FATIGUE OF PIEZOELECTRIC PROPERTIES IN PB(ZR,TI)O-3 FILMS

Piezoelectric properties of Pb(Zr,Ti)O-3 thin films are investigated a s a function of the number of bipolar (switching) and unipolar (nonswi tching) voltage pulses. The longitudinal piezoelectric coefficient d(3 3) decreases with bipolar fatigue reflecting the decrease of switchabl e polarization. Simultaneously, a strong vertical shift of piezoelectr ic hysteresis loops is observed, which is considered as the buildup of fixed internal polarization due to the pinning of ferroelectric domai ns in a preferred orientation. Piezoelectric fatigue induced by unipol ar (nonswitching) pulses is considerably smaller than the fatigue unde r bipolar conditions and can be described by the internal bias field w hich shifts piezoelectric hysteresis loops along the field axis. (C) 1 996 American Institute of Physics.