Electromechanical properties of a ceramic d31-gradient flextensional actuator

We examined the static axial displacement of a ceramic d(31)-gradient flextensional transducer both experimentally and theoretically, Two lead zirconate titanate systems, (PZT)/PZT and PZT/ZnO, were studied. The PZT/PZT transducers consisted of two PZT layers of different d(31) coefficients. The PZT/ZnO transducers consisted of a PZT and a ZnO layer. The PZT/PZT transducers were of an inner-type dome structure. The PZT/ZnO transducers were either nat, or had an inner- or outer-type dome structure by varying the thickness ratio between the two layers or the Sb2O3 content in the ZnO layer. An inner (outer)-type transducer has the large-d(31) layer on the inside (outside) of the dome structure. For the PZT/PZT transducers, the axial displacement varied with the thickness ratio and reached a maximum when the two layers had similar thickness, in agreement with the calculations, With a conductive nonpiezoelectric layer, the PZT/ZnO transducers had higher axial displacements, which varied with the thickness ratio and the Sb2O3 content, than the PZT/PZT transducers. With 6 wt% Sb2O3, the transducers were flat and the measured displacements at various thickness ratios were similar to the calculated values. With 4 wt% Sb2O3, the transducers were of an outer type. The measured axial displacements were about twice the calculated values, suggesting an enhanced d(31) value because of the tensile bending stress in the PZT layer, The scaled axial displacements of the PZT/ZnO transducers with 4 wt% Sb3O2 were comparable to that of the Rainbow transducers. With 8 wt% Sb3O2, the displacements of transducers with thin PZT layers (less than or equal to0.3 mm) were lower than the calculated values because of increased conductivity in the PZT layer.