Properties of PZT multilayer actuators

PZT (lead zirconate titanate) multilayer actuators have small volume, fast response, low power consumption, and low driving voltage. The fabrication of such parts, however, has some limitations. The use of AgPd for inner electrodes allows maximum sintering temperatures of only about 1100 degrees C. This can be achieved by a modified ceramic process and by the choice of appropriate material compositions. The internal stresses due to the combination of piezoactive layers and thin metal electrodes have to be minimized by suitable geometric design. Bimorph or plate actuators operated in the length extensional mode have an appropriate geometry so that the influence of the multilayer technology on the piezoelectric properties can be studied. These properties are given as a function of the number and thickness of the PZT layers. By comparison with calculated values the separate influence of the internal electrodes can be shown. Data for bimorph actuators with 30- mu m PZT layers and with a driving voltage down to 9 V are presented.<>