measurement and analysis technique has been developed to quantify the complex contributions to the nonlinear dielectric and converse piezoelectric response in ferroelectric ceramics. The electric field dependent response was quantified in two important bulk ceramic piezoelectric systems, Pb(Zr _1-xTi_x)O₃ and (1-x)BiScO₃- xPbTiO₃ (BS-PT), at low frequency and room temperature. The nonlinear response was shown to obey the Rayleigh law in the specific field and frequency ranges reported. Analysis of BS-PT perovskites with different crystal structures revealed a ferroelectric phase dependence on the magnitude of the nonlinear contribution to the dielectric and piezoelectric responses. The magnitudes of the nonlinear coefficients, which quantify the irreversible extrinsic response, were found to be smallest in the ferroelectric tetragonal phase, larger in the rhombohedral composition, and highest at the morphotropic phase boundary. Finally, this work provides strong evidence that the same loss mechanism dominates the nonlinear portion of both the dielectric and piezoelectric responses in piezoelectric ceramics. Analysis of these contributions supports an earlier theoretical model inferring that non-180° domain wall motion in bulk ferroelectric ceramics is a major factor in the piezoelectric and dielectric responses. These results link the observed Rayleigh law behavior to the mechanistic domain wall model commonly employed to describe the extrinsic response of ferroelectric ceramics.