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Ferroelectric materials with high photovoltaic properties are of interest for new optical devices such as photostrictive ceramic actuators. However, fabrication of these devices requires development of materials exhibiting high photovoltage and photocurrent. In pursuit of these high performance photostrictive materials, the present research examines the influence of illumination intensity, degree of polarization, and sample thickness on the photostrictive response of WO3 doped lanthanum-modified lead zirconate titanate (Pb, La)(Zr, Ti)O3 ceramics prepared by oxide mixing process. A model for calculating the optimum sample thickness for maximum photostrictive response is proposed. This model agrees well with experimental results, and should be useful in designing photostrictive devices.

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The anomalous photovoltaic effect, i.e., substantial voltage generation exceeding band gap energies, by homogeneous illumination in the non-centrosymmetric materials is a wellknown phenomenon. This mechanism is fundamentally different from those observed in heterojunctions/homojunctions (i.e., solar cells) based on semiconductor materials with a symmetric crystal structure. Recently, light induced strain termed as Photostriction, has been demonstrated in noncentrosymmetric perovskite ferroelectrics as lanthanum-modified lead zirconate titanate (PLZT) ceramics. PLZT ceramics have gained considerable attention due to their large photostrictive responses. When a light is illuminated on a polarized photostrictive bimorph, a large photovoltage of the order of kV/mm is generated across its length in the spontaneous polarization direction which results in strain generation by converse-piezoelectric effect and caused the bimorph to deflect in the direction away from the illumination. The photoactuation has been demonstrated in PLZT ceramic wafers as two different kinds of actuators, (i) photo-driven relay and (ii) photo-driven micro walking machine. These materials are also promising for the photo-acoustic device (e.g., Photophone) of the optical communication system. However, photostriction being a recently observed phenomenon, is far from optimum condition. It is expected that the optimization with respect to materials and microstructural characteristics will lead to a substantial enhancement in the photoactuation efficiency. Increasing the photoactuation efficiency will eliminate the need for electrical energy, and will open up numerous possibilities of contactless actuators. In this paper the influence of composition dependence and impurity doping effects on microstructure and photostrictive responses of PLZT ceramics have been investigated.

Photostrictive materials, exhibiting light-induced strains, are of intemt fm future generation wireless remote control photo-actuatars, micro-actuators, and micro-semors applicatim. (Pb, I.,a)(Zr, Ti) 0, (PLZT) ceramics doped with WO, exhibit large photostriction under uniform illumination of nearultraviolet light. Using a bimorph configuration, a photdrivtx relay and a micro walking device have been demonstrated. However7 for the fabrication of these devices, higher response speed must be achieved. The present paper reviews a new theoretical model for photovoltaic effect first, then enhanced performance through sample thickness and surface characteristics, finally its potential fuhue applications.