Nonlinear behavior of piezoelectric lead zinc niobate - Lead titanate single crystals under AC electric fields

The nonlinear behavior of the dielectric and piezoelectric responses of <001> oriented Pb(Zn_1/3Nb_2/3)O ₃-xPbTiO₃ (PZN-PT) single crystals for x = 4.5% and x = 8% have been investigated as a function of AC electric fields and DC bias field. At relatively low applied fields, the polarization and strain of PZN-PT single crystals poled along the 〈001〉 direction show little hysteresis and have a linear dependence on the applied field, which is a consequence of engineered domain stability. Hence, the dielectric and piezoelectric coefficients of the material do not exhibit any field dependence. However, when the applied electric field exceeds a threshold value, the strain and dielectric responses become nonlinear. The dielectric and piezoelectric constants are a function of the applied field, and hysteresis loops are observed. The results suggest that the observed nonlinear behavior in the PZN-PT single crystals is caused by domain motion/switching in response to the large AC fields. Applying a positive DC bias can effectively stabilize the domain configuration in the crystals and enhance linear responses. The threshold field, at the onset of nonlinearity, is found to have a linear relation with DC bias field in the field range investigated.