BENDING ACTUATOR USING LEAD ZIRCONATE TITANATE THIN-FILM FABRICATED BY HYDROTHERMAL METHOD

Thin films of lead zirconate titanate (PZT) were fabricated by the hydrothermal method which consisted of two steps in the hydrothermal process: "nucleation" and "crystal growth" processes. The PZ nuclei were formed by the reaction at 140-degrees-C in a solution containing 4N potassium hydroxide. The growth rate of PZT crystals decreased at temperatures below and above 120-degrees-C. Bimorph-type bending actuators were made using as-deposited PZT films. The actuators showed large and visible electric-field-induced displacement even at driving voltage less than 10 V. From the displacement-voltage curve of an unimorph actuator and that of a heat-treated specimen, it may be concluded that the polar axes of PZT crystals had an orientation toward the substrate, giving rise to the piezoelectric effect without poling procedure.