A low-working-field (2 kV/mm), large-strain (>0.5%) piezoelectric multilayer actuator based on periodically orthogonal poled PZT ceramics

In this work, we proposed a special designed multilayer actuator based on the periodically orthogonal poled (POP) PZT ceramics. Only the in-plane poled regions of the neighboring PZT layers were bonded together thus the large reversible switching strain in these regions can always be employed. A six-layer actuator was fabricated and testing results show that it can output actuation strains over 0.5% under a low field of 2 kV/mm at 0.1 Hz, about 3.5 times of that in conventional PZT actuators which is less than 0.15% under the same field. Furthermore, the output large strain is fairly uniform, which varies from 0.50% to 0.53% along the period direction, in comparison with that varying from 0.35% to 0.59% in a single-layer POP PZT. The large actuation strain drops quickly with the increasing frequency, and stabilized at about 0.2% under 2 kV/mm at or above 1 Hz. The low-frequency large strain is very stable and keeps unchanged after 20 k cycles of operation. To solve the charge accumulation problem during successive unipolar loading/unloading, an asymmetric bipolar field from −300 V/mm to 2 kV/mm is applied and meanwhile the actuation strain turns to be more uniform, only varying from 0.51% to 0.52% at 2 kV/mm. The low driving field, large strain of the proposed actuator makes it very promising in low-frequency, large strain/displacement actuation areas.