Development of piezoelectric ceramic actuators with graded porosity

The objective of this study was to develop bending-type piezoelectric ceramic actuators having functionally graded microstructures (FGM). Porosity-graded lead zirconate titanate (PZT) ceramics were selected as a model material. Miniature porosity-graded actuator samples with three layers of different porosities (0, 10, 20%) were fabricated by sintering layer-stacked powder compacts that consist of PZT and pore-forming agent (PFA) powders in air atmosphere, whereby stearic acid was added as a pore-forming agent. In order to fabricate PZT/Metal or PZT/Polymer FGM actuators using porosity-graded PZT ceramics as a preform, another pore-forming agent, polymethylmethacrylate (PMMA) powder was also used to increase open porosity. The electric-field-induced deflection characteristic of the beam-shaped actuator samples was measured with electric strain gages, and compared with the values calculated from the modified classical laminate theory using the elastic and piezoelectric constants of the non-FGM porous PZT ceramics. It was found that the experimentally measured deflection values of the obtained actuator samples well agreed with the calculated data. An optimum porosity profile that gives the largest deflection was also determined by the modified classical lamination theory.