Nonlinear behavior of piezoelectric lead zinc niobate-lead titanate single crystals under ac electric fields and dc bias

The nonlinear behaviors of the dielectric and piezoelectric responses of 〈001〉 oriented Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) single crystals for x=4.5% and 8% have been investigated as a function of ac electric fields and dc bias fields. 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. A positive dc bias effectively sta...