Nonlinear piezoelectric behavior of ceramic bending mode actuators under strong electric fields

The nonlinear electromechanical behavior of cantilevered piezoelectric ceramic bimorph, unimorph, and reduced and internally biased oxide wafer actuators is studied in a wide electric field and frequency range. It is found that under quasistatic condition, linear relationships between actuator tip displacement-electric field, and blocking force-electric field are only valid under weak field driving. With increasing the driving field, electromechanical nonlinearity begins to contribute significantly to the actuator performance because of ferroelectric hysteresis behavior associated with piezoelectric lead zirconate titanate (PZT)-type ceramic materials. The bending resonance frequencies of all these actuators vary with the magnitude of the electric field. The decrease of resonance frequency with electric field is explained by the increase of elastic compliance of PZT ceramic due to elastic nonlinearity. Mechanical quality factors of the actuators also depend on the magnitude of electric field strength. No significant temperature increase is observed when actuators are driven near resonance frequency under high electric field.