Journal of the American Ceramic Society, Vol.88, No.4, 997-999, 2005
Ceramic-ceramic actuator composed of two piezoelectric layers with opposite poling directions
A ceramic-ceramic actuator composed of two piezoelectric ceramic layers with opposite poling directions was developed. One layer of the actuator had a high coercive electric field (PZT (Pb(Zr,Ti)O-3)-I; E-c = 1.1 kV/mm), while the other had a relatively low coercive electric field (PZT-II; E, = 0.6 kV/mm). The actuator was fabricated by cofiring a green compact composed of the PZT-I powder on top of the PZT-II powder. When an electric field > 1.1 kV/mm was applied to the sintered body, the whole specimen was poled in one direction. Subsequently, by applying a field between 0.6 and 1.1 kV/mm, only the PZT-II layer was switched to the other direction. When an electric field was applied to this oppositely poled two-layer specimen, one layer of the specimen expanded while the other layer shrank. As a result of these reverse dilations, the actuator was bent into a dome shape, yielding a large axial displacement at the center. The displacement of this actuator with dimensions of 20 mm (diameter) x 1 mm (thickness) was 16 mu m at 0.9 kV/mm.