Recent improvements in the optical and electrooptic properties of plzt ceramics

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Abstract
Continuing studies on the improvement of the optical quality of lanthanum modified lead zirconate titanate (PLZT) ceramics have shown that (1) bulk residual porosity and (2) chemical inhomogeneity are primary factors contributing to optical losses in thick plates of the material. This paper describes methods by which both of these major faults in the ceramic can be virtually eliminated. In addition, the optical and electrooptic properties of the improved material are presented and compared with those of previously available materials. Successful methods of eliminating residual porosity and enhancing chemical homogeneity resulted from studies which led to improved hot-pressing techniques and chemical preparation of the PLZT powders. Essentially all of the residual porosity was eliminated by introducing an oxygen atmosphere during the hot-pressing process. Chemical homogeneity was improved significantly by using high purity liquid solutions for preparing the PLZT powders. A combination of lead oxide and solutions of lanthanum acetate, zirconium alkoxide and titanium alkoxide was found to yield consistently good results. Optical transmission measurements were made on one-millimeter thick polished plates of representative PLZT compositions. Three sets of plates were prepared from (1) mixed oxides conventionally hot-pressed, (2) mixed oxides hot-pressed in an oxygen environment, and (3) chemically co-precipitated powders hot-pressed in an oxygen environment. For each composition measured, the optical transmission increased progressively for materials (1), (2), and (3). Moreover. materials (2) and (3) were progressively more homogeneous than (1) when viewed between crossed polarizers. Electrooptic measurements for materials prepared by the three techniques discussed above showed no significant differences in electrooptic properties.

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