Electromechanical properties of a ceramic d(31)-gradient flextensional actuator

We examined the static axial displacement of a ceramic d(31)-gradient flext ensional transducer both experimentally and theoretically, Two lead zircona te titanate systems, (PZT)/PZT and PZT/ZnO, were studied. The PZT/PZT trans ducers 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 transducer s 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 thicknes s ratio between the two layers or the Sb2O3 content in the ZnO layer. An in ner (outer)-type transducer has the large-d(31) layer on the inside (outsid e) of the dome structure. For the PZT/PZT transducers, the axial displaceme nt varied with the thickness ratio and reached a maximum when the two layer s had similar thickness, in agreement with the calculations, With a conduct ive nonpiezoelectric layer, the PZT/ZnO transducers had higher axial displa cements, which varied with the thickness ratio and the Sb2O3 content, than the PZT/PZT transducers. With 6 wt% Sb2O3, the transducers were flat and th e measured displacements at various thickness ratios were similar to the ca lculated values. With 4 wt% Sb2O3, the transducers were of an outer type. T he measured axial displacements were about twice the calculated values, sug gesting an enhanced d(31) value because of the tensile bending stress in th e 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.