Development of Functionally Graded Piezoelectric Actuator for MEMS(Micro Electro Mechanical System) by Powder Process Technology

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The purpose of this research is to develop the piezoelectric actuator with functionally graded microstructure(FGM) that has a higher mechanical reliability than the conventional non-FGM actuator aiming at the application of the piezoelectric actuator to the micro electro mechanical system(MEMS). The obtained results are described as follows.1. The electrically induced strain in a PZT piezoelectric plate could be gradually changed by introducing compositionally graded structure of PZT/Pt or porosity-graded structure into a PZT piezoelectric plate. These actuators had no adhesive interface at which the fatigue failure take place, and could electrically make a bending deformation.2. The bending displacement property of the FGM piezoelectric actuator depended on the composition profile, and there existed the optimal composition profile that the bending displacement become the maximum. Moreover, the optimal composition profile could be easily predicted by the modified lamination theory.3. T … More he PZT/Pt compositionally graded piezoelectric bimorph actuator with the optimal composition profile exhibited nearly the same bending displacement as the non-graded bimorph actuator. Therefore, PZT/Pt compositionally graded piezoelectric bimorph actuator is estimated to have enhanced mechanical reliability without degradation the bending displacement characteristics. On the other hand, porosity-graded monomorph actuator exhibited a bending displacement characteristics that inferior to the non-graded unimorph actuator. Then, the profile design of physical properties for improvement of the bending displacement characteristics was attempted by modified lamination theory. As a result, it was predicted to be able to improve the bending displacement characteristics by introducing the profile with decreasing the piezoelectric constant and increasing the elastic modulus and the dielectric constant into the FGM monomorph actuator.4. The porosity-graded piezoelectric preform that have high open porosity and that is suitable for the achievement of the profile design for improvement of the bending displacement characteristics could be obtained by powder processing technology. This means that it is possible to fabricate the FGM monomorph actuator with the higher bending displacement and mechanical reliability by infiltration as a next process. Less