SHEAR RESPONSE OF LEAD-ZIRCONATE-TITANATE PIEZOCERAMICS

The piezoelectric shear strain S-5 of several commercial lead zirconat e titanate (PZT) piezoceramics was evaluated under the nonresonant con dition in a sinusoidal ac-field E-1(t) applied perpendicular to the po ling direction. Results obtained on donor doped (soft PZT) and accepto r doped (hard PZT) ceramics are compared. At fields sufficiently below the limiting field E-lim, necessary to electrically depole the sample , we find a linear, nonhysteretic relationship between S-5 sind the po larization P-1. In soft PZT ceramics, the effective piezoelectric shea r coefficient d(15)=S-5/E-1 shows a pronounced ac-field dependence whi ch was fitted according to d(15)(E-1)=d(lin)[1 + (d(nl)E(1))(alpha)] w ith alpha approximate to 1.2. The results indicate that irreversible m otion of non-180 degrees walls causes the nonlinearity of PZT and the contribution of 180 degrees walls to the linear and nonlinear coeffici ents is negligible. The analysis of the relationship between linear an d nonlinear coefficients obtained at different ceramic systems suggest s that there exists another extrinsic contribution to the permittivity in PZT which may not be attributed to domain wall motion but may be r esponsible to the dielectric dispersion at microwave frequencies. (C) 1998 American Institute of Physics. [S0021-8979(98)00607-0].