| Piezoelectric ceramic materials are widely used in numerous applications for both sensing mechanical force and producing actuation under an applied electric field. In some applications such as manufacturing of optical instruments and semiconductor chips, a displacement of a few hundred microns with a precision positioning of 0.1 μm is required. Piezoelectric ceramics are well suited for such a positioning accuracy, however, the strain in these ceramics is only on the order of 0.1% due to the relatively low values of their piezoelectric coefficients. Therefore, many novel actuator designs have been developed to amplify the field-induced displacement of piezoelectric ceramics.; In this investigation, four different piezoelectric actuator systems have been developed and studied including dome, spiral, telescoping, and multi-material multilayer bimorph by the FDC technique. The FDC materials-dependence build parameters were identified and optimized for the prototyped actuators. Among these actuators, monolithic spirals demonstrated very large field-induced displacements, and therefore, were studied thoroughly. The spiral actuators (3, 0.06, and 28 cm in diameter, width, and effective length, respectively) produced displacements of up to 1,900 μm under an electric field of 1.1 kV/mm. This actuation behavior is far superior to any commercially available actuators to date. Finite element analysis of spiral actuators was performed using ABAQUS. The results of analysis were in good agreement with the experimental findings. Both the displacement and resonant frequency of the spirals were tailored by altering the geometric parameters including length, wall width, height, and the number of turns. The blocking force of the actuators was on the order of 1 N. The properties obtained are advantageous for high-displacement, moderate-force applications where bimorph or monomorph actuators are currently employed.; A new type of monolithic multi-material bending type actuator was developed based on a co-fired piezoelectric, 0.65PMN-0.35PT, and electrostrictive, 0.9PMN-0.1PT multilayer structure. The investigation aimed to replace the bonding agent (conductive epoxy) in conventional bimorph actuators with a co-fired ceramic-ceramic interface. This may eliminate the cracks or peel off at low temperatures, as well as, creep at higher temperatures. In addition, the new process not only reduces the processing steps and cost, but also increases the reliability of these bending actuators over those with an epoxy interface. Preliminary experiments showed that a displacement of 32 μm can be achieved at 500 V(DC). Incorporating a self-bonded multimaterial into spiral geometry is expected to enhance the displacement of such structure significantly. The processing and electromechanical characterization of these actuators are investigated in this thesis. |
