Hysteresis Analysis of PLZT Actuator Based on the Photovoltaic Effect and the Viscoelastic Effect

Compared with the traditional actuators, the photostrictive actuators have huge advantages in applying in the hostile environments. The cantilever structure made of PLZT bimorph is used to increase the mechanical displacement because of the smaller photostrictive displacement of one PLZT patch. However, when one side of the PLZT bimorph was irradiated by the ultraviolet light with wavelength of 365nm, the response of the photodeformation is far slower than the photovoltage and the photocurrent, which prevents it from using in the high-frequency dynamic applications. In this study, a novel mathematical model of PLZT patch based on the photovoltaic effect and viscoelastic effect was proposed. And the tip deflection equation of PLZT bimorph was derived by the linear theory of viscoelasticity and constitutive relations of PLZT. And then the factors influencing the tip deflection were obtained by using the numerical analysis. Simultaneously, the hysteresis phenomenon of PLZT patch was explained.

Experimental Investigation and Finite Element Modeling Analysis of Photostrictive Optical Actuators

Photostrictive materials are lanthanum-modified lead zirconatetitanate (Pb, La)(Zr, Ti) O3 ceramics doped with WO3, called PLZT, exhibit large photostriction under uniform illumination of high-energy light. Photostrictive materials are ferrodielectric ceramics that have a photostrictive effect. Photostriction arises from a superposition of the photovoltaic effect, i.e. the generation of large voltage from the irradiation of light, and the converse-piezoelectric effect, i.e. expansion or contraction under the voltage applied. Photostrictive materials offer the potential for actuators with many advantages over traditional transducing electromechanical actuators made of shape memory alloys and electroceramics (piezoelectric and electrostrictive). Drawback of traditional actuators is that they require hard-wired connections to transmit the control signals which introduce electrical noise into the control signals; on the other hand PLZT actuators offer non-contact actuation, remote control, and are immune from electric/magnetic disturbances. The main goal of the research work is to investigate the feasibility of utilizing photostrictive materials as an optical actuator for Micro-Electro-Mechanical-Systems (MEMS) applications. In this investigation process both experimental and computational approaches have been implemented. In the experimental part of this research, a test set-up has been designed and developed to measure the photostriction effect of a PLZT thin film on a silicon wafer as smart beams. The experimental set-up includes high pressure short arc xenon lamp with lamp housing, power supply, lamp igniter, hot mirror, band pass filters, optical chopper, and laser sensor with sensor head and controller.1 μm PLZT thin film on the silicon wafer sample has been tested as a cantilever beam with different light intensities, and focusing the light at the different locations on the PLZT cantilever beam. The experiment has been performed for continuous and pulses of lights focusing on the PLZT optical actuator. An optical chopper was used to make pulses of light on the PLZT cantilever beam. Also, a computational finite element method useful for design of systems incorporating thin film photostrictive actuators has already been developed by the authors. The element has been implemented in an in-house finite element code. This derived finite element for continuous illumination of light on the photostrictive thin film has been used to investigate the application of photostrictive actuators for the different structures and various boundary conditions of microbeams with various actuator locations and length intensities. A successful conclusion of these tasks will affirm the potential of the PLZT optical actuator to use in the MEMS devices.