Electrooptic, PLZT devices

These lead-based materials (PZT, PLZT, PMN) form a class of ceramics with either important dielectric, relaxor, pie2oelectric, or electrooptic properties, and are thus used for appHcations ia actuator and sensor devices. Resistive properties of these materials ia film form mirror the conduction processes ia the bulk material. Common problems associated with their use are low dielectric breakdown, iacreased aging, and electrode iajection, decreasiag the resistivity and degrading the properties. 

Haertling, G.H. (1991) Electrooptic ceramics and devices , in Engineered Materials Handbook Volume 4 Ceramics and Glasses, ASM International, p. 1124. Haertling and Land (1971) developed the PLZT system of transparent ferroelectric ceramics. 

A special class of materials that is also ferroelectric are electrooptic ceramics. Materials such as lanthanum-modified lead zirconate titanate (PLZT) produce excellent electrooptic devices. These polycrystalline ceramics exhibit voltage-variable behavior—that is, they can be switched from optically transparent to opaque by the application of voltage. Most of these devices, which are used for shutters, modulators, and displays, are processed by hot pressing to full density. Experiments in many laboratories are being carried out to tape-cast these materials into thin sheets. The main problem encountered to date has been the ability to sinter to full density. The use of nanosized powders has helped in this regard. The ability to tape-cast large sheets could open a wide variety of applications for these materials. 

The PLZT ceramics show large changes in birefringence by switching the polarization and these materials are of potential use in optical memories and displays. " However, the electrooptic properties utilized for such devices depend on the grain size. ... 

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